Tuesday, April 21, 2009

Is this thing on?

One of the justifications for machine vision inspection is that a vision system will never get tired or lose concentration. While that’s true it doesn’t guarantee that the system is actually operating. Take this story, for example: it’s reported that a vision system was left “in program mode” and as a result, failed to detect incorrect wiring.

So what’s to be done? Here are two suggestions to improve the robustness of your systems:

1. Check that the system is functioning at least once per shift by running a bad part past the camera and verifying that it gets rejected.

2. Ensure that all inspected product is diverted to the ‘reject’ area unless a ‘pass’ signal is received, AND the system is in ‘run’ mode. In other words, only allow good product inspected in ‘run’ mode to continue through the process.

Something else you might want to consider is giving each person with access a unique password, and creating a log file so you know who was on the system and when.

Lastly, this problem also links in to traceability. If you discover that the vision system hasn’t been running, wouldn’t it be nice to know how many parts or assemblies might be affected?

More on this tomorrow.

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