Making Backlit Panels Laser vs CNC Engraving

[goldenfab]

I have a customer that came to me wanting some avionics back light panels. He is wanting me to machine the front panel out of acrylic or poly carbonate. His idea is to paint and then laser engrave to illuminate text(I don't have a laser setup). This would be prototype and maybe small run production. I know a guy that has a laser but is not interested in taking on work and said its tricky to get the paint to burn off and not damage the plastic. I heard you could sandblast away the paint using a mask but I think this is going to be troublesome with small lettering.

-Am I going to get good results using an engraving bit on my CNC mill (I only have a 4k spindle so its going to be slow going but it should not be too big of an issue for small quantities)?
-Should I recommend acrylic or poly carbonate?
-Any paint suggestions?
-Are there other processes I should consider?

 

[DDoug]

I think you need to work up some samples.

Is paint gonna stick to lexan ?

 

[Scottl]

Burning paint off cleanly with a laser is often a multi-pass deal even on metal. Plastic substrate would be even slower.

I would think a laminated label might be more effective, or silk screening over plastic. There are companies that do both quite well and can make a durable product even in small quantities.

Silk screening in particular lends itself very well to low volume and stencils are easy to photo-reproduce from computer artwork.

 

[RyanT]

You aren't necessarily concerned about cutting too deep since the laser will leave an attractive frosted finish which could be desirable for backlighting. I'd probably paint/engrave the back for protection.

Some types of paint will turn into gooey burnt gunk instead of vaporizing. Stick to acrylic if its going into a laser.

Raster engraving acrylic is very slow, other options might be better.

 

[John Welden]

Here you go: Done..

Inventables: 2 color reverse engravable Acrylic

I'm sure just about any sign shop could make the parts you want.

 

[John Welden]

If *edgelit*, that material, due to the coating, will basically absorb all the light in a short distance as it travels down the material. If just an opening in a transparent material is needed, any painted acrylic, pc or other clear plastic can be used, or cut vinyl (which would leave the smooth surface undisturbed), and yes about any sigh shop, or someone with a laser engraver can do it. An edge-lit light guide with any complexity/size is a different problem.

The op asked for backlit.

 

[Mooner]

If laser engraving, use Acrylic only... Polycarbonate does not cut cleanly with a CO2 laser (burns / melts / smells nasty) and can release benzene (carcinogenic) or cyanide (poisonous) gasses.

 

[goldenfab]

I think you need to work up some samples.

Is paint gonna stick to lexan ?

I don't know. I'm hoping for some advise on this.

Inventables: 2 color reverse engravable Acrylic

I'm sure just about any sign shop could make the parts you want.

Cool I'll check into this. Thanks for sharing.

 

[MJR7]

i once made an overlay for an updated instrument panel using polycarbonate. i believe it was .187" or .250" thick but memory fails. aircraft was an antique grumman amphib that we completely restored. some instruments, mainly engine ones, had no internal lighting and we didn't want to clutter up the look of our modern panel with stand off lighting. the overlay of course, matched the panel layout and i cut chamfers on the backsides of certain instrument holes so as to allow light to pass thru to those instruments needing illumination. lexan presented no issues with paint. i used white deltron and painted both sides of the panel, two coats on the rear side and several on the front side. i then painted the rear side black and the front side a color the customer requested. we used aircraft style cylindrical lights that passed thru the overlay and screwed into sockets placed where needed to both fasten the overlay to the instrument panel and also allow light to travel within the overlay. of course, the backside of the overlay instrument hole chamfers and fastening holes in the overlay were left unpainted. the lights had caps or heads on them with rubber seals and were made in such a way as to allow finger tightening. all of the placarding was done by a very skilled local engraver using the standard mechanical engraving equipment of the day. engraving depth was thru the topcoat into the white deltron making sure to not reach the clear lexan. when the panel was lighted, the placarding was easily viewed since it was all lit up from the light traveling within the lexan and the instruments needing illumination looked like they were internally lit. this amphib had extensive breaker panels, throttles, mixture controls, flap controls, etc. all forward and rearward overhead in the cockpit. all of these panels were made the same way and all labeling/placarding was internally illuminated thru the overlays.

 

[MaxPrairie]

Find someone with a laser willing to do it and raster the lettering on. Acrylic cuts really nice in the laser.

 

[surplusjohn]

I have done this with silk screen ing. Easy. Lexan 8020 is a graphic arts film intended for this. Membrane switches are made this way. Plexi works too. Cut film works also and offers some effects not available with silkscreen. Resolution is greater than you may guess but not as fine as silkscreen. I know this is done with ink jet also requires a 6 color head so to dispense a pigmented white blocking layer. I question the sharpness.

 

[OnePerfectTool]

I have a customer that came to me wanting some avionics back light panels. He is wanting me to machine the front panel out of acrylic or poly carbonate. His idea is to paint and then laser engrave to illuminate text(I don't have a laser setup). This would be prototype and maybe small run production. I know a guy that has a laser but is not interested in taking on work and said its tricky to get the paint to burn off and not damage the plastic. I heard you could sandblast away the paint using a mask but I think this is going to be troublesome with small lettering.

