PPAP is often treated as a pile of paperwork to submit. Each of its 18 elements actually answers a specific question about whether a supplier can make good parts consistently. What they are, what they prove and how to pass first time.
A supplier submitted a PPAP package of more than two hundred pages for a small automotive clip. It was rejected within a day. The dimensional results came from a different revision of the drawing, the capability study used 30 parts from a single cavity of a four-cavity tool, and the process flow diagram, PFMEA and control plan described three different processes. The paperwork was thick. The evidence was thin.
The Production Part Approval Process, defined by the AIAG, is often seen as bureaucracy. In reality, every element exists to answer one question: has the supplier proven that its production process can consistently make parts that meet every requirement, at the quoted rate?
The 18 elements
- Design records: the drawings and specifications the parts are made to, at the correct revision.
- Engineering change documents for any changes not yet on the drawing.
- Customer engineering approval, where required.
- Design FMEA, if the supplier is design-responsible.
- Process flow diagram: every step from receiving to shipping.
- Process FMEA: how each step could fail and how failures are prevented or detected.
- Control plan: the controls, measurements, frequencies and reaction plans for each characteristic.
- Measurement system analysis studies, usually Gauge R&R, for the gauges in the control plan.
- Dimensional results: every dimension on the drawing measured on parts from the production process, usually per cavity.
- Material and performance test results.
- Initial process studies: capability for special characteristics.
- Qualified laboratory documentation.
- Appearance approval report, for parts with appearance requirements.
- Sample production parts.
- Master sample, retained for reference.
- Checking aids: fixtures and gauges used for inspection.
- Customer-specific requirements.
- Part Submission Warrant: the summary declaration signed by the supplier.
The submission level, from 1 to 5, set by the customer, determines which elements are submitted and which are retained by the supplier for review.
What the elements prove together
The core documents tell one connected story. The process flow lists the steps. The PFMEA analyses the risks at each step. The control plan defines how each risk is controlled. The MSA proves the measurements in the control plan can be trusted. The dimensional and capability results prove the controlled process makes good parts. If these documents disagree, the story falls apart, which is the most common reason submissions are rejected.
How to pass first time
- Start PPAP planning at the tool kick-off, not after the last trial.
- Confirm the submission level and customer-specific requirements early.
- Make the production run real: production tool, production process, production people, production rate, typically a significant run rather than a handful of shots.
- Measure every cavity, against the current drawing revision.
- Run Gauge R&R before capability studies, not after.
- Use enough data for capability, and check stability first, as we described in understanding Cp and Cpk.
- Make the process flow, PFMEA and control plan match each other and the actual floor.
- Review the whole package internally before submission.
PPAP beyond automotive
Many medical, industrial and consumer manufacturers use PPAP or a lighter first article inspection process. The principles are the same: prove capability with evidence before full production starts. It is a natural conclusion to a well-run trial program.
