Low Volume Plastics Manufacturing Strategies

Plastic components are vital components of many engineered products, frequently representing 20–40% of the product value. While injection molding is the most common process for economically producing complex designs in large quantities, a large initial monetary investment and extended development time are required to develop appropriate tooling. For applications with lower or unknown production quantities, designers may prefer another process that has a lower development cost and lead time albeit with higher marginal costs and production times. A methodology is presented that assists the designer to select the most appropriate manufacturing process that trades off the total production costs with production lead times. The approach is to develop aggregate component cost and lead-time models as a function of production quantity from extensive industry data for an electrical enclosure consisting of two components. Binding quotes were secured from multiple suppliers for a variety of manufacturing processes including computer numerical control machining, fused deposition modeling, selective laser sintering, vacuum casting, direct fabrication, and injection molding with soft prototype and production tooling. The methodology yields a Pareto optimal set that compares the production costs and lead times as a function of the production quantity. The results indicate that the average cost per enclosure assembly is highly sensitive to the production quantity, with average costs varying by more than a factor of 100 for production quantities varying between 100 and 10,000 assemblies. Each of the processes is competitive with respect to total production cost and total production lead time under differing conditions; a flow chart is provided as an example of a decision support tool that can be provided to assist process selection during the product development process and thereby reduce the product development time and cost.