Optimum mold finish for compression molded Viton parts...

[quizzical1]

Hi All,

We are working with a Viton GF600S material and require the best finish possible. Does anyone have any experience as to what the minimum mold finish should be (e.g. 8uIN, etc.) for the part to have the smoothest texture possible? Part thickness is .050" x .69 dia.

Also, is there a point of "dimishing returns" where going finer in finish does not produce any smoother texture on the molded part? We are considering either chroming, Aluminizing, TiN or NiCo Tef coatings to aid in release. Anyone have experience or a preference?

Thanks,

Glenn

 

[patprimmer]

Not particularly with Viton, but with thermoplastic elastomers and injection moulding the limit is usually mould release. to smooht and it wont eject.

Apart from that mirror finish is possible. I don't know the actual numbers that produce a high mirror finish, but sometimes the fillers if present limit the finish no matter what the mould finish is.

Regards
Pat
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[RubberDog]

By the experience with all the elastomers in seals, the most common is chroming.
Not for the release, but for the finishing.
Attention that you need to redo it from time to time.

The GF is a peroxide grade FKM, which is already little difficult to demold. The best is if you can work on the recipe and have it incorporation of demolding agents. We barely uses demolding agents in compression (always semi-permanent mold release) and none in injection molding.

The excessive usage of mold release can cause the reverse, and you have more mold depositions which will cause the surface defects.

What is the finishing standard on the parts? 3601 Class S?

 

[quizzical1]

Thanks Patprimmer and Cortarelli,

We're considering electro polish the molds to an 8uIN finish then Electrolyzing to eliminate mold release agent use.

As for a finish standard - what do you recommend for the best finish attainable for Viton?

Glenn