Systems Approach to Manufacturing Quality
When issues arise, rather than question the dedication, mindfulness, and intelligence of our people, we look to the system. Instead of inspecting quality into the product, manufacturing quality is achieved through 1) design of the product and 2) monitoring and improving the process. First the process must achieve a state of statistical control. Even a stable process will experience some variation due to two types of causes: Common Causes of Variation and Special Causes of Variation.
Common vs. Special Causes of Variation – Common causes of variation are routine or random and exist even when the process has not changed. Special causes of variation are assignable to exceptional process changes. “Fixing” the process for a common cause of variation can counterproductively worsen the process.
The Quality Plan – The ISO 9001:2008 Quality Management System defines and monitors the critical quality data for each production process and part. Critical Dimensions are finalized. Gages and Range boards are designed as and where necessary.
Ticket Log – The Customer Service and Quality teams maintain a ticket log for internal and external issues and positive and negative customer feedback.
CAPA System – Recurring and major tickets are escalated to the CAPA system for Root Cause Analysis. Once the manufacturing process is stable, most special causes of variation are actually caused by the system, not by the people. This means Root Cause Analyses should look at the system to ask “What in our system allowed this to happen?”
First Article Inspection – The Quality Engineer performs the First Article Inspection on new or changed components and subassemblies.
First-In Audit – Each time a part is rerun, the Quality Inspector will perform a First-In Audit to confirm the specifications are met.
In-Process Inspection – The Quality Inspector will pull production samples twice per shift to monitor the stability of the production process.
Final Inspection – When a lot has completed production, the Quality Inspector performs the Final Inspection to approve the lot for shipping.