- December 05, 2011, Timothy J. Walker
Dear Equipment Builders,
I am writing to file a formal complaint.
Would you buy a car in which, instead of speed, the dashboard displayed only fuel consumption or motor rpms? When the police officer pulled you over for speeding, you could say: “I was only burning 0.12 gallons per mile,” or “My motor was only turning at 150 rpms.”
This would be great if we all drove the exact same car, but the relationship between gas consumption and rpms will differ from car to car to truck to tractor. That’s why the dashboard reads miles per hour.
But, my dear equipment supplier, when you get out of your car and get to the office or shop floor and build your winder, slitter, or nipped process, this concept of displaying the process variable that is critical to running successfully seems to get lost. Please, please, could you please help me understand how your equipment creates force in winding and nipping processes?
What am I specifically talking about? Winder torque set by air pressure, winder torque set by motor amps, winding contact rollers controlled by air pressure, unwind brakes controlled by air pressure, unwind brakes controlled by amps, nipped roller controlled by air pressure, and anything controlled by a mysterious percent or zero to ten knob.
You know who you are, giving me an operator control panel with pressure gauges and motor currents. That is so 1970s. When I ordered the equipment, we talked about my winding tensions in force and nipped processes in terms of nip load (pounds or pounds per width, maybe kilograms or newtons). With our requests, you made some calculations to figure motor or clutch size and air cylinder diameters and leverages. It was all engineered with a force of tension, level of torque, or force of nipping.
But then when you were done with your calculations and sized all the appropriate components, well…you closed your file. Then, when it was time to design the operator panel, you somehow spaced out that forces and torques were ever considered. You gave me this knob or display for air pressure or current. To this, I sarcastically say—thanks so much. That makes everything so perfectly unclear.
So I now have two winders: one from supplier A we bought in the 1980s and one from supplier B we bought in the 1990s. We also have two slitters, one from supplier C and one from supplier D. How am I supposed to explain to my operators that 40 psi and 10 amps are the same when you move from one machine to another? Wouldn’t it have been nicer if you would have done the math for us and provided either an operator control panel that controls winding tension and nipping in terms of force, not air pressure and motor amps?
What is the motive for this? I don’t think it is just laziness or ignorance. In some cases, at least 20 and 30 years ago, it was a cost decision. Adding a multiplier to make a display proportional to load was cost prohibitive. Though that doesn’t explain why your operations manual couldn’t have included a chart or equation to let us work out the air pressure to load relationship or what torque you expect from that motor current setting. Was it that you didn’t want your equipment supplier competitors to know? If so, they followed your lead and didn’t give us the operator panel we need either.
What? You’d like to make it up to me? Okay. Can you make the following pledge? From this day forward, every machine I make will include one of the following:
- A display, graph, or equation of what torque or tension I expect from the motor or clutch amps or air pressure
- A display, graph, or equation of what force I expect from nipped process air pressures
Now, that wasn't so hard, was it? I'm not hard to please. Umm, one more thing: Could you send me this info for the slitter I bought In 1987?
Web handling expert Tim Walker, president of TJWalker+Assoc., has 25 years of experience in web processes, education, development, and production problem solving. Contact him at 651-686-5400; firstname.lastname@example.org; www.webhandling.com.