Page 44 - MetalForming November 2010

George Keremedjiev has been writing this column for more than 20 years. He regularly consults with metalforming companies worldwide and provides metal- formers with training on the appli- cation and implementation of sen- sors for die protection. For more information on his seminars and consultancies, contact:
Tecknow Education Services, Inc. P.O. Box 6448
Bozeman, MT 59771
phone: 406/587-4751
fax: 406/587-9620
www.mfgadvice.com E-mail: gk@mfgadvice.com
Bunkering—Part 6
This final installment of a series on the fundamentals of electronic sensors for die protection explores how sen- sors need to be properly installed with- in dies to make them last, in many cases, longer than the dies themselves.
You’ve heard it many times, “The sensors keep breaking.” Smashed pho- toelectric sensors, in a cadaver drawer, join fellow crushed proximity sensors, mutilated fiberoptic cables and tortured beyond recognition laser and camera sensors. What is wrong with these sen- sors that they seem to almost pre- dictably not last beyond a few days or a few weeks in the pressroom?
First, nearly all of the damaged sen- sors that I have seen were destroyed by operators in the pressroom or by fork- lift drivers as the dies were being moved. The reason? The sensors were improp- erly mounted. Electronic sensors are not designed to be hit, crushed, smashed, dented, poked, chipped, scratched, stabbed, filed, sharpened or hammer hit. The sensors are designed to sense and their housings are relatively fragile when compared to the robust- ness of tool steel.
Electronic sensors need to be shrouded within blocks of steel or alu- minum to protect their delicate innards from being damaged. The best shops have dies where spotting a particular tool’s sensors is very difficult. The sen- sors are fully imbedded within the tool- ing, much like the sensors in modern combustion engines. Such protection makes it extremely difficult for a sensor or its cabling to be damaged.
Exceptional care also must be given to the protection of all sensor-related wiring. There must be no exposed wires. This can be accomplished via two pop-
ular methods. The first involves routing the sensor cables within metal tubing. The second approach is to mill channels in the lower die plate and place the sen- sor cabling within these channels. The channels have oil drain holes so pools of oil are not created within them. The channels then are covered with plates that are screwed in place.
“Do I really need to do this?” The simple answer is yes. The amount of time wasted by a typical stamping company replacing damaged sensors, not to men- tion the cost of the replacements and associated labor, can be exorbitant. There also is the cost of downtime as produc- tion is stopped to replace the sensors. Do the numbers for your shop, and deter- mine what you are spending per month on the total cost of sensor replacements.
This and the past five installments detailed the fundamentals to the prop- er utilization of electronic sensors in all forms of tooling. The detection of var- ious targets, the effects of target motion, the realities of what we call color, the importance of optical issues when using photoelectric sensors, the mutual inter- ference that can be encountered between sensing fields and the impor- tance of proper sensor installations— these and other related factors make it mandatory that sensors be selected properly and placed within the dies with care and attention to detail.
Electronic sensors work very well. In many cases, they are designed to have life cycles that exceed the majori- ty of press-stroke counts that a die will encounter in its lifetime. Superb detec- tion coupled with outstanding mount- ing techniques make electronic sensors the ideal cost-cutting mechanism for today’s press and toolrooms. MF
METALFORMING ELECTRONICS GEORGE KEREMEDJIEV
This CD-ROM presents dozens of George’s columns as well as papers and exclusive new presentations covering all aspects of die protection and part-quality inspection, starting and maintaining sensor programs, the role of controls in in-die sensing, and the benefits of a sound sensor program. Order it online at www.metalformingmagazine.com.
42 METALFORMING / NOVEMBER 2010
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