Therematron - The Case

At last I have almost completed the case for the Therematron. The process of creating this case was a test case for using the CNC router to make all the pieces of a wooden case which will have no nails or screws and is held together with glue. I wanted a process where I did not have to handle the wood apart from holding it down for cutting to pulling up the final piece. This was a trial of patiences.

Having purchased the 3040 CNC Router from BilbyCNC here in Australia I wanted to use its abilities to the maximum. I had initially purchased the unit to create front panels and printed circuit boards. I've perfected the creation of single sided printed circuit boards with a total of 9 boards now created with one of them being about A4 in size. But to extend the use of the router I thought about using it to create wooden cases.

I designed up the case in SketchUp which I've previously posted. Due to the limiting nature of the free version of SketchUp I returned to using Freehand to design the panels for the case so I would have two dimension pieces. Not ideal. So each panel was designed in Freehand but one of the disadvantages of using a 2d vector package is that it is not 3d and what I was creating was several 3d pieces of wood. 

So initially when cutting the pieces of wood I would need to cnc route one side and then flip this piece of wood over to cut away excess wood to make the tongue part of the joint. The problem was that my alignment was not accurate enough. I needed to be half a millimetre accurate for all these snug joints to work. I cut a whole case before I realised there was to much error in my work.

A rethink was needed. I had to make the pieces of box with only single sided cuts. So this is where I decided that instead of making the the piece with tongues out of one piece of wood, I would cut  grooves into the wood and use pieces of mdf a bit like dowels. I was a little worried that this method would not have enough strength to hold the box together but it has. What has possibly helped to strengthen the case is the several pieces of square aluminium tubing which will be the mounting points for the front panel.

Therematron Case without front and rear panels
The picture above is the current state of the case. Its constructed of marine ply because I happened to have some left overs in the shed. You can also see the aluminium bars where the front panel will mount. The side pieces of aluminium are angled so they are mounted to the side pieces of wood and can then also be mounted to the front panels. The nice thing about creating all the holes on the CNC router is their accuracy. So I can easily cut an angled section out for the square tubing and have it perfectly line up with the opposite side panel. For me to do this without and computer controlled router would be beyond my patiences.

Here are the diagrams out of Freehand for one of the side panels. The other panel is just mirrored.

The outside of the left panel

The atomic symbol on the side is just a retro nod to the Interociter of This Island Earth fame.

The inside of the Left Side Panel
So what is shown here is the inside of the left panel. The red outline is the outline cut of the wood. The green areas are 8mm deep routed pocket cuts and the yellow areas are 2mm deep pocket cuts. The reason the square cuts have discs in their corners is so the rounded 3.175mm end mill cutter can give me square corners for the aluminium tubing. Note that I made these discs a little larger than they needed to be so that the 3.175mm cutter cuts the line in one run instead of raising the Z axis and cutting the discs separately. This is something you learn to do with a router so that the cuts are more efficient. The yellow pockets are where the angle aluminium sits and is countersunk to 2mm so once the 2mm thick aluminium is mounted it is flush to the wood.

The holes to mount the tubing and angle aluminium are 0.5mm larger than their mate so the mating is not overly tight.

Shows the aluminium having been mounted
(note that the angle pieces are little short which is
just because that's what I had in the shed)
The front, base and top pieces of wood are simpler as they only need to join to the sides and don't have any special parts.

The case clamped together
It was quite a challenge to put glue in all the joints and place all the aluminium in at the same time.
Here you can see the MDF dowels on the base
So I've learnt that it can be done. And when I make my next case I will be able to knock one up in a day or so.

The next stage of the Therematron is to cut the front panels. This is also a new stage. I initially had reasonable success with using 0.2mm engraving bits with signbond composite panel but found that I quickly blunted them so I will trial using 0.5mm endmill bits very soon. Stay tuned.