Page 22 - MetalForming July 2015

Die Protection–
Don’t Do This
Lack of testing, poor wiring practices, using the wrong sensor, nuisance stops... the ways to fail when
employing sensors to protect your tools are many. Avoid
these pitfalls to reduce costly headaches.
BY JIM FINNERTY
crushed sensor when anything larger than one material thickness—such as a piece of broken punch—ends up under the stripper.
Neglecting Bench Testing
Successful sensoring demands bench testing. Try out a sensor setup first on the bench to ensure that it will work in
Bench testing provides the opportunity to try a sensor setup before placing it on a die and in the press. A well-stocked sensor lab will likely pay for itself the first time that one of those ideas that ‘looked good on paper’ proves ineffective in practice.
Both new and experienced sensor users make mistakes. While experience may be the best teacher, learning from the failure of others is much more efficient. With that in mind, let’s consider the most common mistakes when using sensors for die protection, and how we can avoid them.
Neglecting the Sensor Location’s Environment
Many times, sensors are destroyed by the very event they’re supposed to detect when that event occurs in an unanticipated fashion. Anticipate all failure modes when installing sensors.
For example, best practice for detecting stripper position at bottom dead center (BDC)—usually for detecting pulled slugs—is to install inductive proximity sensors in the bottom die. This ensures that the stripper descends completely at BDC. Sometimes a user will install the sensors in the upper die behind the stripper so that they will actuate at BDC if the stripper is too high by one material thickness. This method, though effective for detecting pulled slugs, will result in a
Jim Finnerty is product manager at Wintriss Controls Group, Acton, MA; 800/586-8324, www.wintriss.com.
20 MetalForming/July 2015
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