Laser-cutting a spacer for the MEGAphone prototype

Together with my students we have continued to make progress on the prototype MEGAphone. I've spoken previously about the current state off the PCB, which as a first revision has a few corrections and bodge-fixes required. This means we have some funny lumps and bumps on it.  Also, we know we need to lift the screen 2mm off the PCB because the red LEDs are too close to each other. So I decided to make a laser-cut spacer to lift the screen. Actually, I will make a set of laser-cut layers that I will stack on top of each other to hold all the top-side parts in place, mainly the screen and buttons and speaker.  This will suffice as a quick-and-dirty case for the prototype, since there is little point making a more sophisticated case for a one-of.

I spent a couple of hours with a ruler and the PCB to work out where all the holes in the plastic spacer should be, and was ready to hit the laser cutter. However, caution says one should test first, before cutting plastic, so I did several test runs just cutting a sheet of paper. Here is the laser cutter doing its thing. Sorry for the poor quality images, I only had my phone as camera, and its camera is getting a bit sad these days.

This turned out to be a great strategy, as I could layer the paper over the PCB, and check the fit of all the cut-outs and holes:

There were quite a few little fiddly bits to get right, as well as some insights from the paper templates that were helpful. For example, the very thin bridge between the buttons I have resting the hole here and the collection of bodges was clearly too thin to work in the plastic:

That was fairly easily fixed with a bit of creative line drawing:

Then a bit more fit testing with the buttons in place:

It's starting to look right :)

Then it was finally time to cut the template from clear 2mm thick acrylic, lay it in place, confident that it would fit, and put the screen and buttons in place so that I could see how it would look:

For a quick-and-dirty one-off this is lookinig pretty nice, I think.  Next step is to cut the layer that will go on top of this, and hold the buttons in place with smaller holes only big enough for the plastic parts, like the blue joy pad here.  It will also hold the rear of the screen in position.  Then another layer will go on top of that, that will have the screen cut out big enough for the black frame around it, and slightly smaller holes again, so that the joypad and fire buttons can't fall out.  I might jet do that one in beige, as I think that will look really nice.  Then I will probably put a couple of clear strips down either side of the screen, so that the screen itself can't fall out, and that will be the top-side of the prototype case.

I'll then repeat much the same process for the rear-side, so that there is an enclosed compartment for the battery.  I'll likely use some spacers bushes on the rear-side, so that I don't need to have too many layers.  Three should be enough, so that the battery is safely held in place.  Then the whole thing will be held together with some screws that go through several 3mm holes that will be present in all the laser-cut sheets, and that line up with matching holes in the PCB.