Rundown of puzzles for IPP33

 

Peppermint, my entry for the puzzle exchange, was digitally manufactured in colorful ABS by Bradley Rigdon at PrintTo3D.  I built prototypes on my SD300, those PVC models were a bit too flexible to give the right "feel" for this particular puzzle.  Each piece is made in two colors, red and white; the colors play a subtle but important role.

 Moiré Maze combines laser-cut acrylic and 3D printed vinyl.  The challenge is to guide a small magnet through the maze from Start to Finish.  That goal sounds simple enough, but it's easy to get lost in the visually-confounding patterns of rings reflected against a mirrored background.

Cubic Trisection is one of the puzzles I also sold at IPP32 last year.  The challenge is to assemble the three pieces into a cube, as shown.  All three pieces are identical, but not symmetrical.  Most users easily assemble the first two pieces, but encounter trouble adding the third.

Puckup is a two-piece assembly puzzle, which I'm selling in transparent material or a red-white color scheme.  Tyler Barrett suggested a somewhat edgier name "What the Puck" but the simpler Puckup name had already been picked up on one of the puzzle forums.

Twisty Trillion is a successor to Puckup whose shape provokes a lot more confusion among users.  Neither puzzle is fiendishly difficult, but Twisty Trillion takes most people a whole lot longer to figure out.  I built them all on the SD300 using transparent vinyl because light reflects attractively inside the puzzle.

I commissioned two copies of a Trillion Pendant to be built as puzzle jewelry--one in brass from i.Materialise, the other in silver from Shapeways.  But neither model was delivered on time--Shapeways lost one of the pieces, and i.Materialise is over 3 weeks behind schedule.  So I salvaged the partly-incomplete silver model by building its other half in luxuriously-dark blue vinyl, which contrasts gracefully with the silver piece.  Frankly, it looks nicer than it would have if both pieces had been silver!

Here's a colorful assortment of marble puzzles, three of which will be available for sale as Bag of Marbles.  The others are experimental designs, which I'd like to test on a few puzzlers at IPP.  In particular, the pink and purple models are two closely-related designs, but my first few testers think the purple one is much harder than the pink one.  Will others react the same way?  IPP is a great opportunity to find out!

More on Moiré

I previously wrote about my Moiré Maze puzzle as if it was finished, but it had all sorts of unfinished details until this weekend.  For example I didn't have suitable packaging until George Bell referred me to Clear Bags which supplied the attractive box pictured above.

I built this inexpensive plastic insert on the SD300 to hold the puzzle safely inside the box.

The closeup above emphasizes two more gripes:

• The Start and Finish are denoted by two bulb-shaped chambers, but there aren't any markings to identify which is which.  I suppose I could supply an instruction sheet, but it could get lost.
• It really needed some sort of mechanism or barrier to keep the chambers separate, to prevent the user from trivially moving the magnet from Start to Finish without tracing the maze.  The acrylic cutting pattern included an eyelet for attaching such a mechanism, but how should I use it?

 

To add markings to the puzzle, I used a KNK Zing plotter-engraver I had recently purchased.  The machine can't handle the bare acrylic pieces so I 3D-printed a template and taped it to a large piece of poster paper, which the machine happily accepted.

To calibrate the KNK Zing to the acrylic sheet, I aligned the the engraver's laser-pointer with a small hole in the 3D-printed template/holder.  And I installed a diamond-tipped engraving tool into the plotter.

Start and Finish are clearly identified after engraving.

And I installed a one-way vinyl flap that permits the magnet to be pulled from the Finish chamber to the Start chamber.  It doesn't let the magnet slide the other way.  The only way to travel from the Start to the Finish is to navigate the maze.

Puzzle Overview: Moiré Maze

I've previously posted about the development of Moiré Maze so here's an overview of how it works as a puzzle.  There are a few clues about its solution but no spoilers.

At left is Oskar's Boston Subway puzzle from 2006.  It's a sandwich of acrylic sheets containing laser-cut channels; the bottom layer has 10 parallel channels running north-south and the top layer contains 10 parallel channels running east-west.  It's a criss-cross grid.  There's a layer in between that selectively connects the top and bottom grids at some places, thereby turning it into a puzzling maze.  George Miller constructed the puzzles and put inside a small magnet the user can guide through the maze using a magnetized wand.

It occurred to me to build a similar layered maze using circles instead of straight lines.  Ultimately I developed two layers of concentric ring-shaped channels, one over the other as depicted at left.  The layer at right is sandwiched between the other two layers to selectively allow the user to transfer between the two sets of rings like a maze.

