advice laser etching buttons

[Stuart Orrell]

Hi Creekers,

I have been asked to help with an automotive prototype part. The client wants paint removing from a SLA model. The model is transparent and then painted black on the visible side. Removing the paint will allow light to shine through. (Like illuminated buttons).

(For those that may not know, a SLA part is a 3d built part formed by a laser firing into a vat of fluid. The fluid solidifies where the laser focuses).

I have already tried this on an existing production part (material polycarb). When the paint is removed, the finish is tarnished Polycarb - no surprise there.

However, the existing etchings on production parts are laser etched and look milky white and seem flush with the original paint.

Does anyone have experience in this area and able to offer advise on getting this same finish? I'm suspecting that there could be a reacion with the paint that causes it to change colour, rather than removing it but that's a wild guess.

Apoligies for the lenghty description.

[Scott Challoner]

Just a guess, but the underlying plastic probably expanded due to the heat of the laser and that's why it appears flush with the paint. If you look at it under magnification, you should see this. I imagine what you want to do is engrave through the paint and not hit the plastic too hard so it stays clear.
If I understand your application, I would use enough power to just get through the paint with a DPI 600 or more and lower your table out of focus by as much as 2.5mm. This helps smooth the engraved area so hopefully you won't get the milky white appearance.

HTH

[Tim Bateson]

The laser doesn't always blast away a substrate. It often only bleaches the color out - such as with anodized aluminum.

[Mike Null]

I'm currently doing some automotive products for the same purpose--that is to remove paint to allow back lighting of indicators.

It is just a matter of removing the paint. The surface will appear milky white but when you shine a light from the back the image will show through quite nicely. It is not a matter of removing plastic just getting all the paint off.

Not difficult.

[Peck Sidara]

I've done some testing on such material, specifically instrument panels for the auto industry where we're removing the black painted coating, allowing light to illuminate from behind.

You could use a C02 laser and if you fine tune the settings enough. you'll remove the black paint, exposing the core color, allowing light to shine through but the marks probably won't be as contrasting as what your customer is currently getting or what I consider to be the industry standard (contrasting white mark w/ enough material removed to illuminate properly).

Success came with using our Ytterbium Fiber laser, FiberMark. I was able to get the contrast they were looking for and ablate the paint for proper illumination.

IMO-you'll have better luck using a the 1.06 micron wavelength of light vs. 10.6 micron C02 wavelength of light.

[Stuart Orrell]

Thanks guys for your advice. Great as always!

I have been testing at 1200 dpi, so maybe overkill here affecting the heat, etc.

I'll give it another try at lower dpi's and play around with the settings.

The finish I am looking for is exactly as per Pecks description "the industry standard (contrasting white mark w/ enough material removed to illuminate properly)."

It may be that my co2 laser is not up to it. However, Mike seems to be getting what's needed, so I'll carry on testing for now.

Thanks!

[Mike Null]

My customer (a Toyota supplier) was satisfied with the co2 mark and I could not distinguish it from the sample they sent.

[Brian Robison]

Can you mask, laser, paint and weed?

[Mike Null]

There is no need to paint so no need for a mask.

[Stuart Orrell]

I just tried 600 dpi and dropped the table by about 2.5mm off focus per Scotts suggestion. I am getting much better results now, much closer to our requirements. Still not quite there but I feel like the solution is close now.

I just need more material to try now.

When I get another sample to try out, I shall continue with my investigation.

Thanks again guys! I was ready for giving up until I received your advice.