Female MDF mold finish

[marcinito]

What would be a best way to get nice finish of lexan face that is being formed in female MDF unsprayed mold? If spraying is a way to go what would be best paint/primer to go with ?

Plastic face has a chrome vinyl applied on back side and I'm trying to get as nice finish on face as I can get.

[JoeBean]

Water & wood glue, or thinned drywall compound, to fill the micro voids of the product. Automotive body filler works too but it's harder to rework. Then sand polish it to as nice of a finish as you can. Apply an enamel and polish it to a mirror finish with polishing compound and a buffer.

If you need a perfect finish you'll still have to polish the polycarb after. Look into chemical polishing. Some good info here:
http://bbs.homeshopmachinist.net/sho...ical+polishing

[marcinito]

Thank you JoeBean for quick response. We sprayed our molds before to acomplish better finish, but life span of these molds being exposed to heat created a problem of reworking them.
I belive beter prep of surface will help, however as always I'm always willing to learn new methods and ways of getting a job done in different way.

[JoeBean]

My experience has been primarily with 1-offs, where heat never caused excessive problems. For extensive heat applications finishing with a high heat paint may help.

[spektr]

MDF female molds are useful for short runs. trying to get life out of them is futile. If you need to run any kind of quantity of part, build real tools. MDF is made of a phenol formaldehyde glue and fine sawdust. It is porous and hygroscopic. It is also dimensionally unstable as it ages due to changes in humidity. It does cut like butter, but there are so many better things ot be using.

I'd suggest back pouring off the tools you have now, creating new tools out of a metal filled epoxy or hi temp urethane. That will live in the real world....

Oh Yeah, figure lexan hits the tool at something around 340 F. Most paints fail. High temp paints need to be post cured above that temp and the mdf wont live.

Scott.