A PFMEA analyzes how each process step can fail, what the effect would be, and how well current controls prevent or detect it. A Control Plan lists how the process is controlled day to day: the characteristics, specifications, measurement methods, frequencies and reaction plans. The PFMEA decides what needs control, and the Control Plan shows how it is done.
What each document is for
| PFMEA | Control Plan | |
|---|---|---|
| Question it answers | What can go wrong in this process, and how bad is it? | How is this process controlled, every shift? |
| Main contents | Process steps, failure modes, effects, causes, prevention and detection controls, risk ratings, actions | Characteristics, specifications, measurement technique, sample size and frequency, control method, reaction plan |
| Who uses it most | Engineering and quality, during design of the process and after problems | The floor, inspectors and auditors, every day |
| When it changes | New process, process change, or a real failure | Whenever the PFMEA, the process or the controls change |
What flows from the PFMEA into the Control Plan
Characteristics that matter
Product and process characteristics tied to high-severity effects, including special characteristics, should appear in the Control Plan.
Current controls
The prevention and detection controls you claimed in the PFMEA should be the same controls listed in the Control Plan. If the PFMEA credits a check, the Control Plan must show it.
Reaction plans
For each control, the Control Plan says what to do when it finds a problem: stop, contain, adjust, escalate.
The gaps that cause escapes
- A risk with no control. The PFMEA lists it, but nothing in the Control Plan watches for it.
- A credited control that is not real. The PFMEA rates detection well because of a check that the Control Plan does not include, or that the floor does not do.
- Weak detection on a severe risk. A severity 9 or 10 risk relying on visual inspection alone.
- Documents out of step. A process change updated one document and not the other.
The free PFMEA to Control Plan check screens for the first and third gaps in a few minutes.
Where IATF 16949 asks for them
IATF 16949 requires control plans in clause 8.5.1.1, with the required contents in its Annex A, and expects risk analysis such as the PFMEA to drive them. Automotive customers usually expect both in the PPAP.
Questions people ask
Which comes first, the PFMEA or the Control Plan?
The PFMEA. It decides which risks need control, and the Control Plan documents how they are controlled. Building the Control Plan first tends to copy existing inspections rather than address the real risks.
Should every PFMEA line appear in the Control Plan?
No. Every risk that needs ongoing control should, especially high-severity risks and special characteristics. Low risks may need no routine control, and that decision should be visible in the PFMEA.
What is a reaction plan?
The instructions for what to do when a control finds a problem, such as stopping the process, containing suspect parts, adjusting and notifying a supervisor.