APQP and PPAP explained
APQP (Advanced Product Quality Planning) is a structured process for developing new products and processes. It ensures quality is designed in from the start rather than inspected in at the end. APQP is an AIAG standard used across automotive supply chains and widely adopted in medical devices, aerospace, and other regulated industries.
PPAP (Production Part Approval Process) is the formal submission a supplier makes to a customer to prove that the production process can consistently produce parts meeting all requirements. PPAP is the deliverable at the end of APQP.
The five phases of APQP
| Phase | What happens | Key outputs |
|---|---|---|
| 1. Plan and define | Capture voice of the customer; define design goals | Design goals, reliability goals, preliminary BOM, preliminary process flow |
| 2. Product design and development | Design the product; build and test prototypes | DFMEA, design verification plan, engineering drawings, prototype build |
| 3. Process design and development | Design the manufacturing process | PFMEA, process flow diagram, control plan (pre-launch), MSA plan, floor plan |
| 4. Product and process validation | Run the production trial; validate that the process produces good parts | Production trial run, MSA studies, initial process capability (Ppk), PPAP submission |
| 5. Feedback, assessment, and corrective action | Launch support; track and reduce variation | Reduced variation, customer satisfaction data, lessons-learned documentation |
The 18 PPAP elements
A PPAP submission typically contains up to 18 elements. The submission level (1–5) determines which elements the customer requires. Level 3 (most common) requires all elements plus a PSW (Part Submission Warrant) with sample parts.
Key elements: design documentation, DFMEA, process flow, PFMEA, control plan, measurement system analysis (MSA), dimensional results, material/performance test results, initial process capability (Ppk ≥ 1.67 for critical characteristics), initial sample inspection report, sample production parts, master sample, checking aids, customer-specific requirements, PSW.
Common exam traps
- APQP is the process; PPAP is the proof. APQP is the planning methodology. PPAP is the submission that proves the plan worked.
- Ppk, not Cpk, in PPAP. The initial capability study uses Ppk (overall) because you want long-term performance, not the optimistic short-term Cpk.
- Level 1 is the minimum, not the maximum. Level 1 = PSW only (retained by supplier). Level 5 = all elements reviewed at the supplier’s facility. Higher levels mean more documentation sent to the customer.
- The control plan evolves across phases. There is a prototype control plan (Phase 2), a pre-launch control plan (Phase 3), and a production control plan (Phase 4/5). They are all different documents.
Practice problem
A supplier submits a PPAP with Cpk = 1.75 for a critical dimension. The customer rejects the submission. Why might this be legitimate?
Show answer
PPAP initial capability studies must use Ppk (overall standard deviation from the entire trial run), not Cpk (within-subgroup, short-term). Cpk can overstate true capability by ignoring between-subgroup variation. Most AIAG requirements set Ppk ≥ 1.67 for critical characteristics on a Level 3 or higher submission.
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