whats the biggest factor when considering the amount of pulls you can get from a mould? what deteriorates? the structural rigidity of the mold or the tooling surface receiving the part?

While I'm not experienced enough to say for sure, I would say that it is the tooling surface that suffers the most. It would depend on a lot of things; mould size and shape, heat cycles, etc. Etc. But I doubt the reinforcement layers are exposed to anywhere near the forces that would stress them too much, so in my mind it's the tooling surface that gets degraded. 

As above there are many factors that will have an effect on mould life. The quality of the materials and manufacture of the mould and the processes the mould will be used for.

Wet lay using poly resin and air cured the mould should last many many pulls, probably more than you would ever need.

Infusion air cured with epoxy, again hundreds of pulls should be possible.

Infusion oven cured at say 60 degrees, should be good for 100+ pulls.

OOA Pre-Preg cured at 90+ plus degrees, 50+ pulls should be achievable.

Choice of release agents also have a bearing as does the shape and size of the mould. Deep sided moulds can suffer shrinkage over time making release increasingly difficult with age / use.

For production runs after the first mould is produced and proven the fist thing I do is wet lay a poly part, including any infusion flanges. This becomes the "master", if the mould becomes damaged or worn I just pull a new mould from the master. You usually get a feel for when a mould is getting past its best. When this starts to happen you can plan some time for making the new mould without loosing production time. Mould replacement really needs to be factored into your costings for large runs of parts. Often a repolish of the gelcoat will get you more pulls. Careful storage of the moulds/masters when not in use helps. If I know a mould is not going to be used for a while I lay some gelcoat in the mould and let it cure before storage. This will help protect the mould from scratches etc. When you want to use it again lay in a couple of layers of CSM, pull that and your good to go.

Warren

Carbon Copies Ltd

thanks guys confirms what i was thinking