Press Brake Backgauging

Backgauges make the press brake more flexible and dramatically reduce setup times.

Complex bent parts that require three or more bends traditionally were problematic for metal fabricators before press brake backgauging.

In today's shops, lot sizes usually are smaller than in the past, meaning more press brake teardowns and setups are required. This creates more idle time for the machine and more material handling for operators. In these cases of low-volume, high-variety work, multiaxis backgauging eliminates the tool changes that were once performed midpart and between parts, reducing production times and the associated costs.

Press brake backgauges are the norm in today's fabrication shop. These time-savers make the press brake more flexible and dramatically reduce setup times. 

"I think today CNC backgauges are really the industry standard," said Paul Croft, applications engineer for bending products at Prima Power North America. "The flexibility that they allow for in programming and setup speeds is unparalleled."

While side gauging and pin gauging were useful ways of ensuring an accurately bent part in the past, with the introduction of six-axis backgauge systems, external jigs and fixtures that were required are no longer needed.

New backgauging systems allow more complex parts to be bent on press brakes.

"Parts that may have been hard-tooled in the past can be bent to high tolerances thanks to CNC backgauges," said Croft.

Backgauging also gives the operator the ability to switch between part numbers very quickly. Programming data can be stored and then recalled, further increasing the flexibility of the machine.

"The ability to store all the numeric position values directly in the program has sped up changeovers immensely," said Croft.

The Gauging

Gauging allows low-EAU (estimated annual usage) parts to be produced cost-effectively.

Gauging allows low-EAU parts to be produced cost-effectively.

Multiaxis backgauges, those with at least two programmable axes (X axis, in/out, and R axis, up/down), are typically viewed as the most popular type, but it's not the gauges themselves that make all the difference.

"The control system is what differentiates one gauging setup from another," explained LVD Strippit Bending Product Sales Manager Paul LeTang. "The backgauge itself has not changed much in years. [It's] the human interface where most of the return on investment is seen now."

It's no secret that press brake parts are becoming more complicated at the same time skilled operators are getting more difficult to find. User-friendly touchscreen controllers address this issue.

"Dimensions are simply keyed into the controller or the program is recalled from storage. Manual setting of gauge stops and associated problems are eliminated," said LeTang.

The CNC now controls part accuracy and repeatability, minimizing manual influences. For parts with multiple bends, productivity can be gained even on low quantities.

Quality and consistency are the most improved, especially with CNC backgauges, according to LeTang.

"Our machines' backgauges have a repeatability of ±0.02 mm in the X axis and a speed of 350 mm/sec. With this kind of repeatability, accuracy, and speed, both quality and production increase," said LeTang.

Software and Simulation

Training is always important. Gauging, which makes the entire process of setting up a press brake easier, also makes training simpler.

Three-dimensional, onscreen simulation should show the gauges, tooling, and part. This can help the operator place and orient the part in the machine.

The ability to program the entire system offline is also important.

Two independent towers make up TRUMPF’s six-axis backgauge.

When the backgauge is programmed offline, the operator needs to know only a few buttons in the 3-D programming system. This, in combination with a DXF file, allows the backgauges to be located quickly and properly, reducing the amount of scrap parts and trial-and-error bending.

"The offline software will apply the position automatically and allows the operator to visually see the locations of the fingers on the part at the machine, even if he has never seen the part and even in your most complex parts," said TRUMPF Product Manager for Bending Shane Simpson.

Gauging reduces setup times because fixtures are not necessary. It also gives the operator a more confident stop position not only front to back, but also left to right.

This is especially crucial for inside tabs so the operator does not have to locate the tool underneath the part, and also for oddly shaped parts.

"Five- and six-axis backgauges allow for the removal or reduction of required fixtures to bend complex geometries," said Simpson. "This type of backgauging also gives operators left-to-right stop positions that improve productivity and reduce the chance of collisions of the side flanges and tools." 

The more complex the part, the higher the requirement for a five- or six-axis backgauge.

"Job shops especially require advanced backgauges because they never know what is coming tomorrow," said Simpson. "OEMs generally know their product run times will be longer, and many times only need a two- or four-axis backgauge." 

That being said, even a lot size of one can be set up quickly on a press brake equipped with a six-axis backgauge.

Backgauge Retrofits

While backgauging is common, fabrication shops that don't have it on their press brakes can add Z1/Z2 capability. With just a few hours of work, additional backgauge axes can be added to an existing machine.

"Gauging is easily retrofitted to any press brake; however, older press brakes have sloppy ram positioning that exaggerates angle variations. In many cases, retrofitting a CNC backgauge to an old press brake just results in making scrap faster than before," said LVD Strippit's LeTang.

For more information, visit www.lvdgroup.com, www.primapower.com, and www.us.trumpf.com.