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Lou Kren Lou Kren
Senior Editor

Where Servo-Electric Presses Fit

January 11, 2022
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How does a servo-electric press work, and when does it make sense—or not—over hydraulic and mechanical presses?

Much has been written on the anatomy and characteristics of servo-driven presses—most commonly for servomechanical presses, a little less for servohydraulic models and not much at all for servo-electric presses. To add to the servo-electric knowledge base, MetalForming quizzed Josh Dixon, a Beckwood Press Co. veteran and recently named chief operating officer for the St. Louis, MO-based provider of hydraulic and electric press systems, including servo models and custom configurations. 

1-Servo-Electric-Press-Beckwood-EVOx-egg-forceMetalForming: How is a servo-electric press put together, and how does it work?

Josh Dixon: From an anatomy standpoint, a servo-electric press features a similar structure to that of a hydraulic press. In place of a hydraulic cylinder for generating force, a servo-electric press employs a roller-screw electromechanical actuator—a mechanical actuator driven by a servo motor. The servo motor replaces the motors, valves, pumps and related components typically found in hydraulic presses with an electric and mechanical drive train.

MF: How does this replacement affect performance?

JD: A servo-electric press features much tighter position and force control than can be achieved with a hydraulic press, offering programmable positional accuracy of ±0.0005 in. And, while mechanical presses excel at achieving the same position at the bottom of the stroke cycle-after-cycle, they don’t allow for a level of programmability where users can easily change it from tool-to-tool or part-to-part. Servo-electric presses maintain many of the same benefits of hydraulic presses, such as full tonnage throughout the stroke, extended dwell and programmable cycle profiles.

A servo-electric press also eliminates the need for hydraulic fluid. From a maintenance perspective, or a desire to move away from fossil fuels, or perhaps an application where hydraulic oil can contaminate a product (food-grade applications, for example), elimination of hydraulic fluid nets a positive.

Energy efficiency provides another big benefit, along with noise reduction. And again, maintenance-wise, users of servo-electric presses need not chase down leaks, faulty valves and deteriorating pumps. Servo-electric systems use far fewer components than comparable hydraulic systems, which means less maintenance over time and simplified maintenance overall.

2-Servo-Electric-Press-ComparisonMF: Conversely, when are servo-electric presses not the ideal options?

JD: In some applications, hydraulic presses provide the better fit, such as the crossing of a certain tonnage or force threshold where servo-electric presses lose cost-competitiveness. Beckwood has built presses with multiple servo-electric actuators and motors grouped together and synchronized, which allow greater force generation than with a single actuator and motor. But at a certain point—six, eight or 10 actuators—the cost can't be justified.

MF: What servo-electric applications can serve metal formers and fabricators?

JD: Servo-electric presses have been in the marketplace for a decade or longer, but traditionally for specific light-duty applications such as crimping or light assembly. That’s the historical niche. But we’re introducing the technology into traditional hydraulic press applications. Many servo-electric benefits carry over from these light-duty applications into more traditional industrial applications.

3-Servo-Electric-Presses-programmingWe receive everyday exposure to a variety of industries and applications—metal and nonmetal, from OEMs to Tier suppliers to job shops, which enables the opportunity for cross-pollination—introducing applications from certain industries to unrelated applications and industries. 

We recently built servo-electric presses for nonmetal trimming applications, composite-forming and compression-molding applications, and even metal ammunition manufacturing—a compression and assembly application. The main benefits of servo on this project are repeatability, consistency and traceability—which the customer could not achieve with their older hydraulic press. Having the ability to track each individual cycle and ensure that all are staying within their tight tolerances is paramount to their continued success.

Another example: an aerospace manufacturer hot forming titanium. Traditionally, a manufacturer uses a hydraulic press with platens that heat to 1600 to 1800 F, employing fire-resistant fluids to decrease the likelihood of a fluid leak resulting in catastrophe. The elimination of hydraulic fluid in an application that heats a workpiece to 1600 F (or higher) offers justification for switching to a servo-electric press with all of the other performance benefits inherent in the technology.

The bottom line: You may have heard about servo-electric presses and think they only serve certain applications, but press manufacturers that understand this technology as well as traditional press technology can help bridge that gap, and show the benefits and the drawbacks. MF

Industry-Related Terms: Forming, Hydraulic Press, Stroke
View Glossary of Metalforming Terms

 

See also: Beckwood Press Company

Technologies: Stamping Presses

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