PPAP Initial Process Studies and Capability

01How to use this chapter

This chapter separates the uploaded assessment criteria from practical KEVOS implementation guidance. The section titled Source-derived assessment criteria preserves the intent, terminology and checklist detail supplied in the uploaded PPAP Assessment. The surrounding handbook guidance explains how a manufacturing or supplier-quality team can organise evidence, perform a readiness review and spot gaps before formal submission. Where the uploaded source states a numeric threshold, edition reference or customer-specific expectation, it is identified as source-derived rather than presented as a universal rule.

Use the chapter in three passes. First, read the purpose and workflow to understand what the element is meant to prove. Second, work through the source-derived prompts against the actual part number, engineering revision and production process. Third, close the red flags and collect objective evidence before the package is released. For large PPAPs, record the evidence location beside each source prompt so another reviewer can repeat the assessment without relying on verbal explanation.

02Handbook workflow

1. Confirm the characteristic populationStart with the approved special-characteristic list and document any measurement agreement where a characteristic cannot be assessed in the planned manner.
2. Verify the process is suitable for capability analysisUse production tooling, gages and fixturing, representative production conditions and a process that is sufficiently controlled for the capability conclusion to be meaningful.
3. Document the statistical methodRecord sample size, study method, distribution/standard deviation and the chart/data supporting the calculation.
4. Compare with the source/customer criterionThe uploaded assessment states a 1.67 Cpk target and a 1.33 Cpk minimum for variable reporting. Use the actual agreed customer requirement where it differs.
5. Control insufficient capabilityFor results below the required value, implement corrective action and special controls. The source specifically asks whether 100% inspection is in place and defined in the control plan when Ppk/Cpk is below requirement.
6. Include attributes and alternate routesAssess special attribute characteristics, supporting process capability, backup operations and critical purchased material/processes.
7. Create the feedback loopUse capability results to influence preventive maintenance, management/production feedback, product testing and future studies after product/design/process changes.

03Evidence package to retain

The assessment is stronger when each conclusion points to a controlled record rather than a statement that the requirement is “covered”. The following evidence set is a practical minimum for this chapter; actual customer and contractual requirements govern the live submission.

• Capability-study report for every applicable special characteristic
• Correct part number and characteristic identity
• Measurement method/device
• MSA evidence for the measurement system
• Sample size and study method
• Mean/standard deviation/distribution and statistical charts
• Production-run evidence
• Production tooling/gage/fixture status
• Corrective-action plan for inadequate capability
• Temporary/special control such as 100% inspection where required
• Control-plan revision reflecting temporary controls
• Alternate-process/purchased-process capability evidence
• Routine update/revalidation program

04Source-derived assessment criteria

• 1.Capability studies shall be performed and readily available on all special characteristics.
• 2.Variable data reporting is preferred for process capability reporting.
• 3.Did the supplier attain the 1.67 CPk target?
• 4.Does all variable reporting meet the 1.33 Cpk minimum?
• 5.Those not meeting 1.33 Cpk shall have a corrective action plan to improve the results and additional special controls until achieved.
• 6.The method utilized to perform studies and calculate capability level shall be documented along with evidence that results are within customer requirements.
• 7.Complete documentation shall be available stating the preventive maintenance, gage and fixture calibration, tooling verification needed to maintain an acceptable level of capability.
• 8.A documented program shall be available for new products or design changes to existing products.
• 9.Was the method utilized for capacity studies based on statistical practices?
• 10.Were personnel trained to perform capability studies?
• 11.Are capability studies performed on all Special Characteristics?
• 12.Are procedures and special controls in place for inspection of processes not meeting 1.33 Cpk or greater?
• 13.Were studies performed utilizing the print tolerances or specification ranges (pre- control tolerances)?
• 14.Were studies performed on alternate or back-up manufacturing operations?
• 15.Was production tooling, gages and fixturing in place for the study?
• 16.Were results utilized in determining preventative maintenance schedules?
• 17.Is Capability assessed for Special Attribute Characteristics?
• 18.Is supporting process capability provided to support product attribute reporting?
• 19.Were correlation studies required and performed?
• 20.Was a study performed on the packaging of products for shipment to Organization?
• 21.Was a study performed on assembly operations and final product conformance?
• 22.Is there evidence of capability results feedback to management and production personnel?
• 23.Are all Special Characteristics from the drawing (and drawing notes) included? If not: is a measurement agreement for Special Characteristic attached?
• 24.Does the data indication that the process is under control?
• 25.Do the results refer to the correct part number?
• 26.Is the measurement method/device noted?
• 27.Are results for standard deviation and the distribution noted?
• 28.Is the sample size per the agreed upon criteria?
• 29.Is the sample size documented within the submission?
• 30.Are all initial process studies completely in English or translated?
• 31.Are statistical charts and data included?
• 32.Was all data taken from a production run?
• 33.Does the attribute data indicating zero (O) defects were found?
• 34.Are controls in place to ensure Special Attribute Characteristics will meet drawing requirement?
• 34.If PPK or CPK is less than required values complete the following: Is 100% inspection in place and defined in the Control Plan? Is corrective action planned and a modified Control Plan included in PPAP submittal?
• 35.Does Supplier have capability documentation for critical purchased material and processes?
• 36.Are procedures in place for inspection of supplier processes not meeting 1.33 Cpk or greater?
• 37.Is there a program to update the studies on a routine basis with suppliers?
• 38.Are capability studies performed on new product and/or design changes?
• 39.Are capability studies performed when process changes are implemented?
• 40.Is there a program to validate the capability study results from prototype or pilot products to full production products?
• 41.Is a mechanism in place to feedback the product testing results to the capability study?

05Common red flags

These are practical review signals derived from the relationships and controls repeatedly required by the source. A red flag does not automatically mean the submission must be rejected; it means the condition deserves documented resolution before approval.

• Capability is calculated from prototype data but represented as production capability
• Process shows instability but only Cpk is reported
• Sample size is undocumented
• Special attributes are omitted from the study plan
• Below-target capability has no containment or corrective action
• 100% inspection is claimed but not defined in the control plan
• Alternate process is approved but has never been studied
• Measurement-system capability is unknown
• Study uses pre-control or internal limits instead of the actual print/specification range without agreement

06Cross-document interfaces

PPAP elements should not be reviewed as isolated files. Check the following interfaces for consistent part identity, revision, characteristic naming, operation numbering and control logic.

07Assessor close-out checklist

• The element is present or a controlled waiver/agreement explains why it is not required.
• The submitted record identifies the correct part number and engineering revision where applicable.
• The evidence is legible, understandable, controlled and traceable to the submitted product/process.
• Special characteristics and known customer concerns are treated consistently across related documents.
• Any nonconformance, temporary control, deviation or interim condition is visible and formally dispositioned.
• Actions have owners, due dates and objective closure evidence where the source expects corrective action.
• The final conclusion can be independently repeated by another reviewer using the package alone.

08Frequently asked questions

09Source and limitations

Primary source: uploaded Production Part Approval Process (PPAP) Assessment / PPAP Submission Assessment, 15 pages, Quality-One. Source sections used on this page: 2.2.11 Initial Process Studies. Approximate source page coverage: 11-12.

This KEVOS chapter is an educational and assessment aid. It preserves the uploaded document's criteria but does not replace controlled customer-specific requirements, engineering specifications, contractual requirements or an official PPAP/APQP manual. Where the source references “PPAP 4th edition”, AIAG methods, Organization systems or Organization-specific targets, those references are retained as source context rather than silently updated or generalized.