What PPAP documents are required for metal structural components?

PPAP (Production Part Approval Process) is one of the five core tools in the automotive industry and serves as a “passport” for hardware structural parts to enter the supply chains of vehicle manufacturers and Tier 1 suppliers.
According to the AIAG PPAP manual, the PPAP document package comprises 18 standard elements, with the submission level determined by the customer based on risk (Level 3 is the default).
This article breaks down, item by item, the documents required for the PPAP of hardware structural parts.

I. Checklist of the 18 PPAP Elements

1. Design Records: Customer-approved design drawings, including all dimensions, tolerances, technical requirements, and referenced standards (stamped parts require ballooning/bubbling to mark key dimensions);
2. Engineering Change Documents: Engineering Change Notices (ECN) and customer approval records since the last PPAP;
3. Customer Engineering Approval: Written approval from the customer’s engineering department, if required;
4. Design FMEA (DFMEA): Failure Mode and Effects Analysis for the design phase;
5. Process Flow Diagram: A complete process map covering stages from incoming material, stamping/welding/heat treatment, to packaging and shipment;
6. Process FMEA (PFMEA): Identification of failure modes, prevention measures, and detection measures for each process step;
7. Control Plan: Monitoring methods, frequencies, and reaction plans for Critical-to-Quality (CTQ) characteristics, aligned with the process flow diagram and PFMEA;
8. Measurement System Analysis (MSA): Gauge R&R studies for critical characteristics, demonstrating that measurement variation is acceptable relative to tolerances;
9. Dimensional Results: Actual measurement data for the full dimensions of production parts, compared item-by-item against drawing tolerances;
10. Material/Performance Test Results: Data on chemical composition, mechanical properties (yield strength, tensile strength, hardness), surface treatment performance, etc., tested according to drawing and customer requirements;
11. Initial Process Study: SPC analysis; Cpk ≥ 1.33 is acceptable, ≥ 1.67 is excellent, and < 1.33 requires corrective action;
12. Qualified Laboratory Documentation: Qualifications and scope of accreditation for the laboratory issuing the test reports (ISO/IEC
    17025);
13. Appearance Approval Report (AAR): Approval of color, gloss, and surface finish for appearance-critical parts (e.g., electroplated or painted components);
14. Sample Production Parts: Physical samples selected from a qualified pilot production run;
15. Master Sample: A reference sample signed and retained by the customer;
16. Inspection Aids: List and calibration certificates for inspection tools, gauges, and other aids;
17. Customer-Specific Requirements (CSR): Customer-mandated requirements such as RoHS/REACH environmental compliance declarations, packaging specifications, and heat treatment certifications;
18. Part Submission Warrant (PSW): The formal cover document for the entire PPAP package, requiring item-by-item signature.

II. Selecting the Submission Level

PPAP is categorized into five levels: Level 1 requires only the PSW; Level 2 requires the PSW, samples, and limited supporting data; Level 3 requires the PSW, samples, and complete supporting data (this is the industry default; Level 3 applies unless otherwise specified);
Level 4 requires the PSW and other customer-defined requirements; Level 5 requires the PSW, samples, and complete data, with the data retained at the supplier’s site for review. Level 1 is common for standard parts like fasteners, while Level 3 or higher is typical for safety-critical or high-risk parts—the customer will explicitly state the required level in the PPAP requirements document.

III.
Key Preparation Points for Structural Hardware Components

For stamped parts, the focus is on dimensional results (springback, burrs, flatness) and material certification;
for fasteners, the focus is on mechanical properties (grade testing) and plating/coating characteristics (salt spray resistance, hydrogen embrittlement); for welded parts, the focus is on welding procedure qualification (WPS/PQR) and welder qualifications; and for heat-treated parts, process curves and hardness reports are required. All testing must be performed by qualified laboratories, and data must correspond item-by-item with the engineering drawings.
Samples must originate from a pilot production run utilizing the “mass production process”—submitting samples produced via non-mass-production methods is the most common reason for PPAP rework.

IV. Practical Recommendations

PPAP is not a one-time event; resubmission or a new application is required following changes to the product, process, supplier, tooling, or materials. It is recommended to organize the documentation package into “18 numbered folders” to facilitate quick retrieval during customer audits. For enterprises preparing a PPAP for the first time, it is advisable to first confirm the submission level and formatting requirements with the customer before organizing a cross-functional team (Design, Process Engineering, Quality, and Laboratory) to prepare the documentation concurrently;
since material and performance testing involves the longest lead time (spanning several weeks), these activities should be prioritized and initiated early.