Page 29 - MetalForming September 2009

edge of the strip and the paddle with the sensor. Either approach is viable. But how does one test the ability of the sen- sor to detect the position of the strip or paddle to within a 0.010 in.?
The toolmaker must be resourceful. He needs to look in the toolroom and quality lab for any device that can move and present the target within a portion of the feed motion and the tolerance of the feed. Say the strip travels 3 in. dur- ing the feed cycle. It would be good to find an existing positioning device that could travel, 1 in. or so (to simulate the approach of the target to the sensor) and has a digital readout that would be 10 times more sensitive than our tolerance of 0.010 in.—in our example, 0.001 in.
One ideal device would be a vertical mill in good mechanical shape that has a digital display with a valid calibration. It may be a manual vertical mill or a CNC vertical mill—it does not matter as long as its mechanical table mecha- nisms are sound and the digital readout is in calibration. Let’s use the example of a manual vertical mill. The toolmaker most probably has been using this ver- tical mill for years and is quite adept at manipulating the various adjustments on it. The sensor can remain stationary and the strip would be moved, or vice- versa. Even though in the real world our strip moves and the sensor remains stationary in the die, it does not matter for our experiment.
One should only use sensors for die protection that operate on low-voltage direct current. Not only is this a safer electrical environment but it allows for the sensor to be tested using a simple and portable battery-driven power supply readily available from several sensor vendors. Our toolmaker will have the sensor powered up with this power sup- ply so that the reaction of the sensor could be monitored during the experi- ment. Of course the vertical mill’s motor is powered off as the experiment does not require its rotary motion. If our
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