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Cleveland Range gets cooking with robotic welding cells |
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 by Jerry Cook
When 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.com
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