My SD300 3D Printer

A Box for Guile

2012-02-12T23:04:00.000-08:00

In 2009 I tried to develop a puzzle titled Guile in the Box by cutting acrylic parts on a laser cutter, but the shapes proved too difficult to cut and I lost access to the laser. But luckily I had built one perfectly-proportioned box using laser-cut parts, and I used it to refine and finish the puzzle. Now I needed a way to build more boxes with exactly the right proportions.

To replicate the box on the SD300 I designed a flat model with hinges that would reproduce the exact interior I needed when the wall panels were folded.

For stability I added a ridge along one edge that could engage tabs on the side walls.

When the panels are folded into the right shape there's a groove around the top rim of the box.

A separate plastic rim snaps into the groove, thereby completing the box.

The finished box matches the dimensions of my 2009 prototype, so now I can build as many as I need.

Rupee Puzzle, rev. 1

2012-02-07T11:03:00.000-08:00

India recently adopted a currency symbol ₹ for their rupee, which elegantly combines elements of the Devanagari letter र with a Latin letter R. I dissected the shape into a puzzle with carefully-disguised cuts like other, traditional letter-dissection puzzles. My effort was concentrated on the complex shapes in the upper part of the Rupee symbol, but the lower part was somewhat hastily finished.

I built my first test model in one piece, but with built-in dividing lines.

After confirming that the overall shape was recognizable I snapped the pieces apart along the pre-cut dividing lines.

It might be very difficult to assemble such a complex shape, so I also built and tested a plastic frame that might be used as a template to help someone assemble the shape. It's a successful proof-of-concept but I'm dissatisfied with the overall shape because it lacks angled serifs on the two bars and the lower leg ought to be connected differently.

In the future I will try to develop a better Rupee dissection that incorporates the aforementioned stylistic features. In the meantime I decided to practice by re-creating traditional dissection puzzle of the letter T. This basic puzzle has been around for a century or more, but it continues to stump people despite its apparent simplicity. Since it's an old design I shared the STL files for the T puzzle as "public domain" at Thingiverse.

Rob's Puzzle Page has some interesting pictures of other dissected-letter puzzles here.

Nikola Tesla and Blue

2012-02-03T11:36:00.000-08:00

Nikola Tesla proposed a Valvular Conduit in which fluid (or gas) flows freely in only one direction. There are no moving parts, but reverse flow is impeded by inducing turbulence at the backward-facing junctions.

I expected it to be an ideal model to build in transparent material, thereby allowing the user to see inside, but I found my model just a bit too transparent. Yes, I could see inside the model but it was hard to distinguish the channels from the walls. Ordinarily I would resolve that by adding a layer of red material, which is strongly colored so it makes a good contrast.

But a friend had recently hooked me up with a carton of dark blue VisiJet LD material, which is 100% compatible with the SD300. I hadn't tried it out yet, so this seemed like a good opportunity to test it.

I built another model of the conduit using transparent material as before, except this time I put in the blue material for just one layer. When I removed the unused material the outline of the conduit emerged in sharp contrast.

The blue material makes the conduit walls stand out vividly.

Now it's easy to distinguish the channel even when looking through the fully assembled model. Fluids can move easily through the conduit from left-to-right because the junctions converge without creating much turbulence, but right-to-left flow is impeded because the junctions divide the flow and force it back across its own path.

Star-shaped verification model

2012-01-30T13:44:00.000-08:00

I developed a set of fit-test models when I was trying to adapt my Wrong Way Nut model to make it suitable for Makerbot-type hobby FDM printers. This is a series of shafts and disks with a star-shaped cross section to be built in various orientations.

The SD300 built the shapes accurately enough that each disk can fit over any of the shafts all 8 ways. But when built on a hobby machine without support material I have a hunch the shaft will be distorted.

Will the corners be blunted because the filament has nothing to anchor it, like the yellow line in this drawing? Or will they extend too far because the unsupported material droops, like the blue line? Or will both effects cancel each other out, yielding a perfect fit?

I can't really guess how this model would behave on a Makerbot, but I shared the test files here at Thingiverse, just in case a hobbyist wants to test it.

Locked Dovetail Triangle

2012-01-27T10:55:00.000-08:00

When I posted my Dovetail Triangle one user suggested adding a locking mechanism while another argued against it. So let's have it both ways: I built a new dovetail mechanism that has a locking mechanism, shared here at Thingiverse, to complement the one that doesn't have a locking mechanism here.

As before, I aimed to keep overhangs within the buildable range of Makerbots and other hobby printers. That imposed some interesting design constraints, which forced me to distribute features of the locking mechanism between the base and lid. But I filleted the internal corners to 0.5mm purely for my own convenience: it's a bit easier to peel unused material out of SD300 models if there aren't sharp internal corners.

At first I built a transparent model and tested it with two black triangular pieces so I could look inside to see how well it was working. It's hard to see, but the picture below shows how the black triangles slide toward the outside of the puzzle when it's lying flat and thus lock the joint.

The black triangular pieces (dark shadows) slide toward the outer corners.

When it's flipped upside down, the contours in the lid cause the black triangles to slide toward the outside edges, locking the joint like the previous picture.

When flipped over the triangular pieces still slide toward the corners.

It worked, but those triangular pieces just didn't slide very well. So I tried using round discs instead. That worked much better because the discs easily rolled around when the puzzle was tipped.

Here's a video showing how the pats work and how the puzzle opens.

I designed the mechanism so it would only unlock when one particular corner of the triangle was pointed downward, because I thought that would be the least intuitive way to hold the puzzle. As it turns out I'd guessed wrongly about that: testers instinctively hold the puzzle with one of the dovetails facing up (to look at the joint, I guess) and hence they naturally hold it with a corner pointing downward. So it isn't especially challenging, but it definitely works!

Return Tool Error

2012-01-26T22:41:00.000-08:00

While the SD300 was building a model on Tuesday night it made a distinctive 'click' noise, just once while it was using the Anti-Glue pens. It didn't sound bad, but it was an unfamiliar sound I'd never heard before.

It never made the click noise again, but a few minutes later it began exhibiting problems putting the Anti-Glue pens away. Eventually the machine stopped with a "Return Tool Error" message. In SD300 lingo the Anti-Glue pens are named Tool #4, Tool #5, and Tool #6 so this message means it was unable to return a pen to its holder.

That wasn't too alarming. Maybe that click noise had been a pen or holder had been knocked loose. I removed the pen from the plotter and carefully returned it by hand. The machine resumed building for one more layer but the error happened again as soon as it tried to use the Anti-Glue pens. I installed a brand new set of Anti-Glue pens, but the error kept coming back.

When the machine had logged 24 consecutive errors I decided to give up. It was late, so I dashed off an email and went to bed. By Wednesday morning I already received two helpful replies from the folks at SolidVision, which recently merged with FISHER/UNITECH. I appreciated the very prompt response but I had to go to work because I only do 3D printing as a hobby, so I didn't have an opportunity to do any troubleshooting until the following evening.

Jason Harris offered me several options, but he suggested the solution might be as simple as squeezing the spring on the affected pen holder. The pens holders are spring-loaded clips, likely the same ones used in Roland DXY-series pen plotters. A spring is supposed to ensure an empty pen-holder is narrower than an occupied one. Could it really be this simple?

Curious, I brought out the calipers and measured the pen holders both with and without pens in them. The openings on the working pen holders were all about 7.9mm wide, but the malfunctioning pen holder was open about 8.4mm. That didn't seem like much difference, but I carefully applied pressure to the spring until the bad pen holder measured less than 8mm, then I restarted the machine.

It worked! Then it worked again! Just to be sure I repeatedly pressed Pause/Resume to make the machine take and return the pen a dozen times, and the pens returned to the holders every time.

This week my SD300 has logged over a thousand build jobs. I've occasionally had issues that resulted in canceling a job or damaging a model, but this is the first time the machine itself had exhibited a fault. In hindsight I consider that a very good record, especially considering how easily the fault was resolved. Admittedly there are challenges cleaning the support material from some models, but the machine itself has never demanded anything more than clearing a jam or replacing spent consumables.

Peppermint Candy puzzle refined

2012-01-25T00:52:00.000-08:00

I took another stab at the Peppermint Candy puzzle which had been vulnerable to coming apart in unintended ways. I carefully refined the curves so each piece would 'reach around' to brace itself against the back side of the puzzle and made the walls thicker so it would be more rigid.

Honestly, I wasn't sure it would suffice. But it worked!

Here's the side with the ball sticking out. The cut in the ball is lined up with the cuts in the shell but it won't open in this position.

The other side of the puzzle looks about the same, but it has a white dome instead of an opening so the ball can't be seen from this side. The parting line forms an S-shape where it passes through the domed part.

Here's a video explanation of the puzzle in detail.

For comparison I ordered a test part built in SLS nylon. It's stiffer than the part built on the SD300, a good thing, but it lacks the contrasting colors. But the colors aren't just cosmetic; my testers thought the colors contributed to the challenge of solving the puzzle.

I built the ball pieces in a very specific orientation in order to put the colors exactly where I wanted them. Here's how the ball looks outside the puzzle shell.

Since the part required a specific build orientation I couldn't really position it for optimal post-processing. Each piece had a thin edge that would have been particularly vulnerable to chipping during cleaning, so I isolated that area in a little 'box' of peeling cuts.

Most of the layers in the isolated box fell away when the surrounding areas were cleaned, so it didn't make the cleaning work any slower. Except when I got to the thinnest part, the isolated box allowed me to gently peel away the last bits of material...leaving the thin edge smooth and intact. As usual, I solvent-dipped the parts to give them greater strength and a slick finish!

MINI Cooper Grocery Bag Hook

2012-01-20T13:32:00.000-08:00

MINI offers a "Grocery Bag Hook" accessory that's supposed to prevent shopping bags from sliding around in the trunk. But bags don't slide around in the tiny trunk of a MINI Cooper, so their accessory seems unnecessary. What I really wanted was a hook that would keep a shopping bag from sliding around in front of the seats, so I designed this simple hook.

This hook attaches easily to the dealer-supplied cup holder accessory. Shopping bags slip neatly into the deep slot so they won't slide around.

I put it online at Shapeways and built a sample in their Red Strong & Flexible material. Don't expect it to be a big seller!

I had replaced the material kit partway through the build, and the tints didn't quite match even though both kits were Amber Transparent material.

Antichron

2012-01-09T01:22:00.000-08:00

A year ago I probably wouldn't have attempted to build something as twisty and complex as Bathsheba's Antichron model. But someone sent me a reduced-size model of it, and I confidently devised a small set of peeling cuts that should have made it an easy build on the SD300. Not so easy, as it turned out.

I got it mostly right. I'd divided the model into four zones in each of the upper and lower sections, so the support material peeled away effortlessly at first.

But when I got near the middle section I found layers of support material permanently wrapped around sculptural features I'd misinterpreted. If it had been properly planned, there should have been additional cuts to divide the support material but I hadn't instructed the SDMove software to make the proper cuts.

Was it necessary to discard the model just because I hadn't set up the build software properly? Probably not, but I decided to free the model so from the rest of the material to get a better view of the trouble spots.

The support material was thicker than the walls of the model so I couldn't just remove them by brute force. So I decided to separate the support layers and snip them one-at-a-time with a small knife. This was tedious but it would free the model after cutting through dozens of layers on each side. That would take a while so I put on an old Edward G. Robinson movie (Scarlet Street) while I worked...and it took most of the movie to free the two models I'd built.

Because I'd scaled down the model by 50% the walls were dangerously thin, about 1.4mm. Somehow I managed to free the first model without any damage, but cracks appeared in the second model while I was cleaning it so I stopped several times and applied Weld-On to strengthen its weak spots. When I finished cleaning the second model (below right) I dipped it in Weld-On 2004 to heal the cracks and give it a nice sheen.

Test Model vs. "Clean Bubbles"

2012-01-06T22:37:00.000-08:00

In Monday's post I concluded that whenever the SD300 has been idle for a week or more that it's wise to either build a Test Model or run the Clean Bubbles maintenance routine to clear bubbles out of the glue delivery lines.

But which method is better? Is there a difference?

I ran some tests, reviewed the logs, and weighed the glue cartridge: a Test Model takes 15 minutes, uses 8 grams of glue, and consumes some PVC material. The Clean Bubbles routine takes about 1 minute, uses 5 grams of glue, and doesn't consume any other consumables.

So Clean Bubbles is better, faster, and more economical.

From now on, when I want to build a model after leaving my SD300 idle for a week I will 1) first clean the glue trap with a paper towel, 2) run the Clean Bubbles routine in SDMove, and 3) confirm liquid glue has been deposited in the trap. (Repeat Clean Bubbles if the trap is dry.)

Bubbles in the glue lines tend to resolve themselves, but it's nice to discover how trivially easy it is to prevent the problem in the first place.

