What material to use for fiberglass lay-ups???

[animuL]

This may not be the exact right forum for this but I am working on a project that in the end I will be producing a few fiberglass "shells". The fiberglass will be molded into shape over a tool that I will cut on the CNC. My first inclination is to glue some MDF pieces together and machine them down to the shape of the mold. The thing is these are quite large pieces with depths of up to 4" that could easily take hours to produce just one and I am needing about 10 of them. I would prefer to use something even easier to cut than MDF, some sort of machinable foam I suppose so long as its compatible with the fiberglass resin. MDF, depending on the depth, I can cut usually at 150-400 ipm. If I could get something easier to cut I can go up to 1200 ipm. If anyone knows of a material that may be suitable for this please let me know.

Thanks in advance!

[High Seas]

Foam - Mate! Cuts FAST and has lost of cheap replacements. f your first time use some cheap Blue Foam (Home Store - of choice) glued up and cut to make sure its how/what you want. Then you could invest in REN Tooling board - or do the seal and layup on the blue for a real test. BTW the foam makes a BIG MESS so MASK-UP!
You can "protect the foam" with a variety of means; tape, acrylic house paint, paper and white glue, etc, etc.
Be sure and test if your foam is compatible with epoxy -- or polyester resin -- find one that works and press on. You didn't say what the product is to be used for - so either epoxy or polyester "may" do the job.
Jim

[keebler303]

The blue foam, pink foam, white "styrofoam" and maybe others will not work with vinylester or polyester resins. They contain large amounts of styrene, which, surprise!, dissolves polystyrene foam. Your mold would disappear like pouring gas in a styrofoam cup.

The polystyrene foam is the cheapest, but you have to use the more expensive epoxy resin so it does not melt.

If you use polyurethane foam, common for industrial roofing insulation, you can use any of the popular resins without concern.

Depending on the quality of the parts you need to make, most foam molds are coated with a few layers of glass and resin and then body worked into shape, just like working on a car.

duratec (www.duratec1.com) has some really nice products for making a nice mold.

After your mold is all good, make sure to wax it good and then make some parts.

Matt