A step-down butt connector has two different conductor ranges in one splice. Supplier approval must therefore verify both ends, the transition between them, and the system that keeps every shipped lot consistent. A certificate or factory tour is not enough. Buyers need a scored, evidence-based audit that connects product requirements to production records and defines exactly how findings affect approval.
This checklist is a supplier-qualification framework, not a substitute for the product drawing, customer-specific requirements, or applicable regulations. Set the audit criteria before the visit and tailor sample sizes to product risk, production volume, and past performance.
Use a Formal, Risk-Based Audit Method
The official ISO 19011:2026 overview covers audit principles, audit-program management, conducting audits, and auditor competence. Apply those principles by documenting:
- Scope: Product families, processes, production sites, laboratories, warehouses, and outsourced operations included.
- Criteria: Approved drawings, specifications, purchase requirements, quality agreements, control plans, and applicable management-system requirements.
- Sampling: Lots, shifts, machines, tools, operators, gauges, and records selected according to risk. Record the population and actual sample count.
- Audit trail: Follow requirements horizontally across departments and vertically from one finished lot back to material, process, inspection, release, and shipment.
- On-site observation: Compare written procedures with actual setup, measurement, segregation, labeling, and operator decisions.
- Conclusion rules: Apply the scoring, nonconformity, and automatic-rejection rules below without allowing a high score in one area to hide a critical failure elsewhere.
Audit samples show whether controls operated in the records reviewed; they do not prove that every item in the population conforms.
Scoring and Approval Rules
Score each audit question from 0 to 5, then calculate weighted points = score / 5 x weight. The final score is the sum of weighted points out of 100.
| Score | Definition |
|---|---|
| 5 | Requirement is fully implemented, effective, and supported by consistent objective evidence. |
| 4 | Requirement is effective; only an isolated improvement opportunity is observed. |
| 3 | Control is implemented but evidence is incomplete or an isolated minor nonconformity exists. |
| 2 | A significant gap or repeated minor failure reduces confidence in process control. |
| 1 | Control is largely ineffective, informal, or unsupported by reliable records. |
| 0 | Required control is absent, evidence is false, or a systemic failure is confirmed. |
Approval: 80–100 points, no automatic reject, and no open Major nonconformity. Conditional approval: 70–79 points, no automatic reject, with an accepted containment and corrective-action plan. Not approved: below 70 points, any automatic reject, or any Major finding that is not contained.
A Major nonconformity is a systemic failure, absence of a required control, or condition that could affect safety, electrical function, product identity, or traceability. A Minor nonconformity is an isolated lapse that does not indicate system breakdown or immediate product risk. Repeated Minor findings may be elevated to Major.
Automatic-rejection conditions include falsified records; loss of finished-lot-to-material traceability; unapproved material, plating, or subcontractor substitution; inability to demonstrate controlled tooling and validation for both connector ends; shipment after a known critical test or calibration failure without documented disposition; or refusal to provide required objective evidence.
Verify the Complete Quality-Planning Chain
The audit must trace at least three critical characteristics through the complete chain:
| Planning document | What must link forward |
|---|---|
| Process Flow | Every manufacturing, outsourced, inspection, rework, packaging, and release step. |
| PFMEA | Failure modes, effects, causes, prevention controls, detection controls, and actions for high-risk items. |
| Control Plan | Characteristics, specifications, methods, frequency, sample size, responsibility, records, and reaction plan. |
| Work Instruction | Approved material, machine, tool and cavity, setup values, visual criteria, measurement method, and abnormal-response steps. |
| Inspection Record | Actual results, limits, lot and equipment IDs, operator or inspector, date, disposition, and release authorization. |
Any critical characteristic present on the drawing but missing downstream is a broken link. Any inspection performed on the shop floor but absent from the control plan is an uncontrolled activity.
