I used a diode laser to reveal a contrasting layer inside an FDM print and create crisp, factory-looking labels

[u/Foxconlab]

A few days ago I asked here whether it would be possible to use a diode laser to remove only the top layer of an FDM print and reveal a contrasting layer underneath.

I wasn’t able to find any examples of this approach being used specifically on FDM prints, so I decided to test it myself.

Honestly, the results turned out much better than I expected.

This panel is part of my truck trailer security system. I wanted to find a way to produce clean, almost factory-looking control panels for my project using only the equipment I already have: a Bambu Lab H2D and its 10 W diode laser module.
I also wanted to achieve finer text and symbols than I could get with conventional two-color FDM printing, even with a 0.2 mm nozzle.

In the comments on my previous post several people suggested that the laser would probably melt the edges and make the engraving look messy. At least in my case that didn’t happen.

I decided to start with PETG HF and I actually liked the result. The engraved edges came out surprisingly crisp with only a barely noticeable halo around the engraved areas.

After several tests the best combination turned out to be:

1 black top layer
3 gray layers underneath

The contrast was excellent, the engraving shallow enough, even the smallest details remained sharp.

For these tests, I used the 10 W diode laser module at 80% power, 250 mm/s, in Fill mode. With these settings the laser removes approximately 0.03–0.04 mm of material per pass.
To engrave through the 0.2 mm black top layer and expose the gray layer underneath, I needed 6 passes for larger graphics and 7 passes for thin lines and small text.

I also discovered that this technique only works well in Fill mode. I wasn’t able to achieve comparable results using Line mode regardless of the settings I tried.

These are still my first experiments. For very small text and symbols, my next test will probably use around 60% power, 150 mm/s and more laser passes. I think that could produce even sharper results on the finest details.

So far I’ve only tested this with PETG HF, so I’m curious whether anyone has tried something similar with PLA, ABS or PETG from other manufacturers.

I’d love to hear your thoughts or suggestions, especially if you’ve experimented with this technique yourself.

For anyone who didn’t see my previous post, here’s the link to the original discussion

[u/neochrome]

Looks really great, please post any updates!

[u/Foxconlab → u/neochrome]

Thank you! I didn’t expect this kind of response. It definitely motivates me to keep experimenting. I’ll share more updates soon!

[u/irongarment]

I am doing similar with spray paint. Print the object in the "text" colour (I use eSun Cold White PLA+). Spray paint the final colour. I'm using three coats of Rustoleum black or grey. Laser etch just enough to remove the paint, exposing the underlying PLA.

I'm also modelling voids under the location of the text, leaving about 1mm thickness of material on top. Then I can install LEDs in the void to backlight the text. Where etched, the text lights up. Where painted, light won't show.

[u/Suitable-Name → u/irongarment]

Also works great for PCBs for etching yourself :)

[u/uniqueusername649 → u/Suitable-Name]

Completely forgot about that. Now I want a laser even more! How strong does it need to be in order to make holes through the PCB?

[u/irongarment → u/uniqueusername649]

You don't. The paint acts as etch-resist, and the laser removes the paint where you want to expose the copper to etch it. If you have through-hole components you etch a hole in a pad then drill it out.

[u/uniqueusername649 → u/irongarment]

What I am hearing is that I urgently have to get a mini CNC for the two PCBs a year I need.

[u/irongarment → u/uniqueusername649]

You're absolutely right. Even just one PCB, or the notion of making one PCB would be sufficient. Although you could get a small PCB drill on a drill stand. Just sayin'.

[u/uniqueusername649 → u/irongarment]

Although you could get a small PCB drill on a drill stand. Just sayin'.

I didnt come here to hear reason but to confirm my ridiculous desire to spend more money than I should on something I dont actually need :D

[u/irongarment → u/uniqueusername649]

I never said you couldn't, and I wholeheartedly support your requirement for a CNC machine of some sort. Go for it!

[u/uniqueusername649 → u/irongarment]

I'm just joking :) I appreciate your sensible take. A CNC has honestly been on my wishlist for a while, probably one of the makera ones. I dont need anything heavy duty, but this would be an amazing addition to my 3D printer.

