LaserUser.com Forum (formerly RDWorksLab)

I've used up a lot of material trying to dial in my process. Laser is an 80W CO2. Material is Rowmark 1/16" UltraGrave acrylic.

The engraving process leaves a residue of white substrate on the colored surface that soapy water (the manufacturer's recommendation) doesn't clean off. Vinegar solution and isopropyl alcohol don't clean it off very well either. Paint thinner and acetone do except a) that takes some of the ink off and b) that loosened ink ends up in the white engraved area so it's not white anymore.

When I run without the compressed air on it looks great. Seems to me though that's a bad idea.

Are there tips that can be shared from those who've dialed in their engraving of 2-ply acrylic for signage?

Thanks.

Acetone will damage the acrylic, which I'm surprised you haven't discovered. I could be incorrect in that assessment. I think denatured alcohol might also be a bad idea.

On the plus side, the soapy water should be applied prior to using the laser. Before I learned to turn down the volume of air, I used dish detergent and water applied with a brush to the work surface. The air flow blew away the soapy water, but the residue was not a problem in that area.

Another aspect of this method is that you can apply the soapy water mixture and let it dry or care little if it dries, as the soapy layer will wash away with water and take the deposits with it.

Regarding "without compressed air" comment; it is recommended to install a flow valve to allow you to turn the air pressure (volume) down while cutting acrylic. You'd want a pressure level sufficient to keep anything from swimming upstream to the lens but not so much that it blasts acrylic residue. It seems counterintuitive, but it works for single ply and will most likely do well with the multi-layer sign material.

When acrylic is exposed to the IR laser, it transitions directly to a vapor (it does not become liquid first). That vapor condenses on cooler surfaces, as you might expect. Or it is carried away in the airstream of the extraction fan. To clean the residue, you need a solvent that will dissolve acrylic. That, as you've stated, is problematic since you're trying to clean acrylic deposits off of a sheet of acrylic.

So, laminar flow extraction will help a little*. Probably so will turning down the airflow from your air assist, as suggested. This could affect cutting depth if the acrylic vapor builds up in the "canyon" where you are cutting and absorbs the laser energy. For deep cuts, you need the air assist to blow the vapor out of the way. You don't want the vapor condensing inside the nozzle or on the lens, so you want at least a LITTLE bit of air assist.

The other common option is to mask the surface of the material being cut. Either leave the paper or thin-film plastic masking in place, and then peel it (and the residue off) after you're done. The alternate way of doing this is by painting the material with liquid soap before lasering, and then wash the soap (and the residue) off after you're done.

* but where is the condensed acrylic going to end up? Probably on the blades of the fan or the interior of the ducting! I doubt it will make it all the way out of the building before condensing.

If you use a gloopy mix of glycerine based soap (just liquified enough to be applied by paintbrush - add water until it is) (Other soap may be possible) applied in a thin even coat will collect the vaporised acrylic which can then easily be washed off. The coating needs to be evenly applied otherwise etching quality may be affected and if missing an area will allow the condensation of vapour on bare acrylic.

when cutting / etching wood masking tape (not overlapped if more than one strip used) prevents staining of uncut unetched areas with resinous gunk from the wood. etching may need more power/slower speeds. You then have the fun of removing all the slivers of tape!

If you look at Russ' videos where he is developing his Ultimate Air Assist [ or is it super ultimate by now?] he explains how you want minimal air assist when engraving [not going thru the material] but need strong air assist for cutting, to blow the debris thru the cut [clean it out]. I use an auxiliary fan to blow across the surface to move the vapors off the material, BTW.

Question.

If you leave the thin-film plastic masking in place, it becomes pretty labor intensive to remove it, especially from the many letters with islands (such as in O). Is there a better technique for removal than to have someone sit with an X-acto knife?

The plastic mask gets laser welded to the substrate as you have found. I always remove it and replace with paper mask that is used in our industry as application tape. That removes better and if you are having problems, water or the citrus adhesive removers like googone will take it off. I also use it to get off the residue if the masking does not hold. IPA [isopropyl alcoh] will make regular acrylic craze and crack from the stress areas along the cuts, most engraving plastics are impact modified acrylic which does not seem to mind IPA. Testing is your friend. Mr. Clean erasers are also very handy for cleaning up plastics.

Genes application tape or tac paper is my go to choice, easy to apply, simple to remove, I find it so handy to prevent residue and as a mask for infill.

The liquid soap version is cheaper and does also work well for residue cleaning.

Yes, I'm discovering it's best to remove the protective film and apply a masking tape. The tape I have leaves too much residue. Please clarify what is meant by "application tape" and "tac paper". When I search I find too much a variety of hits.

Thank you, this is very helpful.

https://www.amazon.com/Vinyl-Ease-Trans ... 79&sr=8-15

Something similar to this- you want paper, not clear- which is plastic. We use R-Tape 4075 here.