Hi folks,
wanted to cut 1mm thick EPDM rubber. This worked in the end:
- 100% laser power with 10W laser
- Cutting speed 80-100 mm/s
- 1-2 passes
- Watch the process! Lots of sparks and flames, I’d say high risk of fire!
- Well ventilated space required
I first tried at 300 mm/s, and succeeded, but only in 8 passes. It seems that heat builds up relatively slowly, so going too fast has not much effect. At 100 mm/s I think I got through in 1 pass, but to be on the safe side I let a second pass run through before I stopped the job. I guess at 80 mm/s you’re on the safe side in one pass.
There were lots of sparks flying around, and they glow for long enough to fall off the print bed. Also, small flames shoot up. So make sure you closely watch the process and be ready to kill a fire.
The smell is awful, so make sure you have good ventilation. However, according to a lot of internet research, the cutting is safe, it does not contain chlorine, but only carbon and hydrogen, but if the fumes are healthy to inhale I cannot say - my guess is: No 
The result is very sooty, so next time I’ll do this, I’ll wear gloves when handling the result. I rinsed it off with a lot of water and had rather black fingers afterwards.
The cut is clean, except for where it directly had contact to the laser platform grid. Perhaps another pass would have burnt away that also. The cut is relatively broad, a lot of material gets burned away, so if you need real precision, add a few fractions of a mm to your shape.
Next time I need something from EPDM, I will consider using classical scissors - it’s a messy thing to laser that stuff
Here’s a photo (the thing is 5 cm left to right), where you can see the effect of the grid platform:
