June 8, 2009
North American fabricators have not been as active in adoptingautomated bending cells as their counterparts in other parts of theworld. But that may be changing. These five questions can help afabricator decide how to justify the case for a robotic press brake.
Dan Aronson, president, P&A Metal Fab Inc., Clackamas, Ore., is no stranger to robots. His company runs six robotic welding cells, and it has a 12-year-old robotic press brake cell as well. Robotic welding cells? That's not too unusual, as welding companies have developed cells that can be picked up with a forklift and software that helps to assuage the fears of new programmers.
Robotic press brake cells? That's pretty unusual. Metal fabricators in North America have shown a general hesitation about jumping into automated bending because of perceived equipment shortcomings and beliefs that a human operator is the only way to ensure consistent bends.
Aronson, who has been in charge of operations for nearly 10 years now, said he would like to see his Amada Astro 100 MHE automated press brake run more frequently, but he hasn't found the right operator to embrace the technology.
"Those robots are only as good as the people that are programming them or running them," he said. Working with an older system, the programmer and operator have to be aware how a part should be properly bent to ensure efficiency and avoid collisions. In short, Aronson said his robot has to be shown how to bend. Once a part has been programmed, however, the automated bending cell is ready to run—no breaks, no excuses.
Global economic pressures now are forcing more North American shops to consider similar automation advancements, and automated bending is a fertile area for investigation.
These five questions can help you make the case for robotic bending in your shop.
Making an automated bending cell work is a matter of having an experienced press brake operator willing to make the automation work, according to Aronson. Fabricators have found welders willing to embrace robotic welding, and the same scenario applies to robotic bending cells.
John Burg, president, Ellison Technologies Automation, Council Bluffs, Iowa, stressed that it's important for press brake operators to move away from jotting down notes in their personal spiral-bound notepads about how jobs are processed to make a quality part. Instead they should make those adjustments to bending programs to guide less experienced operators or the robot, in the case of automated bending. Only with that type of openness to change and willingness to work with new technology will an automatic bending cell be successful.
On the other hand, Phil Picardat, a product manager for Amada America Inc.'s Astro bending robot systems, said that manufacturing software has progressed to the point where even a shop floor novice can run the most advanced bending cells. The days of spending several days to teach a robot how to do a couple of simple bends for a run of 5,000 parts is over.
"It's application-dependent, but it's a broad set of applications," Burg said.
Specifically, Burg pointed to three types of jobs that are suitable:
Aronson gave his own take on what makes sense.
"It has to fit the work envelope, and it's got to be within the weight limits of the press brake. Obviously, if it fits that, I would say that we are pretty open to what we put in there," he said.
Aronson said the key to his robotic bending cell is that a nearby press brake operator oversees a manual brake and the automated cell. The opportunity to perform two bending jobs simultaneously—one on the automated cell and one on the manual press brake—always made sense to Aronson, even if the job on the robotic press brake took extra time to set up when compared to a traditional brake.
All sources will agree that programming of robotic bending cells has improved tremendously over the years and helped to eliminate the need for a robotics engineering degree to program an automated cell.
All a programmer needs is a CAD model, and upon submission of the data, the software will generate a recommended bend sequence and instructions to run the cell. In some instances, software might need to be checked with an actual inspection of how a part runs through the bending sequence, but other software developers indicate that this might not even be necessary.
Picardat said that software programs now come with 3-D simulation models that mimic robot and press brake functions, which act to check and visually confirm the bending sequence before instructions are sent to the machine.
In most instances, programming can be done offline, ensuring that the automated bending cell is not interrupted.
You can't talk about robotics without talking about safety. The question is whether a fabricating shop wants to invest in a physical barrier or a more open safety system using light curtains. Both have trade-offs.
A safety cage is the least expensive solution, but it does eat up floor space, always a premium in a metal fabricating shop. For example, a bending cell from one major machine tool builder measures 40 by 17 feet, which includes the loading robot, but does not include room to accommodate the safety enclosure. For a cramped shop floor, this might not make sense.
For those interested in light curtains, take note that they could be going off when least expected.
"The problem with light beams, not that they shouldn't be used, is that most people don't know where they are. Someone might be casually walking through a shop, wave their arm, and they shut down the cell unknowingly," Burg said.
However, the use of light curtains provides the perception of a more open shop and might make sense for the company with tight controls over people entering the shop floor and very clearly marked cell boundaries.
The need to invest in quick-change tooling was mentioned previously. Taking that investment another step is the emergence of automated tool libraries (see Figure 4).
Based on the programming, these libraries automatically load and unload in both the upper and lower toolholders. These tool changers also have punch and die inverters that rotate tools for mounting in either of the toolholders.
Picardat said it's all about labor hours. "It helps to justify the purchase," he added.
That's particularly obvious when you can have one press brake operator tending two brakes. But Burg warned that the focus should really be on equipment utilization. If the automated machine is not making parts, it's not making a return on investment.
To increase equipment utilization, a company should look at all aspects of the cell. Setup in many cases can be equal to processing time. What good is an automated cell if it doesn't have quick-change tooling? How much faster can the part be processed with a six-axis backgauge instead of the traditional two-axis version?
"People are preoccupied with cycle time," Burg said. "It certainly needs to be considered, but in many cases improving cycle time will have little effect on the number of parts made in a shift or a day. Keeping the press brake bending parts more of the time will have a much greater effect on throughput."
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