Page 62 - MetalForming July 2012

Tooling Technology
The Domino Effect of
Precision Die
Changes
easily lift the die, and then hydraulically clamp the die from the side.”
Reduced WIP—Let the Dominos Fall
Tank heads and bottoms run on three of the firm’s 23 mechanical presses—two 550-ton presses and a 400-ton press. Operations are hand-fed, single-hit and run at eight to 10 strokes/min. Dies typically stay in the press for 2- to 6-hr. runs, to feed the plant’s six assembly lines, as well as to build inventory. Of course, reducing work in process (WIP) is an ongoing goal, as it is for most OEM pressrooms. Krauss cites reduced WIP as one of the many domino effects of the plant’s quick-die-change (QDC) initiatives.
“Our Kanban levels are at about 1.5 shifts,” Krauss notes, “down significantly, and we’ve reduced changeover time by as much as 28 percent for our most challenging dies. Also, improving the effectiveness of our die changes has led to a 10- percent boost in productivity from those three presses.”
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 sen- sors 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, includ- ing an air-hydraulic power unit and pressure switches on each
A Rheem Water Heating plant enjoys the benefits of installing new die lifters and clamps on three of its biggest presses. Thanks to a reduction in die-change time by as much as 28 percent on its most challenging dies, productivity on three big presses has climbed by 10 percent.
BY BRAD F. KUVIN, EDITOR
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 press- es 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.
Late in 2009 the firm embarked on a leaner approach to die changes for its heaviest hitters—three presses and some 25 dies used to form water-heater tank heads and bottoms from hot-rolled steel to 0.312 in. thick.
“We wanted to give our die setters a solution that, as they inserted a die using a die cart,” says manufacturing process engineer Jeremy Krauss, “would automatically align the die set to the press bolster, have enough capacity to
60 MetalForming/July 2012
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