Another mystery solved

2012-01-02T00:39:00.000-08:00

I think I solved another mystery or two.

Jason Harris at SolidVision told me when I was setting up my SD300 that it might give a false 'replace cutting knife' error around layer 4 or 5 if the build material wasn't stacked tightly at the edge of the build table. It happened to me once in June 2010 the first time I used my SD300 after a long vacation.

A British SD300 user once told me that he tended to build several batches of models near the end of each month. His first build job would usually be sticky and the support material would be hard to remove, but all subsequent jobs would be normal. He worked around the problem by always building the built-in Test Model if he hadn't used the machine that month.

Today I built my first model since 17 December 2011, so my SD300 has been sitting idle for two weeks. I noticed something strange immediately. Normally the SD300 starts by bonding a layer of PVC onto the build table with an even layer of SolGL adhesive, but this time the adhesive was spotty. The adhesive appears here as dark spots underneath the red plastic--it should have been spread under the whole sheet, not just little spots as here.

Then I noticed a shiny droplet of SolGL glue near the edge of the table, on top of the PVC sheet. I'll bet it dripped there when the SD300 measured the material height with its micrometer, which is attached to the same unit that spreads the glue.

Ordinarily the machine's next step would spread anti-glue (masking fluid) onto this surface with a device like a felt-tip pen, but the droplet of SolGL glue would obviously contaminate the pen so I paused the SD300 and wiped up the glue with a paper towel.

Then I let the SD300 continue building to see what would happen. The next layer had fewer bubbles than the first, and the following layer didn't have any bubbles at all. I'm guessing air had seeped into the glue delivery system while the SD300 sat idle, but the air had all been cleared out now.

I wondered if I should cancel the job and start over now that the problem had apparently cleared itself up, but out of curiosity I let it keep running. Lucky thing, since what happened next was a revelation.

Starting at layer 4 in every job the SD300 automatically verifies the condition of the cutting knife by cutting a test pattern at the edge of the table. When this build reached layer 4 I heard a loud noise from the media feeder clutch which usually signals a cutting-knife failure. I watched closely as the SD300 automatically repeated the knife test a second time: the knife was good but the material was too loose. The machine raised the table and repeated the test again: the test succeeded this time, but the leverage from the knife dislodged the material so the PVC sheets loosened from the table.

The SD300 started building layer 5 by ironing a new sheet to the top of the model. Ordinarily it measures the stack with its micrometer to confirm the thickness of the last layer, but this time it started taking repeated measurements over and over. The red light came on and the SD300 displayed "HEIGHT CHECK ERROR" on the panel.

In my experience, the SD300 tries not to abandon a build if it can possibly continue so I tried pressing the material back onto the table and pressed the continue button. The SD300 obediently measured the model several times more, apparently trying to get a usable measurement, but stopped again with the same error.

The logs demonstrated the SD300 had made a good-faith effort to continue, but with the material flopping loose from the table it couldn't get a measurement within 446 microns. This was an error of over 100% because the last layer had only been 188 microns, so there was no sensible way the machine could have compensated.

So the only solution was to cancel the job and start again. Then it worked just fine, which makes sense in hindsight:

The air bubbles in the glue lines had formed while the machine was idle. The bubbles would have cleared themselves within a few layers, but I could have cleared them manually by using the Clean Bubbles function in the SDMove maintenance utility.
The droplet of SolGL glue was also caused by the air in the glue lines. It could have contaminated the anti-glue pens, but the contamination would have eventually resolved itself.
A height check error within the first few layers of a job probably indicates there were bubbles in the glue lines, but the problem has already resolved itself by the time it's been detected.

All these issues are self-rectifying within a few layers, so I accept my British friend's solution as the simplest: just run a Test Model build job whenever the SD300 has been sitting idle. A test model uses very little material and it gives the machine an opportunity to work these issues out of its system without needing to understand them. Or I could just ignore these potential issues, since the worst that seems to occur is that I might have to re-run a job that fails within the first few layers.

Rapid Evolution of "Candy Ball"

2011-12-22T12:05:00.000-08:00

Over the weekend I built a simple test model that inspired me to work on a new (but familiar-looking) puzzle design that rapidly evolved in the next two days...

As an experiment I recently built a two-part shell that fits over my existing Green Marble puzzle, following exactly the same contours when the two pieces are precisely aligned.

I added a dash of green color to the model while it was being built, just to help identify the parts. Serendipity! The green calls attention to a swirly shape like a yīnyáng on the surface of the outer jacket.

The marble sticks out of an opening in the jacket, opposite the green yin-yang, and it can turn freely inside the jacket. By coincidence the swirly shape can be replicated by moving the marble around but doing so causes the marble to block the whole puzzle from being disassembled. Could I design a new puzzle that deliberately includes such a hint at a false solution?

Next I built a whole set of parts based on the same curved geometry as Green Marble with a 2-part inner ball and a 2-part outer shell. The shell includes a round dome centered on the swirly shape, opposite an opening where the ball sticks out. I switched between red and white material, hoping the coloring scheme might emphasize the illusion. The colors remind me of peppermint candy.

The ball pieces fit inside the shell pieces, then the whole thing screws together. It looked cool, but the screw action was a bit too pronounced for my taste.

The color coding worked perfectly. The white dome formed a ball-like shape with the same swirly shape as the green puzzle.

On the opposite side, the marble could be turned until it also exhibited a similar swirly shape. The contrasting white color on the ball further emphasized the swirly shape, but the puzzle won't open when the swirly shape is exposed. The camouflage works very well, but there were plenty of other details I disliked: the correct solution required too much unscrewing, the jacket pieces were too flexible, and the ball was too hard to maneuver inside the jacket.

Applying what I'd learned, I designed a whole new model from scratch without using any of the model data from Green Marble. It looks very similar to the last model but there's less twist and the geometry is better optimized for the ball to move inside the container.

As it turns out, the newest design has an easy-to-find method of taking it apart without aligning the pieces as intended. If the ball is turned so the white portion sticks up at the top as shown here the outer shell can be gradually withdrawn by pushing it to the left while the ball rotates and unscrews itself within the jacket.

Looking back, the previous version didn't have that problem because the red section was wider and the twists had overlapped so there wasn't as much freedom to move the jacket independently of the ball inside.

This design evolved rapidly until it reached a dead-end, so now I have an opportunity to go back a few steps and see if I can develop it into a fresh puzzle.

Hands free memo holder

2011-12-13T12:07:00.000-08:00

I had intended this memo holder to use a marble to grab papers behind a wedge-shaped panel. But the marble didn't work very well so I 3D printed a plastic cylinder that worked better. It works by sliding papers up into the slit behind the cylinder, whereupon the force of gravity traps the paper between the cylinder and the back plate.

There are two versions, one plain and one with slots added for hanging lightweight articles. After a little more experimentation I modified the cylinder into a barrel with a fat middle section. That held papers better than the cylinder. I rebuilt the memo holder with side walls oriented for better transparency to illustrate how it grips papers by the wedging action of the red barrel.

Here's video that illustrates how it works...

This particular note holder was attached to the wall using a small Command brand adhesive strip.

I also made a refrigerator-magnet version by trimming a square from a worn out magnetic pad from my SD300 and gluing it to the back of a memo holder.

STL and STP files for this model are shared here.

Helical Burr Followup

2011-12-10T23:00:00.000-08:00

After my Helical Burr Experiment had required sanding to make the pieces fit together, I refined the data and built a second model just to fix the problems with the first. The new one (on the right) fits together smoothly, but it still has impractically-thin walls so it's just another experimental prototype.

I'd intended to design it so the parts could only be put together in one specific sequence, but testing the new model revealed a slight flaw: one of the pieces could be put on (or taken off) out-of-sequence because I'd only blocked movement in one of the two directions it might move. I probably wouldn't have discovered the oversight without building these test models.

Here's a movie demonstrating how the puzzle works and revealing the design oversight.

One of the pieces had some exceptionally thin edges, which came out kind of wispy the first time so I tried building it in a horizontal orientation for comparison. The new orientation is probably a bit stronger, but the difference isn't compelling. Both parts work about the same.

I will probably start over from scratch because of the thin walls and un-blocked movements, but I consider it a very successful experiment nevertheless.

Adapting the Magic Screw for Makerbots

2011-12-06T14:21:00.001-08:00

Last month I shared my Wrong Way Bolt model, but home users found themselves unable to build functional copies of it using hobby-type 3D printers like the Makerbot Thing-o-Matic. The model's geometry seemed to fall within the rule-of-thumb limits, but I looked closely at individual 'slices' of the model and thought about what would actually occur when it was built using a hobby extruder.

Here's what might have happened.

At left is a slice of the trick nut, color-coded with shades of red to indicate the region to be built for the present layer. Bright red areas are supported by the layer below while dark-red areas are unsupported overhangs. When an hobby-type 3D printer tries to build the overhang marked with a circle its extruder would follow the path in white but the thread of extruded plastic won't have any support. As a result, the thread will be pulled into a straight line between the two points where it's supported by the layer underneath. The Makerbot would probably build some of the overhang, like the diagram at right. It would probably need multiple layers before it could build that whole overhang, but each layer moves the overhang to a different place (because it's a screw) so the hobby-printer wouldn't have a chance to catch up.

The model could probably be adapted for hobby-type printers by designing the threads with a goal of eliminating the concave shapes. Overhangs could probably be built with very high accuracy so long as they didn't have curves or corners in the unsupported regions. So I designed a trick thread with a cross-section whose overhangs form straight lines, like so...

I don't own a Makerbot (nor any other hobby printer) so I don't really know if this will be any more buildable than the model I'd originally designed for my SD300. But it's a starting point, in any event, as the trick threads function correctly and I'm sharing the source data so other users can adapt it if needed.

This new model and its source data are available from Thingiverse here so anyone can download it and edit it.

Roxanne's Videos, addendum

2011-11-19T22:43:00.001-08:00

In response to my last post, Roxanne graciously posted a new video honoring the Rox Box puzzle box I made for her last year, and which I discussed in an earlier post.

Just to clear up a little confusion, I engraved the gemstones but I didn't actually build them. These were lab-grown gemstones, technically real rubies and sapphires but not natural rubies and sapphires. Gem Select has a nice, balanced explanation of synthetic gem stones here if you're curious. It's informative and respectful, but they don't trade in synthetic gems so they aren't pushing a product.

The clear plastic 'windows' in the Rox Box were literally 3D printed already-assembled by building the majority of the puzzle using white material, then switching to transparent material for the last few millimeters. This is how the model looked when it came out of the printer, embedded in a solid block of white material with a few layers of clear material (at right).

After I cleared the material from the inside of the models I could see through the windows, but the parts were still embedded in unused support material from the build process.

Peeling away the material around the exteriors revealed the finsihed Rox Box parts, complete with their transparent windows for the top and bottom. This is how the puzzle box looked the first time I got to see it!

Roxanne's puzzle videos

2011-11-17T16:08:00.000-08:00

Roxanne Wong is an extraordinary puzzle collector whose YouTube channel is crowded with reviews of puzzles by various ambitious designers throughout the world. A few are puzzles I've previously discussed or worked on.

George Bell's Dice Box
I built these hinged parts to George Bell's specifications, as described in an earlier blog post.

George Bell's Exploding Ball
George allowed me build my own Exploding Ball last year. In this video Roxanne exhibits a colorful version of it.

Air, by George Hart
This puzzle inspired my Rhombic Dodecahedron puzzle. George Hart's web page shows examples of the pieces assembled and unassembled.

Cuburr
Cuburr is uniquely optimized for the SD300 build process, as described in an earlier post.

Helical Burr Experiment

2011-11-08T11:07:00.000-08:00

After seeing my Rhombic Dodecahedron Puzzle Bram Cohen casually suggested a puzzle in which one particular piece has to be put in last. That is to say, a puzzle in which the pieces must be assembled in a particular sequence.

The picture above shows how the idea might be adapted to one of my swirly 'marble' puzzles: the four pieces must be assembled in the sequence illustrated above because each new piece blocks the movements of the previously installed pieces.

Anxious to try it out, I built a set of pieces without checking their dimensions. But I encountered some delicate, thin walls while I was peeling the models out of the support material.

VisCAM revealed some astonishingly thin, wispy structures on the thinnest piece. Some of the walls taper down to less than 0.1mm near some of the edges. It held together only because the super-thin portions are anchored to the thicker 'backbone' up the center!

It took a lot of slow, cautious work to free this thin part from the leftover plastic but it came out intact! Dipping the piece in plastic-welding solvent made it strong enough for functional testing, despite a few frayed-looking edges where the walls taper down to nothing.

Reviewing the measurements it became clear that the super-thin walls had occurred as a result of how two spiral-shaped channels gradually converged inside the puzzle. Luckily the thin piece would be amply protected by the thicker piece when the puzzle is assembled.