Eight Core Audit Areas
1. Product and Contract Definition
Audit question: Are large-end and small-end conductor ranges, barrel geometry, material, plating, insulation, strip length, tooling, performance requirements, labeling, and change-notification duties unambiguous? Evidence: Controlled drawings, application specifications, contract review, revision history, and approved deviations. Sampling: Current documents plus three recent orders or customer configurations. Pass: Records use matching revisions and both ends have defined acceptance criteria. Major warning sign: One generic wire range or undocumented customer-specific requirement. Corrective action: Contain affected orders, reconcile requirements, assess shipped product, and update document controls. TONFUL’s step-down butt connector guide provides useful application questions for this review.
2. Process Flow, PFMEA, and Control Plan
Audit question: Does risk analysis drive production and inspection controls? Evidence: The complete planning chain, including reaction plans and revision approvals. Sampling: One active product family and three critical characteristics traced end to end. Pass: Documents agree and shop-floor practice matches them. Major warning sign: High-risk PFMEA cause without prevention, detection, or reaction control. Corrective action: Reassess risk with a cross-functional team, revise linked documents, retrain personnel, and verify effectiveness.
3. Materials, Plating, and Sub-Suppliers
Audit question: Are base metal, plating, insulation, adhesive, packaging, and outsourced processes approved and traceable? Evidence: Approved supplier list, specifications, purchase records, certificates, incoming results, plating test records, and change notices. Sampling: Three incoming lots, including at least one outsourced plating lot where applicable. Pass: Identity and results match requirements and link to finished lots. Major warning sign: Certificate-only acceptance without identity verification, or an unapproved source. Corrective action: Quarantine affected material and product, verify composition or coating, assess shipped lots, and strengthen sub-supplier controls. See TONFUL’s terminal plating guide for relevant material questions.
4. Tooling, Setup, and Restart Controls
Audit question: Are forming tools, crimp dies, cavities, machines, setup parameters, and maintenance uniquely controlled? Evidence: Tool IDs, approved setup sheets, maintenance history, wear criteria, and first-piece records. Sampling: Two active tools or cavities and records from a normal start, tool change, material change, and downtime restart. Pass: Authorized settings and first-piece acceptance exist before release. Major warning sign: Generic dies, unidentified cavities, bypassed interlocks, or production before first-piece approval. Corrective action: Stop production, segregate output since the last verified setup, inspect risk characteristics, restore controls, and retrain authorized setters.
5. Measurement Systems and Laboratory Capability
Audit question: Can the measurement system reliably evaluate critical dimensions and electrical or mechanical performance? Evidence: MSA or GR&R for key dimensions, method validation, calibration traceability, gauge status, pull-force, resistance, and cross-section records where specified. Sampling: All gauges used for selected critical characteristics, one current MSA study, and three recent test reports. Pass: Studies meet the organization’s approved criteria; equipment range, resolution, and status are suitable; results identify the acceptance-source document. Major warning sign: Expired calibration, unsuitable resolution, or incapable measurement system used for release. Corrective action: Stop affected inspections, assess results since the last valid state, recalibrate or replace equipment, and repeat validation. TONFUL’s crimping-tool calibration guide and pull-force testing guide support the evidence review.
6. Process Monitoring, SPC, and Reaction Plans
Audit question: Are critical and high-risk characteristics monitored at a justified frequency, with effective reactions to instability or nonconformance? Evidence: Control charts, Cp/Cpk or another applicable capability study, sampling plans, inspection records, alarms, segregation, and restart approvals. Sampling: Three recent lots across shifts and any out-of-control event from the last 12 months. Pass: Capability evidence is appropriate to the data and process; acceptance criteria come from the approved plan; reactions are timely and traceable. Major warning sign: Selective data removal, control-limit tampering, or continued production after an out-of-control signal. Corrective action: Contain the affected interval, investigate special causes, verify tooling and material, re-establish stability, and update PFMEA and the control plan.
7. Competence, Authorization, and Calibration Control
Audit question: Are operators, setters, inspectors, laboratory staff, and release authorities competent and formally authorized? Evidence: Training matrix, qualification method, expiry or reassessment rules, authorization list, calibration certificates, and gauge-status labels. Sampling: Personnel observed on each audited shift plus five instruments across measurement types. Pass: Assigned work matches current authorization and calibration is traceable to recognized standards. Major warning sign: Unqualified personnel releasing product or an overdue gauge used for acceptance. Corrective action: Suspend authorization, review affected records and product, retrain and requalify personnel, and improve status controls.
