Page 33 - MetalForming August 2012

press functions described above. The three motion curves:
• Sinusoidal—closely approximates the operation of a standard part-revo- lution press.
• Proportional—closely approxi- mates the motion of a hydraulic press, with equal timing-adjustment incre- ments throughout the stroke.
• Asymmetrical—offering high-res- olution programmability near the bot- tom of the stroke.
“Within the asymmetrical and most flexible motion curve, we programmed three variable-resolution curves into the control,” says Finnerty. “All of the curves are proportional through the top of the stroke, but then feature high-resolution areas near the bottom. This allows a stamper to set sensor-monitoring win- dows or time limit switches to very small increments (as small as 0.001 in. of slide motion on a 2.5-in. stroke).”
The control can monitor and direct as many as 10 stages of slide motion, although Finnerty says even the most complex jobs experienced so far have required control of only five stages (defined as a change in slide direction, not speed).
“Lastly,” adds Finnerty, “the control is self-learning, enabling it to capture the motion profile for a job when operating in the ‘learn mode,’ and storing the data as part of a part recipe.”
No need for the operator to enter parameters for each program—which can become quite complex for servo- press applications.
Obey the Speed Limit
For a final word on the new-found speed and flexibility arriving with the move to servo-drive presses, we spoke with Anchor Danly’s Ray Osborne, director of engineering for the maker of die sets and precision components. While total control of the ram and the ability to “do things that you can’t do in a conventional mechanical press can take stampers in directions never before experienced,” says Osborne, he also sounds a note of caution.
“Everyone thinks that once the press moves off of bottom-dead center
(BDC),” Osborne says, “that the work is done. But the rapid upstroke accelera- tion and velocity from 180 deg. to top- dead center (TDC) can seriously impact the performance, over time, of a host of press-system components. In-die tap- ping units, cam-slide units, ball-bear- ing guidance systems, nitrogen sys- tems, pad-retaining hardware and other components are potentially in jeopardy.”
To illustrate, Osborne describes a servo-press installation where he record- ed digital video to illustrate what can happen to ball-bearing cages when the ram accelerates rapidly from BDC and quickly reverses direction from TDC. It’s not a pretty sight.
“When the ball bearings are disen- gaged from the preload (during the upstroke), the ram reverses direction and accelerates downward so quickly
connect everywhere
Network your factories and offices with SmartPAC 2 and LETS (Line Efficiency Tracking Software)
Take advantage of
SmartPAC 2’s built-in Ethernet connectivity to communicate over your network.
Send and receive text messages, display setup sheets stored on a central server, back up your tools to a remote location, and view pressroom status over the network and internet. When you connect your equipment to LETS, you can collect production data, feed critical parameters reports automatically, view machine status in real time, and schedule a prioritized job queue for each machine.
To learn more about Wintriss Controls, please call 1-800-586-8324 or visit www.wintriss.com. ®2011 Wintriss Controls. All rights reserved.
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