As I'd hoped, the pieces can only be assembled in a specific sequence. But unfortunately they fit together too tightly, so the last piece wouldn't go in.

I tried to improve the fit by sanding the pieces, but the PVC is just too soft for hand sanding so I resorted to a high-speeed abrasive wheel. This improved the fit and gave the pieces a nice smooth feel.

Perhaps it's a bad habit to keep building models with such thin walls, as they're extremely vulnerable to breakage while cleaning the model. But even though they could break during manual cleanup, they don't pose any sort of danger to the build process so the main penalty is the tedious labor. The SD300 can safely attempt any sort of ridiculous geometry, even if the STL file is riddled with defects, and the worst that might happen is the model might be disintegrate or consume excessive labor during post-build cleaning.

Making signs with deeply-engraved letters

2011-11-01T14:38:00.000-07:00

This amusing Do Not Disturb sign was adapted from a humorous sign in the animated TV series Moral Orel. A Thingiverse user shared the design in several formats so it could be built using a laser cutter, robo cutter, or 3D printer.

I built it on the SD300 by starting with ivory/white material for most of the build and then substituting red material for the last layer. That resulted in neat, sharply-defined letters in deep relief.

I liked the joke so I took it a step further, designing a door hanger and sharing it as a derivative design. I flattened the design a little, but kept some depth because the relief makes the graphics look attractive.

"Screwy" Screw

2011-10-20T00:35:00.000-07:00

A Thingiverse user saw my Wrong Way Nut video on YouTube, which showed two nuts traveling in opposite directions on the same screw thread. He was inspired to create his own version of it, which he named Screwy Screw. Full marks for that name!

It was interesting to see how he came up with a similar solution, yet made some vastly different aesthetic choices. Most conspicuously, his Screwy Screw is much larger than my own bolt model.

Here's a quick video comparison of Screwy Screw against samples of Wrong Way Nut built on my SD300 and another sample built by Bradley Rigdon courtesy of http://printo3d.com/

Here's a closeup of the FDM samples of Wrong Way Nut, built by Bradley Rigdon. Notice the funny patterns on the side walls? See below.

Below is a closeup comparison of a nut built on the SD300 (red) and one built on a Dimension by Stratasys (blue). Both build processes produce these wave-like patterns, often referred to as "chatter", as a result of very subtle vibrations that occur as the machine changes direction at the corners. The marks don't affect the model's tolerances--in fact they're hard to see except by examining the model's sheen under a bright light source as here.

STL files for Wrong Way Nut are downloadable from Thingiverse here.

Gear O'Clock

2011-10-16T15:26:00.000-07:00

Last week Bradley Rigdon shared Gear O'Clock, a novel clock that indicates the current time using a large geared ring with numbered tabs around its rim. This week I posted a set of Accessory Parts to adapt or customize Gear O'Clock.

Bradley used a clock movement salvaged from an inexpensive wall clock he bought at Wal-Mart. I set out to adapt the parts for use with an ArtMinds clock movement from my local Michaels craft store.

For the benefit of Thingiverse users, here's a detailed explanation of my accessory parts:

Clock Drive Gear slotted NO SUPPORT.stl has a slotted opening that fits over the threaded hour-hand shank on the craft-store clock movement. It took some effort to avoid excessive overhangs so the part retains its buildability on hobby 3D printers. I added a wide opening on the back side of the gear because some of the craft store movements have big shanks (like this one).

The slotted-shape of the shank keeps the Drive Gear synchronized with the shaft, just as a conventional hour hand would be. The clock movement kit includes a threaded brass ring that screws over the Drive Gear to secure it in position.

Some of the clock movement kits have short shanks and others have really long shanks like the one illustrated here, so I added a small fence inside the deep gear teeth so the driven clock gear won't tend to walk out of the back side of the Drive Gear.

Bradley's Clock Base ring is 10 inches in diameter so it can't be built in one piece on the SD300, nor on most hobby 3D printers.

Clock Base div4.stl divides the Clock Base into four parts, which can be spliced using the number tabs at the 3, 6, 9, and 12 o'clock positions.

The number tabs are keyed into holes in the Base Ring, so I glued one number tab to the end of each of the four parts.

Then join each piece to the next by hooking it into the keyed holes and injecting glue between the surfaces. Notice how the diagonal join ensures a gradual transition from one section to the next so the gear won't snag when it turns in the clock. Be sure to attach the numbers counterclockwise relative to an ordinary clock!

My revised Drive Gear exposes a hole for the clock's second hand, so I designed Clock Seconds Gear.stl to cover the hole and add a little animation to the clock.

This gear has a hole and a slot in the back to accommodate the original second hand from the clock movement kit. The original second had can be left intact or clipped off.

After the Clock Seconds Gear is attached to the second hand parts, it pushes into the exposed opening in the clock shank.

The craft-store clock movement has a built-in wall hook so it wouldn't fit in Bradley's enclosed Clock Mechanism Mount. Clock Mechanism Mount cutout.stl adds a cutout to accommodate the movement's wall hook.

Some clock movement kits feature a moving pendulum, which adds even more animation to the clock. So I built the even-larger Clock Mechanism Mount Pendulum.stl mount which has another cutout on the bottom for the pendulum mechanism.

Clock Gear Pendulum.stl is a gear-themed pendulum for use with the pendulum-type clock movement kit.

For further reference:

The original Gear O'Clock files are located at Thingiverse
My accesory files are located at Thingiverse here
Bradley's video shows how the clock should be assembled at YouTube
Here's a video showing my clocks with moving second hands and pendulum.
An online shop that offers all sorts of clock kits at http://www.klockit.com/

Rhombic Dodecahedron Puzzle

2011-10-13T11:40:00.000-07:00

I just shared a simple Rhombic Dodecahedron Puzzle at Thingiverse, consisting of four identical pieces that fit together to form a solid shape. The concept is very similar to my previous marble puzzles and cubic trisections, but using four parts instead of just two or three.

The idea of using a shape with four-way symmetry was inspired by George Hart's Air puzzle, which is described on his web site and briefly demonstrated in a YouTube video by Roxanne Wong.

Like my previous dissection puzzles, the pieces have a distinct orientation so they only fit together if they're all pointed the same direction. Technically that means my puzzle only one-eighth as many duplicate solutions as Air but that doesn't mean it's any harder to solve.

Here's a video that demonstrates how the puzzle works.

Power Interruption

2011-10-11T15:03:00.000-07:00

Last weekend a brief blackout interrupted the SD300 while I was recording a video. I kept recording and captured the SD300's recovery when the power came on again a minute later. This video is embarrassingly awkward and rambling, but it's potentially interesting because most 3D printers can't recover as elegantly as the SD300 did in this video. (More on that below.)

The SD300 is connected to a netbook running on batteries, so it recorded exactly what the SD300 was doing when the power went off. The log says it was "Taking logical tool 4" which means it was picking up the 1mm Anti-Glue pen for masking fine details, whereupon it suddenly encountered a "WriteFile Error" because the SD300 had lost power and stopped responding.

When the power came on again, the log recorded how the computer re-established its connection with the SD300. Because the SD300 remembered it had been building a model it calibrated the Z-axis to the top of the model instead of the top of the build table.

Recovering from a power failure isn't always so effortless as it was here, but it's usually quite manageable.

The computer didn't lose power. If the computer had also lost power then it would have been necessary to reboot and start the SDView software again. The computer saves a copy of the current model on the hard drive so it can recover and continue if the computer is turned off during a build.
The SD300 just happened to get interrupted between changing Anti-Glue pens. As a safety measure the SD300 won't initialize until it detects all pens are parked in their storage holders. If it had lost power while it was actually using a pen then it would have requested the user manually return the pen to the storage holder before it would re-initialize.
Additionally, if the SD300 is interrupted while the top layer of the model is still attached to the material roll then it would need to cut it free before it could initialize the Z-axis. If that had occurred, the SD300 would have adjusted the table to a safe position, reset the XY axis, and requested permission from the user to "Trim layer?"

Triangular Dovetail Joint

2011-09-28T01:11:00.000-07:00

Woodworkers have made trick dovetails for years, probably centuries. I designed this trick joint because I hadn't seen any triangular dovetail joints. Not surprisingly, it has been done before.

All three exterior sides show identical dovetail-like joints, which makes it look impossible to open.

But the pieces don't slide like a conventional dovetail.

The two pieces rotate until they gently let go of each other.

There's a hollow cavity inside, so it can be used as a puzzle box. Not that anyone would be terribly puzzled--it looks odd, but it's easy for anyone to open once they pick it up.

This is a simple, traditional puzzle box so I've posted the STL files at Thingiverse for anyone who wants to play with it.

Spring-o-sphere

2011-09-20T12:43:00.000-07:00

Schorhr's Spring-o-sphere model on Thingiverse looked like a perfect example of a model that's unsuitable for building on the SD300: very thin walls surrounding a large trapped volume. But that made me curious, so I included the Spring-o-sphere in a batch of models back in June.

I anticipated there might be trouble peeling the support material away, so I put a box of peeling cuts around the Spring-o-sphere so it would be isolated in its own little 'brick.'

As expected, it was tedious peeling away all the enclosed material a tiny bit at a time. Right at the start the little hook broke off the top, so I expected more breakage.

But the rest of the material peeled away without any further breakage.

The body of the spring proved to be surprisingly resilient. On close examination I could see lots of little loose ends. These are unsightly but they don't seem to weaken the spring.

Evidently this unexpected resiliency was imparted by the long overlap between layers. There's exactly 1 layer of red material in the model, but red band shows how that layer extends a long distance around the spring, thereby giving it ample distance to be bonded with the layers above and below.

It's a nice container for holding shiny objects.

Despite my relative success building this Spring-o-sphere, I still regard it as a model that's basically unsuited to the SD300 build process. But the experiment suggests I could choose to build such a model in a pinch, provided I'm willing to sacrifice the model's visual appearance (eg: broken hook, loose ends) and invest extra effort (eg: repair hook, tedious peeling). I certainly wouldn't recommend doing this sort of model routinely, but it's nice to know I could.

More Assorted Stuff

2011-09-04T01:38:00.000-07:00

I like puzzles, so I built this Mysterious Wood Joint in transparent material. According to its creator, the joint was adapted from a wood joint used in Osaka Castle. At first glance it looks impossible, but the pieces go together easily when oriented correctly. I wonder if the design could be further modified to make it more like a puzzle.

An SD300 user sent me a picture of a chain they'd had trouble building, which inspired me to attempt one for myself. Problems had occurred when the chain was positioned with alternate links vertical & horizontal like the yellow chain at left. When I built the chain, I positioned it so all the links were positioned at 45° angles relative to the build platform.

I built the model with a single peeling cut running down the center of the chain, which allowed the first half of the support material to peel away easily. But I had to fish out scraps of leftover material behind the links.

After peeling away the other half of the support material I had to fish out the last scraps with tweezers again. But that's okay because it took only a few seconds for each link.

The finished chain had a uniform texture.

I built a 50% scale version of Free Falling Maple Seed becauseI needed an arbitrary model at least 2 mm high to get some layer-thickness measurements from the SD300. The layer lines form attractive, delicate patterns.

These 45-RPM record adapters required minimal material because they're only 2 mm thick.

To add color to the adapters, I stopped the SD300 halfway through the construction of the model and scribbled between layers with permanent markers. This is the middle layer in the model; the color showed through after the rest of thelayers were bonded above this.

A Peek into Peeling Cuts

2011-08-31T15:57:00.000-07:00

I've received several questions about peeling cuts and removal of the extra material, so here's a brief peek at peeling cuts with my recent screw & nut projects.

The SD300 builds by ironing layers of PVC film on top of the build platform one-at-a-time, and selectively bonding and cutting each layer of PVC film. Regions that belong to the model are bonded to the layers above and below, and unused material is left in-place (as to act as support material) until the build is finished.

Before building these four bolt models (yellow) I added one long peeling cut (blue) to divide the unused material into two halves. The layers of PVC will be stacked parallel to the table, so the peeling cut is perpendicular to the actual layers of the model.

There's no single "right" way to arrange peeling cuts. You could add as many peeling cuts as you want so long as there are enough cuts to free the model from the surrounding material. Here I arbitrarily added an extra peeling cut to isolate some of the support material into two sub-regions.

Thanks to the extra cut, the material peeled away from two of the screws at a time instead of all four. It took longer than it might have, but there's no harm in making extra peeling cuts. Peeling cuts only affect the unused material, they don't cut into the model itself.

The nuts were a little more complicated. I don't put small cuts inside hollow models like I used to because I've learned a better way to remove the material inside holes. (I'll explain that below.) I added peeling cuts between adjacent nuts, but not inside.

Solido provided strong forceps to help peel away material. Those forceps are great for most models, but they're awkward for cleaning material from holes like these so I bought a set of hobby probes.

