Foam Mold for use with Vacuum

tomcat · Post by **tomcat** » Fri Jul 20, 2012 9:41 am

hmmm, that seems very interesting interesting.
It would save a lot of work and fiberglass/epoxy. Nice idea with the plastic packing tape and mold release; will have to remember that one; I also guess it's very easy to just replace the tape once you pull the skis form the mold and you end up with a nice, clean mold all over again.

nfaust · Post by **nfaust** » Fri Jul 20, 2012 9:46 am

With the skateboard, I had epoxy-laden fiber right on the packaging tape, and I definitely "lost" (ie - broke off) some of the mold when I was removing the board. It wasn't a big deal for me as I was only making one.

I guess it depends on how tightly you control your epoxy. If you're going to have alot of overspill, I would assume you run the risk of breaking off some of the mold.

Perhaps a thin sheet of AL or melamanine (something that will flex to the contours) over the top of the mold would be a better option if you're planning on reusing the mold.

twizzstyle · Post by **twizzstyle** » Fri Jul 20, 2012 10:51 am

There's no way you'll get even remotely flat bases if you're just laying a ski straight onto foam. You absolutely need to sheet it with something (sheet metal, some kind of stiff-ish plastic sheet, or formica might work)

tomcat · Post by **tomcat** » Fri Jul 20, 2012 12:04 pm

You're absolutely right about it twizzstyle; I think I just got too excited in the moment thinking I could make things even more simple.

I'll have to think about what material to use so it can easily take the contour of the mold, but still offer enough support to get the bases flat.
I guess it's a lot easier to just use screws if one has wood underneath...

Maybe the initial idea about using fiberglass wasn't that bad as it seems that way there isn't a problem to get it to the shape of the mold.

Do you think that it would be enough just to cover the fiberglass surface with a plastic sheath that doesn't bond to epoxy, or is that just asking to get the skis glued to the mold?

Also, would there be any problem with base flatness from the texture of the fiberglass?

twizzstyle · Post by **twizzstyle** » Fri Jul 20, 2012 12:32 pm

Whatever the surface of your mold looks like, will transfer to your base. If you have a tiny speck of dust, you'll get a big dimple in your base. If it's a rough fiberglass texture, that will show up on your base too. It can all be sanded out, but it's not ideal.

It'd be cheaper to just get some formica and glue that to the foam, it will form to the shape no problem. As for how to prevent things from sticking, that's what mold release wax and parchment paper are for!

tomcat · Post by **tomcat** » Fri Jul 20, 2012 12:40 pm

I'll try to look for some formica; never worked with it yet.
At first I was thinking about using some 0.3mm aluminum sheet, but I don't really think I can bend it precisely enough to the mold shape.
Good to know that the mold surface has to be as close to perfect as I can get it; since you said that even some dust can cause base flatness problems...

Thanks for the advice again

bcohen5055 · Post by **bcohen5055** » Sat Jul 21, 2012 1:48 pm

Foam works great as a mold for vacuum bagging, I have some photos showing a part I made entirely out of styrofoam molds (not skis) it worked great. What has been mentioned about surface finish is absolutely true. There is an amazing polyester based surfacing primer called duratec that will produce a perfect mirror finish on the mold after a bit of buffing. They sell a styrofoam safe version that works great but requires a spray gun with a large nozzle.

I'll post some photos of the process tomorrow

I've been thinking about possibly making skis this way, I'd use 2 pieces of MDF with pink insulation foam set in-between for the mold profile, rough cut with a hot-wire and finish with a large sanding block, not too different from how core profiling with a router works. Then Duratec and bag the skis, here in Colorado I can pull about 20" Hg of vacuum which should fine.

nfaust · Post by **nfaust** » Mon Jul 23, 2012 5:13 am

twizzstyle wrote:It'd be cheaper to just get some formica and glue that to the foam, it will form to the shape no problem. As for how to prevent things from sticking, that's what mold release wax and parchment paper are for!

Agreed, that sounds like the easiest/cheapest method.

hegan · Post by **hegan** » Mon Apr 28, 2014 1:43 pm

Anyone ever tried using a router on Polyshield or the pink Insulation Board? If so how did it turn out?

twizzstyle · Post by **twizzstyle** » Mon Apr 28, 2014 5:33 pm

I've CNC'd stuff out of pink foam on my CNC router (which just uses a Porter Cable router spindle). Worked ok, but if the speed/feed rate wasn't right it would melt, rather than cut.

MadRussian · Post by **MadRussian** » Tue Apr 29, 2014 3:31 am

Pink foam not the best product to use. Better would be yellow foam or ISO board similar but not the same what you can buy in Home Depot. Also it's available in 2 pound density and 4 pound density (4 pound density fairly expensive).2lb you can buy at roofing supply company they may or may not carry 4lb. 4lb can be purchased from insulation supplier this will be special order material

hegan · Post by **hegan** » Tue Apr 29, 2014 4:34 am

Well I found some old pink installation in my basement and did a test run on the CNC. The results was nice it made a nice smooth cut with no melting. Going to try making my mold with that and see it goes, if it doesn't work I'm only out 15 bucks.

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Foam Mold for use with Vacuum