While every component is designed to fulfil a unique set of operational requirements, there are a number of common principles which will reduce the time and cost of obtaining an economic component. Many of these are self-evident but some require an understanding of the differences between moulding thermoset rubber and moulding plastics.
Parts will be obtained at minimum cost when there are no surprises in the design, supply or use. Good communication and early contact with suppliers, particularly during the development of new parts, will highlight potential areas of uncertainty and allow them to be overcome. Advice at an early stage can often add functionality to the design which saves cost in other areas e.g. easing assembly, simplifying design or reducing tolerances required in other components.
The key determinants of cost are cycle time, the number of cavities in the mould, material cost and the need for manual operations before or after moulding. Cycle times for rubber generally range from two to ten minutes, although the cure time for heavy parts may be much longer than this.
Reducing the mass of a component not only reduces the material cost, but may also reduce the cycle time. This is especially true for parts with thick sections. Where zero defects are required, due recognition of process capability is required in order to prevent unnecessary quality inspections after moulding. Checks that are not built into the process will inevitably add to the cost.
