PFMEA Stamping Example (Progressive Die)
Process overview
The scope is a progressive-die stamping of a structural bracket from 1.5 mm cold-rolled steel, on a 300 t mechanical press with coil feed, integrated leveler and in-die sensing. The die is a 12-station progressive with blanking, forming, piercing, trimming and cut-off. The PFMEA addresses everything from coil receiving to outgoing dimensional check; die design and material specification are upstream.
Process flow
- Coil receiving and incoming verification
- Coil loading on de-coiler + leveler
- Lubricant application to strip
- Strip feed into press (gripper or roller feed)
- Progressive die operations — blanking, forming, piercing, trimming
- In-die sensing for misfeed, slug detection
- Part separation and ejection
- Burr and dimensional sampling
- Final inspection and packaging
Common failure modes
- Wrong material — supplier mix-up, the highest-severity row because it is invisible until forming or service.
- Cracking at forming radius — material at low end of thickness spec combined with die radius wear; the classic stamping field failure.
- Burr beyond spec — punch-die clearance drift; safety hazard and assembly issue.
- Mis-feed and die crash — pilot pin wear, feeder slip, sensor failure. Catastrophic when it happens.
- Slug pull — slug rides up into next station; marks subsequent part and can damage the die.
- Tool galling and surface scoring — lubrication starvation; cosmetic and dimensional impact.
- Springback drift — slow drift over coil life as material lot changes; only caught by SPC on critical features.
Representative PFMEA table
| Process Step | Failure Mode | Effect | Cause | Prevention | Detection | S | O | D | AP |
|---|---|---|---|---|---|---|---|---|---|
| Coil receiving | Wrong material grade or thickness | Forming cracks; springback drift; field failure | Supplier ticket error or coil mix-up | Incoming material cert + hardness check + thickness micrometer | Heat lot traceability label on every coil | 8 | 3 | 4 | High |
| Coil leveling | Inadequate leveling — residual coil set | Camber; mis-feed in press | Leveler roll wear or wrong gap | Leveler PM schedule + setup check | Feed sensor for camber + visual on first strip | 6 | 4 | 4 | Medium |
| Lubrication | Insufficient lubricant on strip | Tool galling; scoring on part surface | Spray nozzles clogged or misaligned | Daily nozzle inspection + lubricant level check | Visual surface check first part each hour | 6 | 5 | 4 | High |
| Press feed | Mis-feed / pitch error | Die crash → tool damage and scrap | Worn pilot pin; gripper feed slippage | Pilot pin PM + tightening of feed rollers | In-die misfeed optical sensor with auto-stop | 9 | 3 | 2 | Medium |
| Blanking | Excessive burr (> 10 % material thickness) | Cut hazard; assembly interference downstream | Punch-die clearance worn | Clearance gauge check at PM | Burr height sampling each shift | 6 | 5 | 4 | High |
| Forming | Crack at forming radius | Field failure on stressed part; customer rejection | Material thickness at low end + die radius wear | Incoming thickness SPC + die radius PM | Crack inspection first / hourly / last piece | 8 | 3 | 4 | High |
| Piercing | Pierced hole diameter undersize | Fastener will not install at customer assembly | Punch dulled or chipped | Punch sharpen interval based on cycle count | Pin-gauge check hourly | 6 | 4 | 3 | Medium |
| Trimming | Slug pull / slug stuck in die | Indent or mark on subsequent part; die damage | Slug ejection geometry inadequate; air ejection failure | Slug ejection design review at die build | Sensor in slug chute + visual on next part | 7 | 4 | 4 | High |
| In-die sensing | Sensor false negative (missed misfeed) | Die crash | Sensor misalignment or contamination | Sensor verification each setup + cleaning schedule | Periodic functional test with go/no-go strip | 9 | 2 | 3 | Medium |
| Final inspection | Dimensional drift missed by sampling | Non-conforming lot shipped | Sampling plan too loose for criticality | AQL per ISO 2859-1 sized to criticality | CMM trend chart by lot + retain sample | 7 | 3 | 3 | Medium |
Example failure chains
| Trigger | Failure chain | Customer impact |
|---|---|---|
| Supplier ships coil 0.10 mm under nominal thickness | Forming stretch exceeds material elongation at radius → crack at corner → escapes burr check, fails at customer install | PPM hit; supplier corrective action; potential field recall |
| Lubrication nozzle 3 clogged overnight | Strip enters die dry on one side → galling on forming station → scoring on Class-A face → cosmetic rejection of lot | Scrap of entire production run since last inspection |
| In-die misfeed sensor drifts out of alignment | Sensor false-negative on a single misfeed → die crash → broken punch + bent die plate → 12-hour press downtime + tool repair | Production loss + tool repair cost + delivery slip |
Current controls
- Prevention: incoming material certification, leveler PM, lubrication daily check, pilot pin PM, punch sharpen schedule, in-die sensor verification at setup.
- Detection: heat lot traceability label, camber sensor on feed, in-die misfeed sensor (with auto-stop), burr height sampling, pin-gauge check on pierced holes, CMM trend chart by lot.
Recommended actions
- Add inline thickness gauge on the strip after leveler — drops material-grade Detection from 4 to 2.
- Convert lubrication daily check to inline flow sensor with reject-and-stop on dropout.
- Move sensor verification from "each setup" to "every shift change" — drops Occurrence on the sensor-failure row.
- Increase dimensional sampling frequency during the first 50 hits after every tool change or sharpen.
Action Priority discussion
The High-AP rows split between catastrophic single events (wrong material, die crash precursors) and continuous-drift failures (lubrication, burr, forming crack). The die-crash sensor row at Severity 9 is AP Medium only because Detection (3) and Occurrence (2) are well controlled — drop either and it promotes to High. This is a good illustration of why AP captures engineering reality better than RPN: the row stays at Medium because the controls are real, not because the multiplied number happens to be low.
Common mistakes in stamping PFMEAs
- Treating coil receiving as a separate quality process, not part of the PFMEA. Material is the dominant source of forming defects.
- Single row for "stamping". A progressive die has 8–12 distinct stations, each with its own failure modes.
- Underrating Detection on burr sampling. Sampling at shift change misses drift within shift.
- Ignoring lubrication. It is the most common cause of surface defects and tool wear acceleration.
- Missing the sensor-failure row. The in-die sensor itself can fail, and that failure is what allows the die crash.
Audit considerations
Stamping audits focus on traceability (heat lot to part), tool maintenance records (PM schedule execution), in-die sensor verification logs, and dimensional SPC linked to the Control Plan. The PFMEA should reference each by document number. Customer surface-class audits additionally look at burr measurement frequency and lubrication control.
PFMEA — Stamping in the Qhubio knowledge graph
How PFMEA — Stamping connects to other FMEA concepts, standards, examples and software.
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