A manufacturer had a costly quality problem and assigned a team of well-skilled people to fix it. After a few meetings they had identified the root cause and made a presentation. The corrective action would require a few changes to procedures and a couple tooling modifications. The cost was high but lower than the cost of not fixing. When the last corrective action task was complete, there was some rejoicing. The problem was fixed. Everyone returned back to their other tasks.
A few weeks later, a technician pointed out that the defect was still showing up in final test.
"No way. We fixed that already."
"Let's see what happens over the next few days. It should be gone soon."
"Maybe a few slipped through but the bulk of the problem was corrected weeks ago."
It turns out that no one was monitoring the situation nor did anyone know the rate of the defects before the 'correction'.
After several weeks had passed, the managing director asked the Quality manager for a report on the defect. How frequently did it occur? When was it corrected? Is there more than one root cause? Why am I still hearing about this problem?
The report included a plot of the daily error rate for the defect in question and it had been fairly steady at 4% for many weeks. In the days following the implementation of corrective actions, the defect rate did not show any sign of improvement.
The managing director was angry. Why is it so difficult to solve this problem? She told the team to reconvene and get back to solving the problem. She also invited a person she knew from outside the company to take a shot at the root cause.
Within two days, the new fellow presented his findings at a meeting and concluded what the root cause was and how to get around it. His knowledge of industrial problem solving was far above the others. As he presented his reasoning, many scoffed at the idea. He had found a clue that every one of a sample of failed items possessed and that none of a sample of good parts possessed. That would only happen at random once in ~ 12,000 times. So, he concluded, it wasn't random. This feature is causally related to the defect. When the team started pondering how this seemingly unrelated feature could cause the defect, they walked through the physics of the process. It soon became clear that this could indeed cause the defect.
Why didn't they detect this the first time they tackled the problem?
Well, it wasn't something that any of them had experienced before. They had nothing in their collective memories related to this particular root cause.
How did the other fellow stumble upon the root cause?
He had no background in their processes so he had to look at the parts for differences between the failed parts and good parts.
This is one case, and yes, a true story, but there are many more just like it. Teams of very smart people taking on a project that requires particular skills they have not yet learned.
Problem solving in manufacturing is the most valuable skill for a couple reasons.
1. It delivers real, bottom line results. When products fail at final test, you've already invested a lot in producing those parts. You aren't just losing the cost of the parts you reject but you are losing the revenue you would have from the sale of those items.
2. For every problem solved, the company gains new knowledge. Specific knowledge about their product, how it is produced and what new item can cause it to fail. This is incremental innovation. The new knowledge might also apply to other current and future designs.
But most companies spend too little time investing in the development of these critical skills. As a result, problem solving teams often fumble around.
There's a lot about problem solving that you need to know to be successful.
Learn advanced techniques for industrial problem solving.
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