Page 21 - MetalForming January 2017

Wrong Right
Fig. 3—Another potential bottleneck to transfer movement relates to lower and upper die components such as pins and bushings. Position these just below the transfer height of the panel when the die is open.
tool design can allow the transfer fin- gers to move into the die space several press degrees earlier. Another example: designing the die to allow for the trans- fer fingers to retract later in the press cycle, by minimizing the height of hanging upper components and raising the height of lower components. The fingers have more time to retract with- out having to slow the press.
“The sooner you can clamp-in, and the longer they can stay in the die space,” Hansen stresses, “the higher the SPM can be; there’s more time avail- able to move the panels. The goal is to quicken the process to the point where you’re still maintaining control of the panels; you don’t want to have to wait for something to get out of the way before clamp-in or clamp-out.”
Don’t Blindly Standardize on Die Components
Another suggestion Hansen offers is to consider customizing the size and shape of gauges and other die compo- nents to alleviate interferences that can inhibit transfer motion and limit SPM. Stampers and die designers might be tempted to standardize on one gauge style and length throughout an entire die, regardless of function, just to save a little via bulk ordering. But, the modest additional cost to cus- tomize gauges based on their function and location in a particular die is easily justified if such a design enhancement allows for more efficient transfer motion and an uptick in SPM.
For example, an excessively tall
gauge on the bottom die requires wasteful lift from the transfer system prior to pitch-forward. Gauges should be just tall enough to reliably locate the part in the die, especially consid- ering that today’s full-servo transfer systems do a great job of accurately and repeatedly locating and positioning parts—anything taller will inhibit over- lap and slow transfer speed.
“You get what you pay for with these dies,” Hansen says, “so the lowest price isn’t always the best idea. Look for die shops that understand this and will look to optimize die-lifecycle cost, not just purchase price.”
Other bottlenecks to transfer move- ment are upper-to-lower tool compo- nents such as pins and bushings or stop blocks (Fig. 3). “These should be positioned just below the transfer height of the panel when the die is open,” says Hansen. “Also, design lower tools to include die lift in place of trans- fer lift. Again, this adds cost to the die but will in many cases significantly boost SPM.”
Finally, Hansen recommends exhausting every effort to add auxiliary motion to transfer stations—use the transfer system to manipulate parts in place of dedicated tip or rotate die sta- tions. Again, this complex motion can be simulated and optimized, including detailed design and placement of rota- tors and fingers. In the end, stampers can reduce the number of die stations, Hansen says, and the stamper receives detailed setup sheets providing setup instructions for the operators. MF

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