Cutting ABS with Onsrud tool

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ivanw
Posts: 11
Joined: Wed Apr 22, 2015 11:33 am

Cutting ABS with Onsrud tool

Post by ivanw » Mon Apr 27, 2015 10:11 am

Hi guys this is my first post here :)

Just got my Shapeoko 2 up and running a few days ago. The main reason I bought this machine is to cut ABS and acrylic. So I tried to do some research and it sounds like ABS isn't as forgiving as like plywood. Some say low very RPM to avoid melting the plastic, some say high RPM with high feed rate. According to some machinists they suggest the latter (1). I understand industrial machines are very different, so I scale down everything quite a bit and surprisingly I have some good results for the first cut:
1.jpg
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2.jpg
Chips ejected
2.jpg (371.14 KiB) Viewed 1475 times
I am pretty satisfied with the surface finish. I used the following settings:

RPM: 12000 (300W DC Spindle)
Tool: Onsrud 63-701 1/16" Solid Carbide One Flute Upcut O Flute
Step down: 0.015625 (guess I can be more aggressive)
Feed: 10 IPM (guess I can be more aggressive)
Plunge: 5 IPM

The bit is suggested by scojen from (1), and I guess it's the major factor of how smooth the cutting job is:
3.jpg
Onsrud 63-701
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It's a bit pricy ($25.83 from amazon (3)) but I tend to think better tools will actually save money in long run. I will try to cut more aggressively after I calibrate my machine and update this thread.

* However I found that I bought the wrong bit - ABS is classified as soft plastic (4), and I should really buy 63-751 (6) instead for the best results. New order made on Amazon, but the 63-701 will use useful for cutting acrylic anyway.

(1) http://www.practicalmachinist.com/vb/cn ... on-163507/
(2) http://www.cnczone.com/forums/general-m ... h-cut.html
(3) http://www.amazon.com/dp/B0020B3VLC/
(4) http://www.onsrud.com/files/pdf/OC-12-P ... atalog.pdf
(5) http://www.onsrud.com/files/pdf/2012%20 ... lastic.pdf
(6) http://www.onsrud.com/files/pdf/2012%20 ... lastic.pdf

Thanks,
-Ivan

EDITED: correct the RPM
Last edited by ivanw on Mon Apr 27, 2015 10:47 pm, edited 1 time in total.

ivanw
Posts: 11
Joined: Wed Apr 22, 2015 11:33 am

Re: Cutting ABS with Onsrud tool

Post by ivanw » Mon Apr 27, 2015 10:16 am

More pictures:
4.jpg
1/8" x 8" x 12" ABS sheet bought from eBay
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These ABS sheets will ultimately become my Car PC enclosure:
Screen Shot 2014-09-18 at 12.21.48 AM.png
Screen Shot 2014-09-18 at 12.21.48 AM.png (152.33 KiB) Viewed 1473 times

cvoinescu
Posts: 4442
Joined: Thu Jul 19, 2012 6:50 pm
Location: Camberley, UK
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Re: Cutting ABS with Onsrud tool

Post by cvoinescu » Mon Apr 27, 2015 11:45 am

That's a very good cut. Thank you for sharing your settings.

Is that really 1200 rpm on the DC spindle? It seems low (without closed-loop control, it would have next to no torque, and with closed-loop control it would probably overheat).
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

ivanw
Posts: 11
Joined: Wed Apr 22, 2015 11:33 am

Re: Cutting ABS with Onsrud tool

Post by ivanw » Mon Apr 27, 2015 10:46 pm

cvoinescu wrote:That's a very good cut. Thank you for sharing your settings.
Thank you. I am very excited with what I can do with my Shapeoko for ABS cutting. I have a delta 3D printer and because ABS can be glued so easily, I can imagine the combination of using Shapeoko (for cutting 2.5D parts) and 3d printer (for totally 3d parts) to greatly improve my efficiency on projects.
cvoinescu wrote:Is that really 1200 rpm on the DC spindle? It seems low (without closed-loop control, it would have next to no torque, and with closed-loop control it would probably overheat).
Sorry it's definitely a typo. It should be 12K rpm.

Thanks,
-Ivan

ivanw
Posts: 11
Joined: Wed Apr 22, 2015 11:33 am

Re: Cutting ABS with Onsrud tool

Post by ivanw » Wed Apr 29, 2015 6:38 am

Tried to be more be aggressive and the cut still looks okay:
output.jpg
output.jpg (307.11 KiB) Viewed 1268 times
Step down: 1/32"
Feed: 15 IPM
Plunge: 10 IPM

Didn't notice anything different from my last more conservative cut. Bit didn't get hot (I paused the job and checked it regularly). No plastic was melted. There are some tiny strings in the pocket though (I actually entered the wrong target depth for the pocket... I made it all the way through the ABS sheet). But all the edges look pretty clean and I should be able to clean those strings with a single pass of very light sanding. I think I can be even more aggressive but I am already satisfied with the current settings.

So yes, Shapeoko 2 can totally cut ABS with a reasonable feed rate and RPM, just get the right mill tool!

Thanks,
-Ivan

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