Help on Plastics Finish

[JWayman]

Hello,

I don't have much experience with plastics, so I am looking for advice.

I have a part machined from a piece of polycarbonate. I want the surface finish to be good enough that it looks clear, not translucent - almost glass-like.

How do I specify that finish on a drawing? I imagine I need a symbol to machine it all over, but what roughness value corresponds to the kind of finish I am referring to?

Thanks for your help.

Cheers,

John

[nrollins]

John,



Machining PC will leave the surface (and the part) "frosted" and thus
translucent - not transparent. The methods for getting the machined surface
back to a transparent state involve either reflowing the surface (with
chemical or heat) or high polish. Much cheaper results can be achieved with
a clear coat of spray paint - but this will not be a perfectly clear - nor
smooth - finished surface and it will not be as durable. This latter method
I have used a lot with SLA parts that need to appear as PC or glass. It
does give a really nice looking "clear" part. But it is far from
"optically" clear. I do not have direct experience with refinishing
machined PC to a polished condition.



So, depending on your actual needs, you have a few options. I would call
the vendor(s) and talk with them to see what they recommend. I would also
call and talk to various prototype shops to see what they would recommend
(here's a good one that I've used: Empire Prototype

[mlocascio]

John Wayman,



I don't think that you can specify that as a "roughness." It would be best
to prescribe it as an operation. It would be best if you put that kind of
requirement in a note.



Michael P. Locascio