Material for mould

[CarbonMike]

Hi,
I need to choose material for making mould for laminating carbon composite. Mould will be machined with CNC machine from 3D ProEngineer file. I heard something about ,,synthetic wood,, or ,,woodplast,, or MDF. I need less expensive material then AL Alloy but stiff enough.

Thanks

Mike

[Unabiker]

I've made molds out of this stuff before: http://www.freemansupply.com/RenShape5440Stylin.htm

You can polish it out so that it is relatively shiney. I've used this to make molds for vacuum bagging and compression molds with nice results.

It is not very cheap, though.

[CNC Pro]

Hey Mike,
I’ve been making molds for a local composite shop; I’ve used a product called Elfoam made by
Elliott foams (www.elliottfoam.com 1-800-545-1213). It comes in different densities and standard sheets sizes of 4’*8’ up to 12” thick. I also saw an article on electroless nickel plating of foam for mold use. It looked very smooth and is supposed to give the long wear characteristics of nickel.
Of course if you’re looking to produce small quantities of parts you could just apply a resin finish over the foam.
From a cost perspective, it’s hard to beat MDF. If you go that route, I’d suggest using a double-refined MDF; it’s just a couple of bucks more that “standard” MDF and the finish quality is worth it.

[Unabiker]

How does MDF react when you put some heat to it, like if it were going to be parked in a 250F oven for 30 minutes during a post-cure?
Is it relatively stable, or does it fart out bubbles that can get trapped in the layup?

[CarbonMike]

Thanks for help guys. I will probably use MDF.

[mxtras]

RenShape is good stuff and so is impregnated mahogany.

MDF will be trouble - depending on your release and your methods. If you are sure the geometry is good and want to make a lasting mold, use something other than MDF. Otherwise, MDF will be fine for a proof mold, maybe. The 'grain' is difficult to seal. You will see the texture on your part surface.

For almost all composites a master is made and the tooling is pulled from the master. This allows to make a non-pourous mold surface from a slightly pourous master.

Scott