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Making laser-cut backlit control panels

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.

Materials

  • 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

Freshly painted panels, ready to cut.

Freshly painted pan­els, ready to cut.

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

Tuning etching settings for good clear lettering

Tun­ing etch­ing set­tings for good clear let­ter­ing

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.

Final painting

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.

My most recent finished panel.

My most recent fin­ished pan­el.

Next steps

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.

 

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