The layers are stacked like this with a mirror on the bottom and a transparent cover on top.  I carefully selected a combination of layer thicknesses and a much thinner magnet to prevent the magnet from becoming turning sideways and becoming wedged between layers, a nuisance Boston Subway sometimes exhibited.

Laser cut acrylic comes with a protective film over the surface.  To avoid getting dust and fingerprints on the layers inside the puzzle, I only removed the protective film after each layer had been assembled into the puzzle.

But there's more to this puzzle than a mere shape variation on Boston Subway--it introduces a visual subterfuge that misdirects the user away from the solution.  The critical secret is plainly visible, even in the photo, but it's tough for a viewer to choose to see it once their mind has resolved the image.  Some testers couldn't even force themselves to see it when the solution was shown to them.

In Boston Subway it was sometimes difficult to locate the little silvery magnet because it reflected the same colors as the neutral mirror and irridescent sheets.  I chose to use a bronze-colored mirror with Moiré Maze to enhance the contrast, so the silver magnet is easier to distinguish against the bronze-tinted background.

As a final touch I gave Moiré Maze a built-in stand that secures the layers and holds the puzzle at a convenient slope for playing.  Initially I'd planned to make the stand with laser-cut acrylic like the rest of the puzzle, but after some experimentation I substituted dark-blue pieces 3D-printed from my SD300 because the PVC material is so resilient that it can squeeze the acrylic sheets tightly together.  If I had made those piece of acrylic, then the stand's outer pieces would be strained in tension and would thus be vulnerable to breakage--acrylic tends to fracture under stress.

Moiré Maze for laser cutter

I took last month's injection-molded prototype for Moiré Maze and adapted it back for laser cutting by projecting it into 2-dimensional layers and tracing their outlines.  I don't own a laser cutter, but plenty of businesses offer laser cutting services including mail-order Ponoko.  But why wait for the mail?

The SD300 can make good simulations of laser-cut parts, given adequate model data.  I created accurate simulations of laser-cut models by first modeling a sheet about the anticipated thickness of the part, about 3.0 mm to simulate the typical "eighth inch acrylic" (which usually runs a tad thin).  To simulate a laser's cutting behavior I cut the outlines using a "thin wall cut" with a 2 degree draft angle.

Models were easy to clean because the sheet-like design meant there weren't any overhangs, undercuts, or loose ends to deal with.  It was easy to stab leftover support material and peel it away from both sides of each finished piece.

I also designed a 2-piece base, shown upside-down here, on which the maze layers are stacked.  The base aligns the maze pieces and holds them together.

The magnetic wand can be stored in a compartment at the top edge of the maze, and it's held in place because the magnets in the wand are attracted to steel beads embedded inside the model.

Above is a brief video tour of Moiré Maze.

Moiré Maze was inspired by Boston Subway, Oskar van Deventer's design for IPP26 shown at left in the picture.  Boston Subway has layers of criss-crossing channels built from laser-cut acrylic, and the goal was to guide a little magnet from "work" to "home" using a magnetic wand.  Moiré Maze substitutes ring-shaped channels for the straight ones, and thereby creates a visual hiding place for its solution even though it's entirely transparent!

Indian Rupee Sign, Rev. 2

My first attempt at making the Indian Rupee into a letter-dissection puzzle was an interesting puzzle-design exercise, but it yielded a fairly uninspired puzzle.  I had designed a frame for the puzzle because most people aren't very familiar with the shape of the Indian Rupee sign, but the frame just made it that much easier to solve.

But I sensed a puzzle in that shape, so I drafted and modified the outlines to explore relationships between all the lines, curves, and angles.  Hidden relationships emerged as the shape evolved.

A new puzzle emerged with so many similar curves and angles that 8 of the 9 pieces could fit together without any of them being correctly positioned.  But was it a good puzzle?  No, not really.  My friends had no trouble identifying the correct positions, and some of them couldn't even discover those "wrong" positions without considerable effort!

The puzzle at right is solved correctly, while the puzzle at left is shown with all the pieces in wrong positions.  It was a failure, but a very instructive one.  So, could I re-design the puzzle so the correct positions were more like those in the puzzle at left?

Starting from scratch I designed a new layout, paying close attention to feedback from my testers.  What emerged was a dissection of a Rupee sign into just eight pieces.  Each piece fits into the frame in more than one location, but most look like there's only one possible place to put them--and it's usually the wrong place!

The classic T letter dissection puzzle requires four pieces for its relatively simple shape, so I'm thrilled to dissect such a complex shape as the Rupee sign with just twice as many pieces.  I had to allow some wacky variations in shape and size, but it works.  Moreover, the frame actually enhances the challenge by discouraging the user from removing pieces that might have been incorrectly placed!

Rupee Puzzle, rev. 1

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.

Making signs with deeply-engraved letters

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.