How do you determine what is critical to your product? How do you maintain quality and minimize variability throughout your manufacturing processes and supply-chain? Critical Parameter Management (CPM) is an engineering practice specifically aimed at understanding and maintaining the robustness of a system through detailed design and the implementation of appropriate manufacturing controls. Critical parameters are derived from the key elements – or the fundamental physics – of what makes your product function. During the detailed design phase, it is too easy to label an excessive number of functional elements as “critical”. However, managing this in a haphazard way takes your eye off what is truly important.
CPM advocates a top-down approach, linking the “critical few” functional requirements to Critical-to-Function (CTF) specifications. This is deployed in a systems engineering approach which links functional requirements to CTFs at the system, sub-system, sub-assembly, component and process levels. This flow-down analysis becomes the roadmap of where to focus your attention during the engineering development cycle. It guides what engineering analyses, testing and reliability studies need to be completed for risk mitigation and pushes these tasks to the earliest point in the design cycle. The CTF roadmap identifies meaningful quality inspection characteristics and, more importantly, it identifies what process controls should be implemented upstream in order to minimize variability on critical manufacturing processes throughout the supply-chain.
An effective CPM analysis empowers the development team to be more explicit with suppliers on what is truly important and communicate your expectations for establishing process capability thereby defining requirements for process validation. It is also essential in limiting “tribal knowledge” and documenting what drives essential performance over the lifecycle of the product, such that if many years later a change is requested, the impact of that change on critical parameters can easily be assessed.