Penta in a Beautiful Box

Penta-in-a-box was designed by Hajime Katsumoto and won a Jury Honourable Mention at the IPP (Puzzle) Design Competition in 2016. The objective of this packing puzzle is to put the five pieces into the box and close the lid completely. It seems easy until you try. 

These puzzles are classics and wonderful to lend to friends to see if they can successfully solve. This puzzle is about a 7/10 for difficulty. 

I decided to try to design as nice a box as possible to go along with this classic. I used an invisible hinge design that was used by Rob Cosman in several of his woodworking videos (YouTube). The hinge worked flawlessly on the first box. I then got ambitious and added texturing, using CNC Kitchen's BumpMesh site. This is an amazing tool, but adding textures to the box added height around the hinge area and restricted the opening. In one of the pictures, you can see that adding increased texture restricts the opening. I could compensate by modifying the design, but it would mean making the walls of the box 1-2 mm thicker. I included a slightly textured version of the box for those who prefer that finish. It works well, but you will need to file slightly around the lip of the hinge to reduce the texture height in that area. 

I looked at adding a flexible snap, but PLA does not flex well over the long term; and prone to breaking; and I wanted as clean a design as possible. I opted for small magnets. The textured box uses a single pair of magnets and the plain, tan box uses 2 pairs. I much prefer the snap of the 2 pairs of magnets. The box will still work fine without the magnets.

The hinge uses a single strand of filament  which you can insert from either end. To finish the look, I use an M2x4mm socket head screw in each end. The length of the screws are 6mm, so cut the filament about 13mm shorter than the width of the box. The screws are optional but help to enhance the look of the hinge ends.

The magnets are 4mm round by (nominally) 2mm thick. Both the screws and magnets can be ordered through AliExpress and total cost is under $10 (Canadian) for at least 30 of each. The 4x2mm magnets from AliExpress are actually about 1.6mm thick and the hole in the box that accommodates them is 1.8mm deep. Use a small amount of super glue to bond the magnets. 

Printing

I used standard PLA for the two boxes. (The light brown is not matte, but that will likely work fine). 

The box is printed at 0.2mm layer height, 2 perimeters and 4 top/bottom walls, 15% infill. 

I printed both the top and bottom at once and used a color change by layer height to highlight the text.

For the pieces, I recommend 3 perimeters and perhaps 30-50% infill to give the pieces a bit more weight.

Solution

I won't post a solution for this puzzle as it is not extremely difficult and solving it is very satisfying. But if anyone needs help, send me a message and I'll give hints, or can send you a solution.