Most of my current arduino projects have had pretty ad-hoc enclosures. You can go a long way with a Jiffy box and a Dremel. Then I bought an embossing label maker to add some text to my boxes (and, OK, everything else — when you have an embossing label maker everything starts to look like an unlabeled thing). My most recent work though has been a pure human interface device. There’s a lot of buttons and switches and displays, and one of my goals for it was to create an enclosure that looked absolutely stunning.
I’ve eventually settled on building backlit panels from laser-etched acrylic, based on a technique I picked up from the MyCockpit forum for simpit builders. Flight sim geek communities are a great resource for learning how to build nice control panels, who knew? I’ve been refining my process to get decent results with a single pass through the laser cutter in my local maker space.
- Acrylic sheet. I use 3mm opal translucent sheet. A square metre cost me $80, and now I have more acrylic than I’ll ever need. At current estimates, including all the failed panels I’ve cut, a half metre is still very generous.
- Spray paint. I’m using a matt grey primer that claimed to be suitable for plastics. It’s been working well so far.
It’ll also need very fine grit sandpaper and masking tape.
Prepare the acrylic
I cut my sheets in to 250mm square sections. For each section, remove the backing paper from one side and spend a minute or so sanding the face very fine wet and dry paper to give the paint a surface to adhere to. Then apply three coats of paint. At the end you’ll have finished panels ready to cut. And, if you’re like me, some freshly painted furniture to boot.
Design your panel
This part was pretty incredibly frustrating for me. I started out working with LibreCAD, a reasonably full-featured 2D CAD drawing program. That made drawing precise outlines and holes for cutting a breeze, but it’s not particularly good at working with text. I wanted real truetype fonts on my panels, and getting LibreCAD to import font faces in a form it can work with ended up beyond me.
My current workflow is to draw text that I want added in Inkscape. Then convert the text to paths, and export it as a DXF file. That file can then be imported to LibreCAD as a block and placed in my etching layer. The software driving my laser cutter doesn’t like the DXF generated by LibreCAD though, so there’s another step importing the final file in to Inkscape to collapse layers, remove dimensions and save a file that can be downloaded to the laser.
That… mostly works. Sometimes the text paths LibreCAD saves just don’t generate easily filled objects and the laser gets confused and it all goes pearshaped. Right now I’m still loading the text blocks in to LibreCAD but only using them as a visual guide. When doing final prep for cutting I still replace the text on the panel in Inkscape, to ensure a happy etching experience.
Cut the panel
I did a dummy cut with holes and a combination of angular and round lettering in all of the sizes I needed. I was using a couple of different sized fonts, and it took me a little while tweaking settings to get a result that looked sharp across the board.
When cutting panels, I order the job so that all of the engraving is first, and the cut for the outline is last. Even though the cutting bed is stationary, warps in the perspex can lead to the panel shifting slightly after the outline is cut.
I learned the hard way that getting excited and removing the paper from the back of the perspex at this point is not a great idea.
The panel is finished, but now has raw edges that look ugly and leak light when it’s backlit. Apply masking tape to the front side, along the edges (leaving it overhang but not stuck to the side of the panel), and covering holes. Then place it face down and apply another couple of coats of paint along the edges.
I’m still working on getting this part right. Previous attempts without the masking tape led to paint bleeding under the edge, leading to visible paint drops or the newspaper I had under the panel sticking to the face. Initial tests with the tape look pretty good though.
Once the paint has dried, the backing paper for the panel can be removed and components mounted.
I’m still working on the best way to backlight these panels. Simply lighting up the inside of the enclosure looks good, but seems a bit bland to my mind. I want to start experimenting with with individually lit panels, possibly by countersinking LEDs in to the back of the panel. Mostly because I’m keen on flickering panels, and changing panel backlight colour. But pretty pleased with the overall look so far.