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issue: February 2007 APPLIANCE Magazine

Metalworking
Metalworking Ages Gracefully


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by David Simpson, Contributing Editor

Metalworking equipment suppliers keep up with the times by offering more flexibility and quick changeover.

Coe Press Equipment Corporation (Sterling Heights, Michigan, U.S.) developed a series of Zig-Zag servo roll feeds for staggered feeding applications of narrow width coil. The feeds deliver maximum material processing of 12-inch to 30-inch coil widths and maximum material thickness ranges of 0.020-inches to 0.187-inches. These press-mounted models provide fast processing velocities (576 feet/minute) and acceleration rates (70 feet/second). Y-axis shuttle travel of 4 inches to 12 inches adds processing versatility required for one-out or multiple-out applications. A ServoMaster 3 dual-axis controller with multiple-out program lets the user easily calculate and set up all machine parameters quickly and accurately. A standard 500-job memory is provided for fast and repeatable set-ups.

It’s hardly surprising that bending, punching, notching, and otherwise working with sheet metal continues to be an essential part of many appliance producers’ operations. For larger products, metal cabinets provide a durable covering and are available in multiple colors and finishes. Sheet metal parts also make up internal structure or working parts, such as dryer drums or heat exchangers. Even as plastics continue to make inroads, sheet metal is a cost-effective and practical choice for many appliance applications.
Since metalworking is a mature industry, most equipment available to appliance companies is fundamentally similar to what was available decades ago. However, equipment suppliers have fine-tuned performance, speeded up tooling changes and added more advanced controls. Suppliers are responding to customer needs for equipment that can handle shorter production runs and more frequent model changes.
“More flexible automation is being utilized today in lieu of the dedicated special automation systems of the past,” observes Ron Demonet, vice president, system sales, Atlas Technologies, Inc. (Fenton, Michigan, U.S.). “The new systems are taking ‘off-the-shelf’ robots, standard forming equipment, and/or quick changeover concepts to develop productive cells. Systems are designed to run multiple parts with minimal changeover time, are easier to maintain and keep running since they are standardized, and may cost less initially.”
Flexibility is indeed a key customer consideration, says Paolo Scolari, project manager, OLMA s.r.l., (Milan, Italy). “Customers more and more do not want dedicated lines; they require lines that allow them to produce more products. Consequently, our R&D department is constantly engaged to develop machines that can support these customer demands.”

Flexible Upgrades

Suppliers agree that a lot of what is new is in the automation arena. “There are new drives, controls and PLCs, with information flowing back and forth,” notes Gerry Jensen, general manager-flexible fabrication, FMI Dahlstrom (Cedar Rapids, Iowa, U.S.). “The controls are constantly being updated, while the pricing has come down a lot over the last decade. The equipment today is more complicated, more critical on quality. It comes in different versions, and is frequently being modified, made smarter and made more flexible.”
“The material handling—to, through and away from—basic processes are critical to productivity,” says Demonet of Atlas. “Effective material handling can increase throughput on existing processes. Quick changeover concepts can also be applied to most metalworking processes to reduce downtime. This increases available production time, which again, means more throughput.
“We are meeting these needs by developing innovative concepts that are simple, flexible and cost-effective. We are applying standard robots in areas where we once designed and built dedicated, fixed automation for a particular part or process. We continue to employ the quick changeover concepts that we developed years ago to increase uptime on both new and existing processes. We also work to utilize customers’ existing equipment and processes in developing more efficient manufacturing cells, which keeps the initial costs to a minimum.”
McIntosh Laboratory, Inc. (Binghamton, New York, U.S.), an audio electronics producer, is one company that has benefited from the more flexible equipment available today. It had previously relied heavily on outside metal part suppliers. In recent years, though, it added metalworking equipment, including a Strippit Inc. (Akron, New York, U.S.) CNC press brake and two Strippit CNC turret punch presses. The company works primarily with 16-, 18- and 20-gauge cold-rolled steel, plus some mirror-finish stainless steel.
The company now produces a large majority of its own metal parts. Rudy Fuehrer, chief production engineer, appreciates the flexibility made possible by his company’s new equipment. “Once we brought production in-house, we got far better control. This is especially useful for us, since we are a low-volume, high-mix type house. We now have the flexibility we need and can even run parts just-in-time.”

APPLICATION SPOTLIGHT: Pressing Out Plasma Screens-This tandem line of seven Komatsu mechanical servo presses installed in Japan produces parts for large screen (42-inch and over) plasma TVs. Examples are rear covers with ventilation holes and other wide structure parts—both metal and non-metal. The presses do not have conventional flywheels and induction motors to create energy as do standard mechanical presses. Rather, they employ a patented drive system using large-standard design servomotors with a torque multiplier that provides over three times the available working energy of a conventional mechanical press. Slide-position accuracy, repeatability and die height deviation are in the micron range with complete control of slide motion (velocity and dwell) at any point in the stroke. Full energy is available in any part of the stroke regardless of the slide velocity. Photo courtesy Komatsu America Industries LLC (Wood Dale, Illinois, U.S.).

