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.
Step 2: If you don't have a laser cutter
Q. Can I make this without a laser cutter?
A. Yes! Megamoonman made one (see comments)
Q. Can I print out the plans and glue them onto the wood to help?
A. Yes, follow the instructions to make the plans, then see the instructions below.
Q. I don't have a CAD program/can't run the software - can I still make it?
A. Yes, please PM me with your wood thickness and I'll make the plans for you.
The plans for making by hand
It's the same process as for the laser cutter, but after you've made the final CAD plans, you print them out to scale. To do this, please check the instructions on step1: Cut your pieces. Regarding printing, with QCad, you can export as a png. So you just need to get the resolution right so when you print you are getting the right dimensions. The dimensions for each slice are 140x100mm.
Step 3: Tips
Take your time between layers. There is not much tolerance in the design for mistakes. A mistake with glue will stop the mechanism from working and you'll never be able to open your box! Don't forget the bearing before you glue on the top layer!
Sand all the pieces
Sand the tops and bottoms of all the pieces to make sure they glue well. Especially sand the moving parts of the mechanisms to make sure they slide well.
Align the pieces
The important places to align are the hinge slots and the catch slot. Make sure these are as aligned as possible (use the hinges and catch to help). Any misalignment at the edges can be sanded off afterwards. Any misalignment in the hinges or catch hole will result in a difficult to open or close box.
To help with the instructions the layers are numbered on the drawing and if possible on the parts themselves. The bottom layer is number 1 and the top is 8. Layers 1, 6 and 8 aren't marked with numbers because they all have patterns on them that you'd see after assembly. Layer 1 is the bottom (maze pattern on the back and hinge slots), layer 6 is the one with the etched maze and website url on, layer 8 is the top (maze pattern on the back, no hinge slots).
Step 5: Preparation
1/- sand the pieces shown
2/- make sure the holes in the hinges are 4mm, so the rod fits well
3/- check the catch is a tight fit in layer 7, otherwise sand it a little
4/- check the hinges are a tight fit in layer 7, but a sliding fit in all the other layers.
Step 6: Layer 1 (bottom) and 2.
Step 7: Check mechanism etching
If they get stuck then you need to check:
1/- the etched rectangles on layer 2 are deep enough (use sandpaper or a dremel to deepen them)
2/- that the sliding pieces are nice and smooth enough (sand them more)
Check again, and when you're happy we can move on to gluing layer 3.
Step 8: Gluing layer 3 onto 2
Step 9: Clean layer 3 and test again.
Then assemble the mechanism as you did earlier, and with layer 4 on top, check everything is still fine.
Step 10: Assemble hinges
Step 11: Glue layer 4 to 3
Now the hinges are in place it's hard to weight it down over the whole box. So I put the box on the edge of the table, use a weight for the larger part of the box, and a bunch of clamps for the hinge edge. See photos.
Step 12: Check etch on layer 4
This is really important to test, because there isn't a nice way of fixing it after you've glued layer 5 on!
If the ball doesn't move easily, remove more material from layer 4. I use a dremel. Ideally you won't have to do this because you'll have got the etch settings right on your laser cutter.
Solve the maze and check the button and catch slider still work. They can get stuck with excess glue, but it's fine if you keep testing them out from time to time.
Step 13: Maze layer
Step 15: Add the magnet
Then with the ball stuck next to the magnet, put layer 6 on top and check that you can free the ball from the magnet with a shake. If not, try packing the magnet out a bit with some waste material.
Make sure you can free the ball from the magnet with a knock or a shake before gluing on layer 6!
Step 16: Glue layer 6 to 5
Then glue on layer 5, then place layer 6 on top, using the hinges and the catch to help alignment. Weight it down and leave while we assemble the lid.
Step 17: Glue layer 7 and 8: making the lid
Leave for 5 minutes.
Step 19: Sand the edges of the box
Check that the box closes properly at the hinge end. Sometimes the hinges can be a little too long (see photo).
Step 21: Glue the lid
Step 22: Catch adjustment
Very carefully, start removing material from the the lower edge of the catch slot, trying it to see if the box locks. Press the button then close the box. Lift the lid a few millimetres and then release the button. As you push the lid closed fully, you should hear a click as the catch slider slides home.