Page 25 - MetalForming Magazine October 2022 - FABTECH

THE CASE FOR SERVOHYDRAULIC PRESSES
Precision control of force and acceleration enabled by servo-driven technology and state-of-the-art press controls translates to energy savings of as much as 80 percent as compared to conventional hydraulic presses. Even so, servohydraulic presses maintain needed force.
hydraulic-press setups has allowed machine builders to eliminate hydraulics previously needed to control ram-cylinder force and direction. That’s important, as while standard hydraulic presses have improved greatly over the years in terms of leakage and wear of pumps, valves, hoses and fittings, stam- pers still, at a time and money cost, must perform monitoring and main- tenance of hydraulic components. And, a lesser hydraulic footprint translates to less oil usage, meaning less need for cooling components for hot oil. With these burdens eased, servohydraulic presses can offer savings to 30 percent in maintenance time and costs as com- pared to traditional hydraulic presses, according to some press builders, along with longer service life.
Though servohydraulic technology does reduce the need for some hydraulic components, those compo- nents remaining have been optimized. For example, Macrodyne employs pres- sure-compensated axial piston pumps with electronic pump control, extreme high-pressure piston pumps and servo- controlled valves, according to com- pany officials, which help deliver pre- cision servo-controlled programmable motion and power when needed.
For its part, Sutherland Presses touts a combination of active fluid manage- ment and advanced servo motors that adjusts fluid volume and motor speed to match the required workload, enabling dynamic adjustment of ton- nage from 10 to 100 percent at any point in the stroke cycle.
And, Greenerd’s new closed-loop servo-hydraulic system dramatically improves stroke depth control, it says, guaranteeing consistent, repeatable results. In many applications, this sys-
tem eliminates the need for “kiss” blocks.
Put it all together and servohy- draulic presses can achieve pressure repeat accuracy of ±1 percent.
Big Energy Savings
Precision control of force and accel- eration enabled by servo-driven tech- nology translates to significant energy savings—as much as 80 percent depending on the application as com- pared to conventional hydraulic press- es—without sacrificing power. For example, AP&T boasts servohydraulic technology that delivers acceleration and deceleration force to 250-percent higher than that of a conventional hydraulic press, thus enabling increased production capacity.
Energy savings occur in many ways beyond precision ram control, as an overview from AP&T on its technology makes clear. Heat loss generated by pressure valves can be avoided, for example, and some servo motors can serve as generators. And, braking ener- gy distributes to motors used for accel- eration and forming via a kinetic stor- age system and central direct-current converter. With energy stored internal- ly, peak loads don’t necessarily require electricity usage from the grid, and stored energy surpluses can be restored to the grid.
Sustainable Solution
Significant energy and oil savings outlined above point to servohydraulic presses as environmentally sound tech- nology that creates a more hospitable work atmosphere. To that end, hearing is believing—servohydraulic presses run more quietly than traditional hydraulic presses. Given all of this, plus
the fact that these presses require less hydraulic components and fewer replacement parts throughout a longer service life, servohydraulic technology represents a sustainable path forward in metal stamping.
Applications Abound
Similarly to servomechanical press- es, automotive is the big application driver that brought servohydraulic presses to North American shores. The need for high forces to shape alu- minum in automotive stamping, for example, cried out for a servohydraulic solution, but press builders had to con- tend with challenges related to high- speed production and the resulting energy usage. They have met those challenges with today’s technology, and automakers and tier suppliers increas- ingly rely on servohydraulic presses for this type of work.
The technology also proves benefi- cial in hot stamping applications where high forces must be held longer on ever-stronger materials. Dialed-in stroke parameters enable more intri- cate and precise work on these mate- rials without overly stressing already stressed tooling. Other applications include motor-bearing press fitting, electrical-connector press fitting, press hardening and composite-material forming.
Find these presses in transfer appli- cations as well, and, of course, in deep drawing, where traditional hydraulic presses have shined for years. Consider servohydraulic presses, uniting the consistently high force delivered by hydraulic presses with the stroke-con- trol capabilities of servomechanical presses, when you need programmable power. MF
22 MetalForming/October 2022
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