Canadian Electronics DPN PIQ

Cleveland Range gets cooking with robotic welding cells

March 30, 2009 Written by 
by Jerry CookWhen it became apparent that manually TIG welding parts was too slow and time consuming, Concord, ON-based Cleveland Range Ltd. decided to explore the potential offered by robotic MIG welding.
“The main goal that we had was to reduce labour time and improve productivity. We were really looking to save on labour,” says  Bob Mohajer, industrial engineer with Cleveland Range.

Cleveland Range, which started operations in 1947, has approximately 190 employees  at its 126,000 sq. ft. plant. Cleveland Range’s Concord facility manufactures commercial cooking equipment such as kettles, mixers, and skillets for various customers in the global market. “We make a variety of customized and special products,” says Mohajer. In the U.S., Cleveland is one of the leading brands in commercial food equipment represented by Enodis USA.

In general, the firm’s part runs average about 50 to 100 pieces. The company is typically working with stainless steel. Because Cleveland Range is producing a high mix of different parts at relatively low volumes, reducing weld time and improving productivity were critical goals along with quick changeover times and flexible processes. According to Mohajer, previously Cleveland Range employed manual TIG welding which provided a high quality surface finish on parts but was too slow.

Mohajer singles out a complex part for a skillet product that was manually TIG welded but was difficult to manually MIG weld. The part is now being done using robotic MIG welding. “Some of the welds were cosmetic welds and others were exposed welds so they have to be high quality welds for the part. There were also very small welds in corners and flanges that were very tedious to weld manually and very time consuming.
“For example, the time study that I did for manually TIG welding an airmix chamber assembly amounted to 40 to 45 minutes per piece because it required six or seven components to be attached at different stages of welding,” he points out.

As a result, Cleveland Range installed its first robotic MIG welding cell in 2006-a Dual Fixed Table (DFT) cell supplied by the Lincoln Electric Co. of Canada, Automated Solutions Group, Mississauga, ON (lincolnelectric.com). According to Mohajer, the DFT system, which Cleveland Range is using to weld smaller parts, has provided significant benefits in terms of reducing weld time and increasing productivity. “Now, using the DFT robotic cell to weld the airmix chamber assembly, including loading and unloading, only takes five minutes.”

Continues Mohajer, “In the department in which we are producing the part for the skillet product, we are missing three welders but because of the DFT robotic cell we have increased production without (filling) the three positions. This is the primary impact of introducing robotic welding operations.”

The DFT robotic cell employs a six-axis Fanuc ARC Mate 120iB/10L robot and a Power Wave 455M/STT inverter power source. The Power Wave 455M/STT is a high performance, digitally controlled inverter power source designed for robotic, automation, and semiautomatic applications. With the Power Wave 455M/STT, the user can program his own waveform or choose from over 60 standard welding waveform programs that offer a broad range of electrode size, type, and shielding gas combinations to provide optimal appearance, penetration, beadshape, and travel speed for each application.

Unlike many conventional power sources, the Power Wave 455M/STT is a flexible machine that allows  Cleveland Range to utilize different processes with the same machine. For example, the firm uses the DFT to weld aluminum as well as stainless steel parts.

According to Mohajer, Lincoln’s Power Wave 455M/STT power source employs the Surface Tension Transfer (STT) process which enabled Cleveland to switch from TIG welding to robotic MIG welding for the same parts and applications without sacrificing quality. STT is designed for applications in which heat input control and minimal distortion are critical.

“Using Lincoln’s SST process we are able to weld thin gauge material using MIG resulting in a very nice surface finish. All of the parts that we have switched to robotic MIG welding were previously done using TIG welding,” he says.

Cleveland Range installed a second Lincoln custom robotic MIG welding cell, the System 55, in 2007. “We installed the System 55 robotic cell in order to weld larger parts and to add production capacity,” he says. “Also, some of the larger parts that we weld are not ergonomic for the welders, so we wanted to improve the process ergonomically as well.”

Continues Mohajer, “We use the System 55 cell to perform heavier welds on larger parts. The fixture on the System 55 cell can hold parts up to 10 ft. in length and 65 in. in diameter,” says Mohajer, adding that the new machine includes an additional tilt/rotate positioner that allows parts to be manipulated to a greater degree.

The System 55 robotic cell comprises a six-axis Fanuc ARC Mate 120iB/10L robot and a Power Wave 455M inverter power source. The Fanuc ARC Mate 120i/10L is an electric servo-driven robot designed for precise, high-speed welding and cutting. It offers an extremely large work envelope ideal for large parts or complex tooling. The robot’s compact yet flexible design maximizes reach capability within confined areas. The ARC Mate 120iB/10L offers fast wrist axes which reduces aircut times and improves throughput. It provides 1885mm reach and 1426mm stroke.

“The fiixturing is important as far as orienting the parts in order to reach them with the robot. It’s important to have good fixturing, good design, and very important to have good repeatability on the parts,” he says.

As a result, in order to further enhance tooling development for the System 55 cell, Cleveland Range also implemented Fanuc’s ROBOGUIDE-WeldPro software package which enables users to simulate a robotic arc welding process in 3D space. This allows the user to ensure that the robot can access all the points on a part before the tooling is actually made. In fact, Lincoln Electric used the software package to develop Cleveland Range’s System 55 cell’s configuration and model the machine in virtual world before fabrication. “The simulation process allowed us to make modifications along the design process ensuring our cell layout was optimized when it shipped to us.”

Even though Cleveland Range had no previous experience with robotic welding, introducing the new process to its operation was simple and straightforward. “It was very easy to learn how to start using the cell and operate it. While it takes time to learn the more detailed (functions) it is generally a fairly easy system to operate. Lincoln has real know-how about welding and integrating robotic welding applications,” he states.
Continues Mohajer, “As we continue to use the two systems, we have learned what parts are more adaptable to robotic welding, how to redesign parts for robotic welding, how to design better fixtures, and what is the optimum process for welding each part.”

lincolnelectric.ca

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