Bending Efficiency Explained

Canadian Industrial Machinery asked John Kemp, bending product manager, Bystronic Inc., to explain how manufacturers can improve the efficiency of their bending operations. Here is what he had to say.

CIM: How can efficiency gains be realized in the programming stage?

Kemp: There are two areas in which programming can affect the efficiency of bending operations.

One is producing the correct blank size. Often designers and engineers call out a radius on the part that is not achievable with the tools the operator has to work with. The operator cannot produce any radius, only those for which he has the tools. Since the programmed radius in most cases does not match the actual radius, the blank size is not correct, and the operator must compensate for this to make the part within tolerance. This slows production and increases scrap.

The second is part design. Today’s press brakes and software create more complex parts more easily now than ever. If you can eliminate secondary operations like welding, drilling, and assembly at the part design level, you may not necessarily reduce the time or cost to bend the part, but you can see drastic reductions in the overall part cost by eliminating these non-value-added operations.

CIM: Do you always recommend offline programming?

Kemp: Not always, but in most cases.

Programming offline, when done properly, will always increase the efficiency and throughput of the bending department. However, in some cases, the gains may not be enough to justify transitioning to offline programming. The idea is to keep the press brake bending parts and not standing still while a program is being made. If your parts are relatively simple and can be programmed in a few minutes on an easy-to-use controller, it becomes harder to justify moving programming offline.

CIM: How important is creating the best bend sequence?

Kemp: Bend sequence is the first and most important portion of making an efficient bend program.

The bend sequence affects the tooling setup, the possible gauging points, and how the operator must manipulate the part from bend to bend. This is most easily done using a 3-D representation of the part in the offline programming software.

The bend sequence can then be proven out by running a simulation of the part offline instead of programming at the machine, where some part collisions cannot be seen until it is too late.

CIM: What’s the role of simulation in press brake bending?

Kemp: Simulation is the final step in the production of a program offline. This shows the programmer exactly how the part needs to be manipulated; if there will be any collisions with tools, backstops, or the machine; and verifies that all programmed positions are possible on the machine.

The best machine controllers can show the simulation to the operator on the shop floor as well.

CIM: Does this make trial-and-error bending a thing of the past?

Kemp: The technology certainly exists to make trial-and-error bending a thing of the past. Unfortunately, far too many fabricators are not taking full advantage of this.

The high-end press brakes of today have the ability to compensate for deviations caused by changes in material and ambient conditions, and the offline programming software exists to create the correct flat blank and a plausible, easy-to-follow program.

There is no logical reason why we cannot take a 3-D file, unfold it, cut it, and form it to print the first time through.

CIM: What role does tooling play in bending efficiency?

Kemp: Setup time is where the most potential savings can be found if you are updating from older technology.

Precision-ground, quick-change tooling is vital to increasing throughput, especially when lot sizes are falling from the hundreds to just a few pieces or even a single part.

CIM: How important is proper setup of tooling?

Kemp: The quick-change tooling of today, when coupled with hydraulically powered clamping systems, makes tool changing almost foolproof. The controller shows the operator which tools to load and where to put them. Some machines even verify that the tooling that was loaded is correct. The operator then clamps the tooling, usually with a push button, and the setup is complete.

CIM: How should tooling be stored when not in use?

Kemp: Tooling should be stored in an enclosed cabinet when not in use, with no load placed on the reference surfaces. The enclosure ensures the tools stay clean so that the dust and dirt accumulation does not foul the bending surfaces during the next use.

CIM: What role does the operator play in press brake efficiency (or lack thereof)?

Kemp: Bending is the most operator-intensive step in most fabrication shops. Very few other operations rely on the operators so much for throughput, [and] the most successful fabricators look for ways to lessen this burden.

Any operation requiring more than one operator because of part size or fatigue should be examined to see if sheet followers or even a bending robot could be utilized. In general, a robot can produce 30 percent more parts than an operator; not because it is faster on a single piece, but because it never stops.

On large or heavy parts the throughput can easily be doubled with the use of a robot.

CIM: How important is understanding bending technique?

Kemp: I would contend that hemming, for example, is the most underutilized bending technique.

Hemming opens up a whole new range of ideas and possibilities for designers and engineers. Instead of thinking about the best way to join these two pieces together, start thinking about how you can utilize a hem to make it all one piece.

CIM: What technology on the press brake itself can improve efficiency?

Kemp: Most press brakes on the market today offer very high accuracy and repeatability.

What separates high-end machines from the rest is the ability to adapt to changes in material properties on-the-fly. Pressure changes caused by differences in thickness or tensile strength change the deflections inherent in the machine. In order to guarantee first-class bending results, the machine must be able to compensate for these changes on-the-fly. If the machine does not, then the operator must do so, and this will cost time and money.

For more information, visit www.bystronicusa.com.