Handling Different Metals

With the higher metal prices of the last few years, it is not unusual to see appliance producers changing metals. In stainless steel, grades such as 304 with high nickel content are costly, and some appliance producers are switching to less expensive stainless grades. These may require an equipment adjustment to handle different metal properties. Another common appliance producer tactic with all types of steel is to go thinner.
“More and more customers require new lines with the capacity to handle different types of material with different thicknesses,” says Scolari of OLMA. “This has forced us to develop new machines suitable to this change. An example is a series of electronic bending machines. The driving of the bender is achieved by an interpolation of two (X and Y) controlled axes. This technology has high flexibility. By changing the bending contrast and reprogramming the interpolation parameters, it is possible to achieve different types of bends/radii.
“Also, we developed systems that allow the quality of the process to be controlled directly on the machine. There is the possibility to self adjust the machine parameters according to the different results achieved due to the different types of materials/thicknesses used. Also, we were forced to develop new ways to transfer the material, which is not dependant on the material type or thickness.”
“The move to thinner materials has created issues in multiple areas,” observes Dennis Boerger, product manager, AIDA-America Corporation (Dayton, Ohio, U.S.). “Tooling becomes more critical when producing parts from thinner metals due to the requirement for smaller punch-to-die clearance. The tolerance requirements for parts produced from thinner materials have been tightened, which puts pressure on the production system. The forming equipment must be capable of producing high-quality parts at high production rates while maintaining maximum up-time. Feeding and transfer systems must be capable of placing material in the tooling with extreme accuracy, while the press must have excellent slide-to-bolster parallelism, through-stroke perpendicularity, low bearing clearances, and an excellent low-clearance slide-guide system. A production forming system that does not meet these minimum requirements is doomed to failure.”
Ronald G. Lain, vice president of process technologies at RWC Inc. (Bay City, Michigan, U.S.) sees thinner metals creating more handling than forming problems. He notes that the technology
for dealing with thinner metals is available, and his company has worked with refrigerator cabinet materials as thin as 0.008 inches. But, he adds, “With the new thinner materials, there is a need for better control of the process and flexibility.”
“As companies choose thinner metals, steel companies have often increased strength to compensate,” points out Jensen of FMI Dahlstrom. “This added strength becomes an issue sometimes, for instance, in roll forming. But there is always a way to get around it. It’s a matter of getting the equipment settings and the conveying equipment set for the lighter gauges. It can be done, but it’s not as easy as some people think. We’ve had a couple customers who dropped a gauge and couldn’t get their parts through their equipment like before. We needed to help them modify the equipment to get it to work right.”

Copper Laser Welding

Many cabinet applications have been getting away from welding and moving toward clinching and riveting, observes Lain of RWC. An advantage is that these methods are not so adversely affected by material changes. However, welding suppliers continue to improve their processes.
Trumpf (Farmington, Connecticut, U.S.) reports that late last year, laser specialists were able to weld copper sheet metal 5-mm deep with a combination of disk lasers of varying laser power. No one had ever been able to do this before. As a highly reflective material, copper is extremely difficult to weld. In most cases, undesirable side effects occur, including blowholes in the weld seams.
The company’s specialists connected together three disk lasers with 4 kW, 6 kW and 8 kW laser output using a special fiber coupler in the application lab. Over 16.5 kW were brought onto the workpieces. The resulting welding speed of 1.8 m per minute stabilized the extremely dynamic melt pool common to copper. The sheets, each measuring 3 mm in thickness, were welded together 5-mm deep as an overlap join with excellent seam quality. For this experiment to be both secure and successful, the disc lasers had to be finely synchronized, which was handled by the Trumpf Laser Network.
Whether this welding application is ready for mass production depends greatly on the welding speed and the chosen focus geometry. More powerful lasers, such as those offered by the company beginning in December 2006, are expected to permit even greater welding speeds and an expanded process window with consistent seam quality.

Significant Changes

In presses, the ability to control slide motion is a significant change, reports AIDA-America. Its ServoPro is said to provide infinite control of slide position, within microns, which cannot be done on hydraulic or conventional press equipment. ServoPro allows stampers to program the stroke of the press for the specific application at hand. This includes the stroke length, slowing down or pausing the stroke to assist in drawing/forming applications, reducing the velocity in blanking, hardware insertion or in-die tapping applications, as well as dwelling under load for coining applications.
“When added to a gap press transfer line, ServoPro can customize the slide motion and stroke length of each gap press to help the stamper achieve optimal performance for each individual tooling station,” says Boerger. “When running different operations, die size is not always the same and some operations take longer than others. With the control provided by ServoPro, the stroke can be set to match the die complexity and the speed adjusted as needed. Part quality improves and lead time is shorter.”
Michael W. Riehn, director of sales and marketing at The Beckwood Corporation (St. Louis, Missouri, U.S.), sees significant advantages in the advancement and integration of electrical and hydraulic control technologies. “Capitalizing on the inherent benefits of hydraulic presses (speed, force and position control) has proven to add considerable cost savings by decreasing setup time and minimizing scrap material costs in the way of bad parts,” he says. “Up-front costs associated with programmable control systems that include job storage and recipe handling have continued to be more attractive. The costs of adding these control features to new presses at the time of order can often be recouped in as little as 4 to 6 months. The hydraulic flexibility provided by these controls can be used to further increase the presses’ ability to quickly make good quality parts immediately after die set-up. Being able to quickly dial in speed, force and position variables to compensate for material inconsistencies saves set-up costs in terms of labor as well as material.”
RWC’s Lain nominates special multi-axis servo-controlled bending cells as a significant change for appliance companies. “They have maybe less overall flexibility than the standard machines, but with higher quality and productivity, they are being used for refrigerator doors made of stainless steel and pre-painted materials,” Lain says.
Even with advances like these, metalworking tends to be more evolutionary than revolutionary. However, it is safe to anticipate continued incremental improvements that will be geared to meeting customer needs. As OLMA’s Scolari puts it, “We strongly believe there is still room to optimize the metalworking processes, and we are convinced that electronics can help us do this.”

Electrolux Makes the Cut with Stainless Steel

 

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