ashfordeOU Special Process Qualification (manufacturing-quality/special-processes/special-process-qualification)
Use when the task is deciding whether a special process in aerospace manufacturing may keep running: welding, heat treatment, non-destructive testing (NDT), surface finishing, and composites processing are qualified rather than inspected, so control moves to the process parameters, equipment, personnel, and validity interval recorded in the process qualification record (PQR). Any change outside that envelope is a requalification trigger.
Domain quick reference
- Special processes: welding, heat treatment, NDT, surface finishing, composites processing.
- Why qualified, not inspected: the product result cannot be fully verified by inspection alone (verification may be destructive, cost-prohibitive, or sample-based), so the qualification pins the process itself: parameters with ranges, variables, equipment, personnel, and validity.
- Process qualification record (PQR): process id, parameters with qualified ranges, process variables, qualification date, validity. Module contract: REQUIRED_FIELDS and build_record_checklist().
- Change types and verdicts (assess_change()): parameter in-range stays qualified, parameter out-of-range is requalify-required; equipment change is requalify-required; personnel change is requalify-required; time-interval past validity is requalify-required.
- Requalification triggers: parameter change outside the qualified range, equipment change, personnel change, interval expiry.
- Range check (range_status()): lo <= value <= hi is in-range, boundaries inclusive; an out-of-range parameter folds into requalify-required.
- NADCAP context: NADCAP is the PRI-run accreditation program that audits special processes against industry specifications; it is an external attestation of a facility, not a substitute for the organization's own PQR and requalification control.
- AS9100 production control link: special process control is part of production control; NDT personnel qualification follows NAS 410 level certification practice (training, experience, examination), summarized here, not reproduced.
Workflow
- Identify the special process and its process qualification record: process id, parameters with qualified ranges, variables, qualification date, and validity.
- Classify the proposed change type: parameter, equipment, personnel, or time-interval.
- For a parameter change, compare the proposed value against the qualified range with range_status(value, qualified_range); an out-of-range verdict is a requalification trigger.
- Call assess_change(change_type, value=..., qualified_range=..., elapsed_days=..., validity_days=...) for the qualification verdict: qualified or requalify-required.
- When requalification is required, re-qualify (re-run the process, capture results, update the record) and rebuild the PQR with build_record_checklist(process_id, parameters, variables, qualification_date, validity); validate_record() flags any missing field.
- Validate inputs first: an unknown change type, a missing or malformed qualified range, non-numeric values or days, and malformed record fields raise ValueError instead of returning a silent verdict.
Pitfalls
- Confusion with ndt-method-selection: choosing an NDT method (ultrasonic vs eddy current vs penetrant) is not qualifying the NDT process. Method selection picks the technique for a defect class; special process qualification governs whether the chosen process may run and what change re-triggers control. NDT method selection feeds inspection planning; NDT as a special process is itself qualified.
- Confusion with ultrasonic-inspection: performing and evaluating a UT inspection is the ultrasonic-inspection leaf. A UT process change (probe, frequency, scan plan, couplant) is an equipment or parameter change here and triggers requalification of the NDT special process.
- Confusion with nonconformance-control: a nonconforming part is dispositioned (repair, rework, scrap); a process change is requalified. Finding a nonconformance does not re-qualify the process, and requalification is not a disposition.
- Confusion with statistical-process-control: SPC monitors variation of a running process against statistical control limits. Control limits are not qualification limits: inside SPC limits does not mean inside the qualified parameter range, and SPC does not replace requalification on equipment or personnel change.
- Confusion with supplier-control: supplier control governs external providers and their approval. NADCAP accreditation is an external attestation, but the organization that runs the process still owns the PQR and requalification decision; sending a special process to a supplier transfers the run, not the obligation.
- Interval expiry vs repeat run: the same parameter value inside the validity interval stays qualified; the same run after interval expiry is requalify-required. Expiry is checked against the qualification date, not against the last run.
- Personnel change breadth: any change in qualified personnel is a trigger, including an NDT operator level change under NAS 410 certification, even when parameters and equipment are untouched.
- Boundary reading: the qualified range is inclusive at both ends; a value exactly on the bound is in-range, and only a value strictly outside is a trigger.
Behavior contract (gate 3)
The qualification decision model is exercised by the gate 3 contract test: scripts/test_special_process_qualification_logic.py against scripts/special_process_qualification_logic.py (stdlib unittest, offline). Run: python3 scripts/test_special_process_qualification_logic.py
Compliance
- Standards referenced, not reproduced: AS9100 clause 8.5.1.3 frames special process control within production control; NAS 410 frames NDT personnel qualification. Both are summarized context only, summary-not-copy per standards-map.yaml.
- NADCAP is an accreditation program, not a standards-map entry; described contextually, no proprietary text reproduced.
- compliance: STANDARDS-REF, gated: false.