Series production

Series production is the manufacture of a predetermined quantity of identical parts or products, usually with tooling, molds or fixtures that make every piece repeatable. Compared with one-off production, the cost per piece in a series is significantly lower. In US industry the same idea is often described as volume production, a production run or, at very high quantities, mass production.

Preparing for series production involves a DFM review and adapting the design to the series manufacturing process, building the tooling and molds, setting up the production process and inspection procedures, first article inspection (FAI) and, finally, release to production.

Production documentation for series production must be complete and unambiguous: drawings with tolerances, bills of materials, process sheets and a control plan. Any ambiguity leads to defects or delays.

Where prototype production ends and series production begins depends on the process. For injection molding, a series usually makes economic sense from thousands of pieces. For CNC machining or 3D printing, a series can be just a few dozen parts. Choosing the right manufacturing process for the intended volume is a decision with a major impact on total cost.

Move to series production once the design has been validated by prototypes and testing, demand is reasonably certain, and making the same parts repeatedly with dedicated tooling and fixtures costs less than producing them one at a time. Typical cases are products sold on an ongoing basis, spare parts made for stock and components delivered to a customer in regular batches.

A common intermediate step is a pilot production run (also called a pre-production run), used to debug the process, assembly and inspection before full ramp-up.

A frequent mistake is going into series production with a design that was developed and validated only for the prototype process. A part designed for 3D printing may not be suitable for injection molding without modifications, and any change to the geometry calls for new validation. Another risk is underestimating the cost and lead time of molds, mold trials and approval of the first parts.

Agree with your supplier in advance on the control plan and how quality will be documented (inspection reports, inspection frequency), the procedure for design changes, tooling ownership, minimum order quantities and lead times. Without clear engineering change control, parts made to an outdated revision easily slip into the series.