January 27, 2011
It's a given that a skilled press brake operator is tough to find. But for entry level workers, what should shop managers be looking for?
Good press brake operators are hard to find. Be it a small or large company, product-line or contract manufacturer, they all seem to have the same problem finding, recruiting, and retaining good, experienced press brake operators.
But think about this: Have you changed the job requirements of your operators as your press brakes have modernized? While some skills, like reading drawings and using measuring equipment, always will be required, other skill requirements have changed as the machinery has changed.
The evolution of all metal fabrication equipment over the past three decades has turned the industry upside down. CNC laser cutting, high-definition plasma cutting, high-speed punching, CNC press brakes, and robotic welding cells have replaced shears, single-station turrets, manual welding cells, and many other operator-driven machines. Technology advances have given us more efficient systems, but they also have left companies reeling to find workers to take full advantage of these tools.
The fact is that most of today’s laser cutting operators couldn’t decipher a G-code string if their lives depended on it. Why should they? So much today is done in CAD/CAM, and a controller with graphical depictions allows the operator to change just about anything he would need to without ever editing G-code directly. So the operator of a profile cutting machine has evolved from one who had to be an expert in G-code and on-machine programming to one who loads programs, monitors material availability, and optimizes the cutting process.
CNCs and, more recently, PC-based controllers have revolutionized fabrication equipment across the board, and the press brake is no exception. Changes mainly have been market-driven. Gone are the days when shops could afford large inventories and part runs in the thousands. Lean manufacturing has driven lot quantities from the thousands to less than 100, and often a single part. This has meant that the machinery must be more flexible, easier to set up, and quicker to program.
For press brakes this has translated into high accuracy. Operators can take advantage of air bending; multiaxis backgauge systems so that gauging of virtually any shape is possible; hydraulic clamping units for fast tool changes; automatic crowning systems to eliminate shimming; and offline programming so the operator does not have to program at the machine.
Those fortunate enough not to remember the days of manual setup may ask, “How could setup possibly take an hour or more?”
It most certainly did, and to illustrate, consider a machine with a single-axis CNC backgauge with no memory. Operators needed to determine the desired flange lengths on each of the bends as well as the bend order. Next the operator input the flange lengths and required tonnage into the controller to make the first bend. When the first angle was wrong (notice I didn’t say “if”), the operator would add shims under the dies or adjust wedges in the toolholder to correct the angle—an action probably required in several areas of the brake bed, depending on the bend length.
How many shims did the operator need to correct the angle? Will one tool set work better than another? The answers often came from trial and error. If an operator worked on a brake with no backgauge, that added 30 minutes or more to the setup as he laid out the part, scribed the bend lines, set the hard stops, adjusted the flange length and squareness, and performed only a single bend at a time.
Experience and know-how really affected how long this all took, which is why decades ago many bent parts were made simple, with more pieces just welded together to make the final assembly (see Figure 1 and Figure 2). Sure, if the design had fewer parts, it would have required less welding. But fewer parts often meant more complex bending of geometries that were either very different or impossible to form on the equipment of the day.
Compare this with modern press brake setup:
So in five minutes, the operator already completed the first part.
Many things beyond the operator’s control need to happen to make the first part as described above—and some are invisible to the operator. First is to provide the operator with the correctly sized blank. Too often because the bend allowance is not calculated properly or the tooling cannot produce the exact inside radius from the drawing, the operator is left to make adjustments to flange lengths. These adjustments are required not because of inaccuracies in the machine, but because of the engineering process. The calculated bend allowance may be off by only a small amount, but because of tolerance buildup, the discrepancy is exacerbated for each subsequent bend. For this reason, the operator adjusts the flange lengths so that instead of all the error ending up on the last flange of the part, it is spread evenly across all flanges.
Second, the accuracy of the machine and the crowning system gives the operator the correct bend angle from the start. Changes in tensile strength, temperature, thickness, and bend position on the bed are all compensated automatically by the machine. Operators of older equipment compensated for this on their own.
Third is precision-ground, quick-change tooling. Hydraulic clamping allows operators to replace a full bed of tooling in minutes. All of the tool sections are small enough for a single person to lift, and the self-centering and self-aligning feature makes it virtually impossible to misalign a tool. This eliminates the time-consuming process of tool shimming, which traditionally accounted for tooling and crowning inaccuracies.
Training today’s operators involves more than having them work with an existing setup and run hundreds of parts. They need to be agile, smart, and, most important, willing to learn. You cannot take someone off the street and make him a bending expert overnight. But with a modern machine you can have an operator bending parts in a day, proficient in a week, very effective in a month, and producing at the top of the machine’s capability within a couple of months.
Some fabrication managers have gone so far as to ask an unusual question during the job interview: Do you play video games?
This makes perfect sense. In her paper “Video Games and Spatial Skills: An Exploratory Study,” Diana Gagnon, a postdoctoral fellow at MIT, described how video games help develop skills involving spatial relationships, talents that may help one operate a modern press brake.
She wrote, “Video games present spatial manipulations within a symbolic representation of space. Therefore, the player may also be learning to use and understand two-dimensional and perspective, symbolic representations of space. By manipulating objects according to the unique set of physical laws that are presented in the game, the player may be internalizing a whole set of intuitive rules of physics and geometry, in addition to understanding pictorial representations of space and spatial relationships.”
In short, a gamer can translate a 2-D image on a computer screen into a 3-D environment in his or her head. This is exactly the skill shops look for in a press brake operator. Can an operator visualize a 3-D part from a flat blank and a drawing? Can he understand the 3-D views shown on the machine controller and interpret them into part manipulations during the bend sequence (see Figure 3 )?
Another skill gamers often bring to the table is an in-depth knowledge of computer operations. With nearly all modern machines having some type of PC-based Windows® controller, having these computer skills is essential to the efficient operation of a machine tool.
Comprehensive bending knowledge is desirable for any new employee, but it may not be required, at least not initially. Again, the changes in metal fabrication equipment have been market-driven. If a shop averages just four different setups per day, and the average setup is 60 minutes, the cost would be $52,000 a year, assuming a shop rate of $50 an hour. Fabricators simply can’t afford hourslong setup times (see Figure 4).
Experienced press brake operators probably learned so much about bending because of the fact that decades ago shops could afford those long setup times. They learned about calculating bend allowances and bend deductions because they had no choice. Today operators can make parts without a complete mastery of these fundamentals.
Of course, someone on staff should know bending fundamentals, and if any technician wants to climb the career ladder, he will certainly need more knowledge. In fact, it could be argued that, when it comes to bending, knowledge requirements have shifted toward the offline bend programmer who ensures that flat part profile sizes are what they should be, and that bend programs and tooling setups allow operators to efficiently produce a good part. For bend programming, it may be easier to train an experienced press brake technician on computer software than to teach a computer whiz bending.
But at the operator level, is it more important to have someone with bending experience who has to learn the computer side, or would it be better to have a computer whiz whom you could teach bending to? Most likely, the answer lies somewhere in the middle. Regardless, that new hire must be willing and eager to learn.
The FABRICATOR® is North America's leading magazine for the metal forming and fabricating industry. The magazine delivers the news, technical articles, and case histories that enable fabricators to do their jobs more efficiently. The FABRICATOR has served the industry since 1971. Print subscriptions are free to qualified persons in North America involved in metal forming and fabricating.