Cutting Acrylic

[tj989]

We are thinking about doing some acrylic working on our shop bot with the possibility of both contour cuts and pocket cuts. I am wondering what we should do to setup our machine to do these cuts easily and cleanly.

We have a Shopbot Alpha 4x8 with a Grizzly Dust remover. Should that be adequate to remove the chips?

Also, if you are cutting acrylic, could you let me know of the feed rates, spindle speeds, and cutters you are using?

Thanks

Edit: Could you let me know how think your pieces are too? Thanks again

[davidp]

Thomas

play around with the feeds and speeds, we cut a lot of 2mm to 15 mm acrylic at 75 mm / sec with a 3mm or 6mm cutter at around 10000 rpm. Use a climb cut. Experiment with your own cutters etc.

We use a CarbiTool TSPL 08S or TSPL04S. For the thicker acrylics we use multiple passes and then a clean up pass but always a climb cut. Acrylic and PVC is much easier to cut than timber but the speeds are more important to prevent the swarf from re welding onto the workpiece.

Regards

David

[jbworden]

Thomas,

When you order your acrylic make sure you ask for cast and not extruded. We use a two flute bit with straight flutes. Since we don't have a vacuum table (yet) that keeps the material from trying to climb the bit. If we have the material tied down really tight we can use an up spiral to help clear the chips out of the cut. We cut in multiple passes with the stepdown no more than 1/2 the diameter of the bit and run it at about 100 ips. I think we could go faster but I've never done the calculation for chip load so that's pretty much a guess. I was cutting yesterday and varied the RPM thru nearly the entire range on the router but it didn't seem to make any difference. The cut was still very clean and the swarf came out in little crinkly worms. We also have a Grizzly dust collection (1.5H cyclone). It does an okay job but it leaves a lot of stuff behind. One day I'll work over the dust shoe and that should help a lot. We're just using the one that came with the Shopbot.

Watch the plunge rate on acrylic. If we try to plunge too fast the router can't cut into the acrylic fast enough and the Z stepper will think it has gone farther than it has. You'll do a lot of air cutting after than because it's lost zzero. I usually keep the plunge down to about 5-10 ips to be safe.

[tj989]

Thanks for the tip guys!

If you don't mind me asking, what do you guys use for to program the shopbot?

We're at the "Fab Lab" in San Diego, which is a new one that isn't even listed on the website. But the software we use isn't very "good" So I'm not sure if it can be setup to do step cuts. I have used mastercam at school which was able to program the steps, but I'm not sure about our software.

Thanks again for the help!