Page 38 - MetalForming November 2012

Tooling Technology
that draw quickly and more accurately. Blankholding force can be reduced, held constant or increased through the draw. Whatever is needed, the stamper just programs it in.”
Ideal for Advanced High-Strength Steel
Forming advanced high-strength steel (AHSS) requires increased press energy and higher cushion tonnages. Nitrogen cushions ramp up process force using pressures surpassing 2000 psi, according to Quander Jr. However, hydraulic cushions operate at pres- sures greater than 4000 psi, with the added benefit of delaying or eliminat- ing reverse tonnage.
“While air and even nitrogen no longer suffice with the pressures used for forming AHSS,” he says, “servo- controlled hydraulic cushions provide much more force. That force, in tradi- tional systems, has a drawback: reverse tonnage. However, this cushion tech- nology delays that force and controls
the return, eliminating the tonnage spike that ordinarily would filter back through the press.
“Also,” continues Quander Jr., “form- ing AHSS sometimes requires dynam- ic adjustment of force and speed in the press. The level of controllability with servo-controlled hydraulic cush- ions allows the stamper to fine-tune part profiles, as well as save energy and reduce wasted work.”
In essence, the cushion matches the speed of the press and dissipates the force to eliminate reverse tonnage, rein- ing in that force to enable stamping of more precise parts.
Increased Productivity and Part Complexity
The advent of servo-controlled hydraulic cushions also provides for increased productivity and greater part complexity, according to the Hyson team.
“Stampers are trying to get the most usage out of their presses,” says Quan- der Jr. “With the trends of increased
part complexity and condensed dies/ stations, stampers need more control- lability in their cushions. This new tech- nology can be programmed to know each part and the tooling required, with the controllability to vary the force in real time.”
The technology ultimately allows for increased production, as Reilly explains.
“Suppose a servo-controlled press operates in pendulum mode where the stroke height varies,” Reilly says. “The servo-controlled hydraulic cushion can vary the return height of the system. For parts requiring a longer or shorter stroke height, the cushion is pro- grammed to make that chzange. Rather than going through a full stroke with every hit, the cushion is programmed to return to a shorter stroke height. This allows for more parts per minute since wasted movement is eliminated.”
Simplified Installation, Retrofit and Programmability
New technology often comes with a dreaded steep learning curve and apprehension about its incorporation. To address those issues, stampers will want to look for servo-controlled hydraulic cushions with their own interfaces and touchscreen controls, independent of press controls. This standalone design eliminates difficul- ties in tying in with press controls. The cushions can be run by remote LCD control panels that operate via local or plant WiFi.
“Stampers will be able to control the cushion with a keypad,” Quander Jr. explains. “They can change heights, pre-accelerations and pressures. Another screen will display the force curves to allow users to see the move- ment of the system, cushion position and the force employed.”
For retrofits, such systems can be installed by tapping holes into the press bed to allow bolts to hold a cushion. A linear transducer is added to provide feedback on ram movement. The hydraulic power unit slides in and con- nects to the control system and it is ready to go. MF
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36 MetalForming/November 2012
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