Someone who doesn't know how to open it will struggle for a long time, especially if you give them no clues. Once you've learnt the gesture, you can open the box in a couple of seconds. My uncle (who is a maker working at a museum) took 24 hours to open it, with a team of interested buddies, an xray machine, a metal detector and large magnets!
Many thanks to London Hackspace, and everyone who has helped me out with learning how to use the laser cutter! Thanks Lou for the good photos! This design has taught me a lot about using the laser cutter, parametric design and designing for CNC. This is about the 12th version, so it's pretty reliable by now. I hope the instructions are good enough!
Tools and Materials
Tools: a laser cutter, a CAD program
Materials: a sheet of 4mm ply, PVA glue, a small rare earth magnet, 2 x 25x4mm springs (you can get them from pens), a 4mm ball bearing and 2 x 10mm of 4mm metal rod (I use brass).
Step 1: Cut your peices
Go here http://www.mazepuzzlebox.co.uk/create and draw your maze. To make the maze harder, use dead ends and junctions where timing becomes more important. Click 'create box' and then enter your material thickness. Click 'generate plans' to get the plans that are correct for the thickness of your material.
Inspect the plans
open the DXF in your CAD program (QCAD is free ) and check things look OK. I use an HPC laser and the software won't import the file as it stands, so I have to save it with QCAD and then it works. I'd be really interested to hear if other software works without having to open and save it in a CAD program.
The finished CAD file has 4 colours, white and grey for the cuts, green for patterns and blue for etched parts. The settings I use on a 30W cutter are:
* etch (blue): speed 200, power 30, scan gap 0.05
* pattern (green): speed 100, power 40
* cut (white and grey): speed 4.2, power 100
It is well worth experimenting to make sure that the etched parts are sufficiently etched. This is hard to explain, but if you look at the plans (image above), the ball rolls on the big etched rectangle on layer 4 with layer 5 (the maze) and layer 6 on top of it. The material is meant to be 4mm, but it is often thinner (my 4mm ply is actually 3.72mm). So we have to etch at least .3mm out of one layer for the 4mm ball to roll in the space between 2 layers.