Wireless sensor allows monitoring of large, two-part die
February 8, 2005
When stamper Ultra Tool & Manufacturing, Menomonee Falls, Wis., ventured upon an opportunity to produce a unique and challenging project for one of its customers, a well-known U.S. motorcycle manufacturer, the company jumped on it and put the pedal to the metal. The road to success, however, would be steeper and more winding than San Francisco's Lombard Street.
The motorcycle manufacturer wanted its three-piece, welded, and reinforced footboard to be re-engineered and produced as a one-piece part. At first the motorcycle maker wanted it manufactured as an aluminum casting, but later decided that this type of construction would not stand up to the rough-riding impact it might encounter.
Ultra Tool proposed to stamp the footboard out of 1/8-inch-thick stainless steel as a one-piece part, which not only eliminated the secondary welding and assembly processes, but also removed the need for costly chrome plating. It also allowed the stamper to pull ahead of its competition—two of the three parts of the original footboard had been supplied by another stamper.
|Forming this footboard as a one-piece-, rather than three-piece component, required changes to its construction that involved a 9-1/2 ft., two-part, two-out die assembly weighing 11,000 lbs. Photo courtesy of Ultra Tool & Manufacturing, Menomonee Falls, Wis.|
"We spent some time prototyping the part to verify that we could produce it in a stamping die," Brad Schmit, sensor application manager, said. "Our engineers, design department, and toolmakers got together and came up with a pretty good representation of what the die could produce. The client was very happy with the results, and decided to go ahead with purchasing the progressive die.
"We quickly realized we wanted to produce the footboard as a two-out part—in other words, we wanted to stamp both the right- and left-hand part in one stroke," Schmit said.
Building separate dies for each part would have required separate production runs and extra setups. One long die could fit into the company's 400-ton press, Schmit said.
The first obstacle the Ultra Tool team had to get around was how to handle and maintain a die assembly roughly 9-1/2 feet long and weighing 11,000 pounds.
"The logistics of trying to handle something of that length and weight were formidable. We started looking at issues like safety, loading, unloading, and how our maintenance department would handle it, and take it apart. We didn't feel comfortable using a forklift to lift a tool that large and heavy for safety reasons," Schmit said.
Schmit said they decided to build the die in two parts. The two die sets, or halves, were mounted onto one large plate, separated slightly, (seeFigure 1) then bolted down to the press bed.
The two die sets, mounted onto one large plate, were separated by a 1/8-inch air gap, which meant that a standard connected sensor system would not work. Photo courtesy of Balluff Inc., Florence, Ky.
Schmit said that once they solved the size and handling problem, the next ramp they had to jump was how to equip it with sensors. Normally one main "umbilical cord" attaches to a die and sends signals to the sensor control box, which is connected to the press.
"Since we needed sensors on both ends, or each half of the die, we had issues," Schmit said. "It would be difficult to get a sensor system to work that required the sensors to touch each other, because the dies were separated by roughly 1/8 inch.
"When the two halves get bolted together, there is a key system on the front and back of the tool. The keys have to line up, and the operator screws in bolts to tighten it up, to pull the two halves together. They touch at this key point, but there's still this air gap between the main halves of the set," Schmit explained.
He said they didn't think soft-wiring the system would be a good solution. "We realized from past experience that anytime you try to soft-wire two different components together, you end up having those connections get broken-usually it's from somebody taking the dies out of the press or doing maintenance on them and forgetting to unscrew the connection.
"There was no good, feasible way that we could come up with, without spending quite a bit of money and making the setup more confusing for the operator."
The distance between the two dies was only 1/8 in., but it may as well have been the Snake River Canyon.
Schmit said that as they were exploring possible solutions, he remembered seeing sensor company Balluff Inc., Florence, Ky., demonstrate its wireless power remote system, and that fueled an idea.
"I was thinking that they had a real good wireless solution that possibly would allow us to take a sensor signal and jump the air gap to a receiver sensor and get that signal into our main box," Schmit said. "The wireless system would mean we wouldn't have to make a physical connection."
Schmit said that when he relayed his idea to Balluff, the company thought it had a good chance of working and sent Schmit a sample power remote so he could test his theory. "The dies are 'connected' by a power remote, which transfers power and control information across the air gap between the two dies," said Tom Draper, marketing programs manager for Balluff (see Figure 2).
The dies now are "connected" by a power remote, which transfers power and control information across the air gap between the two dies. Photo courtesy of Balluff Inc., Florence, Ky.
"We spent a day or two in the lab with some good results," Schmit said. "I brought it [the power remote] into the lab, hooked a sensor up to it, and measured out that 1/8 inch air gap that I was trying to simulate. Then I actuated the sensor by passing a target in front of the sensor face, simulating what was going to happen in the tool. It worked beautifully," he said.
"There are four sensors in total operating in the die, plus the power remote system," Draper explained. "One 8-millimeter inductive proximity sensor senses the leading edge of an opening in the steel sheet after the first hit is made, ensuring that the whole strip is positioned for the second and subsequent hits. Two photoelectric sensors on the left side of the die assembly verify that both the right and the left footboard are correctly ejected from the die. Finally, on the far left, there is an arm with a sensor on it that looks for a tab to verify that what is left of the stainless steel strip, weakened by the parts removed from it, remains in the correct position on the die," Draper said.
If material is not in the correct position, the "in-position" proximity sensors protect the die from crashes and subsequent damage, according to Draper. Photoelectric sensors verify that both parts have cleared the cutoff opening, and also that the opening they fall through is not jammed or clogged. Otherwise, the die could close on two thicknesses of material, which would cause a die crash.
Steel mounting blocks were built to protect the transmitter, sensors, and receiver. "We were very careful to protect them by putting them in steel blocks, which pretty much made them gorillaproof," Schmit said. "The sensor system was a significant investment, and we didn't want it to be damaged by a forklift, by somebody dropping something on it, setting it down, turning them over, or doing maintenance.
"As we designed the sensors holders, we knew that we needed to maintain that 1/8-inch air gap, so we took that gap measurement and designed it into the holding blocks."
The sensor system now has been operating successfully for 10 months. "Our customer is very satisfied, and we definitely look forward to repeat business with them," Schmit said.
Schmit said he believes that successes like this one contribute to the company's overall success and growth.
The 35-year-old stamping and tool company has $17 million in annual sales, 87 employees, and three facilities.
"Ultra Tool walked away with a little more confidence that we have the capabilities to take a very difficult project from start to finish and supply the customer with exactly what they're looking for."
Not one to hog the limelight, Schmit shares credit with others in the company. "It wasn't just the Sensor Department that made this work. It was everyone from all departments, from sales to engineering to design to sensors to the press floor."
Schmit added, "One of the other important things to mention is that for us [U.S. fabricators] to remain competitive in today's global market, I think a company has to do these difficult types of projects. What we're seeing is more and more work-the easier work-going overseas. We believe the very difficult jobs are still going to stay here. That can be challenging, but if we're up to those challenges, we can do it."
Editor's Note:Implementing a stamping sensor program requires gaining cultural acceptance.
Ultra Tool & Manufacturing Inc., W169 N5954 Ridgewood Drive, Menomonee Falls, WI 53051, 262-703-0455, fax 262-703-0468, www.ultratoolmfg.com
Balluff Inc., 8125 Holton Drive, Florence, KY 41042, 800-543-8390, fax 859-727-4823, email@example.com, www.balluff.com