Cutting Cast Acrylic on a CNC Router

Multiple passes with the right cutter will give you an excellent edge. December 6, 2006

I cut some 3/4" (thick) x 24" (diameter) cast acrylic circles on our point-to-point machine. I had some problems - rough cutting edge and material melt. How should I set up feed and speed (rpm) for my 1/2" double spiral router bit?

Forum Responses
(CNC Forum)
From contributor G:
Make 3 passes 1/4" deep and 24.1" diameter. Use the last pass to take off .050". 300 ipm at 18000rpms. Onsrud 53-638. Play around with the feed speed - you may be able to go faster.

From contributor R:
The double spiral bit is the problem. Look at Onsrud cutters designed for cast plastic. No more melt, no more rough edges. Their catalog also has the feeds and speeds.

From contributor E:
For your material, I suggest using a single flute up/shear. The CP tool will provide you with an excellent edge finish. We (Courmatt) have had our shelves made for the upcoming IWF, with a perfect edge finish.

From the original questioner:
Thank you all - I think I got enough information to start making sample pieces.

From contributor J:
I couldn't agree more with the other contributors. You have to make sure you are using the correct tool. Please check to make sure the acrylic is not vibrating. Vacuum hold-down is one thing - vibration is the seed of an ugly edge. 3/4" thick is heavy. Use a high density, low profile sealant, and watch those tools. Give your product an edge you can be proud of.