Page 46 - MetalForming April 2012

Metalforming Electronics By George Keremedjiev
Gizmos and Gadgets for Feed Monitoring— Patient Clear-Headedness Trumps
Rushed Bumbling
The hardest part of any serious sensor application lies in its starting point. It’s easy to become overwhelmed by urgency in the pressroom and toolroom, and right- ly so. No one wants the same die issue to ever again express itself as a die repair or scrapped parts. This is one of those clear examples where patient clear-headedness always trumps rushed bumbling.
Let’s look at a very common photoelectric-sensor appli- cation and see if we can agree that, despite its popularity, external sensor mounting cannot possibly be the right choice. Your die arrives in the pressroom without sensors on it, never mind why. Wisely, you decide to, at the very least, install a feed sensor to check strip progression. This very point in time is akin to the famous Yogi Berra quote, “When you come to the fork in the
typical rationalization for these devices. From shop to shop where these homemade gadgets find use, the initial thinking usually centers on a promise to have a die built and running sooner than is realistically possible. The toolmaker (we’ll call him “Bill”) promises to ensure that the gizmo will work for the first few runs, and then, when he has the time, will mount the sensor within the die.
Well, you know the rest of this story. With each setup, Bill must head into the pressroom and patiently work for sev- eral minutes, sometimes an hour, to get the gizmo to work. Over time he becomes quite skilled at making the critical adjustments needed, and even appears willing to come in on nights and weekends, as needed, to perform these adjustments.
Meanwhile, the shop takes in six more dies that also lack feed sensors. Thus, the common logic becomes to have Bill be available to tweak all seven dies and their external feed sensors. He complains, is provided an assistant to help, but eventually becomes aggravated and quits, as does his assis- tant. Panic, sweat, yelling and even cursing ensue as the company scrambles to hire and train Bill’s replacement.
In retrospect, does this scenario—locating the feed sen- sor on the outside of the die—really save time and money? Keep in mind that even if Bill makes the proper adjust- ments, once he walks away who’s to say that the gizmo won’t inadvertently (or perhaps purposefully) get bumped out of adjustment?
The above scenario has been playing out in hundreds of stamping shops for decades.
Many shops proudly describe to visitors their homemade mechanical wizardry invented over the years to accommo- date external feed monitoring. Never mind that only one tool- maker can make the wizardry work, as it’s often too cum- bersome and difficult for most anyone else to master.
If this sounds like your pressroom, please take a deep breath, step back and ask yourself: Is the entire creative process needed to develop external feed-sensing installa- tions actually costing more time and money than what’s being saved? Spending a few days to properly prepare dies to accommodate in-die feed sensing will typically pay off quickly and easily. Just how many Bills do you think are out there willing and able to perform near-surgical adjust- ments on external feed sensors? And, should you luck out and find one, what are the odds that he will hang around long enough to keep the externally sensed dies running properly? MF
road, take it.”
You have two
Does locating the feed sensor on the outside of the die really save time and money?
choices as to how to
implement the sensor.
The clock is ticking,
production needs
parts and everyone
appears to lack
patience for anything
deemed complicated. So, like most in your situation you choose to install the feed sensor externally rather than with- in the die.
Some of the most creative, convoluted, homemade gizmos I have ever encountered are of this variety. Namely, a mag- netic clamp holding a diverse array of interconnected steel rods extending into space to position the photoelectric sen- sor just right, in order to detect the arrival of some strip or part feature at the end of the feed cycle.
“But we saved time and money doing it this way,” is the
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, con- tact:
Tecknow Education Services, Inc. P.O.Box6448
Bozeman, MT 59771
tel: 406/587-4751 | fax: 406/587-9620 www.mfgadvice.com
gk@mfgadvice.com
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MetalForming/April 2012
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