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Cuting unknown material

Hi all,

We just got a new laser at work. It’s a ULS2.30 with a 30W laser tube in it.

I’m no expert just yet, but I went ahead and tied to cut some holes in a plastic lid. It turned out okay but I was hoping for better results. The lid is from a blue electronic project box that’s 2x4 by 1" with lid.

The problem is I don’t have this type of unknown plastic to make test cuts. So what can I do for best results?
For the record I know about the danger of some plastics that produce poisonous gases when cut. But the amount of cutting was very small and vented outside.

The attached sketch shows the setup I had.

The laser has pre-set values for ABS that I used as a starting point. With the actual thickness only a 1/16" at the point were the cuts were being done I increased the speed. The power is at 100% but the speed was changed from 3% (1/4") to 6% which I believe I went closer to 8% for 1/16". The plastic flamed up only a little at the corners and left ruff edges. The cut outs I was able to break out with force and I cleaned up the edges with a knife.

If anyone has done this type of cutting, please share any details.

Thank for any help.

Arne,

You should first verify that your optics (all mirrors and the lens) are clean, and that you have the laser focused properly on the surface of the material you’re cutting and not focused on the bed of the machine. Being out of focus by 1/4" can make a huge difference.

When using a low-powered laser tube, such as the 30W that you are using, you might see better results by using multiple passes at a slightly higher speed, rather than using a very slow speed. This could also reduce the amount of burning/flaming. Another thing you can try to help keep the part as clean as possible is to apply masking tape to the surface before cutting.

While ABS is a popular material for enclosures, you might also be working with a polycarbonate lid. You should note that while it’s safe to cut, it does not cut well. Laser-cut edges on polycarbonate will have a noticeable discoloration (yellow/brown), which is unfortunately unavoidable; the discoloration can usually be cleaned up with some sanding (or perhaps by using a dremel drill).

You might also want to consider further researching the material before proceeding. Aside from the fumes being potentially hazardous to your health, it might also be causing permanent damage to your laser cutter! (E.g. if your material contains chlorine, cutting it could produce hydrochloric acid as a biproduct, which will corrode your machine.)

I hope this information helps!

- Arthur

This is great post for me, You should also note that all Laser cutting rule materials are infrared transmitting, even opaque colors. For an IR-blocking material, you might consider ABS instead.