Special Characteristics Matrix Worksheet for APQP
Special characteristics are the features and process parameters your customer or you have flagged as high-risk for safety, regulation or fit and function. Everything downstream in APQP, from PFMEA to the capability study, must trace back to them. This matrix keeps that traceability in one place.
| Char ID | Drawing feature / balloon | Requirement | Customer symbol | PFMEA ref | Control plan ref | Gage / method | Capability study | Study sample size | Owner | |
|---|---|---|---|---|---|---|---|---|---|---|
Symbols for safety, critical and significant characteristics differ by customer. Use the symbols your customer's drawing and specific requirements define.
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How to build the matrix
Start with the drawing, specification and customer-specific requirements, and list every flagged feature with its requirement and customer symbol. Add any internal special characteristics you identify from the design FMEA or process knowledge. For each one record the PFMEA row, control plan line, gage and whether a capability study is needed. A characteristic that does not appear in all four places is a gap.
- Take symbols from the customer drawing exactly
- Add process characteristics, not only product features
- Cross-reference by ID, not by free text
- Record who owns each characteristic
Why traceability matters
IATF 16949 expects organisations to identify special characteristics, include them in the control plan and manage them with the customer's symbols or equivalent. Reviewers sample a characteristic and follow it from drawing to measurement. If the PFMEA row, control plan line and gage cannot be found quickly, the finding is usually about the system rather than the part.
Reading the example
The example lists a bore with a completed capability study, a safety thread controlled by a go/no-go gage where a study is not required because the data is attribute, a cleanliness requirement still under study, and a position feature that is required but not yet started. The totals show how many characteristics exist and the study sample load. Replace the rows with your own list.
Common mistakes
Frequent errors include listing only dimensions and forgetting process parameters like torque or temperature, using internal symbols a customer does not recognise, and updating the drawing without updating the matrix. Review the matrix at every drawing revision and when customer-specific requirements change. Keep the characteristic ID the same in your ERP inspection plan and MES if you track it there.
Frequently Asked Questions
What is the difference between special, critical and significant characteristics?
Names vary by customer. Generally safety or regulatory characteristics are the highest class, followed by critical or key fit and function items, then significant ones. Always use the classification and symbols defined by your customer.
Do special characteristics always need a Cpk study?
Not always. Variable characteristics usually require a capability study, while attribute features may use another demonstration such as a defined sample with zero failures. Your customer's requirement decides.
Where do special characteristics come from?
They come from customer drawings and specifications, regulations, the design FMEA, and your own PFMEA and process knowledge. IATF 16949 expects you to identify them and show how they are controlled.
Can I export the matrix?
Yes. Use the export buttons for Excel, CSV or PDF and attach the file to your APQP folder or PPAP submission.
If characteristic IDs are tracked in an ERP inspection plan, Netray can help check them against your matrix read-only.
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