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Sensors Have Needs

By: George Keremedjiev

Sunday, January 01, 2012
 

A recent column explained what must occur during die setup to ensure proper function. Here we’ll focus on the needs of the die sensors. In the words of Aretha Franklin: R-E-S-P-E-C-T.

All too often I see electronic sensors mounted in s that would unnerve a juggler, standing on a high wire during a hail storm. I’ve seen, for example:

• Photoelectric sensors mounted using homemade, flimsy sheetmetal brackets that easily become displaced as the die is moved in and out of the press;

• Proximity sensors and associated cabling bathing in oil-filled tooling pockets and channels;

• Feed-monitoring inductive proximity sensors whacked head-on by the end of the strip with each feed cycle;

• Connector junction boxes mounted on the edge of the lower die plate with multiple stab wounds from forklift drivers; and

• Photoelectric sensors with such severe skin and paint damage that their lenses not only are clouded but deeply scratched beyond recognition.

Certainly common sense should prevail in these examples, and remediate action taken. But no—the abuse continues in shop after shop. To quote playwright Arthur Miller, from Death of a Salesman: “Attention must be paid.”

Although electronic sensors can withstand a surprising amount of environmental calamities, including shock, vibration, fluids, over or under power-supply voltage and changes in target positions, I’ve never seen a category within a sensor’s spec sheets titled “Abuse Factor.” I am not kidding here—sensors simply are not designed to withstand poor mounting techniques or physical abuse. Sensors must be isolated as best as possible from physical attack by people and machines—please bury them within blocks of steel or aluminum.

“Yes, but,” I can hear it as I write this, “we do not typically embed electronic sensors within our automated assembly machines. What’s so special about dies and other forms of tooling that they need such shrouding and bunkering?”

The key word here is “automated.” Unlike an assembly machine that employs robots, pick-and-place mechanisms, conveyors and the like and operates with little if any human intervention, a stamping die requires regular physical interaction with humans—toolmakers, setters, operators and forklift drivers. This makes stamping dies and tooling completely different from automated assembly machines, and so it is a mistake to apply sensor-mounting approaches and philosophies from assembly areas them to your stamping dies.

This is one instance where basic common sense in one area of a factory does not apply in another, and why stampers must leave sensor selection, testing and implementation to the supervision of a tooling expert. The good, solid and highly competent common sense used to install sensors in the assembly process will, by itself, simply be an invitation to catastrophe within the pressroom.

I ask everyone reading this column to envision, just briefly, that you are an electronic sensor, with special needs. Once you start to think this it becomes apparent why you should go the extra mile to ensure the proper mounting of your die sensors and cabling. MF

 


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