June 4, 2010
A new press brake and tooling purchase leads to a new way of thinking about manufacturing, including the reduction of batch sizes and work-in-process.
When John Soler walks to the sheet metal shop, he sometimes glances at an odd sight: a 175-ton press brake with a 12-foot bed and a 6-inch-long tool set forming a small, thin bracket. Seeing this, the vice president of manufacturing at American Security Products Co. (AMSEC), Fontana, Calif., knows the operator is following the company's new modus operandi: Produce only what's needed, when it's needed, as quickly as possible.
It may seem counterintuitive, but bending such a small part on a huge press brake takes less time than sending it through the company’s three lower-tonnage machines, which are old and less accurate. And the run of small brackets will be finished soon enough. The metal safe manufacturer rarely runs batches of more than 50, even for standard parts used on most of the company’s products.
It wasn’t always this way. The sheet metal shop has fewer press brakes than it did a year ago but benefits from greater throughput now, despite the funny-looking brake setups now and then. How the company got here is a story of serendipity, changing mindset, and management foresight. Remove any one factor, and the story likely would have had a different ending.
Last year AMSEC had six operators running six press brakes of early 1980s vintage. They worked with racks holding a dozen or so sets of European-style tooling. That was a fair number, but a quick look at the bending operation revealed why. They were coining and bottoming. The only way to attain a perfect 90-degree angle on the older machines was for the punch to press the metal completely into the die cavity. It was impossible for them to air bend and obtain an acceptable level of accuracy.
But for Soler and Kevin Ellis, production supervisor, this wasn’t top of mind. After all, the existing press brakes and tool sets produced more than enough parts to meet the demand of the assembly department. What presented issues were the thicker, longer parts. The sheet metal department had brakes of 110 tons and less. A few years ago Soler even sold off a few old 50-ton machines. Why have those when higher-tonnage machines could bend everything from 22- to 10-gauge mild steel? (The company does make heavy safes made of thick plate, but those are only plasma-cut and welded, not bent.)
The thinking was that another high-tonnage system would make the bending department more flexible, with more machines able to bend any component the shop might encounter. For this reason, AMSEC managers first set their sights on a 175-ton, 12-ft.-long Accurpress Edge CNC press brake (see Figure 1). The new brake could handle large, thick workpieces and wouldn’t have the maintenance issues of the older machines.
Then managers tentatively considered quick-change tooling technology—and the potential of an entirely different approach.
Until last year additional setups were something to avoid, and for good reason. Because the brakes were primarily used for coining, nearly every tool changeout required the operators to manually remove both the punch and die and replace them with another tool set. They would jog the ram down to ensure the punch was properly seated into the ramp clamps, and then tighten them with an Allen wrench, the way they had done for decades. They then would run a few test parts to verify a good setup. After that, they finally started the batch, which usually came in quantities of 100 or 500.
Soler and Ellis did a good deal of due diligence, but even after all the research and ROI calculations, both said that investing in tooling was a hard choice. The plan called for an upgrade to precision-ground punches and dies, along with a hydraulic clamping system, all from Wila. But with a dozen tool sets already on the floor, why invest in even more?
Three factors changed the way people at AMSEC thought about bending. First, the accuracy of the new press brake and new tooling system meant they could air-bend, which allowed one tool set to bend parts of multiple geometries. AMSEC bought two American-style, 30-degree acute punches matched with one acute die, along with one American-style gooseneck punch and die set. Those three tool sets can bend 90 percent of what the sheet metal shop processes. The rest is formed with existing European-style tooling.
Second, the machine’s 18-in. open height and 10-in. stroke length could handle workpieces with long return flanges efficiently and quickly, thanks to the ram’s fast approach speed. Deep gooseneck punches and acute punches with reliefs machined onto the back side helped here as well. This allowed a few more inches of bending before the return flange would interfere with the back side of the punch.
Third, operators could use hydraulic clamping to change out tooling in less than a minute (see Figure 2). The Wila clamping system, which ties into the brake’s hydraulics, seats, centers, and aligns the tools automatically. Inside the clamping system, hardened pins, aligned with the tool’s self-seating grooves, lift the tool to exactly where the shoulders rest against the clamping system, emulating the operator’s jogging action during a manual setup. Only this time the operator doesn’t need to tighten the manual ram clamps, an action that often can misalign a tool ever so slightly, sometimes enough to throw a precision bend out of tolerance.
”With hydraulic clamping, you don’t have to do adjustments every time you set up,” said Chris Miano, sales engineer with North-South Machinery, Brea, Calif. Miano assisted AMSEC with its press brake and tooling investment last year.
Although the technology has been a boon to AMSEC’s sheet metal shop, Ellis and Soler conceded it probably would have been a wasted investment if it wasn’t for a change in company culture. The sheet metal shop is but a small part of the overall organization, which employs 222 (190 in production) and operates out of 150,000 square feet of production space. The culture change led to the lean manufacturing initiative that, in turn, dramatically reduced batch sizes. Without smaller batch sizes, a quick-change tooling system wouldn’t have done much for overall productivity.
