Page 25 - MetalForming January 2011

the nut spins around the screw, con- trolling ram movement.
Gear-driven screw designs are sim- ilar, except that the pinion gears are in direct contact with each other. A motor rotates the pinion gears, which in turn rotate the ballscrew 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, pul- leys 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 ballscrew designs.
More Efficient, More Accurate
The benefits of trading up to an electric or hybrid machine are wide- spread. The most obvious advantage is the environmentally friendly and ener- gy-saving aspects of the technology. Electric press brakes eliminate the need for hydraulic oil and can reduce ener- gy costs by as much as 50 percent. That means no messy oil changes or detri- mental effects to the environment caused by disposing of old oil. Using typical industrial energy costs, a 100- ton hybrid brake can save a fabricator about $900/yr. Hybrids also are effi- cient, using one-third the amount of oil as hydraulic brakes.
While greater efficiency has helped fuel interest in electric and hybrid designs, the improved accuracy and
repeatability from the machines also has fabricators taking interest. They know well that when using hydraulic press brakes, ram repeatability becomes compromised as the hydraulic fluid warms over time—typically by around 50 F in 2 hr.—which transmits heat to the frame. This can cause the ram to shift by as much as 0.006 in. In addition to this worrisome shift, warming also can cause seal weeping and radiant heat- ing of the shop floor. Electric and hybrid models avoid these problems, ensuring accuracy within 1 to 5 microns.
Some hybrid and electric press brakes go one step further to ensure accuracy: they’ll employ automatic thickness sen- sors to gauge sheet thickness at each pinch point during bending.
Unforeseen Savings
Some fabricators might argue that they don’t need the high level of speed and accuracy that hybrid or electric press brakes offer. But if they consider all of the indirect and long-term cost savings possible with electric and hybrid press brakes, the return on investment quickly becomes apparent.
For many fabricators, the peace of mind they gain knowing that their press
brakes will produce bends to exact specifications—without needing adjust- ment due to changes in oil tempera- ture—is reason enough to make the switch to electric or hybrid. For others, the 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 forms a part designed to fit precisely into an assembly with one or more additional components, the smallest degree of variance can make a huge difference in assembly time. If the parts don’t fit together properly because the press-brake ram may have shifted slightly, additional work, or even total rework, may be required to bring a component up to par. While this sce- nario is particularly relevant to fabri- cators that bend complex parts from thin sheetmetal, where even tiny incon- sistencies can ruin an entire batch of parts, most manufacturers can benefit from using a more precise press brake.
Put simply: Hybrid and electric press brakes can help fabricators substan- tially streamline downstream opera- tions, saving time and money and increasing customer satisfaction.
Added Bonuses
While accuracy and fuel efficiency are driving fabricators to invest in hybrid or electric press brakes, other benefits await. First, hybrid and electric technologies deliver much faster cycle times, making shops more productive and profitable.
Also, fabricators using hydraulic brakes must invest time and money to inspect and maintain valves, tanks, pumps, filters and seals. Hybrid press brakes require much less maintenance as they use significantly fewer valves; electric press brakes are virtually main- tenance-free.
Electric and hybrid press brakes also make for a much nicer shop-floor atmosphere. They operate more quiet- ly than do hydraulic press brakes, and don’t cause messy oil leaks or generate residual heat. MF
Software Takes Bending to a New Level
Hybrid and electric technologies aren’t the only innovations shaping the press-brake market. New programming software is improving the usability and accuracy of press brakes, in a very cost-efficient way.
Some software systems feature 3D modeling and simulations that simplify press-brake programming and opera- tion, even for relatively inexperienced operators. These sophisticated systems can automatically position backgauges and compute optimal bend sequences.
What’s more, some software features interactive process simulation that can provide detailed, configurable simula- tions of any press-brake operation. Operators and programmers can view (and adjust) animated backgauge movement, ram stroke, and part inser- tion and retraction, as well as potential collisions.
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MetalForming/January 2011 23
The latest bending software for press brakes features 3D modeling and interactive process simulation to help guide the bending process.