Key takeaways
- PPAP is a submission that proves the production process, not a folder of certificates assembled at the end.
- For a stamping, the process flow, PFMEA and control plan are the documents that show the die is understood.
- Dimensional results should cover every cavity and every drawing characteristic, with the gauge named.
- The PSW is the summary, and it is only as good as the evidence behind it.
What PPAP is for
The Production Part Approval Process is a structured way for a supplier to show that the production tool and process can make the part to the drawing, at the quoted rate, repeatedly. It originated in the automotive supply chain and is now used well beyond it because the logic travels: prove the design record, prove the process, prove the measurements, then ask for approval.
For a stamped part, the submission is a test of the die. A part can be made by hand, by laser or by a prototype tool and look correct. PPAP asks for parts from the production tool, run at the production rate, with the process documents that show how the tool is controlled.
The pack is therefore a mix of documents and evidence. The documents describe the plan; the measurements and test results show that the plan worked. A pack with strong documents and thin evidence is a common failure, and so is the reverse.
The 18 elements, grouped
The standard list has 18 elements. Reading them as four groups makes the pack easier to build and easier to review, because each group answers a different question.
- Design: design records, authorised engineering changes, customer engineering approval, design FMEA, appearance approval report.
- Process: process flow diagram, process FMEA, control plan, customer-specific requirements.
- Evidence: dimensional results, material and performance results, initial process studies, measurement system analysis, qualified laboratory documentation.
- Samples and approval: sample production parts, master sample, checking aids, part submission warrant.
The process documents that carry the most weight
The process flow diagram should follow the part from coil receipt to packing. For a stamping it should show the die stations at a level that makes sense: blank, pierce, form, coin, trim, separate, deburr, plate, inspect. It should also show the inspection points and the rework loops, if any.
The process FMEA should start from that flow. The common failure modes on a stamping are a slug left in the tool, a miss-hit, galling, a cracked bend, a short feed and a wrong coil. Each should have a cause, a detection method and an action. A PFMEA copied from another part with no mention of the die is a red flag.
The control plan is the link between the FMEA and the inspection. For each characteristic it should name the specification, the measurement method, the sample size and frequency, the control method and the reaction plan. If the control plan says a dimension is checked every hour but the inspection record shows one check per shift, the pack contradicts itself.
The measurement system analysis supports the control plan. A gauge that has not been studied cannot support a capability claim. For a stamped part, the study usually covers the calliper or fixture used for the critical dimensions, plus any functional gauge.
Dimensional results and the drawing
The dimensional results section should report every characteristic on the drawing, with the nominal, the tolerance, the measured value and the pass or fail result. The drawing should be ballooned so that each result can be matched to a feature.
For a multi-cavity or multi-station tool, the results should cover each die position. For a progressive die, the part is made across stations, so a single sample does not prove that every station is correct. Take parts across the run and identify the station that produces each feature.
The results should also identify the gauge and the datum scheme. A position result without a stated datum cannot be checked by the customer. If the drawing uses a functional datum that is not the same as the manufacturing datum, the report should say how the two were related.
Material, performance and the initial study
Material results should include the mill certificate for the coil, the grade, the temper and the thickness, plus the plating certificate and thickness measurements on the functional areas. If the part is made from pre-plated coil, the coating thickness and adhesion belong in the pack.
Performance results depend on the part. A terminal needs a crimp pull test and a cross-section. A contact needs a force and resistance check. A busbar needs a millivolt drop across the joint. A structural stamping needs the tests named on the drawing. Do not substitute a generic test for the one the drawing asks for.
The initial process study reports capability on the characteristics that the customer designates as special. The study needs enough parts to be meaningful, taken from a stable run. A capability index calculated from twenty parts made in one hour is a snapshot, not a process capability. State the sample size and the conditions.
| Group | Core documents | Stamping evidence to expect |
|---|---|---|
| Design | Drawings, change records, design FMEA, appearance approval | Current revision, ballooned drawing, approved colour or surface sample |
| Process | Flow diagram, PFMEA, control plan | Die station list, failure modes for slugs and miss-hits, reaction plan |
| Measurement | Dimensional results, MSA, capability | All characteristics, gauge study, multi-cavity results |
| Material | Certificates, performance tests | Mill certificate, plating thickness, pull or resistance result |
| Approval | Samples, master sample, PSW | Production parts, signed master, completed warrant |
The element list is defined by the applicable PPAP standard and the customer-specific requirements. The table maps the groups, not a substitute for the standard.
The PSW and submission levels
The part submission warrant is the one-page summary that ties the pack together. It states the part number, the drawing revision, the material, the submission level, the reason for submission and the supplier declaration. It should be signed by someone with the authority to stand behind the evidence.
Submission levels run from a full pack to a warrant with limited evidence. The level is set by the customer, not by the supplier. A supplier that sends a level 1 submission when the customer asked for level 3 has not met the requirement, even if the parts are good.
The reason for submission matters too. A new part, a tool change, a material change, a drawing change, a process change or a lapse in production can each trigger a submission. If the reason is a tool transfer, the pack should show that the new tool produces the same result, not just that the part passes.
Where stamping packs usually fall short
The most common gap is a control plan that does not match the process flow. The second is a PFMEA with no actions for the failure modes the first article actually found. The third is dimensional results that cover the easy dimensions and skip the critical ones.
A fourth gap is the master sample. The sample should be signed, dated and kept under control, and it should represent the approved condition. A sample that has been handled, dropped or plated after approval is not a master sample.
A fifth gap is traceability. The pack should link the sample parts to the coil lot, the tool, the press and the date. Without that link, a later problem cannot be bounded. The records do not need to be complex, but they do need to connect.
Keeping the pack alive
PPAP approval is not the end of the process. The control plan, the PFMEA and the inspection records should be updated when the tool changes, when a defect appears or when the volume changes enough to alter the process.
A useful discipline is to review the pack at the same time as the annual layout. Compare the current process with the approved process. If the die has been repaired, a station has been added or a supplier has changed, decide whether a new submission is required. That decision should be recorded, even when the answer is no.
Keep the approved pack, the change history and the master sample together. When a customer audits the programme, the ability to show the approved state and every change since is more convincing than a thick folder with no history.
Frequently asked questions
Is PPAP mandatory for every stamped part?
It depends on the customer and the industry. Automotive programmes usually require it. Other buyers may ask for a first article inspection only. The useful question is which elements the customer actually needs, and that should be agreed before the tool is built.
Who signs the PSW?
A person with the authority to declare that the production process meets the drawing and the customer requirements. In practice that is usually a quality manager or a plant manager, not the engineer who ran the samples.
What is a level 3 PPAP?
Level 3 is a full submission with the warrant and supporting evidence sent to the customer. Level 1 is a warrant only, level 2 is a warrant with samples, level 4 is a warrant with customer-defined evidence and level 5 is a review at the supplier. The customer sets the level.
How long should PPAP records be kept?
For as long as the part is in production plus the retention period the customer requires, which is often one year after the last shipment. Check the customer-specific requirement, because some programmes ask for longer.
Sources and further reading
- AIAG PPAP, Production Part Approval Process, 4th edition
- IATF 16949:2016, Quality management system requirements for automotive production
- Qumek PPAP reviews for progressive-die stampings
Qumek Engineering Desk
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