Bending is second on the list of “Four Essential Steps From Sheet Metal to Finished Product,” and bending machines are mostly manual. That’s changing though as automated bending becomes more reliable and affordable. As we’re always looking for faster and better ways of making our metal fabrications we took a look at what automation has to offer.
How sheet metal is bent
In metal fabrication most bends are put in by press brake. The heart of the press brake is its upper and lower tools. The lower tool has a ‘V’ section and the upper has a mating wedge or angle profile. Put the sheet between the two and the wedge forces it down into the ‘V’, creating the bend. (“Bending Your Metal Fabrication into Shape” gives more detail.)
The press brake operator lifts a cut blank from a stack, orients it, slides it in between the tools until it hits the back stop, and brings down the upper tool. Putting in additional bends means withdrawing and reorienting the sheet, sometimes flipping it over for bends going the other direction.
That’s hard work, especially on bigger blanks which sometimes need two people to handle. It’s easy to make a mistake that puts a manual press brake bend in the wrong place, makes it to the wrong angle, or leaves it out completely.
This is where automated press brake bending comes in.
Press brake automation
To be precise, it’s handling the blank that gets automated. While really high volume operations can justify dedicated bending systems with lots of hard tooling, for fabrication shops like ours it’s robotic bending that makes most sense.
In a robotic press brake bending system a robot takes the place of the operator. A stack of blanks is presented to the robot, which takes one off the top.
To ensure the blank is gripped precisely the robot typically places it in an orientation stage. This is just a slope with two raised edges. The blank slides down and stops against the sides. Here the robot picks it up again and takes it to the press brake.
With the blank in place the press brake cycles and the bend is made. If more bends are needed the robot repositions the blank as necessary. Then, when the part is finished the robot either stacks it or puts it on a chute or conveyor.
The people who work here at Wiley are fast and accurate, but they are only human. They get tired and occasionally mistakes happen. All that bending and twisting is hard on their backs too.
Robotic press brake bending is faster and more consistent than a human worker. The robot doesn’t need breaks, so it actually works more hours per day, and it doesn’t make mistakes. All of that means more capacity and higher quality.
An automated press brake bending cell like the one we described isn’t cheap. Plus, it needs engineering support to program new jobs. Offline programming is possible but robot programs usually need some on-machine touch up. That stops production and can consume a lot of metal blanks while speeds and positions are ‘dialed-in’.
Changeover time is another issue. While it takes only seconds to load a program press brake tooling must also be set up along with grippers, stacking systems, conveyors and so on.
When automation makes sense
If you raced a manual press brake against an automated system it’s easy to see how the manual machine would be making parts some time before the robot really got going. With a long enough run the automated system will get ahead, but for smaller quantities manual wins. And that’s especially true in a ‘job shop’ environment where every job is different and needs a new robot program.
Automated bending offers speed, quality and injury prevention but has drawbacks too. It’s expensive, needs engineering support, and takes time to set up. For shorter production runs manual bending comes out ahead.