As far as I can see online, EVA foam seems to be laser-safe, and the Dallas Maker Space has it listed as a safe material for their lasers, but I couldn’t find it in our wiki of listed materials.
Would it be okay to cut/engrave EVA foam on Asmbly’s lasers?
Yes it’s “safe”, but the laser can’t ever form a thermal lance in foam. The cut depth is then limited by the optics depth of focus, and more power makes very little difference.
A stock 2" lens dof can cleanly cut about 1/2" of foam, and the edge will have some bevel to it. It is possible to go deeper but there may be a lot of melting.
A 4" lens- the longest commonly available (more or less) could do about 1" foam. I do have a 4" but I have not played with it yet, it would need a bit of specific tubing to match a different air assist fitting size which shouldn’t be a big deal.
I think I’d recommend CNC over the laser if you had no issue with the bit’s radius making those inside-corner fillets. A sharp 1/8" o-flute would do it easily. If possible, the rare downcut o-flute would probably do the best.
I wouldn’t recommend CNC, I would recommend a hot knife. You can make a setup similar to a bandsaw and follow a pattern cut out of plywood on the laser
For now, I’m just looking to engrave a design into the foam, rather than cutting through it. So if I’m understanding correctly, it sounds like engraving a shallow design would be fine, but cutting through it (or engraving deeper designs) would be better off on the CNC machine or with a hot knife.
Does that sound about right? And would any particular one of the Asmbly lasers be better (or worse) for this than the others?
It’s safe and the materials are cheap so you may as well give it a try.
Seems like it works pretty well, these jobs look clean
Tarkin would probably do a bit better than Dorian with its stock lens.
The 4" lens that would make a big difference in ultimate cut depth in foam is something I only have for Tarkin. But this would take a bit of work to try out.
I looked on the wiki for safe materials. I couldn’t find if this on the banned list. I am wanting to cut Nitrile (Buna-N) sheets. I don’t think it contains chlorine. Let me know if I’m wrong on the chlorine front and if it is banned?
EVA and nitrile (NBR, n-buna) cut very well. Over 1/2" benefits from a 4" lens. Cutting 1" is slow and has poor wall quality with the standard 2"
I cut 2.75" dia 1" thick and got a very straight wall. By naked eye it looked perfectly straight, calipers only showed a slight deviation
Harbor Freight “puzzle” floor fatigue mats are a cheap source of big pieces of EVA material. However, warning- the pieces have very poor QC on thickness. Like 11mm-13mm.
The colorful thin, stiff craft foam sheets are EVA. Many are self-adhesive. Check the adhesive sheet for chlorine via Beilstein test
These IS a flexible foam made from PVC that looks and feels very similar to NBR. I believe it sometimes used in black weatherstripping foam with a self-adhesive face but I’m not sure
When in doubt, always do the Beilstein test with copper wire to test for chlorine before putting in the laser
I’m cutting 1/16". Do you any speed recommendations?
I’m going to be cutting some 1/16" inch in the future too. Looking forward to hearing how it turns out for you!
Self-adhesive EVA foam of about that thickness is already in Tarkin’s library
I’m thinking of cutting it tomorrow afternoon. Would you be available to meet tomorrow afternoon to help with the laser? I haven’t used it in a while. I have some scrap we can test with prior to final cutting?
I used Dorian. I cut at 40% speed. I can’t remember if the speed setting is percent or mm/s. The cut was a bit sooty. I cleaned the mirrors with Danny’s blessing post my cut. I don’t know how dirty the mirrors were prior to me cutting. I went home and used some dish soap to wash off my cuts. Also the smell is awesome.