cheapest sheet materials for 3d milling

Hi,
I am wanting to make a silicon mould of a piece I will be milling (so that i can reproduce it)therefore the aesthetics of the original aren't important- when i've done this before with pieces that are 2d (or comprised mainly of 2d parts) i've used plywood with a little beech for any small 3d bits. As i'm sure everyone here knows, solid timber can be quite costly, just wondering if anyone has any alternative, cheaper suggestions that can hold 3d designs to a depth of about 14mm.
Thanks in advance,
Mark

Some form of hard foam? Would this work?

Machine wax, here's one supplier, there are others, http://trycut.co.uk/
It's quite expensive but there's no waste as it just remelts back to a block.
So after the initial cost each part made is essentially free

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Originally Posted by EddyCurrent

Machine wax, here's one supplier, there are others, http://trycut.co.uk/
It's quite expensive but there's no waste as it just remelts back to a block.

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Nice find. Might look at this too for 'stuff'.

There are some recipes on line for home-brewed machinable wax, one involves Paraffin Wax, old carrier bags and an old deep fat fryer, must try it some time :D

Was snooping around looking at the waxes and came across this.

http://www.collegeengineering.co.uk/...ials/testfoam/

I think these waxes and foams are a great idea to test out tool paths on a complex piece before risking it on the real thing. They are not cheap though...

Quote:

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Originally Posted by EddyCurrent

Machine wax, here's one supplier, there are others, http://trycut.co.uk/
It's quite expensive but there's no waste as it just remelts back to a block.
So after the initial cost each part made is essentially free

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That's very interesting, any thoughts on the spindle speed and feed, I have visions of melted wax everywhere!

Quote:

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Originally Posted by mark84

That's very interesting, any thoughts on the spindle speed and feed, I have visions of melted wax everywhere!

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Id guess its similar to alu but its only a guess. Perhaps ask the vendor and let us know your finding please. Also interested in this.

Whatever it takes to keep friction down and without deformation of the wax, a relatively slow spindle speed but a relatively high feed rate. ("relatively" meaning, I don't know an exact number for certain )