From DC to AC at GM
|With the new AC drive, the robotic arm now holds reinforcement bars securely in place while they are being welded. Also, mechanical wear on the cams has been decreased for smoother starts and stops.|
The GM Grand Blanc plant faced the problem of how to economically incorporate aluminum stamping into its T-12 line, which kicks off with a 1962 vintage Danly 1,000-ton single action stamping press. The press produces 12 different parts, which are then trimmed, detailed, and sent to assembly plants. With press speeds of up to 1,100 rpm, the aluminum going through the line would have been shredded, at best. So things had to slow down to about 700 rpm.
According to Jon Yager, controls engineering supervisor, part of the challenge was to create the versatility to stamp both aluminum and steel. "We looked into installing a variable speed drive on the press," explains Yager, "so we could stamp the aluminum at the slower speed and the steel at the original speed." To achieve variable speeds, GM chose a 1336 Impact AC drive from Allen-Bradley (Bloomington, MN).
|The "guts" of the 1336 Impact AC drive contains the technology that enables independently controlled speed and torque on the GM T-Line stamping press and welding line.|
The drive features AB's Force Technology, a field-oriented control that permits independent control of speed and torque. Direct control of torque over the motor speed range is provided by the drive, which helps the motor and drive generate torque levels high enough to cycle the press back to ready position. A key switch installed on the stamping press enables operators to switch from "steel mode" to "aluminum mode."
The 1336 also features the Quick Motor Tune procedure, which walks users through the process of entering simple motor data. The required parameters surrounding the data entered is automatically loaded. Also contributing to the drive's versatility is a digital I/O, a configurable analog, and several communication ports to accommodate various types of communication devices.
The Impact worked out well enough to be retrofitted into a welding station to improve control of robotic arm movements. It is also being considered for a blanking line that cuts steel from a coil.
Destacking the Deck
|Along with stacking and destacking sheet metal, DCT provides washers, roll coaters, and press-to-press transfer devices.|
Destacking systems from DCT Automation (Warren, MI) are designed to feed sheet metal blanks into stamping presses. The turnkey systems can be engineered in several configurations, including cage-type, cageless, transfer bar, and robotic. One consequence of the growing use of nonferrous metals in the automotive industry is that the traditional magnetic destacking system just won't work for sheet materials, no matter how hard you try. So DCT produces blank feeding systems that use "air knives," "rooster combs," and vacuum lifting to separate and lift the sheets. Of course, they also offer the traditional magnetic type.
|Various automotive components stamped using the Ameriform fluid, which contains no chlorine, silicone, or animal fats.|
It looks like milk, and it is nontoxic, but pressworking, not refreshment, is its purpose. Ameriform, from Denatech, Inc. (Flint, MI) is actually a dry film lubricant used for pressing, deep drawing, and other metalforming applications. It is sprayed onto metal to be formed and allowed to dry. Once dry, the metal can be formed, and can move on to other applications (including welding) without needing to be washed. It also doesn't drip or leave waste in the die like the traditionally used oil-based stamping fluids. The environmentally friendly lubricant exceeds the new regulations set forth by the National Institute for Occupational Safety and Health (especially the standards for airborne fluids and mists). Useable with all ferrous and nonferrous metals, including tin-coated steel, copper, brass, and other metals prone to staining.
Need Die Springs?
Check out the latest catalog from the Producto Machine Co. (Bridgeport, CT). Types range from nitrogen gas to urethane—and more.
|The LJ500 has a closed height of 32mm and a force rating of up to 1,000 lb.|
Also available is the LJ500 nitrogen gas spring from DADCO (Plymouth, MI). Designed for limited shut height applications, the spring is available with various stroke lengths. A linked model is available for filling, monitoring, and adjustment of the spring from outside the die.
Keep `Em Movin'
Automating even the largest presses or most complex pressrooms is something Orchid International(Brentwood, TN) has been doing for a long time. Nearly any combination of robotics, blank loaders, in-press transfer equipment, quick-die change systems, storage and retrieval equipment, and other accessories can be integrated into a turnkey system. The company also offers in-die maintenance systems such as washers and openers/rotators.
The Wichita line of pneumatic clutches and spring-set power-off brakes from Warner Electric (South Beloit, IL) are designed for stamping presses and press brakes. Available in 12 sizes and torque ratings from 1180 lb. to 346,800 lb., the combination units use an external hose design to eliminate machining an air line into the shaft. According to the company, air pressure for clutch engagement and disengagement result in true power-off braking.