Press Brakes Go Green—and Save Green
Electric press brakes eliminate the need for hydraulic oil, reduce energy consumption
February 1, 2011
Hybrid and electric press brakes are here to stay.
Next-generation hybrid and electric press brakes are here to stay—and they’re leaner, greener, and more reliable than ever before.
Offering high accuracy; clean; quiet operation; and faster cycle times, these machines can alleviate many of the common headaches associated with metal forming. So, how do they work?
Traditional press brakes use gear pumps to pressurize lines that deliver oil from the tank to the pistons. Gear pumps are fairly reliable, but they aren’t without their disadvantages. For one, they continuously draw power even when machines remain idle. They are also noisy and can cause machine vibration. Worst of all, temperature changes from the hydraulic oil heating up over time can cause perceptible shifts in the ram, interfering with production specifications. Hybrid and electric designs eliminate the gear pump and other elements of traditional press brakes.
Hybrid press brakes employ both hydraulic and electric technologies.
In all cases, hydraulic power moves the ram, as with traditional hydraulic pumps. A hybrid pump, however, is energized only for a fraction of the day and delivers positioning that does not rely on valve operation for precision control. This design also eliminates changes in oil temperature, which can have an adverse effect on press brake operation.
Some hybrid press brakes work with a motor that has a sealed shaft that reaches into the hydraulic tank. The shaft is attached to, and has direct control over, a piston pump, which delivers hydraulic pressure to move the ram—but only when an operator steps on the foot pedal.
With electric press brake technology, electric motors directly control ram movement with help from belts or gear mechanisms that drive heavy-duty ball screws. Belt-driven ball screw designs incorporate timing belts that encircle the motor’s pinion gear and another gear that sits directly above the screw. The ball screw turns in and out of a nut attached to the ram, or the nut spins around the screw, controlling the movement of the ram.
Gear-driven screw designs are similar, except in that the pinion gears are in direct contact with each other. A motor rotates the pinion gears, which in turn rotate the ball screw to operate the ram. Because of the metal-to-metal contact, this design is slightly noisier than belt-driven designs.
Some systems use pulleys to drive the ram. In a pulley-driven design, pulleys line the upper ram, wound on a common belt that pulls the ram down thanks to the force-multiplying effect of the pulleys. The pulleys pull down against springs that push the ram up after the bend. Ram repeatability is slightly lower with pulley systems than with ball screw designs.
Energy-saving Technology
The benefits of electric or hybrid machines are many, with the most obvious advantage being the energy-saving aspects of the technology. Electric press brakes eliminate the need for hydraulic oil, which means no mess oil change, and can save up to 50 percent on energy costs.
Typical industrial energy costs indicate a 100-ton hybrid brake would save about $900 per year.
Hybrids are efficient as well—using one-third the amount of oil that hydraulic brakes do.
While fuel efficiency is a plus, something else drives most manufacturers to purchase a hybrid or electric machine: accuracy and repeatability.
Hydraulic press brakes compromise repeatability as the hydraulic fluid warms over time, usually around 50 degrees F in two hours, transmitting heat to the frame. This can cause the machine’s ram to shift by up to 0.006 in. In addition to this shift, warming can also cause seal weeping and radiant heating of the shop floor. Electric models and hybrid models don’t have these problems, ensuring accuracy between 1 and 5 microns, respectively.
Some hybrid and electric press brakes also feature automatic thickness sensors that measures sheet thickness at each pinch point during the bending cycle. This comes in handy since sheet metal thicknesses aren’t always exact from shipment to shipment, causing imperfect bending results.
Unforeseen Savings
Some manufacturers may argue that they don’t need the high speed and accuracy that hybrid or electric press brakes offer; however, if they consider all the indirect and long-term cost savings possible with electric and hybrid press brakes, the advantages quickly become apparent.
For many manufacturers, the peace of mind they have knowing that their press brake will produce bends to exact specifications—without needing adjustment because of changes in oil temperature—is reason enough to go electric or hybrid. For others, the actual frustrations they’ve endured from problems with inaccurate bending, such as unnecessary costs and stress, are what push them to upgrade.
For example, if a manufacturer bends a piece that is designed to fit exactly with one or more other components, the smallest degree of variance can make the difference. If those pieces don’t fit together because rams have shifted slightly, additional work, or even total rework, may be required to bring a component up to par.
While this scenario is particularly relevant to manufacturers who bend complex parts and thin metal because even small inconsistencies can ruin an entire batch of parts, most manufacturers can benefit from a more precise press brake.
Other Bonuses
Accuracy and fuel efficiency are two of the main reasons manufacturers choose hybrid or electric press brakes, but there are a host of other benefits. Hybrid and electric technologies deliver much faster cycle times, making shops more productive and profitable.
While hydraulic brakes have valves, tanks, pumps, filters, and seals to check and maintain, electric press brakes are virtually maintenance-free. Hybrid press brakes, while still using hydraulic technologies, also require less maintenance as they have fewer valves.
New Technologies, Better Bending
The latest innovations in press brake technology have helped fabricators improve productivity and efficiency and cut costs. In addition to the obvious advantages, hybrid and electric technologies make for a cleaner, quieter, and more environmentally friendly shop floor. Add to that the stress relief that comes from less maintenance, higher accuracy, and fewer hassles, and it’s easy to see why hybrid and electric press brake technologies are catching on.
For more information, visit www.mitsubishi-world.com.
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