The probe's sharp point stabs neatly through several layers of unused material in the hole. Tipping the probe lifts the material so it can be pulled away.

Once the ends are free, the material can be pried out by hand.

The layers of extra material have been glued together in a chain. But these layers didn't just pull out freely; I carefully tugged at the edge of each sheet to tear out the next one, one-at-a-time.

Sometimes one layer of support material tears free of the next, so it's necessary to insert the probe and pry the next layer loose before continuing the chain.

After clearing the holes, I removed the rest of the support material from the outside.

Most observers notice there's a high proportion of unused material in each build, which is true. It's roughly like a CNC mill that custom-builds a block for each model, building up the layers additively and then peeling them away material afterward. But it's generally economical because the process is energy-efficient and uses raw material that costs 10 to 15 times less per unit-volume than other 3D printers in its price class. Nevertheless, the cost per model can vary widely from one sample to the next depending on how efficiently the material is utilized.

The SD300 can't directly re-use the leftover material, but it's recyclable as PVC scrap (recycle code 4) by bagging and tagging it and delivering it to a commercial recycler. It can't go with household recycling, so I collect the SD300's scraps in a separate bin. It could also be discarded as ordinary trash since it doesn't contain anything harmful.

Wrong-Way Nut video on YouTube

2011-08-29T13:00:00.000-07:00

I built an enhanced version of my Wrong-Way Nut model and posted a new video on YouTube here.

Watch for better pictures and...perhaps...an explanation. Better still, can you explain how it works?

George Bell's Dice Box

2011-08-10T09:59:00.000-07:00

George Bell designed this box puzzle as a conventional 3D object. It's an example of a coordinate-motion puzzle in three dimensions: its four pieces interlock and slide together to form a box if-and-only-if all the pieces start in exactly the right position and all four must be moved simultaneously.

Here's a full set of parts built on the SD300 with a contrasting red color on some sides. (It rather resembles a stop sign, doesn't it?) George's puzzle is perfectly functional, but I was still compelled to tinker so that I could exploit the SD300's peculiar capabilities.

My first modification was to transform the puzzle into a flat form with living hinges and a tuck-in tab.

When my modified piece is folded and the tab tucked in, it forms a solid shape identical to George Bell's original 3D model.

It can be assembled exactly the same as George's original model, but now all the faces have a lustrous sheen because they're all built parallel to the shiny surfaces of the PVC material.

Then I added small cylinders, raised about 0.18mm above the surfaces to resemble dice pips. And I changed material for exactly one layer while building to give the dice pips a contrasting color.

But there were sharp corners when the flat panels were folded, so George took over again and modified the design.

George's next revision rounded off the corners, so the puzzle really does look like a chance die now!

Because the puzzle starts as a set of flat panels, I decided to package it in a plastic bag with the four panels intertwined in a flat configuration. To solve the puzzle, the user removes the pieces from the bag, separates them, folds them into solid objects, and must figure out how to slide them together.

The puzzle was now named Dice Box. We packed instructions inside each bag.

I built over a dozen sets of Dice Box puzzles over the next few days, so George could take them to the International Puzzle Party.

About half the puzzles are transparent and the other half white.

Orange, Green, and Blue Marble

2011-08-07T10:01:00.001-07:00

George Bell graciously took several sets of my Bag of Marbles puzzles to the International Puzzle Party in Berlin this year. Currently I have three styles of marbles, distinguished by color.

Orange Marble was my first design, a puzzle with two interlocking pieces that slide together unintuitively. It was created by accident as part of a design that I abandoned while studying Bram Cohen's Trapped Marble prototype. Although the two pieces are different from each other, they can be flipped relative to each other and they slide together symmetrically.

Green Marble is another two-piece design. This time the two pieces are identical, but they only fit together when the pieces are oriented in one specific orientation.

Blue Marble is based upon the same curves as Green Marble but divides a sphere into three pieces instead of merely two. Most people fit two of the pieces together easily, but instinctively try to insert the third piece upside-down...which doesn't work.

Here's how a batch of Blue Marble pieces looked shortly after I'd removed them from the SD300 and removed some of the support material.

Unprocessed pieces have a translucent sidewall finish. It's attractive, but I wanted a shinier smoother finish.

To smooth the side walls I dipped each piece in Weld-On 2007 solvent for 30 seconds.

After their solvent bath I laid the pieces on baker's parchment to dry. Parchment is non-absorbent and the wet pieces don't stick to it, so it's an ideal disposable drying surface.

Eventually I plan to add other Marble styles (and colors) to the series as I think of new challenging features to add.

Wrong Way Nut

2011-08-06T09:12:00.000-07:00

A moderator on my favorite puzzle-building forum called attention to a YouTube video entitled Magic Nuts and Screw Threads in which two nuts are shown unscrewing in opposite directions on the same threaded rod.

I don't have any inside information about the trick nut in the video, but I conjectured I could build a nut that would behave like that. The threas on my first test model turn a bit tightly, but it works!

I will record a better demo video later. It could use a little refinement, and the screw threads need to be a lot longer for a better demonstration. But it's sure gratifying when a new idea passes the proof-of-concept test on the first try!

My first functional Yoshimoto Cube

2011-08-05T10:55:00.000-07:00

Ultimately I would like to 3D print a fully-functional Yoshimoto Cube in one piece, but I really need a solid reference model to help me visualize the design. So I used the SD300 to build the individual hinged panels and glued them together one-by-one.

This black one is almost assembled; the hinged panels at right will be joined with the already-assembled group at left.

I built and assembled a pair of Yoshimoto cubes, one in black and the other using transparent amber.

The geometry of a Yoshimoto Cube is peculiar and confusing, so it'll sure help to have a physical model for reference! So far I've observed a few details that could enable me to build the model in one piece.

Yoshimoto experimentation

2011-07-29T14:02:00.000-07:00

In July 2010 I saw plans on Thingiverse for building a kit that could be assembled into a Yoshomoto Cube, which is a type of folding puzzle. At that time I didn't have much experience with hinged models, so tried to adapt the concept.

I built a pair of experimental models that had hinges in each axis, some horizontal some vertical. This picture shows the two models before I'd finished removing all the support matieral; they look like they're attached, but I subsequently separated them.

One separated, the models could fold along the hinged connections. They were somewhat delicate (and tiny!) but each could be folded into many shapes just like a Yoshimoto cube.

Careful folding and unfolding would permit the model to change shape until it was inside-out from its starting position. The model on the left has been inverted, while the one on the right has been returned to its starting position.

Also like a Yoshimoto cube, the inverted and non-inverted models could be nested together in such a way that the combined pair could still be folded in all the same ways as before.

After a few hours' of use both models broke along one of their vertically-oriented hinges. I didn't continue with the project at that time...and now a year has passed by.

Recently I've gained a lot of experience building models with built-in living hinges, so I want to try experimenting with the Yoshimoto cube again soon.

Flexible Burr...Cuburr?

2011-07-21T23:39:00.000-07:00

Here's a picture of the current revision of my flexible burr puzzle. I've adopted a scheme with a distinct color for each type of part.

Assembling the parts depends heavily on the flexibility of the material, as the parts must be distorted to fit through each other.

It looks like a mess, but the puzzle is almost solved.

The last step is to fold the faces flat and hook the corners together so it holds a cube shape.

I carved the puzzle's name "Cuburr" into one of the faces in the 3D data, which caused the SD300 to trace it like line art.

That last trick exploits a limitation of the SD300's build process: in the STL data the letters were rendered as cutouts in flat wall, narrower than 1 mm. The SD300's XY plotter can cut with 0.1mm precision, but regions narrower than 1 mm are left bonded to the layer beneath; you have to pry them mechanically if you want them removed. For situations like this, it's a convenient way to emboss line art onto a flat surface.

A flexible burr puzzle

2011-07-14T00:11:00.001-07:00

In 2002 George Miller devised an unusual puzzle titled Three Card Burr, made by laser cutting slots into three ordinary playing cards so they could be interlaced together. Interestingly, there's no practical way to disassemble the cards after the puzzle has been solved.

I was inspired by George Miller's Three Card Burr puzzle to create a more complex puzzle to exploit the SD300's ability to build sheet-like structures by creating a 3D model whose geometry can be mapped to the build material. I designed this flat model whose middle section is nominally 0.51mm thick, so it will be built using three thicknesses of 172-micron PVC sheet. The adjacent areas have two 0.34mm thick panels stacked one above the other and attached to the middle section by a 0.17mm thick strip to act as a hinge. The whole model is about 120mm x 70mm x 0.9 mm.

Here are my first 3 sample models, built in transparent material.

Like Three Card Burr assembling the puzzle begins by carefully interlacing the sheets together. It wasn't as difficult as I'd expected because the resiliency of the PVC material enabled me to flex the puzzle without tearing it.

Once the pieces are interlaced together, the hinged panels fold out and interlock at the corners to form a cube. This part was far more difficult than I'd expected because each corner depends upon its neighbors for stability, which meant each corner would come apart when I tried to assemble the next corner. I'd forgotten to allow for the thickness of the material in the corner dimensions, so the panels warped from excess tension.

Not bad for a first try, though. It proves the concept is basically sound; now I just have to adjust the dimensions and add something to make the corners more stable. Maybe a small tab or hook?

Eurofighter

2011-07-12T10:38:00.000-07:00

Solido provided a sample model that demonstrates an interesting way to exploit the flexible PVC material. The model prints out as a number of flat, semi-rigid parts with living hinges and flexible tabs.

Fold the parts at the hinges and pass the tabs through openings in another piece.

These tabs tuck securely into the underside of the wing piece, thereby snapping the pieces together.

When all the pieces are assembled in this way, you get a modernized plastic version of the good old 'paper airplanes' we used to make from paper.

This gives me some fresh ideas for foldable models!

Assorted "stuff"

2011-06-28T12:31:00.000-07:00

I'm continually building models and often forget to share them, so here are pictures of some recent projects.

I built a three-piece puzzle in transparent plastic. While it was building I used a permanent marker to add three splashes of color between layers, using the technique from an earlier post.

Once assembled the transparent material catches the light and the colors seem luminous!

I built this simple-but-elegant Mini Stand for iPhone & iPod Touch. While it was building I switched between black and white material to incorporate a subtle, decorative stripe. It's a small model so I built 3 of them side-by-side using no more material than just building 1.

A Thingiverse user created a script for Duplicating House Keys using the free OpenSCAD tool to create the model data. But it only makes keys for old Kwikset KW1 lock cylinders, so I think it'd be interesting to update the script for the newer KW10 models.

This Recursive Reuleaux Triangle is the first model I built that was pre-assembled. The parts were built already-interlocked in grooves so the triangles can slide around freely but they can't come apart.

Pixobox Studio provided the data for this detailed figure of a Human Head. I had reduced its size to 28% to fit it within volume left over for another model I was building. The Z-axis layering is plainly visible at this low resolution, but it has excellent XY surface detail. There's some tiny text on the sidewall, just below the chin.

Here's a view of the back of the statue, showing the surface details in the hair and more tiny text carved into the back wall of the figure.

Last month I ran into a challenge trying to disassemble part of my car. This spring needed to be tightly compressed to open another access panel, but it's offset from the opening where it's awkward to reach with ordinary tools. So I simply built my own tool with the SD300.

So I 3D printed this simple plastic tool, which has two built-in elbows that reach around and compress the spring. The tool has 1cm thick walls, so it was extremely strong...which was lucky because I had to be surprisingly forceful to release the spring completely!

Building hollow parts "as solid"

2011-06-14T17:52:00.000-07:00

Unlike most other 3D printers, the SD300 builds solid parts faster than hollow ones of the same size. Hollow parts require just as much material as solid ones, so I generally make my designs as thick and solid as I like.

But I know many designers who optimize their designs for Shapeways White Strong & Flexible material, so they typically design hollow parts with very thin walls to minimize costs. The SD300 isn't very suitable for very thin freestanding walls, but could I build such models if I just left the support material embedded inside? Would it sacrifice functionality or strength?

A colleague graciously lent me a set of STLs that had been optimized for the EOS with exterior walls only 0.8mm thick and I set out to build them with peeling cuts arranged to leave the support material trapped inside.

I built a small batch of test parts without any trouble. Because the support material is trapped inside they feel like ordinary solid parts, but they aren't quite as transparent as solid parts usually are. The interiors are somewhat cloudy, undoubtedly because the SD300 cut and masked the material inside to facilitate removal. They looked perfectly acceptable, although I have my doubts about their durability.

It went well enough that I tried another batch, then another. A big piece broke off while I was peeling the last batch of parts. The chip (at top right) is still attached to the support material, and the pin is pointing to the surface where the chip broke off. If you look carefully you can see the thin, triangular border which was the only region that had held it together. Not surprising, really.