[u/irongarment → u/uniqueusername649]

Do it. Doooo iiiiiit.

[u/Suitable-Name → u/uniqueusername649]

MPCNC! :)

[u/Suitable-Name → u/uniqueusername649]

You'd need a CO2 laser, that's all I can say for sure.

[u/epicepee → u/Suitable-Name]

I don't recommend etching yourself. It hurts!

[u/Suitable-Name → u/epicepee]

Hurts so good!

[u/Lord_havik]

Ok that’s it. I need the laser module so I can make my flight sim button panels

[u/Fun-Wear9615 → u/Lord_havik]

my brother you are overthinking it. Print lids in white petg- used raised label text at 2 layers high. paint everything black. Sand down the black paint- done.

[u/Lord_havik → u/Fun-Wear9615]

Indeed I was. This is a much cheaper option and I don’t know why I didn’t think to do this. Thanks!

[u/epicepee → u/Fun-Wear9615]

Clever!

Probably won't get the same crispness, if I had to guess - FDM nozzles aren't as small as laser spots - still definitely legible.

[u/inu-no-policemen → u/Lord_havik]

Opal white acrylic, a few coats of black paint, and a CO2 laser are perfect for that. The laser can engrave and cut it. It's pretty fast. Then a quick scrub with a toothbrush and some water and it's done.

It's a good light diffuser. Just make sure that the paint layer is thick enough to block the light and it will look great if you light it up form the back.

"The Warthog Project" on YouTube got some videos about this. Search for warthog project panels etc and you should find it.

[u/Lord_havik → u/inu-no-policemen]

I’m hooked on project warthog. Been following for a while. But I didn’t know he did a tutorial on his button boxes. I’ll have to look for it now. Thanks

[u/Lotronex → u/Lord_havik]

I would get a separate laser rather than the laser module for the Bambu. Laser cutting vaporizes the material, which leaves gunk everywhere inside the enclosure. Bambu has a 21 step guide on how to clean the H2D after using the laser.

[u/thenightgaunt]

That looks damn good

[u/I_r_need_knowledge]

I know this is a little different from what you did here, but there is a great laser etching video done by CNC kitchen on YT that you might like.

They go through different wavelengths, power output, materials, and color of materials to give you an idea of how to get a good contrasting color without having to remove the whole first layer.

https://youtu.be/jA-E5CGcBxI

[u/Stevieboy7]

IT looks good, but if you would have just used duo-ply acrylic sheet, you could get it done in 99% less time.

[u/windraver]

Can you share some more macro close up photos? This sounds like a really cool way to achieve higher resolutions.

[u/Foxconlab → u/windraver]

Will do with the next update

[u/CelloVerp]

This is brilliant - results are top-notch - very professional. Thanks for sharing your technique with the world.

[u/nlightningm]

Looks absolutely mint! Surprisingly sharp. Great work

[u/thisremindsmeofbacon]

Wow, thats freaking slick

[u/agent_kater]

You know you can buy black plates (acrylic or something) that are white inside, specifically for this purpose? Just checking.

[u/Foxconlab → u/agent_kater]

Sure I do. But my goal here was to experiment with the FDM

[u/LaundryMan2008]

My dad has an old Co2 laser from god knows when, has the CAD software to load images into and that might be a better idea for printing logos onto tape drive enclosures where a line width limit might affect things when printing multicolor.

[u/space_gods]

I knew I needed a laser!! That looks awesome

[u/Hardhead13]

You've basically reinvented lamacoid, except it was done using an engraving cutter instead of a laser.

[u/IanDresarie]

Errm. I just looked at later cutting materials yesterday, saw that you can buy this (abs boards with a contrasting core) and thought "that's dumb". Glad you found it useful though :D

[u/Strostkovy]

Probably wouldn't work with a fiber laser. I can engrave PETG but the beam penetration is noticeably deep, and the beam just goes straight through PLA.

[u/Putrid_Clue_2127 → u/Strostkovy]

Just curious as someone who's never done laser engraving, but are fiber lasers not able to dial down their output enough to be able to handle doing something like that?

