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Thread: Debugging a Punch Press Controller

  1. #1
    Supporting Member rgsparber's Avatar
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    Debugging a Punch Press Controller

    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.

    If you are interested, please see

    Your comments are welcome. All of us are smarter than any one of us.

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  2. The Following 3 Users Say Thank You to rgsparber For This Useful Post:

    Jon (Oct 27, 2016), Paul Jones (Oct 20, 2016), PJs (Nov 4, 2016)

  3. #2
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    Thanks Rick! We've added your Relay Logic Simulator to our Miscellaneous category, as well as to your builder page: Rick's Homemade Tools. Your receipt:

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  4. #3
    PJs is offline
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    Very interesting read Rick. A novel approach to troubleshooting and quite a spreadsheet! The relays in series like that seems familiar for your reasons stated. A friends father back in the day worked on the trolley system in the City and the counter emf and voltage spikes were were huge issues on the switching system and life of the contactor/relays...IIRC they were done like you described. Curious how they found it was the encoder? Thanks for sharing it! ~PJ

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