I repaired the break by putting the piece back and running welding solvent (Weld-On 2007) over the model. The solvent helped glue together the surface of the model, but the support material remained safely un-bonded so it could still be peeled away. Apparently the SD300's Anti-Glue coating works against Weld-On.

I test-assembled some of the parts; they didn't fit together as accurately as parts built from solid STL data. That makes sense in hindsight. Using "hollow" STL data meant the interior material wasn't continuous because the SD300 had made cuts for the interior walls and had masked the interior layers with Anti-Glue.

So the experiment answered my basic question, could I build STLs that had been optimized for EOS or other thin-wall technologies? Yes, I could build test models with restrictions on their usefulness:

The support material would have to be left inside, so hollow STLs built as-solid would be much heavier than a hollow model built on an EOS.
Such models would not be as strong as solid models, despite their solid appearance, because the interior isn't bonded together like solid models.
Such models aren't as dimensionally accurate as models build from solid STL data.
Such models aren't as transparent, even when built with transparent material.

If I intend to build parts on the SD300 I would not design them with thin walls like these, but the technique is potentially useful for verifying the basic size, shape, and dimensions of STL data that's optimized for another build process.

Efficient peeling cuts revisited

2011-06-08T10:10:00.000-07:00

Here's another example of how to arrange peeling cuts for efficient cleaning of an SD300 model. The user adds peeling cuts (the purple walls) while preparing to build models in the SDView software. Peeling cuts don't affect the model, but they instruct the SD300 to cut the support material that surrounds the model so it can be torn away conveniently.

When I had just learned to use the SD300 I tended to put peeling cuts between each individual model to isolate them, resulting in lots of small areas that had to be cleaned one-by-one. But I eventually learned to arrange models so the peeling cuts could be joined and streamlined, peeling several models at once.

These nine models have two continuous peeling cuts that follow the geometry, so the two exterior regions can be peeled away in an easy continuous motion.

After the two outer strips have been removed the models are still connected by leftover support material between them. Much of this can be peeled away in the same manner, as the top and bottom areas are continuous just like the other strips were.

There's still some support material embedded in the middle layers between models, but it doesn't have to be removed layer-by-layer like the other strips. Instead I just loosened up the support material by squeezing a probe between layers in several places...

...then I gripped two adjacent models and gently twisted them to-and-fro, which gradually loosened the support material between the two adjacent pieces. In about 10 to 15 seconds the leftover material was loose enough to free the two adjacent pieces, and I moved on to the next pair of embedded models.

All told, it took less than ten minutes to completely clean these models. The same batch of models probably would've taken a half hour or more if I had isolated them with individual peeling cuts. Back when I was just learning to peel and clean models it probably would've taken over an hour, so experience helps too!

Splice in the feeder?

2011-05-19T23:29:00.000-07:00

When there's about 1-2 meters of material left on a PVC roll the SD300 usually stops and asks the operator to replace the materials. After removing the used roll I recently noticed what appeared to be a double-thickness where two sheets of PVC were spliced together. I believe this is how all kinds of rolled media are typically manufactured such as paper, tapes, newsprint, etc. I guess the SD300 is programmed to leave a little bit of material on the roll to avoid pulling a splice through the feeder into a model. But could it happen anyway?

I had a weirdly malformed build last June. Now I wonder if it was caused by pulling a splice into the model?

When I'd partly peeled the model there was a giant gap in the support material (right) and the model was slightly split. The model was otherwise okay so I didn't worry about it, but luckily I saved some pictures.

More evidence.

While peeling that model I found a piece of leftover support material that seemed to have a double-thickness along one edge. Was this a splice? It seemed odd enough that I took a picture of it.

The SD300 software archives all the machine's activity so I went back and reviewed the 7 June 2010 logs. (I knew when it occurred thanks to the date on the pictures.) There were several new bits of evidence:

During the build I had paused the SD300 at layer 41. I think I remember putting in a low PVC roll to use it up.
At layer 50 it had used up the entire roll and pulled the end of the material into the feeder, causing the feeder to jam. I'll bet it had pulled the splice into the model at this point.
At layer 51 the cutting knife broke. It was a well-worn knife so the breakage wasn't unexpected, but I'll bet it got broken by the splice in the previous layer.
At layer 68 the iron bridge unexpectedly moved on the Y axis, causing an error. I don't really understand the significance of this, but that's the only time it happened in over 600 logged builds.

Mystery solved 11 months later?

Maybe. Regardless, I learned several useful principles from reviewing these pictures and logs:

Don't reload a nearly-empty PVC roll. The SD300 needs to build many layers before it can accurately calculate how much media is left on the roll, and a low roll could run out before that. Saving a few meters of PVC isn't worth ruining a model or breaking a cutting knife.
If the SD300 does completely empty a roll, check to see if a splice got pulled in. It's probably not common, but I would've cancelled the build if I'd seen it.
When a cutting knife breaks inspect the model to see if there's anything irregular. The breakage might have been caused by an unusual bump or bubble.

Animated Geek Campfire

2011-05-14T21:12:00.000-07:00

When I started using my SD300 last year I enthusiastically downloaded a number of models from Thingiverse just for the satisfaction of building a variety of models, including Geek Campfire by jonschwartz. I intended to put lights inside it, but it sat unfinished on my workbench for almost a year.

Last week I was inspired to finish the campfire when I stumbled across some inexpensive Flameless LED Tealights at a local store. I disassembled several of the lights, soldered the LEDs together, and inserted them into a Geek Campfire Stand, which I designed and uploaded back to Thingiverse.

Since I got the idea from Thingiverse, I want to return the favor: I designed the stand's geometry to be buildable on a Makerbot or similar homebrew 3D printer. It can be built upside down, without supports, positioned diagonally in a 96mm x 96mm footprint on the build platform.

The LEDs poke through irregularly-spaced holes, positioned to match the holes in the bottom of the campfire model.

When the LEDs are turned on it exhibits a pleasant, flickering effect.

I also uploaded a narrated video of the stand to YouTube.

Trammel of Archimedes

2011-04-18T23:29:00.000-07:00

I haven't been feeling very creative this week, so I downloaded the Trammel of Archimedes model just to build something interesting.

As I've done on many occasions I wanted to build a two-color model, but I tried a new approach: I remotely monitored the log by putting the SDM_Printers folder on my network. That enabled me to pause the printer just before the model reached a height of 24.3mm (which shows as 24300 microns in the log).

While peeling away the support material I found a weak spot in a thin wall, probably caused by a bad weld. I applied a drop of Weld-On 2007, which repaired the weak spot by causing the PVC to bond to itself without adding any glue or filler, so it wouldn't affect the dimensions.

The cleaned parts take full advantage of the contrasting colors.

Here's a quick video showing how the Trammel of Archimedes traces an ellipse.

Traffic cones with light pipe

2011-04-10T17:10:00.001-07:00

I've been watching for an opportunity use the SD300's ability to embed light-pipe-like transparency in a model, so I decided to adapt a Traffic Cone model I stumbled upon at Thingiverse.

I built the models upside-down, with a few layers of red followed by several millimeters of transparent layers to form a window between the interior cavity and the outside walls.

As usual with hollow models I chose to clean the leftover material out of the cavities before I removed the exterior supports. That makes it simple to hold onto the models because they're still embedded in the model block.

When the exterior support material was partly cleared I tested the light-pipe effect by shining a flashlight up through the bottom of one of the models. Light shone brightly through the transparent layers!

Here's a quick clip showing how it looks on an animated light table, illuminated from below. There's probably enough volume to fit an LED and button cell battery entirely within each model.

Some ball-shaped toy variations

2011-04-03T12:30:00.001-07:00

A puzzle-making colleague requested a variation of my 2x2x1 design cut down to its bare core so it could be used as a foundation for other puzzles. I'm not sure what he wants to use it for, but I built a sample.

I'd designed it with flat spots on the top and bottom, but otherwise it formed a smooth ball when assembled. It's hard to grab onto and it would probably be difficult to attach anything to it due to the smooth surface.

Coincidentally another friend suggested another variation with thin projections. I didn't build it exactly as he'd described, but it gave me the idea of adding a rim around the equator for grip.

The rimmed version is easy to operate. It's not a real puzzle, but it would be an acceptable desktop toy.

Twirlicue Puzzle Pendant

2011-03-31T23:36:00.000-07:00

Shapeways built my Twirlicue pendant in solid silver and I received the parts today.

The two pieces can be assembled so they merge together into a slender, twirly shape like this. It looks simple enough, but there's only one way to put it together so it's a bit trickier than it looks!

Here's the finished Twirlicue pendant compared with the first prototype I'd built on the SD300. I enlarged the silver model over the original design because it was hard to hold onto.

The assembled pendant can be hung from a chain or cord and worn as a necklace.

Shapeways sells each piece for $44 USD (plus $10 for an optional polished finish) and it takes two piece to form a complete Twirlicue Pendant so it's not a dirt-cheap puzzle. But it's pretty!

Conjoined Vica Illusion sculpture

2011-03-29T22:42:00.000-07:00

When I was preparing to build a full-size version of Chylld's Vica Illusion Sculpture I noticed SDView, the SD300 build software, displayed the model at an angle that would allow two of them to be conjoined by making a second copy and overlapping it with the first. SDView won't ordinarily build if two models overlap, but it merges the meshes if the model is exported. The exported file can then be built as a single mesh with two overlapping shells.

My previous test-build showed me how to arrange peeling cuts for efficient removal of the support material, but I didn't have experience with the conjoined area so I programmed SDView to leave an isolated region of support material between the two halves. This worked out really nicely because it kept the two halves stable until I was ready to remove the last bit of support material connecting them.

The conjoined sculpture isn't as elegant as the original but it's novel. And that's all I wanted.

Another test in leftover build volume

2011-03-27T14:18:00.001-07:00

I've been admiring the data for Chylld's Vica Illusion Sculpture but I've been reluctant to build it because I would want to build it in a horizontal orientation, and I admit I'm unsure about arranging peeling cuts. On the one hand I could play safe by arranging peeling cuts to isolate each part of the sculpture, but so many isolated zones could result in a lot of unnecessary work to clean away the supports. Did I really want to build a throwaway model just to determine how many peeling cuts are necessary?

There was a small empty volume in the build envelope for an unrelated model, so I decided to build a scaled-down version of the Vica sculpture just to test it. This is essentially a "free" model so I ambitiously tried the simplest peeling cut layout I could think of, dividing the model into only 4 zones, of which 2 were exterior regions that would be peeled away normally.

The 2 exterior regions peeled away effortlessly while cleaning up the principal model, leaving the Vica sculpture embedded in a small cocoon of its own. The top surface shows the outlines of the remaining two zones that need to be peeled away.

It went surprisingly well, so I'm glad I aimed for such simple layout. The only issue was a region near the center of the model, where a handful of layers needed to be peeled from the topside of one part of the sculpture while the same layer extended to the underside of the other part of the sculpture. A few strips of material had to be loosened and tucked (or pulled) through an opening in the sculpture.

That issue could be remedied on future builds by adding an additional peeling cut (arrow) to separate the support layers near the middle of the model. It doesn't need to run the full height of the model because the problem only affected the innermost layers.

Despite that one peeling problem, and the model's thin structure, the model held together very well because the last region to be peeled formed a nice keel-shaped backbone that reinforced the model while I was clearing the exterior sections. This material peeled away effortlessly because it wasn't entangled with the rest of the model.

So the downscaled model emerged intact and attractive. Even at this reduced size the walls were thicker than 3mm, which puts the model within the SD300's optimal safe-build range. There's exactly 1 layer of red material through the model's exact center, so the red marks indicate where the sculpture's structure passes through its midpoint; a cool bonus feature!

Bradley's iPhone 4 Case Mod

2011-03-21T21:37:00.000-07:00

Before I got my own 3D printer I always liked doing business with Bradley Rigdon at printo3d.com because he was always happy to try experimental ideas, so long as they were reasonable. For example in 2008 he shared a video of a Rubik-style cube that was built already-assembled on a Dimension SST 1200es in collaboration with another puzzle designer.

A longtime supporter of 3D printing in general, Bradley was lucky enough to get his original iPhone case built in Desktop Factory's unique additive process before they ceased development.

I recently built Bradley's updated iPhone 4 case on the SD300.

The new case has tiny letters embossed on the inside, so small that I couldn't remove the plastic inside. But the cuts were sufficiently clear and legible that it wasn't really necessary.

I installed a new XY cutting knife at the start of the build, but it broke part way through so I reinstalled the old knife to finish the model. This is the first time I'd seen a new knife fail so quickly, so I hope it was just a freak accident.

Regardless, it offered a rare opportunity to compare the cutting quality of a new knife to a worn one. On the model at left you can see a slight transition in sidewall texture where the knife was replaced. The new knife produced walls with a clean, lustrious texture while the old knife had a slightly frosty texture.

The finished model has a fold-out kickstand and tripod mount.

