Page 20 - MetalForming August 2010

Better Press Brakes
ple, if there’s 8 ft. of tooling installed in the brake and the operator goes to make one 2-ft. bend in the sequence, the LEDs will only light above that particular 2-ft. tooling section to show the operator where to position the blank. This leads to fewer setup and production mistakes and improved productivity, regardless of operator skill.”
Another way manufacturers help support operators during setup is use of
the press brake’s backgauges to guide tool positioning. As part of the press- brake setup program, the backgauges will index to each location where the tools are to be set. Then the operator simply has to slide the tool against the backgauge finger, lock it down and hit the “Go” button on the controller, to sig- nal the backgauges to move to the next tool-set position.
“This setup assistance and other fea-
tures allow any operator in the shop to set up even the most complex job,” adds Simpson, “with optimum assurance the setup will be correct, regardless of his skill level. This allows shop manage- ment to make purchasing decisions based on their own set of rules and press-brake specifications, rather than leaving buying decisions up to the oper- ators, who often will prefer a machine based only on their own experience level with that machine’s manufacturer. That’s not the best way to make a pur- chasing decision, and new technology features such as OLP software and setup aids act as equalizers.”
Bend-Angle Accuracy
“Tolerances are tighter than ever,” continues Simpson, noting that many fabricators that once specified ±0.030 in. tolerances now quote 0.010 to 0.015 in. tolerances. “Also, parts formed on press brakes have become much more com- plex as fabricators look to streamline designs, use fewer parts and eliminate welds. That places tighter requirements on bend-angle accuracy —in the past, a part formed to a 1-deg. tolerance could be corrected in a welding fixture. As two- and three-piece assemblies become one complex formed part, fabricators lose that luxury.”
As a result, parts have to leave the press brake perfectly formed, and this is where measuring bend angle in-process and the ability to make real-time adjust- ments in the press brake come into play. Each manufacturer has its own way of doing this, says Simpson, including use of pressure sensing or lasers to measure bend angle from both sides of the work- piece.
For example, says Simpson, Trumpf ’s angle-controlled bending (ACB) process measures material variance, sheet thick- ness and grain direction to help ensure bend-angle accuracy.
“Grain direction has become a crit- ical variable,” says Simpson, “particularly when material prices creep up. When that happens, fabricators will nest blanks for processing (in a laser-cutting machine or a turret press) to optimize material utilization. Therefore, blanks
18 METALFORMING / AUGUST 2010
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