Corrective Action

Corrective action is a critical component of ISO 9000.  The standard specifically requires a documented procedure that describes the corrective action process.

Quality can be free, but it can also be very expensive.  Consider the following example.

A company I was working with was having a problem with a supplier part.  A pneumatic valve appeared to fail at the customer’s assembly plant.  We couldn’t tell if the product was defective from the supplier, we were making it defective, or if the customer was handling the product improperly.  But it was clear that the product coming back from the end customer was defective.  The valve just didn’t work.

Not knowing the source of the problem, we began adding fixes:

•             100% inspection of the incoming valves
•             Added a test fixture to test the valves in a final assembly
•             Reduced the voltage to the valve to weed out any borderline valves
•             A neophyte decided that more is better so the valves were tested 10 times instead of once (as if you can inspect quality into the product)

Still the customer reported defects.  We proposed that the customer test in a piece of test equipment like ours so we could determine if the product was acceptable on arrival, and before it was installed into the customer’s product.  The customer balked.
Finally, a year after the problem initially arose, the customer realized that the wattage of the solenoid should be a quarter watt, but they had specified a 1 watt coil.  Low and behold – problem solved.

If you were to watch the manufacture of the subassembly today you will see an operator testing the valve 10 times.

Depending on who you talk to, there are 4 or 5 or 8 steps to corrective.  Here are my five:

1. Problem Statement
1. State the requirement
2. State the non-conformance
3. State the objective evidence of the non-conformance
2. Containment Plan
1. When did the problem start
2. What are we doing to control the bleeding while we are looking for a solution (short term fix)
3. Root cause analysis
1. There are a myriad of techniques, such as fishbone analysis, control system model, etc.
2. Expect there to be more than one root cause.
4. Corrective Action Plan
1. What will be done to eliminate the root causes?
2. When will it be implemented?
5. Follow Up
1. Was the implemented corrective action effective (did it eliminate the root causes)?
2. Was the short term fix removed?

Corrective action is not rocket science, but root cause analysis can be difficult.  In many cases we see that once the fix has eliminated the pain, it tends to stay in place, and no root cause analysis is performed, or if it is performed, the short term fix is not removed.  Adding inspection and testing which would otherwise not be necessary increases quality cost (and product cost) while not eliminating the source(s) of the problem.

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