Bradley ambitiously wanted to peel the supports himself making use of his experence with Dimension's BST break-away supports, so I give him this video documenting how I'd cleaned the model. It's rather dry, but it was intended to be instructive not entertaining.

Twirlicue prototype

2011-03-13T00:35:00.000-08:00

On Thursday I learned Shapeways has permanently added solid silver to their material choices. Plenty of service bureaus offer precious metals, but Shapeways makes it so hassle-free that I wanted to devise something new just to exploit their new capability.

I designed a twirly shape that resembles a twisted potato chip, which is intended to be both a puzzle and a pendant. I built test models on the SD300 before sending it off to Shapeways. Just experimenting, I tinted the models by applying permanent markers to the exposed surface partway through the build process.

Here are the colored markers beside the finished parts. A visual illusion makes it seem as though the colors 'bleed' through the layers, but that's just an optical behavior of the transparent material.

I designed the models to be exceedingly thin because silver is such an expensive material, so these test models are also very thin. Consequently a piece broke away from one of the models when I was cleaning it.

The 'puzzle' is to assemble two pieces as shown here, which will allow them to be strung onto a necklace chain. The chain is a 1mm Sterling Silver box-link chain.

Here's another view showing how tiny and thin the test parts are compared to a US one-cent coin. I don't ordinarily build such thin parts on the SD300 because they require a huge investment of extra attention to remove the supports. It took at least an extra hour to clean these six parts, and I broke one.

Flexible Snake from Thingiverse

2011-03-07T23:35:00.000-08:00

Sometimes it's exciting to build models like this Long Snake by Zomboe from Thingiverse, just to see how they adapt to the SD300's unusual material properties. This one was particularly easy to lay out on the build table with a single peeling cut running down the 'backbone' of each model.

I switched colors during the build to give the snake contrasting stripes.

After building, leftover support material tended to cling inside all the narrow slots so it required a little extra force to tear it free. It went quickly, but I had to pick a few stray pieces out of the cavities afterward.

Each snake has a flexible spine consisting of a 0.6mm wall running the length of the model. The concept could probably be applied to other arbitrary solids to make them springy and flexible.

Adding color between layers

2011-02-25T21:46:00.000-08:00

The SD300 doesn't currently offer green material, so someone recently asked how I made the green marble I pictured in previous post in November. I had been experimenting with applying color during the build, a technique I recently repeated to produce three variously-colored marbles during a single build.

I stopped the SD300 about half way through building a batch of marbles, and applied colored markers to the interior of the models where the next layer was about to be welded on.

The ink was applied after the machine and finished applying Anti-Glue, but immediately before it ironed the next sheet. This timing ensures the machine won't come into contact with the ink, thereby protecting the cutting knife and Anti-Glue pens from contamination. My SDPause utility stops the machine at the right time.

Even though they've only been tinted only between two layers, the finished parts vibrantly exude color due to the translucent behavior of the material. That's all just a lighting effect: ink didn't (and couldn't) bleed between layers.

Better Cleaning with Booze

2011-02-23T22:05:00.001-08:00

The SD300 builds each model atop a re-usable magnetic pad, which clings to the build platform. Each model starts by 'gluing' a foundation layer of PVC to the magnetic pad; plastic residues eventually accumulate until the magnet has to be replaced. Luckily it's really inexpensive.

Solido encourages regular cleaning of the magnetic pad with "an alcohol based cleaner." I had initially tried isopropyl rubbing alcohol. At 91% strength the alcohol evaporated too quickly to be useful, but at 71% strength it was only modestly effective. I tried cleaning with some grain alcohol I'd bought to remove wax from some work clothes and discovered it worked much better than isopropyl. Ethyl rubbing alcohol worked better still!

Each build leaves a bit of residue on the magnet, as shown here. This magnet has been used over two dozen times, but this tiny bit of residue is from only the last build because I've been cleaning it after every build.

It's effortless to clean the magnet after every build because I keep it in a mist-spray bottle. One disadvantage of Ethyl Rubbing Alcohol is an offensive odor imparted by the USP-mandated traces of acetone and ketone, presumably to prevent anyone from drinking it. (Blech!) But these additives might account for its excellent solvency.

After spraying with alcohol I clean the magnet with a microfiber cloth, which seems to be more-effective than paper towels. The whole cleaning job takes less than 20 seconds because I keep the cleaner and cloth handy, and it's a worthwhile habit.

Here are four used build magnets, showing how the surface of each one held up better as I learned better cleaning habits. The oldest one, at left, has white areas where models stuck so badly they started to pull the surface apart. Each magnet lasted longer than the last, but eventually they need to be replaced because the surface eventually loses its nonstick 'release' capability even if it's kept clean.

Light pipes via transparency

2011-02-14T23:33:00.000-08:00

Inverting some previous builds I've been embedding a transparent band within opaque parts, such as these Puzzle Sphere pieces. The transparent band can act as a light pipe. There's another picture here of the assembled puzzle.

Similarly I built a batch of various Marble puzzles with embedded clear bands.

Here's one piece on a light table, showing how the clear band transmits light.

When two pieces are assembled into a Marble, the clear band in one piece transmits light through the other.

Here's an unrelated part I happened to build at the same time. It's a purely mechanical part, but it also includes a transparent band because the SD300 was building it with the same materials as the Marbles. The color-change doesn't affect the strength of the part.

Diamond by Bre Pettis

2011-02-06T23:22:00.000-08:00

Yesterday Bre Pettis shared a simple diamond shaped STL.

I'm working on a puzzle-themed pendant for holding gems, so I build Bre's diamond for reference.

Although it doesn't sparkle like a real gem, the transparency and internal angles catch the light very attractively on a light table.

Here's a picture of it beside several of my test models for the gem pendant.

SlideTab in 3D

2011-01-30T23:25:00.000-08:00

In January, Chris K. Palmer shared on Thingiverse specially-developed tabs to enable paper templates to be folded and joined together into 3D objects. It's also described at Shadowfolds.com. (I've previously featured a selection of his Sphericon models.)

Could the concept be translated into 3D models representing the same flat surfaces with slots, tabs, and hinges? At the very least, could it be made compatible with SLS?

I started my efforts by adapting the flat squares that can be assembled into a cube. It eventually worked, but only after I'd reduced the maximum wall thickness to 0.6mm. The hinged tabs required thin spots less than 0.2mm thick, too thin for reliable production by SLS.

Next I adapted the triangle models, which could be assembled into a tetrahedron (pyramid), an octahedron, or an icosahedron. But these required excessively-thin walls, like the cube, so the STLs aren't very share-able.

His "hat" models required even greater flexibility, and hence even thinner walls. It takes a lot of flexing to interlock the tabs.

Here's a partly-assembled Rabbi's Hat model.

It's not very dignified, is it?

So I didn't really meet my goal. The STL files are buildable in LOM because it can exploit the inherent strength of the unbroken source material, but the models aren't portable to other 3D printing processes. An SLS machine could build the individual parts (with careful handling) but I doubt they could be assembled.

Bacteriophage by LMDM

2011-01-18T22:47:00.000-08:00

Here's an excellent work by someone else:

The Laboratório de Material Didático Multimídia encourages the use of multimedia to promote science education in Brazil, particularly materials sciences. In 2010 they acquired equipment for building solid models including CNC mills, RapMan (from BitsFromBytes), and a Solido SD300 Pro.

Illustrated here is a bacteriophage they assembled on their SD300, using source data created in Google Sketchup!

The model was built as a flat sheet only 5 layers thick, yielding parts that are then folded and glued together.

Consistent with LMDM's philosophy, they produced an animated video that graphically shows viewers how to assemble the bacteriophage model.

Naturally they've posted a YouTube video showing the whole process of building the model, the assembly animation, and the finished model.

Multi-color 3D printing video

2011-01-16T00:08:00.000-08:00

I posted an HD video that illustrates multi-color builds with the SD300...

YOUTUBE: SD300 Pro Multi-color 3D Printing

The thin model in the video is an adaptation of Chris K. Palmer's Slide Tab Polygons that I'm trying to convert to STL. It's 0.5mm at its thickest point, 0.18mm at the thin hinges.

Here's a lower-resolution copy of the video in case you can't access it on YouTube...

SDPause, a utility for pausing at specific layers

2011-01-15T22:51:00.000-08:00

I've been building a lot of multi-color models by swapping out material kits at strategic times during the SD300 Pro's build process. The software didn't allow me to schedule when the machine would pause, so it originally required me to watch the machine carefully.

For my Rox Box model, I built the model upside down starting with the transparent layers first. Once the machine had finished building the transparent 'window' I swapped in the white material and let the machine build the rest of the model. That was simple because I only had to switch materials once.

But Oskar's Cookey Tribute puzzle was over 600 layers thick, and it took almost 30 hours to build because I was building multiple models at the same time. The model entailed multiple color-transitions, so I doubted I would be able to manually intervene at all the right times. I needed something automatic!

So I created a computer program SDPause that watches the SD300's build progress and automatically pauses whenever it reaches the layer entered in the box. That ensures the machine will pause whenever the model requires a different color material. Even if I'm not home, it will pause and wait for me to change the material and manually resume.

Email me if you want a copy of SDPause; my contact info is listed in my profile. SDPause should work with the original SD300, SD300 Pro, and Invision LD.

Some things I've learned about switching material kits:

I generally change the glue cartridge with the PVC roll so the materials will be consumed at a predictable rate. This also ensures the installed cartridge always has sufficient glue for whatever PVC roll is installed.
I generally don't change the Anti-glue cartridge and pens. Instead I just replace the Anti-glue cartridge when the default material kit needs replacement, or if support material doesn't peel away easily. The machine won't suddenly run out of Anti-glue, unlike the main glue supply.

Building a custom packing insert

2011-01-06T22:52:00.000-08:00

I wanted to ship the parts from my previous Torus project, and they fit very neatly into a small flat-rate shipping box. But I was worried adjacent pieces might slip under each other if the box was bumped, since they're slightly wedge shaped. That could cause them to puncture the container.

So I designed a thin, hinged packing spacer and built it on the SD300. It's less than a millimeter thick, so it barely used any material.

The spacer emerged from the printer in a flat shape, but easily unfolded to form two channels would would keep the parts from overlapping during shipping.

The spacer divided the parts perfectly without occupying any space in the box. I'll probably build custom packing material like this for future shipments, since the material is thin, flexible, and strong in this format.

Frivolous Christmas!

2010-12-25T12:53:00.000-08:00

All the kids are grown up, so my folks host a white-elephant gift exchange where the whole family brings a lot of unmarked gifts and we take turns picking and unwrapping. Many of the gifts are genuinely desirable items (eg: Roomba, a camera, etc.) but we try to have silly, fun gifts warpped in imaginative or frivolous ways. For example, I bought Hamasuta the Happy Hamster from American Science and Surplus. This motorized "hamster" scrambles around in its clear plastic ball, much like a real hamster.

It looks rather like a coconut when the ball is wrapped in tissue paper, so I decided to put misleading hints on the box to suggest it really was a coconut.

I boxed it in one of the transparent Puzzle-box Gift Cubes I'd built on the SD300 so the coconut-shaped tissue would be visible, and added a humorous label to imply it's just a coconut.

Another example of the family's theme of fun & silliness is this box whose attached card includes a drawing of an "inflamed colon." The inset shows it's just a play on words, not something gross!

The family reassembled my gift-cube boxes with the colors mixed in a peppermint-candy color scheme, which fits the holiday theme. I wish I'd thought of that!

Puzzle-box Gift Cube

2010-12-21T16:35:00.000-08:00

While using the SD300 to build some packaging I was inspired to build a puzzling group of six-piece boxes, which are held together solely by the interlocking tabs. I posted the files at at Thingiverse.

There are six parts to each cube, so I designed a variant that has six stacked parts that build all together at the same time.

The stacked version emerges as six parts, each separated by a single uncut layer of support material.

The boxes can be scaled down to smaller, thinner sizes. However the smallest box is impractically thin: with walls only 0.34mm thick, the parts are so flexible that it was almost impossible to assemble!

With effort I've managed to pack gifts inside some of the boxes, packing the excess space with tissue paper to disguise the contents. It's a novel presentation, and a bit puzzling to take apart.

Sphericons

2010-12-16T00:46:00.000-08:00

Chris K. Palmer modeled these novel Sphericons based on a mathematical discussion by Colin J. Roberts and Paul J. Roberts. His models included 4mm holes to accommodate widely-available 3.2mm magnets (like these) plus glue to cement them into place.

I scaled to model to 75% so the holes would be 3mm, slightly smaller than MagCraft N5NO566 disc magnets (3.2mm x 1.6mm). The resilient PVC material had sufficient 'flex' to permit the magnets to be forced into them.

Once the magnets were installed, I briefly soaked the parts in PVC welding solvent.

The solvent caused the PVC material to return to its square-ish shape around the magnets, securing them neatly in the holes.

