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Author Topic: Turning plastics  (Read 395 times)
Garyhlucas
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« on: June 03, 2017, 17:07:11 pm »

 A recent discussion on another forum brings this up as the stringy stretchy plastic chips are a chore.  So it seems like a good feature for lathe MOPs would be a chip break function for roughing. Either by pausing the feed,  or a tiny reverse of the feed which would eliminate the need for the G4 function. So you'd need to program feed increment and reverse distance, similar to a peck drill done for the same reason.
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Gary H. Lucas

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lloydsp
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« Reply #1 on: June 03, 2017, 21:01:22 pm »

Gary, that's a good idea, but it would really suck for a 'finish pass'.

Those same plastics that tend to make stringy chips also tend to 'over-cut' some (cutting a few-tenths deeper than the actual tool engagement).  Any interruption in the the feed would cause a 'snipe' where the feed stopped.

So... if such a feature were to exist, it would be smart to use it only for roughing.

I turn a lot of Acetal, so I feel your pain! <grin>

Lloyd
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Garyhlucas
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« Reply #2 on: June 03, 2017, 23:04:58 pm »

Lloyd,
I know what you mean. I was only thinking of roughing. I just did a PVC part in our 10" SouthBend and it took a long time because of chip wrapping as I took a 4" diameter down to about 3" and then bored it through to 2". We mounted a lathe chuck on the spindle of the CNC to turn small  plastic parts. We gave up because chip wrapping was so bad. We went back to spiral milling which is much slower, but you can walk away for 20 minutes and do other work.
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Gary H. Lucas

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stevehuckss396
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« Reply #3 on: June 06, 2017, 01:13:04 am »

I don't turn a lot of plastic but when I do I just catch the beginning of the string with the shop vac. It just disappears into the vac and never wraps around the part. It works every time and if you take the time to mount the hose you could walk away between parts.
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Garyhlucas
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« Reply #4 on: June 06, 2017, 02:05:59 am »

We've tried that, as I used to do this all time. On the parts we do now the strand doesn't pick up from pass to pass.
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Gary H. Lucas

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 http://a-little-business.blogspot.com/
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