Laser engrave on acrylic sheets

[jedizhi1 (Jedizhi)]

Hello makers,

Just want to ask if there’s a specific laser to engrave on acrylic sheets?

thanks!

[NedMan (Ned Hill)]

You will want to use a CO2 laser. UV diode lasers don’t work on clear acrylic.

[mcdanlj (Michael K Johnson)]

This is because acrylic is opaque to the far infrared light in CO2 lasers, which means it absorbs that light.

Visible light goes through acrylic. If you use colored acrylic, its colorant/dye may absorb light from a visible light laser (such as the common blue lasers) but it won’t generally engrave cleanly.

@NedMan

UV diode lasers

Actually, far ultraviolet lasers, especially UVB or UVC, ought to work with normal acrylic. But the common laser engravers are 405nm wavelength deep blue visible lasers, not UV.

Thorlabs says

Laser diodes, which are capable of converting electrical current into light, are available from Thorlabs with center wavelengths in the 375 - 2000 nm range and output powers from 1.5 mW up to 3 W.

This covers UV to near infrared with diodes.

A good set of search terms here is “acrylic transmission curves” — here is an example that shows how similar clear plastics are:

https://www.gsoptics.com/transmission-curves/

Note that there are a couple plastics there that are transparent to UVA (longest wavelength ultraviolet).

This writeup of the difference between normal acrylic and UVT acrylic shows the visible light spectrum:

[jedizhi1 (Jedizhi)]

Thanks @Nedman, will diode lasers wont work?

[NedMan (Ned Hill)]

No, see @mcdanlj 's explanation above.

[mcdanlj (Michael K Johnson)]

Just updated it to clarify UV vs blue lasers because I missed “UV” at first read.

[NedMan (Ned Hill)]

Ah, thanks for that @mcdanlj . I tend to lump these low wavelength diode lasers as “UV” lasers but as you correctly point out that’s not necessarily true.

[donkjr (Don Kleinschnitz Jr.)]

Depending on what you are trying to do you can coat acrylic to engrave a contrast with a laser diode.

This video shows practical material engraving and cutting using 15w dual diode system from NEJE:

Neje A40640 40w laser modul [unbox / review / first test] best laser modul modul i try

[HalfNormal (0.45 NACL)]

I am impressed at how the laser is able to cut through thick wood. Unfortunately the base cost is still a lot more than a good CO2 laser.

[Ranjit (Michael Skuczas)]

I seen a YouTube where a gentleman explained how he does it using a steel plate, though he did use a galvanize to start he found out it’s not such a great approach, fumes. Can’t remember the link but search on Google should have it pop up.