8. Traceability, Nonconformance, Change, and Recall
Audit question: Can the factory contain a defect quickly and identify every affected material, process, finished lot, and shipment? Evidence: Lot travelers, labels, ERP records, nonconformance and CAPA files, deviation approvals, change notifications, and recall-drill reports. Sampling: Trace three finished lots backward and forward; review one Major or recurring issue, one engineering change, and the latest mock recall. Pass: The defined traceability target is met within the supplier’s approved time, quantities reconcile, changes are authorized, and CAPA effectiveness is verified. Major warning sign: Mixed lots, manual relabeling without authorization, unreported substitution, or missing shipment scope. Corrective action: Freeze affected inventory and shipments, notify required parties, complete containment and root-cause analysis, verify corrective action, and repeat the traceability drill. TONFUL’s manufacturer red flags adds broader sourcing indicators.
Executable Audit Matrix
The minimum samples below are starting points for supplier qualification, not universal acceptance-sampling requirements. Increase them for high-risk products, new processes, poor history, multiple sites, shifts, or tools.
| ID | Audit Question | Risk | Evidence to Sample | Sample Size Requirement | Finding | Score | NC Level | Owner | Due Date | Closure Evidence |
|---|---|---|---|---|---|---|---|---|---|---|
| A1 | Are product and contract requirements complete for both ends? | Critical, 15% | Drawings, specs, orders, revisions | Current set + 3 orders | To complete | 0–5 | Major/Minor/None | Assign | Date | Evidence ID and verifier |
| A2 | Does Process Flow → PFMEA → Control Plan → WI → record remain linked? | Critical, 15% | One planning chain | 3 critical characteristics | To complete | 0–5 | Major/Minor/None | Assign | Date | Revised links and effectiveness |
| A3 | Are materials, plating, and sub-suppliers approved and traceable? | Critical, 15% | Incoming and outsource records | 3 lots | To complete | 0–5 | Major/Minor/None | Assign | Lot evidence and disposition | |
| A4 | Are tooling, setup, first-piece, change, and restart controls effective? | High, 15% | Tool and setup histories | 2 tools; 4 event types | To complete | 0–5 | Major/Minor/None | Assign | Revalidation records | |
| A5 | Are MSA, GR&R, calibration, and laboratory methods suitable? | Critical, 15% | MSA, gauges, test reports | 1 MSA + all selected gauges + 3 reports | To complete | 0–5 | Major/Minor/None | Assign | Valid studies and calibration | |
| A6 | Do SPC, capability, sampling, and reaction plans control risk? | High, 10% | Charts, capability, reactions | 3 lots + 1 event | To complete | 0–5 | Major/Minor/None | Assign | Stable data and updated plan | |
| A7 | Are personnel competent, authorized, and using in-status gauges? | High, 5% | Training and gauge records | Each audited shift + 5 gauges | To complete | 0–5 | Major/Minor/None | Assign | Qualification and status proof | |
| A8 | Do traceability, CAPA, change control, and recall work in practice? | Critical, 10% | Lot trails, cases, drill | 3 lots + 1 case + 1 change + 1 drill | To complete | 0–5 | Major/Minor/None | Assign | Verified closure and repeat drill |
Assign a unique evidence ID to every sampled record, photograph, interview, and observation. For each finding, record the requirement, objective evidence, affected sample count and population, immediate containment, owner, due date, and closure verifier. A corrective action is closed only after implementation and effectiveness evidence are accepted; submitting a plan is not closure.
Close with a Controlled Sample Build
Finish qualification with a controlled run using the intended small- and large-end wires, approved material, production tooling, and normal operators. Confirm first-piece approval, dimensional results, both-end crimp evidence, electrical and mechanical testing required by the product plan, lot labels, packaging, and record linkage. The source and limits for every acceptance decision must be the applicable drawing, specification, qualification plan, or customer requirement, not an invented universal value.
Share the application package with TONFUL when requesting samples or supplier-audit evidence. Define wires, constructions, tools, environment, validation documents, annual volume, packaging, and change-notification expectations before approval.
