Flatness 1

[TheMotionGuy]

Hey guys,

Does anyone know what kind of flatness I can achieve when having Nylon 101, Delrin, or Teflon machined? Is asking 0.05 asking too much? (need to know for each material if you have experience working with them).

Thanks,

Dale

 

[MintJulep]

Over what distance?

 

[TheMotionGuy]

14"

 

[Pud]

I should think 50 thou is quite achievable.

H

http://www.tynevalleyplastics.co.uk

 

[MintJulep]

And how beefy is the part?

Delrin I know, and the others I suspect, is notorious for for having lots of residual stress in stock blanks from the casting or whatever manufacturing process.

I tried to have a helix machined out of a 1 inch delrin rod once and wound up with an unusable corkscrew because of the stress release during machining.

So the answer I think is "it depends".

 

[TheMotionGuy]

It is a 1/2" thick 14" x 14" plate of (nylon 101, delrin, or teflon). Will have shallow surface details and what not. It is going to be a vacuum plate. But i want to do it as cheap as possible, hence plastic and not metal.

 

[Pud]

I would have thought aluminium would be cheaper than plastic.
Modern CNC stuff machines it pdq.
H

http://www.tynevalleyplastics.co.uk

 

[TheMotionGuy]

Well, when I had it quoted, they wanted $1200 to do it out of stainless, and $300 for Nylon 101. I will look into aluminum tomorrow, thanks.

 

[shawnpeter]

Your mat'l specs change as rapidly as my woman's moods.

I've had similar results as MintJulep. I had some face milling done on delrin and when it was unclamped from the table it was slightly warped (measured fairly uniform before but had a visible surface curve afterward).

 

[TheMotionGuy]

We changed materials so drastically because we decided to take a different route on what we were going to provide as the end-product. But thank you for sharing your experiences with the residual stress issues with Delrin.

 

[btrueblood]

We have parts waterjet cut from 1/2" PTFE sheet, then double-disk ground to a flatness of <.005 over 12" or so. Dunno about other materials.

Teflon will creep more than the other plastics, and this can be an issue if you don't handle/ship/store the product in a way to maintain the flatness.

Have to agree that a good cast and stress-relieved aluminum plate makes much better tooling than the plastics. Google Mic-6 I think it's called.