HELP - Cutting Extruded Acrylic


#1

I’m a new Glowforge Plus owner and I just tried cutting 2 different types of extruded acrylic for the first time. One is a mirrored extruded acrylic (mirrored only on one side) and the other is a translucent holographic extruded acrylic.

When I cut each of them, there are small but very visible imperfections around some of the curves and edges of each piece. I am hopeful that someone with more experience can look at the defects in these cuts and recommend manual settings that might help cut these materials better?

They are 1/8 thick acrylic sheets from Canal Plastics with clear film protection that I left on for cutting. I used the medium acrylic proof grade cutting settings.


#2

You’re supposed to remove that clear film for cutting, and I would recommend using a paper mask on the front (at a minimum) to keep from having reflection issues with the laser for placement purposes.

Paper masking on the back will help with any potential flashback as well, so it’s not a bad idea.


#3

I cut the mirrored acrylic on the back so the mirrored side was down, not facing the camera. So the alignment isn’t an issue. Do you think removing the film will help with the fracture marks I’m seeing in the pictures of my cut items?


#4

Unfortunately, the fracture marks are a response to excessive forces in the acrylic that happen when the plastic is exposed to the high heat of a laser. It happens in tight corners, where the machine will pause for a fraction of a second before proceeding…it dumps excessive heat into one spot and that weakens the plastic. I believe that other people have had good luck with annealing the acrylic (170°F in an oven for an hour) to prevent that from happening, but what I generally do is adjust the design to remove tight corners (round the design.) Other people like to use dogbones to keep those cracks from forming as well.


#5

So what we are seeing in the pics was cut face down? Looks like flashback (the beam cutting through and bouncing back off of the honeycomb tray).


#6

The gold mirror was cut with the mirror side facing down towards the honeycomb tray. The hologram acrylic is the same on both sides but the side facing down is the only side with these fractures. So maybe that does make sense that it would be flashback. Would it help to have masking underneath?


#7

Yes, having paper masking on the backside would help, if that’s what is going on.


#8

I don’t have much experience with extruded acrylic, but conventional wisdom is that it performs worse than cast when laser cutting, so bear in mind that you’re doing this on Extra Challenge Mode. :slight_smile:

Since this is requesting manual settings, I’m going to move it to Beyond the Manual.


#9

I picked up a few sheets at Blick not realizing they aren’t optimal for lazer use. When trying to use a speed and power setting that would cut through in one pass the pieces would always melt. The best luck I’ve had is using two passes. With two passes you can also keep the original plastic masking on. Not sure what my settings were in the end, currently away from my main computer.


#10

Great idea! Thank you.


#12

My settings are 2 passes at speed: 175 and power: 100.

I’ve seen from other post that the mirror might cause problems but hopefully this helps.