Ellis commented, “Before, we only seemed to know two numbers: 100 and 500. It used to be like we were going to battle. We’d shear as much as we could, punch as much as we could, and bend as much as we could. If we needed more of something, we’d throw more operators and more machines at the problem.”
Sheet metal production used to be managed by a traditional work order system. Those in the welding and assembly department ordered what they needed to replenish stock, and the sheet metal department would fulfill it. And they typically would order more than they needed as a buffer against an unforeseen demand spike. After all, you can’t assemble safes without its metal components at the ready. So what if they piled up? At least the parts were there, ready when needed.
But they still had to wait for parts. Here’s why.
American Security Products sells its ability to customize. Some safes are sold from a catalog as stocked items, but most are sold with a safe body fabricated to a custom size, each using common internal components—small brackets and the like. Previously the assembly department would order heaps of those standard components, which would keep the shears, punch presses, and press brakes continuously busy. A blank would be cut and then sit on the floor for days before space opened up on the press brake operator’s schedule. The operator, after all, had a backlog of several large batches—500 of this, 100 of that, another 500 of this—that kept the ram in almost perpetual motion over multiple shifts.
Meanwhile, when a custom order for a safe body came in the door, it was delayed until operators reached a convenient stopping point between large batches of standard parts. At worst, a custom part would get lost in a sea of work-in-process (WIP). This meant that a more urgent custom safe body had to wait to be formed and, sometimes, found among all the WIP.
Soler, Ellis, and other shop managers had been studying lean manufacturing for several years, and during the past year rolled out the new concepts to the shop floor. Today a simple replenishment system governs the volume of standard components produced. Operators produce enough to fill marked bins to a certain level—nothing more and nothing less. When assemblers use the components, the bins empty, which triggers demand for more parts.
Batch sizes now range from 10 to 50. This has minimized WIP; between operations, parts may sit on the floor for a few minutes or hours instead of days. A batch of 50 may take only a few hours to flow through the entire sheet metal department, from shearing to punching to bending.
”Reducing the number in the batch sizes was a big deal,” Ellis explained. “It has allowed us to shear material, send it immediately to the punch, then to the press brake.”
Small batches also allow the sheet metal department to produce custom orders virtually on demand. The shear may need to finish only 10 or so parts before it can be loaded with blanks for a customized safe body. And a last-minute schedule change doesn’t faze the press brake operators. Air bending at the brake means they don’t need to change out tools after every batch. But even if they do need to change tooling, it takes less than a minute.
Soler still chuckles when he sees 1-in.-wide brackets being bent by a 6-in.-long tool set, sitting alone on a 12-ft.-long bed. The shop still uses its older press brakes to coin certain brackets, especially ones with internal holes, which would fold and buckle if they were air-bent. But generally, it’s actually faster to send more parts through the new brake and let the older machines sit idle. The new press brake is now the most utilized machine on the floor. The controller can store more programs than AMSEC will ever need, and it offers the ability to program offline with a bend programming module interfacing directly with SolidWorks®.
Meanwhile AMSEC’s equipment wish list looks much different than it did a year ago. Managers have changed their view of low-tonnage machines. One or two modern, 50-ton press brakes would suit very well, particularly for those small brackets.
In the long run, the company hopes to emerge from the recession leaner and smarter. Business last year declined 20 percent—not as bad as some, but still a sizable amount. The slowdown’s effects, thankfully, were softened because of the company’s lean manufacturing efforts. To attain even greater efficiency, shop managers hope to pursue a staged bending concept, with three or more tool sets placed next to each other along the new brake’s 12-ft. bed (see Figure 3). The new tool sets could be set up in a row: a gooseneck next to an acute-angle punch, next to special tools for hemming or offsets, for example. A worker would call up the program, insert the tools, and start the done-in-one operation, bending and hemming in one setup.
AMSEC would need to upgrade its existing backgauge, which now moves in X (away and toward the operator) and R (stroke position). Staged bending would benefit from a backgauge with two automatic fingers (Z1 and Z2) that move across the bed to hold workpieces behind each tool set. But as far as equipment investment goes, that’s about it.
By itself, new tooling wouldn’t have changed much at American Security Products. According to sources, what it really took was changing the old manufacturing mindset, away from long batches and that keep-the-machine-running attitude.
If a machine’s running, it’s not making money; it’s just making parts. Those parts don’t produce cash until after they’re assembled into a safe and sold to the customer. If it takes forever and a day for a product to be shipped, all that extra shearing, punching, and bending is just wasted effort.
”To be honest, the way our [bending operations] work now isn’t how we envisioned it, and it was very difficult to change the old manufacturing mindset,” Ellis said. “But we’re very happy we did.”
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