Just doing its job

Over my years in machine vision I’ve had numerous run-ins with the Third Shift Vision Expert. (In other parts of the world he might be called the Nightshift Vision Expert.) This is the helpful gentleman who makes a few adjustments to “improve” the performance of the system. Inevitably, these “improvements” aren’t discovered until the morning shift clocks in, at which point an engineer is summoned to the shop floor to put the system right.

So why are these Third Shift changes made? In my experience, the number one reason is that the system was failing too many parts, usually resulting in a junior or inexperienced supervisor panicking that he wouldn’t make his quota. As a result, thresholds are adjusted, or the system is bypassed completely.

Does this mean that the vision system performs worse at night? I doubt it. A more reasonable explanation is that product quality is lower on the night shift, and the vision system is doing its job by kicking out more nonconforming product. The supervisor should be directing his attention to the process and not to the process monitor.

The real solution is to require, or compel through appropriate process controls, consistent product quality regardless of time of day. In the short term though, I advocate tamper-proofing the vision system, and creating interlocks between it and the production line such that product can’t be made without being inspected.

In other words, let the vision system do its job.