Consistent part quality is vendor dependent and requires ongoing monitoring. Careful selection of suppliers is a most important concern. Suppliers and supplier materials/processes are not all the same.
- Buy only from qualified vendors.
- QML concept required for improved quality. PEMs procured to best commercial practice may not provide the consistent quality and interchangeability of the current QPL/QML approach.
Commercial grade PEMs are not normally screened as part of their manufacturing process, to remove manufacturing defects, which may result in "infant mortality" failures.