We had two suppliers of parts for one of our subassemblies. A wood products company provided the cabinet and a plastic injection molder provided the top cap. Assembly took place at the wood products company. These folks complained that the plastic caps were so badly deformed that they could not hold tolerances to fit the screw holes in the wood cabinets. Consequently, about 1 in 12 were rejected. The wood guys blamed the plastic guys and vice versa.
I went in with an open mind and a few measuring tools. After a briefing at the wood supplier I went straight to the inventory area and started measuring a particular dimension. This was hole "D" and the dimension of interest was the distance to an edge. After measuring many parts I had the following frequency distribution.
It turned out that ~ 10% of our sample measured above 0.70 and as you can see in the histogram, that represents a different group of parts than the rest. It is close to the 1 in 12.
Without the data the discussion was going nowhere as each supplier blamed the other. But the data revealed something that was confirmed right away. One out of the 12 workstations was set up incorrectly at the hole drilling operation in the Wood Products factory. It was an easy fix to a months long problem.
Industrial problem solving is a scientific endeavour. It requires data and analysis.
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