By Brad Kuvin, Editor
Article from July, 2012 issue of Metal Forming.
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(Partial article. Use this link to read it in full):You’ve done a good job of staging dies in roll-off die racks near the presses in which the dies will run. You’ve installed bolster arm extensions to ease forklift access and ensure safety, and invested in die carts. What’s left to eliminate wasted time from die changeovers?
Answers can be found deep within the 650,000-sq.-ft. Rheem Water Heating plant in Montgomery, AL, where a quick-die-change (QDC) program has made life easier for die setters working on three of the plant’s biggest mechanical presses. Until recently, setters working at those three presses took pry bars in hand to jockey and align dies weighing as much as 20,000 lb. Checking for accurate die alignment by inching the ram down and manually prying the die into position was a time-consuming and tedious process.
The capital improvements made early in 2010 to improve QDC revolved around allowing the operator to roll in their die sets on roller-type hydraulic lifters. Dies roll in under fixed, mounted ledge clamps installed on the press bed. Once the die lifters lower, the bed clamps pressurize with the flip of a switch. Then the upper hollow piston clamps advance into position by the pneumatic travelling clamps. Proximity sensors monitor the extend and retract positions of the air cylinders. Once in position, the clamps are pressurized. Upper clamps are protected by a slide-mounted connection block that creates dual diagonal clamp circuits.
All of the QDC apparatus was provided by Hilma, including an air-hydraulic power unit and pressure switches on each clamp circuit. These switches provide feedback that ensures the press runs only when full operating pressure is available. The die-lifter circuit includes a relief valve that dumps pressure back to the oil reservoir if the rollblocks are overloaded.
“As the two 550-ton presses already had quick-change clamps on their rams, most of the recent work for this project was done on the 400-ton press,“ recalls Krauss. “We fabricated a 3-in. ram plate, cut wire/utility pathways into the plate and fabricated covers for it, so we’re able to run all of the sensor and air cables out to minimize the footprint. The alternative would have been to use swing clamps on the outside, to keep the utilities out of the way. However, using hollow piston travelling advance clamps proved to be a less-expensive and more-effective solution.”
The Hilma QDC package includes a ready-made control panel that ties in the valve manifold, pressure switches, actuation switches and the run circuit. “If we lose any of the pressure switches,” Krauss says, “it kills power to the flywheel, preventing the press from stroking.”
Read the full article on
Metal Forming’s web site