Core tools
The control plan: where your PFMEA meets the shop floor
A PFMEA is analysis. A control plan is what the analysis becomes at six o'clock on a Tuesday morning when the shift starts and someone has to decide what to check, how often, and what to do when it drifts. If the PFMEA is where you think about risk, the control plan is where you do something about it - every shift, forever.
It is also the document most brutally cheapened by the template market. Search for a control plan template and most of what you find is a grid with half the columns deleted - the hard half, the half that makes the document work. So it is worth being precise about what a real one contains and why every column earns its place.
What a control plan actually says
One row per characteristic, walked through the process in routing order. Each row answers a complete sentence: at this operation, on this machine, this characteristic matters this much, it must sit within this specification, we evaluate it with this method, at this sample size and frequency, controlled by this method - and if it goes wrong, here is exactly what we do.
The genuine AIAG structure carries that sentence in columns:
- Part / process number and operation description - where in the routing we are.
- Machine, device, jig, tooling - what does the work. When a characteristic depends on a specific fixture, that fact is control information.
- Characteristic (product and process) - what we are controlling. Product characteristics are features of the part; process characteristics are the settings that produce them (torque, temperature, feed rate).
- Special characteristic class - the CC / SC / HI flag that says variation here threatens safety, compliance or function. These flow down from the DFMEA and PFMEA.
- Specification and tolerance - the actual numbers, on the plan, so nobody walks to a drawing cabinet mid-shift.
- Evaluation and measurement technique - the gauge or method. If it is a measurement, it deserves a Gauge R&R behind it; a control plan built on a gauge nobody has studied is a wish.
- Sample size and frequency - the honest trade between risk and cost, written down.
- Control method - how control is maintained: error-proofing, SPC, first-off inspection, checklist. Error-proofing beats detection every time it is available.
- Reaction plan - the column cheap templates delete first, and the one that matters most at 6am: contain what, quarantine how much, tell whom, restart when.
How the PFMEA feeds it
The linkage rule is simple and it is the audit trail IATF-style assessors walk: every High and Medium Action Priority line in your PFMEA should land in the control plan as a controlled characteristic. The PFMEA found the risk; the control plan shows the ongoing control that manages it. Run the check in both directions:
- A High AP failure mode with no control plan row is an unmanaged risk wearing a completed-analysis costume.
- A control plan row with no PFMEA line behind it is either wasted inspection effort or a sign the PFMEA missed something - find out which.
Do that reconciliation once per review cycle and the two documents keep each other honest. Their phase matters too: the plan is issued for Prototype, Pre-launch and Production in turn, with pre-launch typically carrying elevated sampling until the process has proven itself.
Three failure modes of control plans themselves
The wallpaper plan. Written for PPAP, laminated, never consulted. Test: ask an operator what the reaction plan is for their operation's key characteristic. If the answer comes from memory of tribal practice rather than the document, the document is not controlling anything.
The everything plan. Every dimension on the drawing gets a row, key characteristics drown in trivia, and the line quietly stops following it because it cannot be followed. The PFMEA is the filter: control what the risk analysis says matters.
The frozen plan. The process changed, the plan did not. Same discipline as the PFMEA: engineering changes, new failure modes and significant NCRs re-open the plan, not the calendar alone.
The genuine AIAG control plan
Full column set with nothing stripped out, phase dropdown, colour-coded CC/SC/HI classes and red completeness flags for missing controls or reaction plans. Same worked example as the Axiom PFMEA, so you can see the pair operating together.