The magnets allow the pieces to be paired to form round, solid objects. The pairing on the left can roll in a straight line, whereas the pair on the right can roll in a circular path.

But the same pieces can be paired so the curves look quite different. These pieces can be rolled along irregular paths.

Here's how the sphericon at left would roll. It follows a straight path with an occasional backstep.

And here's it's counterpart, at right in the previous picture. Its path is a bit more crooked.

What's a Torzle?

2010-12-11T23:25:00.000-08:00

George Bell drew my attention to a puzzling twisted torus artifact, described in detail by George Hart's web page where he shares pictures of various specimens and some history.

I built a large set, pictured above, and two smaller sets of parts. With the smaller parts I arranged the peeling cuts in a serpentine fashion, so the material peeled away in a long snake-like path.

I added splashes of color to the smaller parts by changing material during the build process.

Here the two batches of miniature parts are linked together serially.

Here's a comparison between the sizes of the large and small model batches.

Adding color with Painted interiors

2010-12-08T22:06:00.001-08:00

Oskar's original Cooksey Tribute puzzles were opaque and colorful, but the replacement I built was transparent and colorless so I chose to paint the interior surface of the cylinder.

I poured bright acrylic paint inside the cylinder and gradually tipped it so the paint gradually flowed into all the nooks.

The finished cylinder is now brightly colored. The ring piece is still transparent so the user can see through it while trying to solve the maze.

The maze is fairly challenging because the opposite sides of the ring must navigate the maze on opposite sides of the cylinder at the same time. After solving the maze, the ring rests neatly at the base of the maze cylinder like this.

Cooksey Maze rings in regal style

2010-12-07T23:47:00.000-08:00

I built a set of rings for the Cooksey Tribute D puzzle cylinders from my previous post. I put layers of black material at the top and bottom of each ring to match the puzzle cylinders by changing the PVC roll while the SD300 was building the model. The black accent gives it a nice touch.

I pulled the support material out of the holes first, just like I had with the cylinders.

After the holes were clear, I peeled away all the external support material to set the rings free.

I also treated the rings with Weld-On 2007 to improve the sidewall transparency. The ring at left is un-treated, the one at right has been treated.

Deep, deep holes & Oskar's Cooksey Tribute D

2010-12-04T22:11:00.000-08:00

I've previously mentioned Oskar van Deventer's Cooksey Tribute puzzles, a series of six puzzles inspired by a premise by Robert Cooksey. I encountered an apparent error in the puzzle while trying to solve the fourth in the series, Cooksey Tribute D.

Oskar confirmed there had been a minor error, and graciously allowed me to 'print' my own replacement copy. Due to the width of the PVC material I discovered I could build two puzzles for exactly the same material cost as one. In fact, I could build three for the price of one if I built two of them upside down.

As usual, the models emerged surrounded by a solid cocoon of support material, which needs to be peeled away. The Cooksey Tribute D puzzle is supposed to be a hollow cylinder, so I concentrated on pulling the material out of the holes before I peeled away the external material. I figured it'd be easier to handle this way.

The hollow interiors are really deep and really narrow, so I couldn't pull out the support material with my fingers. Before long the only tool that could reach into the hole was a probe I'd bought at my local hardware store.

As it turns out, the probe was the perfect tool for hooking into the X-shaped peeling cuts in the support material. This was an unusually challenging job because the holes were 11 cm deep, with 650 layers of support material. Luckily the probe made relatively quick progress, snagging several layers at a time.

When the holes were finally cleared, the block looked like this. It reminds me of a part from my '75 Scirocco's exhaust system. (I don't really miss that car.)

With the hollow interiors cleared, I began the easy job of peeling away the external supports to free the models.

Rattleback twins

2010-12-01T23:09:00.000-08:00

On Tuesday evening I saw a model of a Rattleback posted on Thingiverse. A traditional rattleback reverses direction when it's spun in a clockwise direction.

I made two models, one with the mesh reversed so it would respond to a counter-clockwise spin. Unfortunately the models were too 'tall' so they tended to tip over instead of spinning. A conventional rattleback, at lower-right, is only half as thick.

Since the model was just too thick, I used SDMove (the SD300 build software) to reduce it 45% in the Z axis and built another set. The new model, shown in red, was much more functional. But it had a flat spot due to the layers in the Z axis, so it wasn't as good as it could be.

So I built a third set using the same mesh, but oriented it to be built on its long edge. This exploited the SD300's excellent XY axis resolution to give smooth, curved contours. (FDM users employ the same strategy.)

Now I've got a left-handed and right-handed pair of rattlebacks, one which reverses clockwise and the other counterclockwise. They're still not optimized, but it's probably as good as it gets by just tweaking the mesh rather than re-contouring the source data.

I uploaded the modified meshes back to Thingiverse for the benefit of other users. Maybe someone will refine it further.

Basic Male Form by Nicholas C. Lewis

2010-11-25T13:17:00.000-08:00

Nicholas C. Lewis uploaded a model Basic Male Form to Thingiverse just as I was starting a build that had a little unused volume in it. On a whim I downloaded his model and scaled it to fit. It fit neatly into the leftover volume, so I got an extra model without using any additional material.

His original was 10 cm high, but I scaled it down to ~2 cm to fit within my existing build envelope, so I got a very tiny but very detailed model from the SD300.

It looks pretty on my $3 light table from American Science and Surplus. It's amazing how easily I can build an extra model for so little effort.

"Snap" assembling a Nut

2010-11-21T21:45:00.001-08:00

I never seem to have the right fasteners on hand for my projects, so I like to design things that can be assembled without screws. This nut-themed shell is designed so two identical halves can snap together, leaving ample room for the mechanism inside.

For testing, I assembled two halves without installing the mechanism. The part was built with a combination of opaque white material and transparent material, which makes it striped.

The round bumps will fall into matching holes when the part is squeezed together. This is a very rigid part with thick walls, but the SD300's PVC material has just enough 'give' to allow these halves to be snapped together securely.

Thanks to the layers of transparent material, the assembled shell includes windows through which the mechanism will be visible in the final puzzle.

Magnet bearings

2010-11-14T23:38:00.000-08:00

I've wanted to develop this, even before I owned an 3D printer.

Oskar's 8-Inch Bolt is a cylindrical incarnation of a hysteresis maze, where the user can move a collar up or down but can't turn it from side to side. The collar has a pin that traces from side-to-side along the walls of a maze, but the user can't steer it. There are very few samples of the puzzle in existence.

I liked the premise of Oskar's 8-Inch Bolt, but the collar operated very poorly due to excessive friction. Sometimes I tried to share the puzzle with other puzzle enthusiasts, but it moved so roughly that only one could even make it work. So I've been developing a low-friction replacement collar.

I designed the replacement collar as a disc studded with 24 magnets, which would be sandwiched between two additional rings of magnets. The magnets are all configured in repulsion, so the central disc tends to hoover. This minimizes friction, yet the magnetic repulsion ensures the ring won't rotate unless it receives some lateral force.

In later prototypes I added a channel with nylon ball bearings so vertical forces won't cause the disc to rub against the other parts. (Nylon is unaffected by the powerful magnets.)

The current prototype seems to exhibit exactly the right behavior. The central disc effortlessly rotates in response to sideways pressure on the pin, but it stops at predefined positions and stays put.

More marbles?

2010-11-08T23:46:00.000-08:00

Maybe I'm stuck in a rut, but I've built a substantial number of test marbles using various build orientations, color schemes, and tolerances.

Some are twisted in the reverse direction. I plan to use them as building blocks for a larger puzzle by gluing some halves back-to-back so they have to be attached to other parts in a specific way.

Despite all the different tolerances, the pieces are similar enough to mix-and-match. When two halves are joined into a single marble they usually hold together firmly, but some pairings will spontaneously disassemble themselves as captured in this video.

Isolated Marble, rev 2

2010-10-30T22:07:00.000-07:00

I refined the curves and angles in yesterday's Isolated Marble prototype and built another today. I gave the model a black stripe to distinguish it from the previous model by changing to black material for 6 layers part way through the build.

It works better than the previous revision, but it reveals more details that need refinement.

The curve was supposed to be smooth, but it exhibits a rough texture like a washboard. That's not a build problem, it's an interference pattern in the source data. A silly mistake, but it'll be easily fixed.

Isolated Marble, a work-in-progress

2010-10-29T21:07:00.000-07:00

Some time ago I tried to develop a variation of Bram Cohen's Trapped Marble puzzle, which is now being sold by Hanayama Ltd as Cast Marble. I tried to modify the cuts as radically as possible, but the puzzle as a whole behaved just like Cohen's original. It apparently lacked novelty, so I stopped working on it.

The challenge in Bram Cohen's original puzzle was to assemble all four pieces; there was no challenge assembling the two-piece marble without the rest of the puzzle. But in the following months, many people have been confounded by the central 'marble' from my prototype. It just doesn't go together as people expect.

The secret to assembling the marble by itself is to withdraw the parts farther than you might intuitively expect, until they elegantly nest and join together. My four piece prototype had been designed to be assembled from a widely-separated orientation, but I hadn't anticipated the two central 'marble' pieces would retain this behavior without the other two pieces. It turns out to be a satisfying puzzle all by itself!

So I've begun exploring designs for a two-piece marble puzzle. To help distinguish each batch of prototypes I briefly installed red PVC for several layers in the middle of the build, which gave these parts a red stripe. For subsequent prototypes I will try swapping-in small amounts of other colors, again to uniquely identify each build.

Built-in color graphics

2010-10-21T22:45:00.000-07:00

This weekend I built some parts with shiny, colorful graphics built-in.

I embossed a thin extrusion of a heart-shape, 0.17mm thick, onto the tops of four parts. For building, I arranged the parts on the table (not as shown) with the embossed graphic parallel to the build platform. (The SD300's build software has a 1-click tool to do that.)

I built most of the model in white material, then switched to red material for the last layer. Hence most of the model was white, but the embossed heart shape was built using red. The excess red material simply peeled away with the supports, leaving the red graphic integrated into the model.

The finished parts have the colorful heart graphic integrated right into the model. Unfortunately, red is the only SD300 material that seems to offer enough contrast for this technique. The "black" material isn't dark in thin sections (but I'm working on a workaround). Solido lists "blue" material for the machine, but dealers don't have any inventory.

Clearing an X with a probe

2010-10-16T21:42:00.000-07:00

It's occasionally handy to have a set of general-purpose probes at hand for cleaning support material from small openings and crevices. They aren't needed for most jobs, but they're invaluable for a few situations.

This model had two blind holes, which I filled with X-shaped peeling cuts. I made sure the cuts didn't touch the walls in order to avoid splitting the material into sections.

After building, the X marks identify the material that needs to be removed from the holes.

It was too awkward to reach inside the holes with the standard tweezers, as there just wasn't enough room to operate the jaws. But the probes are perfect because the thin point can hook under the X. The probe's point is small but not sharp, so the slightly blunted tip doesn't scratch the model.

The X disappeared after the last layer of support material was removed, visually confirming the hole had been cleared completely. When I had used tweezers for similar jobs I'd always scratched or gouged the bottom of the hole; the probe worked much better.

X Marks the peeling cut

2010-10-09T22:19:00.000-07:00

In one of my first posts I suggested running a peeling cut through holes to give the forceps something to grab onto when peeling away the supports. But it's not so good to run a cut through a large hole (or hollow area) because it divides it into two sections, which could take twice as long to peel. It also reduces the size of the Z-folds, so the support material is more likely to tear instead of coming out cleanly.

So I've begun adding an X-shaped peeling cut inside hollow areas, not touching any walls.

At first the X-shaped cuts don't look useful because they don't touch any walls, which goes against the standard convention for peeling cuts. But they conspicuously identify the leftover support material.

The X provides a convenient location to grab the support material without touching any walls, thereby preventing the forceps from scratching the model.

The Z-folds work better because all the sides are clear of peeling cuts. Even if the material tears during peeling, the X provides a safe place to get hold of the remaining layers and begin peeling again.

FInally, my second failed build

2010-10-06T01:06:00.001-07:00

Ordinarily, the SD300 tests the integrity of the XY cutter at the completion of each layer by using the cutter to separate the model from the material and then attempting to rewind the material onto the source roll. When a cutter is worn out the material remains attached to the model and the machine emits a distinctive noise from an internal clutch.

The machine had a relatively new XY cutter, so I was surprised to hear the slipping-clutch noise which usually indicates a worn out cutter. The machine's log seemed to express the same astonishment, "the cutting knife is new and the previous layer was OK." Evidently the SD300 concluded the XY cutter was too new, so it just tried to continue building the model until I intervened.

Normally the machine can continue to build the same model after the XY cutter is replaced, but inspection revealed this model was full of air bubbles. The glue hadn't been spreading properly so the layers weren't welding together. This model would be defective, even if the rest of it built perfectly.

