I am intrigued by the possibility of casting polymer components for metal working machines at home. I have quite a bit of experience in using epoxy for laminating but not much in casting. So I decided to do some research into the area. I looked at the big guys such as http://www.itwpolymercastings.com/

In theory it is relatively simple in that you cast a mixture of epoxy resin, metal fillers and Quartz aggregate into a mould at room temperature. Metal reinforcement will be required in certain areas including inserts for screws etc. The tricky bit is selecting the right resin, fillers and aggregate. The normal resin used for laminating isn't any good because it sets too quickly and causes exothermic runaway when large volumes set i.e. the depth of the resin is more than a few millimeters. Just try leaving a pot of epoxy to set and you will see what I mean.

I have been in contact with a local producer of epoxy (http://www.crosslinktech.com/ ) and they think they have a suitable product that is used to make moulds. This is a blend of epoxy and aluminum power. This has a much longer cure time so the heat buildup is less. However, even this you can only cure to a depth of about 4" at a time. The trick is to pour a little in, let it get to the point it is just about to gel and then pour more in. Once it is fully poured, an elevated post cure is recommended to get the full mechanical strength of the epoxy.

To make the mould, it should be possible to use a split wood structure which is sealed and a suitable release agent applied. For one-offs it wouldn't even mater if the mould was destroyed. For bigger runs, a GRP mould or steel mould could be made.

At the moment, I am trying to locate a suitable source for quartz aggregate. If I can find one, I am going to do some small scale experiments. There are still lots of unanswered questions:

1) What is the best type of aggregate

2) How to compact the mixture to avoid air bubbles

3) What is the best design/material for structural re-enforcements