Poor finish on ABS

[Pathonomic]

Having a problem with my ABS work stock having bits pull up as the mill passed over it.

Attachment 274050



The pictures show how it only seems to occur in one direction. It's happened on both sides of the material at various orientations at various depths of cut. For all orientations, the material pulls up when the mill moves from top to bottom. The specs of the cut:

• Bit: 0.5" 2F carbide square end mill (not sure on other mill specs, it was a pretty generic mill)
• Material: ABS (picked up from local plastic store)
• DoC: 0.005", 0.010", 0.025"
• Stepover: 1/3*diameter; 0.1667"
• Feed: 100 IPM
• Path: From center to outside, counterclockwise
• Mill direction: counterclockwise
• Held with vacuum chuck

I'm running a DIY CNC mill so it's understandable that there would be some imperfections. I had a few ideas about what was causing it, but I was hoping more experience people could help to rule some of them out maybe. Right now I'm thinking it could be:

• Spindle is misaligned some, about the Y-axis
• The cut isn't deep enough for the feedrate
• The end mill characteristics aren't suited for plastic
• I should be cutting inside-to-out clockwise

Let me know if there's anything else I'm missing.
Thanks

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[bhurts]

Try a straight flute router bit. If it's just fuzz it will only take a few seconds with a razor blade to scrape off.

Ben

[Pathonomic]

Thanks for the quick response, I've been scraping so far, but it leaves the finish slightly rougher still than mill finish. And I guess it doesn't show in the picture but the vertical-movement toolpaths leave ridges that I'd rather not have in the stock. Would a straight flute bit help with that too?

Thanks

[louieatienza]

Thanks for the quick response, I've been scraping so far, but it leaves the finish slightly rougher still than mill finish. And I guess it doesn't show in the picture but the vertical-movement toolpaths leave ridges that I'd rather not have in the stock. Would a straight flute bit help with that too?

Thanks

If you have ridges you might want to check spindle tram... You might rid of the rough spots just by that. You can also try bull endmill or endmill with a small corner radius like .020...