by Noelle Stapinsky
Measuring technology and offline programming are fundamental for press brake operators to maintain consistent angular accuracy
As more and more job shops and contract manufacturers are being dealt shorter run orders, press brake operators are faced with a series of challenges. It’s not the machinery that’s to blame–precision press brakes are very accurate, have a pretty high rate of repeatability and most machines repeat at ± 1°.
What today’s operators are inundated with is material variations and accounting for springback throughout the bending process.
Whether it’s bottom or air bending, there are so many elements operators need to account for, such as different tensile strengths, material properties, grain direction, and thickness variations, all of which determine the lower dead point (travel depth) required to bend a particular angle. Stainless steel presents grain direction issues and will springback more than mild steel, for example; and exotic materials such as titanium or other structural steels have huge springback during a press brake bend.
Structural steels and hot rolled steels can also vary in hardness from one spot to another.
“There’s really no solution for those types of materials, [operators] just adjust on the fly… there’s really no consistency in the way they react,” says Scott Ottens, bending product manager, Amada America Inc.
“What shop floors also run into are variations in material chemistry that arise because steel blanks often come from different suppliers. Even if the thickness is identical, there are often some mechanical property variations from sheet to sheet as supplied from the steel mill or service centre,” says Bill Bossard, president of Salvagnini America. “In today’s environment, lot sizes are shrinking. We see a general demand for make-to-order or kit type manufacturing.”
Usually, an operator will account for a few parts to be scrapped to dial in angle accuracy. They’d bend a part, make an angle correction, continue through the various bends to tune in the form features and then toss it, and sometimes there are multiple parts that get tossed.
“It’s quite often that the operator will see one piece of raw material in front of the machine, and they don’t have an opportunity for a set up piece because that one piece has to be a good piece,” adds Bossard. “Therein lies the challenge.”
Bending on the fly
Inline laser and external measuring technologies have really come into play to reduce setup times and to achieve that first good part.
Using a real time measuring device, Vincent Iozzo, product manager for TruBend, TRUMPF Inc., says the operator doesn’t have to worry about doing angle corrections and dialing the part in. They can just take a first piece of metal cut from a laser punch, bring it to the machine and get a good part.
TRUMPF’s Automatically Controlled Bending (ACB) laser technology was first developed for its flagship TruBend 5000 series. This angle measuring tool is put into a setup plan and has probes that measure the material live inside the bend line. TRUMPF also offers an external AC laser that can read material from the outside of the press brake. It’s available on the TruBend 3000 and 5000 series.
This laser technology is activated on every single bend. “So no matter what bend they’re on, the machine is providing feedback and re-hitting that part. That takes less than a second to do. So even though there’s additional time, it’s saving the operator from pulling the part out and measuring it,” says Iozzo.
And since it’s only measuring springback for a specific bend, it doesn’t care what the thickness variation is or what the grain direction might be. To prove this, TRUMPF does a demo with three pieces of material–stainless, aluminum and steel. Iozzo says, “without changing the program or making any modifications to the bend, we’ll bend all three and they’ll all be ± one point of a degree off 90.”
Salvagnini’s MAC2.0 optical laser measuring technology is also an inline device that measures springback and generates a corrected value that’s sent back to the CNC control.
“The ram is then repositioned to final depth to create that part to the accuracy desired,” says Bossard. “But it’s not just a measuring device, there’s a whole raft of additional features including cylinder repositioning, crowning on the bed of the press brake, or level of ram via linear scale.”
Inline measuring technology can also account for any grain direction. Ottens says that sometimes when you cut on a laser and don’t orient the parts the same way, grain direction can become a problem as you turn the part to bend. “With a measuring device, you can choose which bends you want to check.”
Amada offers BI (Bend Indicator) sensors that use probe and laser technology to help maintain bend accuracy while processing materials that vary in thickness and grain direction. The BI-S probe type and BI-L laser type sensors provide fabricators with trial-free bending. Ottens says bend angles are measured and adjusted on the fly to provide the correct angle on the first bend and to monitor and adjust angles throughout a production run.
Indeed, angular accuracy has been the biggest problem for press brake operators, and while technology such as measuring devices have kind of addressed it, there are a couple of other issues facing the fabrication industry– accurate blank development and a declining skilled workforce.
“If you go to a typical job shop… the parts have been designed by an engineer for a customer. The engineer might be using a standard bend deduction chart,” says Ottens. “So with air bending, the V-opening affects your bend deduction, but the engineer might not be taking into account what tooling or V-opening the operator is going to use.”
Of course, if a blank is off, it’s going to be a struggle for the press brake operator to get an accurate part.
This is why offline programming is becoming essential. “The first thing you apply to an offline program is what tools are going to be used and from that you can calculate a correct bend deduction. Then you can calculate a blank, kick that back out to your blanking software and punch or cut a correct one,” says Ottens. “We utilize a two software package. On the CAD side we have software called Sheetworks where solid models or 2D models/files can be imported and corrected. The software also automates a number of typical engineering processes.”
On the bending side, the file would be pulled into Amada’s Dr. ABE bending software, a CAD software that creates programs for the press brake. Those programs are saved on a server that operators can access at the brake control. When the operator calls up a program, all the information needed to process the part – tool setup, bend order and a 3D graphic of the process – is available on screen.
While operators can use offline programming live in front of the machine, Iozzo recommends having a secondary source pushing programs to the press brake. “At the end of the day your press brake will not make money unless it’s going up and down. If an operator is programming, he/she isn’t producing parts.”
For bending, TRUMPF’s Techzone can be integrated directly on the machine control and can program about 200 parts in less than four minutes. But for an entire shop solution, TruTops Boost will incorporate all technology on the shop floor.
“The idea for both technologies is that I can load a 2D or 3D model and automatically produce NC code for any machine I want. This all happens in a matter of seconds,” says Iozzo.
Salvagnini just released its Stream Former offline software package in January. It’s designed for both press brakes and panel benders. “Offline programming is going to be very important for all sorts of forming. That’s where the industry is going and where everybody has to get to,” says Bossard.
Offline programming also addresses the declining skilled workforce issues according to Iozzo. He says the number one complaint he hears from customers is that it’s impossible to find a person to stand in front of a press brake and produce good parts.
“Offline programming allows you to bring in a newer, greener person and, with a little training, still produce good parts.”
As more fabricators are served up smaller run sizes, the pursuit of attaining a first part, good part is imperative to stay in the game. With such technology at your side, process efficiencies will surge, and those press brakes will keep going up and down. SMT