Engineering creep

Last month I was approached by one of our readers who presented me with a problem.

Andy Wilson

Last month I was approached by one of our readers who presented me with a problem. His task was to inspect bar codes on the bottom of containers as they moved along a production line. After discussing his task in depth it appeared that he did not want to analyze the bar codes as they moved along the line but merely to verify that they were present.

Upon further investigation, I found that it was simply necessary to flag the product codes as they moved along the production line and then – since they were moving rather slowly – to alert an operator to remove the item for manual inspection.

Since the bar codes were printed on the bottom of the package and, with the production line being two feet from the ground, there was ample room for a vision system to be installed to inspect for the presence of the rather large bar code label. All that was required was a sensor to detect the presence of the label and then to trigger a warning light to alert an operator whether the package had its bar code attached.

Surely, this was the easiest machine vision task that could ever be accomplished!

Indeed it was - that is until I enquired about the price that our reader was prepared to pay. My answer, unfortunately, was rather typical of what some expect to pay for even the lowest cost fully installed vision system – around $1500. Needless to say that informing our reader that the price of engineering consulting was now approximately $200 hour and that an integrator would charge about $2,000/day for this task was met with a rather cold reception.

What could be accomplished to perform this task for the price he requested? I suggested mounting a smart camera below the conveyor to image the boxes as they passed along the conveyor. Using software from a number of smart camera vendors, this task could be accomplished and the camera used to interface to photoelectric cells to trigger both the camera and a warning light. Our reader seemed rather pleased with this solution.

Then, engineering "creep" slowly crept in. Using such a sophisticated camera, the presence of the bar codes could be both detected and validated. This would also provide feedback to bar code printer operators to ensure the bar code printer was working correctly. I also suggested that rather than simply alerting the operator to the presence of the product, the system could trigger rejection mechanisms so that boxes could be rejected and inspected on an hourly and perhaps daily basis rather than as they were produced. This, of course, would require reworking of the production line which would add cost to the final system.

Needless to say, this was not exactly what our reader required. Such problems are not uncommon in the machine vision industry. Indeed, good systems integrators will always be careful to listen to the needs of their customers and obtain detailed specifications of what tasks need to be accomplished before embarking on specific projects. If engineering "creep" creeps in, however well meant, it will cost time and money that the end-user may not be prepared to pay for.

Andy WilsonAndy Wilson, Editor in Chief
andyw@pennwell.com

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