When faced with most problems dealing with processes, products, or service, quality professionals typically implement two types of remedial actions which were handed down to us by experts like Dr. Joseph M. Juran, Dr. Frank Gryna, et al. “Control of nonconforming product” and “root cause analysis with corrective action” are two separate and essential processes.
Upon discovery of nonconforming product a myriad of things should happen. The three immediate actions are to (1) ensure no more nonconforming product is being produced until resolution is determined, (2) ensure all nonconforming material has been contained, and (3) answer the question, “What is to be done with the segregated material?”
Typically the first action is taken before the nonconformance issue has been brought to the attention of the appropriate decision-makers but don’t ever just assume this. Almost all quality professionals have experienced times in which manufacturing continued to run because no one said “stop!” so make sure this happens immediately.
It’s imperative that all product known or suspected of having a problem must be contained and prevented from reaching ‘downstream’ internal operations or even worse, external customers. If it’s been determined that nonconforming product has escaped the facility, the need to recall must be assessed including any ‘need to know’ communication and the method of return. These are serious decisions that frequently have many mitigating factors so the appropriate functional groups must be involved.
The issue of “What is to be done with the segregated material?” needs to be determined. There are essentially four decisions that can be made. (1) Scrap the nonconforming material and thereby lose all completed value-added work. (2) Rework the offending material, which often requires that customers be notified. (3) Use as is. However, there can be varied versions of this action: (a) Waiver by design control or (b) Waiver by customer. (4) Derate the product. For example, a component intended for a one purpose has a minor flaw which prevents its use as intended, but it can be used “as is” for other commercial applications avoiding significant loss of revenue.
Root cause analysis with corrective action addresses two questions: Why is the product nonconforming? And how do we permanently avoid having more of it in the future? Rooting out the reasons for internal and/or external failures is fundamental to customer satisfaction, cost of quality improvement, and even a matter of survival in the marketplace.
The problem’s root cause must be identified and eliminated. Other approaches might provide some temporary relief, but they will never produce a lasting situation. If we attack and remove only the symptoms of a problem, the situation can become worse. The problem will still be there, and there may no longer be an easily recognized symptom that can be monitored. Eliminating first or higher level causes can temporarily alleviate the problem, but the root cause will eventually find another way to manifest itself in the form of another problem.
Several quality tools would be of assistance: brainstorming potential root causes, affinity diagram to group categories, cause and effect diagram, tree diagram.
The classic approach to root cause analysis of a problem is to ask why? (or why not?) a number of times. Five is the typical number often quoted as ideal but this is not a concrete number. If problems are addressed before enough questions are asked, the problems, while diminished, can just ‘run and hide’ only to recur at some future point.
It is important to know how deep is ‘deep enough’ before probing deeper. These can provide some guidance: (1) There are no more relevant answers to why? (2) Common sense indicates that no more why? or why not? questions are needed to solve the problem. (3) The corrective action to be taken appears to be a permanent fix.
The focus of the investigation needs to be on the quality system. How did the system allow the problem to occur in the first place? Where is the weakness in the system? The goal is developing more system-based improvements as opposed to finding someone to blame.
Conducting thorough investigations and ensuring follow through will improve product quality. It can also save the organization significant expense and can even lead to lower production costs in the long run. Finally, higher quality and lower cost are two descriptors regularly associated with world-class organizations. Is there any other side of the fence to be on? Quality professionals are best positioned to lead this ongoing continuous improvement effort. If you’re not intricately engaged now, there’s no time like the present to make a difference.