I'm working on some CNC cut foam patterns, and after some advise on which products/methods to use to get a suitably surfaced pattern for taking the mould...

The surface isn't perfectly smooth, with many small pockets from the machining process - see attached image (slightly worse in places)

My original plan - (and have ordered these bits) was to use your epoxy coating resin with glass bead & silica and then brush/spray onto the surface - do you think that will be sandable to a suitable surface finish? should I be looking at adding some 163g woven glass over the part? These are largish parts for car bodywork...

Many Thanks,
James

Hi James,

Thanks for your post. Finishing a foam pattern up to a high gloss ready for pattern making is something we discussed in reasonable detail in this thread:

http://www.talkcomposites.com/56/Foam-Pattern-to-a-Gloss-Finish

Please take a look but if you have any other questions then feel free to post back into that thread.

All the best, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Thanks Matt, I did have a quick read of that thread and it wasn't clear on whether I should be coating with glass or just adding a pattern coat, (for filling the foam grain and for strength)


I'll give it a go with what I've got, and perhaps if it won't fill the imperfections i'll coat with glass....

James

Hi James,

If you're considering scrimming with glass first (which I think you should) then do it first! - If you put a decent finish on using just a gel finish and then decide you need a glass scrim cloth (usually to add strength to the pattern) then you'll spoil the finish of the pattern with the glass and have to then resurface that with filled resin/gel.

Single layer of 160g glass and epoxy resin straight onto your pattern. Cure it off, give it a quick flat

--Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Thanks very much

One other question,

Would you still use the epoxy coating resin for skinning with 163g - or something else?

James

Hi James,

Yes, the Epoxy Coating Resin is perfect for pattern finishing. I'd say it's the best of our resins for this application. You can mix in some microballoons as well, if you wanted to make it more sandable.

--Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

Great, have ordered enough bits to do it...

can I lay up the skin by hand or would I need to vacuum bag the whole part?

Thanks again,
James

By hand would be the way to go when skinning a pattern like this. You actually want it to be resin rich so that you've got some resin to sand into so hand laminating is the right choice.

--Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

OK great, will let you know how I get on! Thanks again