Page 28 - MetalForming April 2016

Hydraulic Presses
This electrical box, accompanying a recently installed hydraulic press, features a VFD (top center), fast PLC (bottom center), and an Ethernet linear-transducer cable—the green cable exiting the right side of the box.
and programmable motion controllers. Finding more and more favor today, says Bisbee, are Ethernet linear trans- ducers, with built-in Ethernet net- working for error checking.
“These transducers also provide
actual position data sent as floating point data,” Bisbee adds—“no more scaling of analog inputs, and no more need for expansive analog cards or encoder cards for the PLC.”
Such improvements in electronic controls, as well as hydraulic components, have enhanced control and accu- racy of slide velocity and tonnage during the working portion of the stroke. This improves part quality and avoids material thinning and other quality issues.
A significant advance in the use of Ethernet as a con- trol network came when control software evolved to allow programmers to seam- lessly integrate the Ethernet- control components of the press line, says Bisbee.
IP address, finding it with the PLC soft- ware and walking through a software Wizard to set all of the parameters.
“The other advantage,” Bisbee con- tinues, “is not so obvious. That’s when a VFD drive goes down after years of use and you have to replace it. A few years ago, the new VFD would be installed and wouldn’t necessarily work right off the bat, because it still carried the default factory parameters. The configuration file (parameter set- points) would have been missing for years and nobody knew how to pro- gram it. Now, after the new VFD is installed and an IP address is assigned to the drive, the parameters easily can be downloaded from the PLC software. No special VFD software is needed, and there is no missing configuration file.”
VFDs, which allow the use of AC drives rather than DC drives in large machines, offer several advantages when running hydraulic presses in pro- duction, which add up to significant energy savings for the metalformer. A VFD starts the motor when the press is ready to do work and turns off the motor when movement of the platen is not required. It allows the motor to run at slow speeds, or even remain off, dur- ing press idle times. And users can pro- gram the VFD to ramp the motor up,
“A good example is a vari- able-frequency drive ( VFD) that sits on Ethernet communications. With its hundreds of parameters to set, configure, read and write to, configur- ing a VFD can be a complex task. Now, though, thanks to software advances, it’s as easy as setting the initial Ethernet
The 20-hp power unit (left) for a 300-ton press was designed with a pump that featured on-board electronics to control flow and pressure, minimizing the number of components and simplifying machine build and maintenance. The complete manifold (right) con- tains only a regenerative circuit, system relief and standard D08 directional valve.
26 MetalForming/April 2016 www.metalformingmagazine.com