Sign in to follow this  
balnh

Glass filled peek

Recommended Posts

Any one machine this before? I have and though it was pretty stable. I scrapped a 1400$ sheet because it twisted up when I decked the first operation down. Any opinions?

Share this post


Link to post
Share on other sites

I've machined lots of PEEK. Do not let heat build up. What did you use to machine the first side? A facemill generates too much heat. The inserts are in contact with the material too long. You are better off using a 1/2" endmill, and performing a "parallel spiral" around the outside, towards the center. This spreads the heat out.

 

Coolant if you can. We were doing biomedical devices, so no contamination was allowed. We used air blast instead. Use a small depth of cut, and a smaller radial step over, with a higher chip load. Make sure you use a sharp endmill. Check the grind, and replace them often. The glass in the PEEK will wear your tools like crazy. Be aware of that. Once the edge goes, it will "push" the material, and generate a lot of heat.

  • Like 1

Share this post


Link to post
Share on other sites

We machine PEEK, mostly on manual machines. Sharp HSS cutters and flood with coolant.

Share this post


Link to post
Share on other sites

Thanks for replying, after rereading my post i realized just how bad my grammar was. A couple of cocktails will do that to me! Yes I did use a face mill. A shear hog to be exact, I suspected that that could be my issue. This is an optical manifold of some sort so coolant is ok. Most GF peek we machine is around 2in sq so we never really experience twisting with this stuff. This part in particular is 8 in long hence why I was face milling which I will rethink that approach. I have good quality aluminum and mills I was running at 400 sFM with a pretty good chip load for my milling ops. Thanks again for the tips.

Share this post


Link to post
Share on other sites

As mentioned in the links that Calnet posted, diamond coated will give you the best tool life. Aluminum tools would be OK, but not the best for your application. How wide is the part? Sometimes clamping in a vise will cause the material to bow, and it will spring back when released. We used to have good luck with using double sided tape to hold the parts when machining to thickness. It was enough clamping force that the part wouldn't go flying, but also wouldn't cause the part to bow when released. We basically used a putty knife to get under the edges when prying the parts loose. As Rekd mentioned, HSS cutters work very well when machining PEEK, as they tend to hold sharpness longer than carbide.

 

Harvey Tool makes some nice endmills with "plastic" specific cutting geometry. If your endmills for aluminum don't work out, you might give these a try. The amorphous diamond coating can be had for not too much money, which is really the way to go if you cut a lot of this stuff. The tool life will be 10-50 times what you'll get from an uncoated endmill...

Share this post


Link to post
Share on other sites

Thanks Colin, I'll look into those. The part is roughIy 8 x 2.5 x .75. only have 3 pcs.i was holding in a vise and planning to rough/rough break pressure after roughing and go back and finish machine. I really think the face mill is really what did it.

Share this post


Link to post
Share on other sites

amorphous diamond coated endmills for the strategies mentioned above. they're not cheap, but they're not near as expensive as they sound. cvd coatings are too thick therefore reducing the sharpness of the cutting edges.

 

example:

 

http://www.harveytool.com/cms/CoatingsChart_16.aspx

 

XjIY5J4.png

Share this post


Link to post
Share on other sites

I looked at my Harvey catalog after reading some of these posts. They aren't to bad price wise. I roughed with a 3 flute .5 endmill on both sides. It twisted .01 or so. Was able to true it up because I left material this time. Took a little longer than I wanted but for a prototype it'll do.

  • Like 1

Share this post


Link to post
Share on other sites

Hahaha.... haha... haaaaaaa... glass filled PEEK sucks to machine. I did the same damn thing my first shot at machining it, used a 1-1/2" AB shear hog for facing and turned the part into a frigging potato chip once it came out of the vise.

 

Everyone has had good suggestions so far, skip around a lot so you're not concentrating heat anywhere, sharp (pos rake, radial relief) tools work well, but better find something with a good coating, since that glass will destroy uncoated tools. Rough and finish in separate ops, reduce clamping pressure to absolute minimum- if you're going to do it in a vise all in one shot, at least put in a M00 and re-clamp with as little pressure as you can get away with. About the only thing I can add, is that you might allow the parts to just kinda sit in a warm place after roughing to allow the plastic to relax a bit. A lot of plastics will stress relieve at room temperature if you give them time.

  • Like 1

Share this post


Link to post
Share on other sites

Yup this stuff kills tools. I Am limping by, next time its a Harvey diamond coated tool. I ended up just doing a bunch of flips so far results have been ok.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.

Join us!

eMastercam - your online source for all things Mastercam.

Together, we are the strongest Mastercam community on the web with over 56,000 members, and our online store offers a wide selection of training materials for all applications and skill levels.

Follow us