Cutting small holes in PU sheet

Community Laser Talk
1

Hey All,

Trying to perforate small holes in 1/4” PU sheet. Approximately 85 durometer. I keep running into an issue where not all holes end up perforating through the material. I can see smoke out the bottom of the material so I am beginning to wonder if the material is closing back on itself.

I’ve tested pretty much every combination of settings, speed, power, different lens focal lengths, etc.

I am using a 60w DC tube laser. I have found that 12mm/s on a .016 diameter hole at 70% power on a 2.5” lens focused to the bottom of the workpiece (I want the hole to be smallest at the one side of the sheet). This seems to get me what I want but only 70% or so of the holes end up being big enough or clearly cut.

The machine has new mirrors and I have made sure the tube/mirrors are aligned.

I’ve played around with air assist pressure from 5psi up to 50psi.

I’m trying to figure out what other settings or setups I could try to get the rest of the holes to come through cleanly.

Any advice would be appreciated before I start losing my wits.

2

The aspect ratio for those holes seems terrible: plenty of heat deposited in a small volume of gooey material. In particular, the speed is probably limited by the overall acceleration around a small circle, so doubling the speed may not have much effect.

I’ve had good results from Dot Mode, which is available only for Ruida controllers, because it combines precise pulse duration and power with very slow motion.

This is a kiss cut through PU vinyl leaving the paper backing (more-or-less) intact:

The laser head steps a tiny distance between each pulse, which makes the layer speed setting irrelevant; the cut ran about 5 mm/s regardless of the layer speed.

Vinyl film is much thinner than your sheet, but tinkering with the Dot Mode power / duration / step size may produce a better cut around the hole.

3

Thanks for the feedback I have seen dot mode in the settings. I will tinker with it.

I have been able to run up to 21mm/s and still make it through the material. Getting the perfect amount of laser dwell is the key, too short and you won’t get through too long and it heats the material creating a melt pool.