Mech is happy to advise on the most economic materials for any application. The company will supply free samples of materials in 4″ x 3″ (approx.) sheets to allow different compounds and hardnesses to be trialed. Of course, any material proposed should be well tested before production commences.
You can Request Material Samples from this site.
Some materials are very expensive, but on small complex parts the material cost may not be that significant. However, on tiny, thin parts, the weight of flash, sprues and runners may be large compared with the component itself.
Each mould is made to allow for the shrinkage of a specific compound. Rubber compounds of the same type have similar shrinkages – harder compounds shrink slightly less. It is possible to change compounds in a mould but the finished dimensions may vary if the shrinkage is different.