A short post about mould making, as not much time to spend on design work, we are setting up a new development workshop at the moment.
Methods to manufacture one off and low volume body-shells…….making moulds from composites
If you want to produce any form of low volume production body-shell, composites are the answer. This is because the tooling costs are low. The tooling cost:- the costs of producing a master buck (the shape and style you want) and the tooling (a mould) to produce the parts required from it.
In the case of composites, the most common- Glass Reinforced Plastic (Fiber Glass or Glass Fibre dependent on where you live). The cheapest form of this is chopped stand mat wetted out by hand using Polyester resins. Using this method we have produced 10 different sets of body-shell moulds in the past.
Using Polyester resins in wet lay, the main advantage is it’s the cheapest system to use. Be aware that not all polyester resins are of the same quality. Reprocessed resins tend to shrink up to 8% and should be avoided as the shrinkage will cause assembly problems as you complete your project.
If you are going to lay up a mould use a quality products such as Neomold or Dsm’s tooling systems. These resins are powder filled and this counteracts the shrinkage of the resin. These are vinylester resins… the next type of resins. These resin are very similar in use to polyesters. You can still use chopped stand mat as they will still break down the binders used to hold the mat together before you wet it out.
Finally there are epoxy resins, these produce the best quality moulds, but they are more difficult to use. They DO NOT break down the binders in chopped strand mat ( you can use powder bond mat but even these binders are slow to break down and take a lot of working) so you must use woven materials. This is not our first choice for a low volume mould, wet laid mould. These system are more suitable for resin infusion.
Making a body-shell mould is not simple, but if you use quality products and follow the correct procedures anyone can turn out a quality mould. In the next few months I will add blogs on making moulds in sections that bolt together to produce complex mould.