Cutting Acrylic - Help me stop melting pls

Hi again, I’m back with another stupid nooby question!

I know this subject has been discussed a few times, and I read each thread - I came out with a few different differing suggestions. I have 5mm acrylic that I’m trying to cut a dust shoe design out of for my spindle, and in the end I used the 1/16" 2F Fish Tail Upcut bit from the Carving Bit Starter Kit and the debris melted and clumped up on the bit. I broke it off trying to remove it unfortunately, but I have a couple more since I bought every bit set from Inventables :sunglasses:

The settings were as follows:

1/16", 2x flute fishtail upcut bit @ 18200 RPM (#2 on DeWalt 611)

40in/min (1016mm) feedrate cutting @ 1mm depth passes

I’m guessing I need to slow down the RPMs and use a single flute 1/8" bit, but what about the feedrate? People suggested both higher and lower rates - the one that made sense to me was a high feedrate with very shallow depth passes to get in and out very quickly without letting things heat up too much.

Can anyone recommend me some settings (preferably using any of the Inventables bits available)? I needs me a dust shoe…

I just cut a new vacuum plate for my Suckit dust boot today.
I used 1/4" acrylic,
1/8 2 flute upcut
75 IPM
12 passes
.02 DOC
Not a problem, super nice clean cut with minimal fuzz

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Usually if it is melting you IPM is too slow.

Try a one flute spiral bit.


From what I’ve always read, 1 flute upcut, and speed up. 40ipm is too slow.

Could also be extruded acrylic instead of cast. Extruded does not cut well with rotary bits; can be done but I’ve had far more issues with extruded acrylic.

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basically melting = heat = too much friction.

So: cut fast and shallow
RPM at lowest setting, feedrate high. 1-flute bits help, but 2-flute is still very much acceptable. DOC less aggressive.

My latest settings were:
70 ipm
1/16" 2-flute
0.01" stepdown
Makita at lowest rpm


I hate acrylic mainly because we build robots. We use polycarbonate exclusively. Much tougher and machines better. Single flute Onsrud 3/16 for cut out and pockets most of the time, 1/8" for helical drills. Fast and shallow or linear milling, trochoilal for thick deep cuts.


I hadn’t even thought of that - I did a little research and it turns out that this Optix brand from Home Depot I’m using is extruded -_-

Thanks for pointing that out…I’ll do a little more research, but I’m guessing I’ll be doing about 1000 passes on it at a micrometer interval…

i’d start with 1/4th of what you did and see if that works :sunglasses:

1/4th of what exactly?

I dunno if anyone here could take a look at my gcode file and tell me if it’s too much stress on the bit or generating too much heat for the ceramic, but the machining time has come out to over 2 hours to cut all the pieces.

This is the gcode file here for my dust shoe design: (2.0 MB)

It’s meant to fit right over the DeWalt 611 and wrap the spindle at the top and bottom for support.

Here’s the device fitted to the spindle and mount:
And here’s all the parts laid out for cutting:

Should I take regular rests and let the bit cool down? I was thinking of spraying some CO2 on it while it’s working to cool it down once in a while, but maybe that’s a poor idea for the carbide bit? I dunno, I just know that I don’t want a repeat of before.

Any thoughts greatly appreciated.

Also, the settings in the gcode file for the machine are as follows (using your suggestions):

16000 (#1) RPM


75”/min —> 1905 mm/min

1/16 2F bit

0.01" —> 0.254 mm depth pass

You would be better off with a bigger bit, 1/8" would be alot better.

Those should be okay

So I can just run this non-stop ?

Why not? 2hrs is nothing. People here have done 20plus carves. Just be around just in case. A forum will only get you so far. Only 1 way to know

I will change it in fusion tomorrow - hopefully the time goes down too. I just wanted to use the 1/16" because I have a couple drill points that size and I didn’t want to change the bit, but that’s really lazy of me. I’ll do an 1/8" and drill the holes manually after.

OK thank you very much - I will see what happens tomorrow I suppose