Fiberglass molds for rotomolding?

[rotomy]

Hello everyone,

I have heard many times about people using composite/fiberglass molds to produce short runs of plastic rotational molded products.

I am wondering if anyone on here knows of some ideas, or can give me some instructions/ideas on how to do this.

So far all I have been able to pick up is to use high temperature vinylester resin and to make sure that no air bubbles are trapped during the layup.

Surely there must be more to it then that? A special high temperature or conductive gel-coat?

Is there an optimal wall thickness of the mold? FRP doesnt conduct heat very well after-all, but too thin and the mold would be far too brittle and weak.

Ok thats where I'm at, if anyone has had experience in this and could give me a little help I'd be so grateful!

Cheers!

[Will Call]

Why would you want to go with composite knowing that it will not conduct heat very well and in my "uneducated" opinion probably wont hold up? Cast molds are almost as easy to make, wont cost much if any more and cast molds have been used forever with good results.

[rotomy]

Hi Will,

Good point... actually my reasoning for Fiberglass molds is for short term proto-typing of products.

I've seen that some rotomold companies out there are able to prototype there products with fiberglass molds that last up to 100 cycles.

For us we often make large products and so all of our final aluminum molds are quite expensive. And I've heard that short term fiberglass molds are up to 20% the cost of a final aluminium mold. The materials are cheaper, the labor can most often be done in-house once you know the method, and there is very little finishing needed. This is what I've gathered so far from trying to learn this method.

However I can't seem to find any solid information about how to tackle this method yet so thought forums would be the next best place to go.

[Len]

From: Sourcebook 2011, from Composites World.
Heading ;Fabricating
Sub-heading: Rotational Molding

Arrowhead Plastic Engineering (765) 286-0533
Centro Incorporated (319) 626-3200
Composite Specialties (949) 645-7032
Global Composite Solutions, Ltd. (781) 871-3700
McClarin Plastics Inc. (717) 637-2241
Quicksilver Innovations (208) 549-5101

These may be firms that fabricate composite parts via rotomolding, but I thought the list might provide some leads to your FG mold question or to an actual FG mold makers.

Hope this helps,
Len