Start with function and geometry
Identify load paths, interfaces, environmental exposure, appearance and the features that drive performance. Process selection should support these needs before optimising for unit cost.
Balance volume and investment
Low-tooling processes often suit prototypes and smaller batches; dedicated tooling can improve repeatability and unit economics at volume. Include tool lead time, life, ownership and modification risk.
Match tolerances to process capability
Processes create different natural accuracy, surface and variation. Secondary operations may achieve critical features, but each added step creates handling, datum and inspection considerations.
Compare the complete route
Evaluate material form, primary process, secondary machining, joining, finishing, inspection and packaging as one chain. A cheap individual operation can be poor value if it complicates everything downstream.