Spring Load Test Records, SPC and PPAP for Customer Audits

Key Characteristics and Sampling Plans

The print or customer specification identifies critical characteristics, commonly load at one or two test lengths, spring rate, free length, wire diameter, outside diameter, and squareness. Convert these into a control plan: which characteristics are measured, with what gage, how often, how many pieces, and what happens on a failure. For high-volume parts, measure on the machine at intervals and plot the results; for low-volume jobs, a fixed sample per lot may be enough.

Make the plan live next to the part number so operators and inspectors use the same instructions, rather than sitting in a binder only the quality manager reads.

Load Testing and Gage Records

Load testers and length gages must be calibrated at a defined interval with traceable standards, and the record should be easy to produce. For measurement systems that matter, customers may expect gage R and R studies as part of PPAP. Each load test result should link to lot, part number, date, operator and instrument, so a later complaint can be traced to the instrument calibration state at the time.

Automated load testers that output data directly reduce transcription errors compared with writing values on a traveler and retyping them later.

• Calibration status and due dates for every gage
• Result linked to lot, operator and instrument
• Out-of-tolerance reaction and containment record

SPC and Capability for Spring Characteristics

Statistical process control on a spring line typically charts load at length and free length from coiler output, using subgroup samples over time. Capability indices such as Cpk are requested in automotive PPAP, commonly with a minimum target set by the customer. The practical points are: collect data from a stable run, use enough samples, and keep the raw data so the customer can see it.

Watch for wire lot changes, since variation in wire tensile and diameter from one spool to the next shows up as load drift, and adjust coil count or coiling parameters per lot where the process allows.

PPAP and First Article Packages

For automotive-type customers, PPAP can include design records, process flow, PFMEA, control plan, measurement system analysis, dimensional results, material and performance test results, capability studies and a part submission warrant. Aerospace customers may instead ask for an AS9102-style first article inspection report. Both packages draw on the same underlying data, so keep it structured instead of rebuilding for each submission.

The cost of a PPAP is real, so quote it explicitly as a line item for new parts when the customer requires it.

Making Audits Easier With Searchable Records

Auditors ask questions like: show the load results for lot X, the calibration record for the tester used, and the wire cert for that lot. If these live in three systems and a filing cabinet, the answer takes hours. Linking by lot number in the ERP or a quality system fixes most of it.

A private AI assistant over your records can retrieve and summarize a lot's full record on request and flag lots missing a test result, but it does not substitute for taking the measurements or for the quality manager's sign-off.