-Am I going to get good results using an engraving bit on my CNC mill (I only have a 4k spindle so its going to be slow going but it should not be too big of an issue for small quantities)?
-Should I recommend acrylic or poly carbonate?
-Any paint suggestions?
-Are there other processes I should consider?

You are welcome to call me. Our company specializes in Bomb Mask manufacturing, as such laser engraving will be no problem.

We do Boeing/Northrop/Government sized jobs and we do Mom/Pop sized jobs... Do not worry about limited production-every customer gets spoiled at our factories.

Stephen G. Elder
Chief Operations Officer
Precision Innovation, LLC
Black Ops
(951) 515-6029

 

[Aykfc]

Where in Arizona are you? I'm in Scottsdale and we do rotary engraving but there is a guy down the street from us who has a laser.

 

[goldenfab]

I'm in Dewey, its outside of Prescott. My customer has yet to get me a final design to quote. If its not something I can do in house I'm thinking it may be better for him to go with a one stop shop for this need.

Thanks everyone for the feedback.

 

[goldenfab]

After a lot of persistence from my customer wanting me to make this happen I figured out a way. The first prototype I painted poly-carbonate with automotive paint and CNC engraved lettering through the paint with a .01" end mill. The results were quite good actually and the back lighting was excellent but there was not enough definition without back lighting.

I found a guy with a laser that was willing to work with me and we figured out a process. Took a fair amount of experimenting with different paint layups and laser settings. I used cast acrylic sheet, several coats of white paint and just enough black paint to cover the white. The black paint was lasered off to reveal the white and presto, the back lighting is even working. I did a clear coat after the laser work. My customer was very happy with the results, I have a second order I am working on now and am expecting more in the future.

 

[Monarchist]

I have a customer that came to me wanting some avionics back light panels. He is wanting me to machine the front panel out of acrylic or poly carbonate. His idea is to paint and then laser engrave to illuminate text(I don't have a laser setup). This would be prototype and maybe small run production. I know a guy that has a laser but is not interested in taking on work and said its tricky to get the paint to burn off and not damage the plastic. I heard you could sandblast away the paint using a mask but I think this is going to be troublesome with small lettering.

-Am I going to get good results using an engraving bit on my CNC mill (I only have a 4k spindle so its going to be slow going but it should not be too big of an issue for small quantities)?
-Should I recommend acrylic or poly carbonate?
-Any paint suggestions?
-Are there other processes I should consider?

Done "many such" for prototype 'tronics.

Easy-peasy is to do the art, "however", on clear Mylar then contact print a 1:1 scale negative (or "positive") with ordinary photographic film.

Mount that behind your acrylic or Polycarb, add a layer (or several) of coloured film(s) back of the clear legends, light it up, and DONE.

Only "machining" is to drill holes cleanly for switches & c.

See "paper drill" - easily DIY'ed for uber-clean cuts in thin materials.

 

[goldenfab]

I thought I would update with my success after a long time coming. I ended up machining acrylic to shape. I shot the panels with a white then black automotive base coat paint. Another member on here Brian (Lamb Tool Works) lasered off the black for the text. I then shot it with an automotive clear coat. After a lot of trial and error we got the process dialed in.

 

[isaac338]

Those look awesome.

 

[mountie]

I'd be curious to see these lit up. Nice work!

 

[thermite]

-Are there other processes I should consider?

Cheap and actually rather attractive way for a hundred years has been to make up the art by printer, hand lettering, wax transfer, later Pee Cee print onto ignorant white paper for a "master'.

And then.. contact print - handy if you knew a photolithographer - onto sheet film of the sort our 14" Roberston through the wall darkroom camera used to make negatives and positives for burning plates for sheet-offset lithographic printing presses.

We'd do these "backwards" so the labels around switches and dials all read "right" when the tough mylar backing was the fingernail-scratch working side, more fragile emulsion side sandwiched against thin opal or milky acrylic that distributed the backlighting. Photo "trade" was again tapped for thin but intense coloured "filter" films where colours were needed - whole panel, or selectively.

If no need of through-lighting, we'd use "metalphoto", and that, too, comes in colours now.

Resolution and great complexity were scary good at "no extra cost", volume production silly fast and cheap - we are talking one SHOT and done photography, after all, so even a rasterized laser-beam printer has to run hard to beat the processing time and CNC pushing a cutter might never if the panel was at all complex as to text and numbers, worse had lots of radial lines around dials to do.

End product had NO resemblance to print and laminate DIY at all. Very "factory" professional looking, rather. First glance, it was presumed to be flat-finished anodized 'loominum. Until the backlights were dialed-up in a darkened ground control room.

It was good enough and durable enough for NASA, COMSAT, NOAA, some other Fed agencies whose initials don't even have names. Replacements for scratched panels were in the envelope with the rest of the docs or invoice. Equipment generally went obsolete and off to scrap before they were ever needed.

Avionics march to their own sets of regs, but those are wotever they are.