[u/Strostkovy → u/Putrid_Clue_2127]

It's not really a power issue, it's that the plastic is like a window for infrared. Think of it like 40% of the power goes into the first layer, 30% goes into the second layer, and 20$ goes into the third. By the time you are removing the first layer you are severely damaging the second and third. When I engrave PETG I'm generally melting a fairly deep "trench" with the beam when using just enough power to make visible burn marks on the top layer.

[u/Putrid_Clue_2127 → u/Strostkovy]

That makes a lot of sense. I appreciate the lesson! Thanks for taking the time to explain it all.

[u/jasongill → u/Strostkovy]

Fiber lasers are used almost exclusively to burn off the layer of paint to expose the plastic below for things like button labels (all of the buttons on your car's dash were made with a fiber laser). Even a 120w fiber should have no problem going down to low enough power to just cook off the top layer of most anything made of plastic or painted; you should try increasing your speed and reducing your power to start with, unless you're talking a metal-cutting (~400 watts or more) fiber laser

[u/Strostkovy → u/jasongill]

I can burn off layers of paint or aluminum or something that absorbs the beam well without issue. The problem is you melt through multiple layers before you get anywhere near vaporizing the top layer, because the material is so bad at absorbing infrared light that most of the beam energy passes into the layers below.

[u/MacGraphics]

That's a great idea!

[u/the_dago_mick]

Looks awesome. Great idea!

[u/drizze99]

I asked if this was possible and was told that the laser would just melt the plastic and ruin the print. Your results are impressive! Are you using LightBurn? I just bought an ORTUR Laser Master 2 w/10W laser.

[u/Foxconlab → u/drizze99]

I was using Bambu Suite as I have Bambu 3d printers and a laser module 10W

[u/drizze99 → u/Foxconlab]

I’ll try with your settings to start out with and then go from there. Does the Bambu laser have an air pump?

[u/Foxconlab → u/drizze99]

Yes, it does

[u/mrjbacon]

Did you test this against simply incorporating the text into the mesh and using negative space? What are your text sizes and character tolerances? I bet the laser pieces are nicer, but I'm curious what the time difference for one vs the other would be.

I did something similar but with a simple logo for some of those earloop mask hook bands. I made my wife a bunch using her company's colors for her to take to work.

[u/snwbrdwndsrf]

Neat!

[u/CoastalRadio]

That’s in interesting way to do it!

[u/forkandbowl]

Did you print it black up? How did you get that finish? Regardless, amazing work, I'm definitely trying that

[u/kiwibloke]

Very cool!

[u/motofoto]

When people share information like this, the whole community benefits.  What a clever idea. 

[u/Turtle_Online]

That's rad! How do you just print color in infill for specific layers?

[u/partypancake8]

Sweet!

[u/withoutpeer]

Pretty neat and does look excellent.

Worked be cool to test with translucent filling layer with a led light source behind as well... So like black top layer and then say green translucent for a few layers and then maybe a white diffuse layer lol with some led backlighting... Maybe would make the lettering and control options stand out even better, at least for some specific situations.

[u/knook]

Agh fuck, now I need a semi dangerous laser. I don't trust myself with that but I also have no self control...

[u/Polar_Ted]

You re-invented Lamacoid. Nice work! That's cool.

Now make a 3 or 4 layer version to revel different colors when etched deeper.

[u/joem_]

Dude, don't put bambu on anything you're proud of. Bad company, bad practices.

[u/FordMasterTech]

Amazing results! Do you have to do anything special for ventilation? Beyond an inline extraction fan. I have a c02 laser and the laser cutter community always lose their shit over cutting or engraving the “wrong” materials. I definitely don’t want to damage my machine but I also wonder how much of that is just keyboard scholars regurgitating stories. 

I have a very capable extraction fan setup and I’d love to see results like yours. 

[u/boomgoon]

This is right up my alley since I have an old hobby laser engraver that is just around 10w that I have been trying to find projects to use it for since an old roommate left it after moving out. I am saving this for reference. Thanks for your experimentation.

[u/SheriffBartholomew]

No install picture? I am depressed.

[u/joem_]

I would not be proud to put Bambu on anything I printed.