Assorted "stuff"

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"

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

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?

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

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

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

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

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

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

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.