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Pressing matters

Servo-electric punching: What’s the draw?

Prior to 1990, punch press manufacturers offered the mechanical press drive, which was reliable but provided little flexibility for ram control of the punch position. In 1990, the servo-hydraulic press drive was launched and with it came greater control of the ram position and added functionality for operations like forming, marking and tapping.

Illustration of a simple, streamlined servo-electric press drive design.

The servo-electric press drive followed, delivering more precise control of ram positioning with the capability of handling a larger range of operations, high reliability and energy efficiency – at least 20 percent more energy efficiency than servo-hydraulic machines. Today, fabricators are increasingly turning to the servo-electric punch press for a number of reasons.

Economics of electric

The servo-electric press drive offers the most energy-efficient punching technology currently available. Direct-drive servo motors drive the ram assembly, eliminating the use of hydraulics. While servo-hydraulic punch presses provide a certain degree of energy efficiency, particularly those models able to regulate the machine’s hydraulic system and motor during machine operation by adjusting to punching speeds or tonnage needs, servo-electric machines are inherently more energy efficient with low power consumption of approximately 20 kVA.

LVD’s servo-electric punch press delivers 20 metric tons of punching force throughout the complete stroke and provides punching speeds of up to 350 hits per min. on 1-in. centers and marking speeds of up to 800 hits per min.

Servo-electric punch presses also have low power usage between punching strokes and while the machine is idle (approximately 0.9 kW idle power consumption). This type of punch press is especially attractive for companies with high electricity usage needs, such as those operating many machines, those with a maximum amperage limit or in countries where electricity is at a premium.

The servo-electric punch press has significantly fewer components than a hydraulic punch press – no oil tank, pump, associated valves, hoses or chillers. Some current models of servo-electric machines have as few as 50 total components with less than half of these parts considered to be “major” components, such as motors, ballscrews, sun gears and gear boxes.

Fewer components mean fewer points of possible failure and, as a result, reduced maintenance costs. That also equates to less downtime, which can be crippling for any business facing tight turnaround times.

Ram control

The latest servo motor technology is able to accurately deliver the punching force, speed and ram control required for every stroke. In fact, the servo-electric press drive provides the ultimate in ram control, not only on the down stroke, but also on the return stroke. As a result, it offers better control of the punching and forming process – punching at high speeds with high accuracy even in thicker materials, and more accurately controlling the height of a form.

Because the ram is driven by servo motors, ram positioning can be held to ±0.001 in. This precise ram control greatly enhances forming and coining applications. Critical operations, such as countersinking and stamping, are now extremely accurate. Having precise ram control is essential when using some of today’s special tooling, such as hinge tools. Through simple programming commands, the operator can retract the ram to a precise return position specified by the tool manufacturer.

Finally, the servo-electric punch press generates less noise when punching. Without the need for hydraulic pumps or chillers to operate, there is an immediate noise reduction. Certain servo-electric punch presses are about 15 percent quieter than their hydraulic counterparts. Controlling noise emissions protects workers and reduces overall noise pollution, a priority for shops embracing green initiatives.

Parts are produced with ease thanks to quick-change die holders, automatic tool lubrication and a loading/unloading system.

Overall, the servo-electric punch press has a lot to offer, but whether it is the right machine for the application involves a careful review with the machine provider that can help weigh the balance of features, benefits, performance and cost relative to the specific needs.

LVD Strippit