Page 53 - MetalForming August 2012

Metalforming Electronics By George Keremedjiev
Take Time to Determine Proper Sensor Timing
There is nothing quite as exciting as the “Aha!” moment that a working sensor application can provide to one’s inventive self. Those of you who implement sensors, and have experienced the hours—sometimes days of exper- imentation—followed by a succession of failures, can relate.
So why does it often take so much time to succeed? As one manager once said, “Surely it should not take so long to properly detect the target. Why can’t someone just write a book with all of the shortcuts and get it over with?”
George Keremedjiev has been writing this column for more than 20 years. He regularly consults with metal- forming companies worldwide and provides metal- formers with training on the application and imple- mentation of sensors for die protection. For more information on his seminars and consultancies, contact:
Tecknow Education Services, Inc.
P.O. Box 6448
Bozeman, MT 59771
tel: 406/587-4751 | fax: 406/587-9620 www.mfgadvice.com
gk@mfgadvice.com
Well, after writing this column for more than 28 years and having been part of thousands of sensor applications, I can categorically and unequivocally state that each and every sen- sor application, even within what appears to be identical dies, boils down to a series of tiny refinements, until the sensor works with the expected repeatability from stroke to stroke. Allow me to explain why.
Imagine two identical dies each housing a dozen sensors monitoring critical areas including strip feed, stripper closures, part ejection and cam return. Now kick our example up a notch and imagine these sensors working in relation to the press stroke via the timing being provided by the die-pro- tection control system. Each sensor is expected to make its detection within a timing window. For example, consider strip feed, where the strip must be in its final position at a spe- cific timing-angle window of the crank, in order for the sen- sor to detect it. Open or close that window without regard to the stopping abilities of the die and one could crash the tool. This can occur even when the die contains a very good feed- sensor mechanism. Timing, as the saying goes, is everything.
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