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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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