Page 20 - MetalForming May 2019
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Selecting Sensors
An industry expert shares some do’s and don’ts when it comes to sensors.
The next generation of sensing technology takes metal forming well beyond the capabilities of, say, proximity sensors. Just how far remains to be seen. However, with the transformation underway, now is the time for companies to familiarize themselves with new offerings and their capabilities. In this Q&A, Marcel Ulrich, sensor product manager at Twinsburg, OH-based Pepperl + Fuchs North America, shares his insights.
MetalForming: What makes in-die sensing advancements so important? Ulrich: The cost of a modest die crash can be as much as $10,000. Typ- ically it’s more. Preventing those occur- rences is a high priority. While the potential for damage and downtime is great, the solution is usually very eco- nomical. Often it’s an $80 sensor. And damage and downtime aren’t the only costs involved. As one of our customers put it: “If there’s an $80 sensor that prevents me from booking a same-day flight to our Mexico facility to investi-
gate a crash, I’m buying it.”
MetalForming: Sounds simple. Are there common mistakes for stampers to avoid?
Ulrich: Selecting the wrong sensor for the wrong application. A common example: overuse of laser-based optical sensors when LED-based models will
work fine. LED-based sensors
have come a long way. They now offer comparable sensing ranges, which equates to optical power to their laser counterparts, and at a lower cost. While laser beams offer the tightest focal point, infrared and visible red LEDs also offer a very precise beam.
Another common mistake: opting for too small of an inductive sensor with insufficient range. This can hap- pen when not accounting for the requirement to recess the sensor to protect it from mechanical impact. We’re really not seeing many installa- tion issues today as we did maybe 10 yr. ago. The reason: Today’s metal for- mers are sensor savvy.
MetalForming: Can you offer some tips for selecting the right sensors?
Ulrich: For optical sensors, one rec- ommendation: Choose infrared when oil and lubricants are present. Infrared tends to ignore oil mist, while visible red beams can detect it, and it’s best for darker colors. Also, remember that the manufacturer’s datasheet sensing range calibrates to a reference object of a specific dimension and material. For example, when inductive prox (proximity sensor) targets the thin sheet edge, the sensor must be much closer than if it were detecting the flat sheet surface. Likewise, a diffuse mode pho-
The miniaturization of durable metal-face inductive sensors improves die protec- tion, increasing uptime.
toeye with a 2-mm light spot won’t see a 1-mm target at its full data-sheet range. The smaller target reflects insuf- ficient light.
MetalForming: What trends should stampers be aware of?
Ulrich: Lightweighting of vehicles continues to drive increased use of inductive sensors for nonferrous appli- cations. While traditional inductive sensors detect aluminum at a reduced range, reduction Factor 1 models, which detect all metals identically, and non- ferrous-selective types provide full range to aluminum targets. Meanwhile, another trend, the movement away from long cylindrical sensors to smaller flat pack styles, provides similar sensing ranges while consuming considerably less real estate within the die or tooling.
MetalForming: What are some of the latest sensor developments that you find most exciting?
Ulrich: Double blank detection always has been tricky. Now there are affordable camera-based sensor sys- tems that detect double blanks at dis- tances up to 1 ft. even with sheet thick- nesses under 1 mm, even while the
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