This article describes a journey I recently completed: fixing a massive punch press.
I was part of a team that figured out why this machine failed and then fixed it. My contribution was the building of a simulator for the relay logic used to control the press. While collecting inputs to drive the simulator, the rest of the team discovered that the shaft encoder was broken.
Four technicians had tried to fix this machine and failed. The building of the simulator forced us to take a rigorous and methodical approach. In the end, this approach uncovered the root cause. The fact that the machine was fixed before the simulator was fully debugged is of secondary importance.
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