New to the Shapeoko 3

Hi everyone,

I did some research on how to find the proper feed rate, etc for different materials and end mills, but it was a LOT of information to take in and due to my lack of experience with CNC Routers, I wasn’t sure if I was doing the calculations correctly. So I could use some help on recommended settings. What values should I put for the parameters shown below if I wanted to machine polycarbonate and Acetal plastics (with a thickness of 1.5mm to 2mm)? I plan to do test cuts with the #102 first (to remove most of the material), then the #282 (to make the 90 degree corners).

end-mill settings

I would really appreciate your help. And any advice on how I can determine these parameters for future projects would be appreciated!

The builtin feeds and speeds are conservative but work well. Did you try using the predefined databases for the tools you want to use. You could compare what the default F&S are to what you came up with. The default F&S are conservative but you can increase them by editing the tool for a one time fix or make a customer database with the tool and set your own F&S.

There is no one answer to F&S. It is trial and error to test out the F&S. However the default F&S for a Shapeoko and the species you are working are a good starting point to modify from.

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Thank you, that really helps. I’ll just start with the default values for the end mills then.

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Are those above the defaults? I’d recommend using a faster feed and a lower depth of cut on polycarbonate.
I ran about 2500mm/min with a 1.5mm DOC while testing in this thread.

If you’re feeling conservative, reduce the DOC, not the feedrate.

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They weren’t the default values. I’ll start with the default values and may test your parameters as well.

As Neil says, move fast with plastics to stop them melting so go shallow instead of slow to start with. Use dust extraction if you can, helps the finish a lot and reduces the horrid mess.

For many plastics it’s worth finding a single flute or even an “O flute” cutter (that’s Oh not zero) as getting the chips out effectively is key to a decent finish. They’re not expensive in small sizes.


Gotcha gotcha, some good advice here. Thank you everyone!