Page 26 - MetalForming April 2016

Hydraulic Presses–
Better Speed,
Control and Efficiency
Modern hydraulic presses have it all, and more, thanks to the ongoing evolution in hydraulic equipment and electronics.
BY BRAD F. KUVIN, EDITOR
Hydraulic-press builders are focused on reducing energy consumption and providing finer control of speeds, positions and tonnages. Repeatability is the name of the game, and by leveraging the capa- bilities of state-of-the-art hydraulics and electronics, press manufacturers have become shining stars for their metalformer customers.
A conversation with Greenerd Press engineers Rob Bisbee and Tim Wilson directs the spotlight toward some of the behind-the-scenes technology that is raising the level of performance of hydraulic presses. Bisbee offers a great example.
“I recently was programming a press with a very fast main-ram down speed of 1450 in./min. We needed to stop the hydraulic platen at a repeatable posi- tion of ±0.001 in. with each stroke, run- ning the press at 10 strokes/min. Thanks to the unique capabilities of state-of-the-art PLCs and a very accu- rate and high-speed linear transducer, we were able to achieve that position- repeatability requirement.
“And even though today’s PLCs are much faster than their predecessors, we see even more demanding applications than the one described above,” Bisbee
Hydraulic presses, when generally not able to achieve the high cycling speeds of simi- larly sized mechanical presses, offer versatility thanks to variable stroke length, die space and pressure.
24 MetalForming/April 2016
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continues. “In some cases we’ll call on dedicated motion controllers, a tech- nology where a handful of suppliers have really stepped up their games. New motion controllers provide those of us in the hydraulics world with super-responsive (less than 1 msec.) hydraulic control loops, allowing hydraulic positioning nothing short of amazing. For example, we had a recent application with two opposing cylin- ders in a master-slave control setup. The cylinders had to come together, but not touch, with a final positional accuracy of ±0.0005 in., at a rate of 12 strokes/min. A top-of-the-line motion controller made that task achievable.”
Controls Lend to Versatility Advantage
Hydraulic presses, when generally not able to achieve the high cycling speeds of similarly sized mechanical presses, offer versatility thanks to vari- able stroke length, die space and pres- sure. A hydraulic press often is the best choice for producing parts with deep, complex forms that require a lot of material flow, and parts that require a dwell at the bottom of the stroke.
Modern electronic press controls provide accurate oversight of speed, position and force thanks to supervi- sory PLCs that receive input from linear and pressure transducers, load cells