I ran some tests which confirmed the culprit was the XY knife, not air in the glue system. I've had other knives wear out, but this was the first occasion where it caused any problem with the model being built. Evidently it had scraped the model surface, creating gouges and voids which prevented the glue from spreading between sheets. Everything worked when I replaced this cutter (shown below) with a new one.

Frankly, I'm pleased to have only two failed builds since I bought the machine in February. That compares favorably with colleagues who use V-Flash and Dimension modelers.

Admittedly I've had bad builds for other reasons, such as bad STL designs or improper layouts, but only two builds have been defective. My first defective build was entirely my own fault, as I'd allowed the glue to run out. This one might have been a freak incident.

Too thin?

2010-09-29T22:16:00.000-07:00

Yesterday I encountered a puzzle designer who'd shared a rough draft of a model with impractical, thin walls. The pictured model is only 19mm high, with many 0.63mm walls and several tapers that were even thinner.

I'd tried to avoid thin walls in my earliest designs for the SD300, but occasionally built thinner walls by chance or miscalculation. Some worked, some didn't, but I always learned something new. So I got permission to build the model, fully aware I was going to have problem with it.

Unsurprisingly, lots of really thin areas broke away while removing the supports. I managed to preserve some walls as thin as 0.5mm by peeling the support material away slowly, one layer at a time. Some undercuts were so narrow I couldn't even reach into them with my curved forceps.

Still, the model emerged sufficiently intact for examination. The channel walls were so thin I could barely get a fingernail inside, and they were noticeably flexible. I dipped the parts in Weld-On 2007, which immensely strengthened the surviving structures.

Surprisingly, the parts can be assembled...barely! The tolerances were inadequate, but they just barely functioned because the channel wall flexes just enough to compensate.

The design doesn't make provision for installing all four parts, so I couldn't assemble the whole puzzle. But it's impressive that it worked at all.

These parts aren't practical due to the overly-tight tolerances, but the model confirms the designer's concept nevertheless. But I certainly wouldn't try to build such thin walls routinely. A comparable model might take 10 minutes to clean away the supports, while this took almost 2 hours. If it hadn't been for the Weld-On dip the parts probably would've broken during testing.

But it shows that the user can venture outside of "good practices" at his discretion. The SD300 will attempt to build any geometry it can process, even if it's not practical. It's the user's choice.

How to Check glue level

2010-09-26T00:39:00.000-07:00

Back in May, I neglected to replace the glue cartridge when replacing the rest of the material kit and ruined a model because the SD300 ran out of glue during the next build. Since then I've tried to always replace the glue cartridge in sync with the PVC roll.

I learned to double-check the glue cartridge's capacity by shining a high-intensity LED flashlight through the side walls, which reveals the glue level as a bright line on the wall.

Today I was startled to discover the glue cartridge was essentially empty, even though there was plenty of PVC left in the material kit. There should've been plenty of glue left. Notice the bright line is all the way at the bottom.

I still had the glue cartridges from two recently-exhausted material kits. There was a little glue left in one of them, but that's how much is usually left over after a kit has been used up. The bright line is near the bottom.

When I checked the other "empty" cartridge the LED light showed it had a lot of glue left in it. Notice how the bright area is well above the bottom!

Probably I got an 'empty' cartridge swapped with a non-empty one when changing between colors recently. I shouldn't leave the empties nearby. It's fortunate I discovered it before the machine completely ran out of glue.

Improved transparency for the Cooksey Tribute puzzle

2010-09-20T22:55:00.000-07:00

EDIT: Just to clarify, I only built the transparent rings in the pictures. The brightly-colored maze cylinders were purchased from Oskar's store at Shapeways.

In a previous post I described how I'd made transparent rings for Oskar's Cooksey Tribute maze puzzles. The transparency enhanced the puzzle, but they were only semi-transparent at best.

I had sprayed the previous parts with Weld-On 2007 to improve their transparency, but I soaked a second set in the solvent for 25 seconds and then permitted it to air-dry for an hour. The results were substantially more transparent.

There's some optical distortion where build chatter has been transformed into wavy lenses, but the new part is more transparent.

So now I'm building a new set of enhanced transparent rings using the solvent soak-dip.

I had discovered the value of a solvent dip long ago, but I'd been using a simpler solvent-spray to make it more convenient. The dip requires a relatively large volume of Weld-On 2007 welding solvent, a solvent-resistant surface, gloves, and ample ventilation. But these results are worth some special effort!

There are additional pictures of Oskar's Cooksey Tribute in my PhotoBucket Album.

Rox shares the Rox Box with Uwe Mèffert

2010-09-16T22:07:00.000-07:00

In August I built a gem-filled puzzle for a widely-known puzzle collector, Roxanne, and named it the Rox Box in her honor. It featured two puzzle-engraved gem stones locked behind clear windows, and the box could only be opened by navigating the lid through a maze in the shape of the word "Rox," Roxanne's nickname. I built only one, so she owns a very exclusive specimen.

Recently Roxanne met Uwe Mèffert over dinner in Hong Kong. Mèffert invented the Pyraminx puzzle, which was popular back in the Rubik's Cube puzzle craze in the 1980s. He still develops and sells puzzles at his web store www.mefferts.com

Roxanne showed him her Rox Box puzzle and kindly sent me a picture of Mèffert playing with it. He praised the way it incorporated her name right into the puzzle!

Mèffert showed some of the puzzles he's developing for his store, and Roxanne shared many of the favorites in her own collection. I'm very flattered she included the Rox Box because I interpret her choice as a sincere expression of appreciation. I'm grateful for that!

Faking a power outage

2010-09-14T23:41:00.000-07:00

Yesterday I noticed the SD300 had mysteriously stopped part way through a build. The computer's status monitor said the SD300 was actively building layer 22, but the SD300's display suggested it was waiting for the computer. Pressing Pause/Resume had no effect.

So I ran the SDView, the SD300 maintenance app, and brought up the machine's log. There were 3 unusual entries that said "Unknown command in file." Had there been a data transmission error between the computer and the SD300? In any case, the log indicated the SD300 hadn't finished layer 21 because it was "waiting for host" to send the last data, but I guess the computer thought layer 21 had been finished and was waiting to send layer 22. Stalemate!

So, how could I resolve this apparent deadlock?

The SD300 has a robust procedure for recovering from power outages, so I pulled the plug for a few minutes to simulate a power outage. That worked!

When I plugged it in again, the SD300 went through its initialization and recognized that it had unfinished model. After verifying the model's integrity the SD300 asked me to confirm that it should resume the model in-progress. Sure enough, it negotiated with the computer to re-load the model data and it resumed building after a 2 minute pause for "Loading."

Using a Pin Vise to clear small holes

2010-09-10T23:14:00.001-07:00

For a while I disliked building parts with deep, narrow holes because leftover support material clings tenaciously inside the holes and solidly blocks them. There's common advice to simply clear the holes with a drill, not my favorite solution.

A colleague suggested using an ordinary drill bit in a pin vise. The pin vise allows the bit to be twirled freely, and the handle provides leverage and strength.

Because its a handheld tool, the pin vise gives tactile feedback that makes it easy to guide the bit to follow the intended path of the hole. I found it helps to run a peeling cut down the middle of the hole, which gives the flutes a loose edge to grab onto.

Surprisingly, the manually-operated drill bit clears away leftover material very quickly yet doesn't tend to cut into the model itself. The model is quickly cleaned up by scraping the drill bit against the sidewalls and withdrawing it to clean the flutes.

George Bell's Exploding Ball

2010-09-02T23:02:00.000-07:00

Yesterday designer George Bell emailed me a file for his Exploding Ball puzzle. The pieces have all sorts of awkward angles, so I just took a guess on how to orient it for optimal building on the SD300.

It would take about 7 hours to build all eleven parts, but I chose to build 3 sample parts because it would only take 3 hours so I'd be able to inspect them before bedtime. It was lucky that I'd printed a couple of samples, as I'd arranged the peeling cuts so they put stress on a thin section. I broke one of the pieces when I hastily peeled the supports away. It wouldn't impair the part's usefulness, but it's unsightly. (Clarification: The part on the right is flat where a tiny piece of the curve broke off; the part on the left is intact, showing how the curve should look.)

I fixed the peeling cuts and ran another build overnight. Today I peeled away the supports quickly, easily, without any damage to the parts. When the parts are assembled, they form a ball that's virtually impossible to disassemble because of the smooth surface and bizarre angles. Even if you get your nails in the cracks you can't pull it apart because your touch tends to hold the puzzle together. But it's supposed to disassemble when it's spun, thanks to centrifugal force.

It took me half an hour to assemble the puzzle the first time, so I recorded a video of my first attempt to 'explode' the puzzle because I wasn't sure if I'd get it put together again. It took several tries. It's lucky the finished model is pretty tough, since I dropped it at lot!

Cooksey Maze

2010-08-28T19:08:00.000-07:00

In the 1970s Richard Cooksey invented a cylindrical maze puzzle, which underwent some development by Pentangle Puzzles & Games but didn't ultimately become a commercial product. Puzzle inventor Oskar van Deventer recently adapted the puzzle and made it available through Shapeways as Cooksey Maze.

Oskar also designed a series of six Cooksey Tribute puzzles, each a different variation on the basic concept.

The ring has two pins that ride in the grooves on the cylinder; it's shaped so the user can choose one pin to lift out of the grooves, permitting the user to switch from one side of the 'maze' to the other. The ring is attractively cut with large openings for the user to look through, but the opaque material undesirably blocks the view of the maze. Oskar said he would have preferred to make the rings transparent, so I offered to try building a set on the SD300.

I built a complete set of six rings, corresponding to the six variants of Cooksey Trubute, using the amber-transparent material. The 3-4mm thick sidewalls aren't crystal clear, but they're sufficiently transparent to give a clear view of objects inside.

Sure enough! The transparent rings give a clear enough view to permit the puzzle to be explored and solved pleasantly.

M. Oskar van Deventer is offering a free Cooksey Maze to anyone who can put him into contact with Mr. Richard Cooksey.

Multi-color build

2010-08-22T22:22:00.000-07:00

I've used clear & opaque material in the same build, so now I tried building with two colors in the same build. Part way through this build I replaced the white material kit with black, resulting in a model block that resembles an Oreo cookie.

The finished parts show a nice, distinct transition from one color to the other.

I assembled the parts into a puzzle and added colored tiles. It looks a bit bizarre, but it shows how two colors can be used together.

Cubic trisections

2010-08-15T22:03:00.001-07:00

A few days ago I explored many novel ways to trisect a cube into three identical parts. Could they be adapted into a puzzle? To find out I printed three samples, each using different parameters.

Each cube is made of 3 identical parts, which slide together (or apart) with a novel twisting action.

Here are the individual pieces of one trisected cube.

Because the model included some spots as thin as 0.3 mm I chose the build orientation carefully to exploit the SD300's ability to build thin layers in the Z axis.

Light reflects and refracts spectacularly inside each model. I don't regard it as a finished puzzle, but the SD300 encouraged me to try out an idea I might have ignored.

Rox Box: Clear and opaque in the same parts

2010-08-04T00:53:00.001-07:00

I built this puzzle box for a collector named Roxanne, and incorporated her nickname "Rox" into the puzzle itself. The box holds the gemstones using the gem holders I built earlier, so I called it the "Rox Box."

The gem holders slide into a plastic insert, which corkscrews into the middle of the puzzle box. Rox's nickname is carved into the walls, which creates a maze the lid has to be threaded through to open the box. This premise was inspired by Teifenbacher's A-Mazing Box at Thingiverse.

It's 3D printed with a combination of opaque materials and clear material to form windows, so the gems are visible when the box is closed. A ruby is visible through the top, engraved with a Rubik's Cube.

A sapphire is visible through the bottom of the box.

To build opaque parts with clear windows I switched between transparent and opaque material while the SD300 was building, which resulted in a seamless transition between the two. Thus the clear windows are integral, rather than being assembled separately.

This was my first attempt to combine two materials, and it worked perfectly on my first try! In this instance I simply arranged the parts so the window would be built first, and started building with clear material. When it had built to a height of 2mm (the thickness of the windows) I selected "Unfeed media" on the front panel, swapped-in the opaque white material, and let it continue building.

Gem Holders

2010-07-30T22:42:00.000-07:00

Last year I learned to engrave little pictures onto various gemstones using a CO2 laser. I got the best results from lab-grown rubies and sapphires (both corundum) which etched to a frosty image that contrasted nicely with the saturated color of the stones.

I wanted to share the engraved gemstones with other puzzle enthusiasts but the loose stones are easily lost, so I designed and built gem holders on the SD300 using black material.

The flexible tabs allow the gem to be snapped securely into place. Each gem can be removed by pushing it out of the holder through a cavity in the back.

I also built a gem holder using transparent material, which slips into an opaque white holder.