Chipbreaking POM/Delrin and similar materials?

[Kai_DK]

Hi.
Turning question.
I would like to get to know if anyone have solved the problem with chipbreaking when working with POM (maybe a tradename, but the same as Delrin)?
I have found that roughing can be done good, with a Sumitomo NS-U insert, 800m/min and feed about 1mm/rev.
However, finishing is a problem.
I use Aluminumtype inserts (like Sandvik Coromant Al-type), to make the shining finish with a low Ra-value, but chips are not breaking, and making a lot of problem further on in the production.
Have anyone found an untraditional solution?
Regrds
Kai

[msomerville]

I have not done a whole lot of work with delrin itself, but I have machined a ton of nylon. One thing I do on my lathe is run and endmill down the diameter I am turning creating a flat side to the piece. That way when I turn it I have an interupted cut that has no choice but to break.

[Kai_DK]

Oh yes, forgot to mention that trick.
It works, in any material, but its not possible to use that feature all the time, and mill can pickup a bush of chips.

[Geof]

Originally Posted by Kai_DK .... anyone have solved the problem with chipbreaking when working with POM (maybe a tradename, but the same as Delrin)?....Have anyone found an untraditional solution? Regrds Kai

What do you consider untraditional ?

I suppose stopping the machine every ten parts when machining from bar stock does not qualify.

We do quite a lot of Delrin parts on both lathe and mill and have never solved the chip problem. We do use coolant which helps a bit because at least the chips don't melt and fuse up into a big mess but we have to clear them by hand most times.

[Kai_DK]

It's excactly that problem, with stopping the machine I was hoping that someone had solved

[Oldmanandhistoy]

Has anyone tried an extractor (shop vac)? I’ve been thinking about trying it next time I have Delrin on the lathe. Only problem I can see is the hose clogging; anyone tried it?

John

[Jarwalcot]

Untraditional method you say?

Place the material in dry ice prior to machining it. This changes the materials characteristics. So, you will need to work through a couple of test runs to determine the optimal bar length:chill time to X number of parts required.

Let us know the results if you give it a try...

Good luck,

[Geof]

Originally Posted by Oldmanandhistoy Has anyone tried an extractor (shop vac)? I’ve been thinking about trying it next time I have Delrin on the lathe. Only problem I can see is the hose clogging; anyone tried it? John

I had an opposite idea to this: Mounting an air nozzle in one of the tool positions and indexing to this to blow chips off the part. Also mounting one somewhere inside the machine so the tools could be moved in front of it to get the chips blown off.

But it sounded too complicated to try in case it didn't work .

[Oldmanandhistoy]

Originally Posted by Geof I had an opposite idea to this: Mounting an air nozzle in one of the tool positions and indexing to this to blow chips off the part. Also mounting one somewhere inside the machine so the tools could be moved in front of it to get the chips blown off. But it sounded too complicated to try in case it didn't work .

Not a bad idea but then think of the mess there would be to clean up.

Geof just out of interest why aren’t you a moderator?

John

[Geof]

Originally Posted by Oldmanandhistoy Not a bad idea but then think of the mess there would be to clean up. Geof just out of interest why aren’t you a moderator? John

When you are machining Delrin or Polycarbonate there is one ***** of a mess to clean up anyway.

Why am I not a moderator? Because sometimes I like being totally immoderate .

[msomerville]

Originally Posted by Oldmanandhistoy Has anyone tried an extractor (shop vac)? I’ve been thinking about trying it next time I have Delrin on the lathe. Only problem I can see is the hose clogging; anyone tried it?

One of the shops that we do business with has a system setup like that, but he is taking long cuts on big diameters so he has something like a 1/2 wide ribbon be sucked into the tube. It works well he even stopped the cut to show me how it picks the chip right back up. His tube was about 2" in diameter so there was no clogging issues. I would think a smaller shop vac might clog but the bigger ones with the bigger hose would probably be alright.

[Oldmanandhistoy]

Originally Posted by msomerville One of the shops that we do business with has a system setup like that, but he is taking long cuts on big diameters so he has something like a 1/2 wide ribbon be sucked into the tube. It works well he even stopped the cut to show me how it picks the chip right back up. His tube was about 2" in diameter so there was no clogging issues. I would think a smaller shop vac might clog but the bigger ones with the bigger hose would probably be alright.

Thanks for that I'll give it a go

John