Page 26 - MetalForming January 2015

The Ongoing Evolution in
Transfer-Die Tooling
Here’s a brief history lesson tracing the move from mechanical to pneumatic to electric actuators to manipulate parts within transfer tooling, and the added flexibility the technology affords to creative metalformers.
BY PAT CULLEN
Transfer tooling and die processes have evolved significantly, driven by several factors including com- petitive market pressures and the desire to minimize scrap and reduce materi- al costs. In-die part rotation meets both of these needs.
Years ago part rotation was per- formed to maintain the workpiece par- allel to the bolster of the press, and to eliminate camming operations. A two- out process was basically a single piece split in half to create left- and right- hand stampings with each hit of the press. Part rotations were handled with cams and slides within the transfer equipment and the finger tooling.
This method, although considered “old school,” still can be effective at times. In cases where there are tight tim-
Pat Cullen is sales manager for HMS Products Co., Troy, MI; www.hmsprod- ucts.com.
Years ago, part rotations were handled with cams and slides within the transfer equip- ment and the finger tooling. This method, although considered “old school,” still can be effective at times.
ing considerations between the press stroke and die stations, or where there is no room on the bolster for an idle sta- tion, a mechanical rotate operation can maintain a precise relationship between the degrees of rotation and the pitch- travel of the transfer unit. The other solution: a true servo electronically line- shafted to the press and transfer motion.
Cleverly Packaged Pneumatic Actuators
Pneumatic actuators also have become prevalent for rotating parts within a transfer die. Packaging and performance of the actuators has improved greatly in recent years, and transfer control systems now can back- check commanded vs. executed motion under the ram. These controls can even provide speed-compensation features to advance the firing point of a signal to a valve, as press speeds increase, to lead the motion.
Pneumatic actuators also can be cleverly packaged to extend or reduce pitch travels on one or both transfer rails. They can grip the workpiece to allow improved handling of long, thin- gauge stampings, or to allow stampers to run unattached doubles. They also can provide blank/part separation to optimize material utilization or to sim- ply provide more real estate between die stations and allow for additional operations within each station.
There are, however, some drawbacks with pneumatic actuations. Many of the product enhancements described on the capital-equipment side are made to mitigate some of these issues. For example, sometimes air-driven actuators can stick. A part incorrectly presented to a die or a piece of transfer tooling out of place can create expen- sive repairs and generate downtime.
Air pressure is supplied at a constant level to a transfer press, and as press
24 MetalForming/January 2015
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