Deburring a Chamfer in Engineering Plastics

[Rekd™]

I've got parts made from platics like torlon, vespel and simitron etc. Many of them have similar features where there is a pocket with a chamfer around the edge of the pocket. When doing the chamfer/wall/top it creates burrs on the edges of the chamfer that are difficult to remove. They simply roll over the edge instead of cutting off.

 

Here's a profile of one of the parts with arrows pointing to where the burrs are...

 

 

I'd like to be able to deburr them on the machine but they just keep rolling out of hte way. Aside from sharp tooling is there a technique that I can use to quickly/efficiently get these burrs off?

 

Thanks!

[Joe788]

I think the best approach would be to get some sort of custom super duper razor sharp diamond tool to cut the chamfer, and avoid the deburring altogether. We had OK luck with Onsrud on some polycarbonate nightmare parts.

[Guest CNC Apps Guy 1]

I've cut torlon before... the ONLY tools that I was able to get to do a decent job were diamond coated. Do you guys have to heat treat it as well?

[Rekd™]

I'm going to try climb cutting the top surface .0005 or less after the chamfer is in to push the burr into the top surface (see below).

 

 

Not sure what I'm going to do about the inside wall. James, we don't do that here but I have suggested it months ago. As you can see the shapes we do are very complex and warping is an issue so heat treating may be the best bet. Have you done it?

[Guest CNC Apps Guy 1]

We sent them out for Heat Treat... That was back in 1994... I seem to recall 450 I don't know how long though. Our parts were used in a Jet Fuel Application. That stuff was so tough on tools, we had no choice but to go to diamond. We were only getting like 10 parts on a .625 Solid Carbide drill. Once we went to diamond, I want to say we were able to at least triple that for that particular tool and the cost was only about 50% more.

[Rekd™]

We are already using diamond tooling. I know there are different methods for different plastics and there is a certain rate you have to get up to temp, stay at temp, then come down to room temp and that affects how it works.

[Matthew Hajicek - Singularity]

I'm going to try climb cutting the top surface...

 

You might be able to do something similar on the sidewall by using a downcut endmill to push the bur down into the work.

[Philcott]

Matt, could you get a custom tool ground to not only cut the chamfer but to skim across the top and side with maybe 1 or 2 degrees of clearance? Inside corners might be an issue.

[Rekd™]

Thanks Phil, I considered that but there are too many different variations in our designs for this to be feasible.

 

Matt, that's genius! Thank you.

[Bruce Caulley]

Rekd,

Like Matt said, down cut, or even straight edge tools will reduce the burr. I actually spent the first 10 years of my trade machining only plastics. When they still made woodworking routers from HSS a good clean chamfer could be had by doing a light conventional cut with a straight flute HSS tool.

 

HTH

 

Bruce

[Rekd™]

Thanks Bruce.

 

I've got our supplier looking for the downcut end mills. I think that's the best approach considering if we deburr them by hand we will eliminate our ability to measure the +-.001 tolerances often put on these chamfers. For the life of me I can't imagine why we would need that kind of tolerance but it is what it is.

 

The beginning of my career back in the early '80s was with plastics, mostly acrylics and nylons. I don't ever remember having the grade of engineering plastics we have now (maybe they were in existence and I just never heard of them) and we never had to worry about these kinds of tolerances.

 

Will let you know how things turn out.

[LancoUSA]

2L Inc. makes chamfer Mills that I use all the time when trying top do critical chamfers. The tip is guranteed to .01" diamter. you would have to have them coated though.