Page 21 - MetalForming April 2011

“The issue of flexibility continues to become more important,” says Beckwood Press president Jeff Debus, “as part volumes continue to come down, leading to more fre- quent changeovers. Quick-die-change systems and programmable control systems with recipe handling are two popular methods for reducing changeover time.
interest in VFD and other energy-saving technology. Manufacturers recognize that there is money to be saved by reducing operating costs with new, more efficient press technology.
Gardner: Hydraulic valving has changed from the basic bang-bang, spool type valves to proportional con- trol valves for electronic control of pres- sure. More companies are requiring an operator interface to set ram pressure and position for part setup with recipe storage to reduce changeover time.
Walkin: The basic characteristics of a hydraulic press—variable slide speed, adjustable pressure and dwell time, and easily adjustable press force—pro- vide the flexibility and reliability need- ed for numerous applications. Some important component improvements include faster controllers; pumps with lower reaction times; accumulator sys- tems to improve speed without increas- ing installed power; and components for building high/low pressure systems and more efficient motors.
McCarthy: The most recent advances relate to controlling platen speed. Elec- tro-hydraulic valves have replaced sole- noid valves, providing proportional control of oil flow and resulting in smoother press operation. For high- speed presses, like those developed for hot forming, high-flow quick-acting proportional valves are a must.
Q:
Dining: We are focused on reducing energy consumption and providing finer control, in terms of repeatability, particularly low-tonnage control. We think we can provide these capabilities less expensively compared to servo presses.
Raye: Not long ago, press makers relied on supplying standard models with a few options, requiring the buyer to adapt production processes to the press’s capabilities. Today it’s the other way around, and hydraulic engineers must know the details of the applica- tion first, and then design the press to
Pump control also has seen per- formance and cost improvements. In years past, flow- and pressure-control features were typically done ancillary to the pump. Now, pumps are available with internal or manifold-mounted capabilities with internal controls. While the unit price of the pump may have increased, the savings from min- imized ancillary components and third-party control devices has made this technology more affordable.
Kirk: Advancements in electrical control systems and closely integrated hydraulic servo-proportional systems make newer hydraulic presses highly efficient, accurate and repetitive. Mean- while, the costs for these advancements have been minimal compared to the benefits realized.
Also, newer valve and pump designs offer substantially higher performance and reliability than previous designs. The economics of using servo-propor- tional control solutions on pumps and valves has greatly improved. This allows manufacturers to offer advanced press- control ability at a competitive price. PLCs now have greater data-handling capabilities and operate at significant- ly higher processing speeds. Other sup- porting computer-based systems can
be readily integrated into the hydraulic- press control system to handle high- speed data acquisition and precise motion control. Closed-loop pressure control can be less than 1 percent of full pressure, and motion control on mul- tiple axes can be achieved with repeat- able position control to 0.001 in. or better.
Schurman (Pacific Press): We see more variable hydraulic pumps for energy savings and press control, and more die-sensing equipment. We’re using “smarter” cushion systems with nitrogen built into the dies, and most press manufacturers, die makers and customers are developing ways to deal with ultra-high-strength steels.
Raye: Motion controllers have for years been used for electric motors and drives, and now have been adapt- ed to accommodate the many vari- ables in a hydraulic closed-loop control system. Traceable data collection and signature analysis are employed by quality-assurance personnel to docu- ment conformance. Also, proportional and servo valves have become more reliable and affordable, offering fea- tures such as precalibrated onboard electronics.
Dining: We’re seeing considerable
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