DeWys Manufacturing, Inc., a custom precision sheet metal fabrication company located in Marne, Michigan, is no stranger to the use of robotic welding units, but a particularly challenging hydraulic reservoir job was putting its current systems to the test. DeWys' robotic MIG welder was producing an excessive amount of spatter as it welded these thin gauge reservoirs used to hold hydraulic fluid. To remove the spatter, operators were spending approximately one minute per part in clean up time, which was adding up to an extra 25 hours a week for the 1,500 parts produced. In addition, to clean the weld spatter DeWys was using a grinder, but the dust and debris created during grinding was contaminating the reservoir's pump. For these reasons, the company was looking for a new way to weld.
"We started investigating units and evaluated three competitive models," said Chris Hawkins, Team Facilitator for DeWys Manufacturing, Inc. "One that was recommended to us was the System 40 tabletop robotic cell from The Lincoln Electric Company. What made this cell different was its use of Lincoln's Surface Tension Transfer® (or STT®) power source which is known for its capabilities to weld on thin material without spatter."
As a test, DeWys team members sent 20 of its hydraulic reservoir parts to Lincoln's headquarters in Cleveland to see what the robotic welding cell could accomplish. "After Lincoln set-up our sample, a few of us went to Cleveland and they demonstrated for us how the System 40 welded the reservoirs. Not only was the quality of the weld excellent, but more importantly the spatter was eliminated and so was the cleaning time. After the demonstration, we were sold and purchased a unit for our plant."
The welding at DeWys is a critical step in the company's full service approach. For the hydraulic reservoirs, the DeWys design team starts by drawing the parts on its CAD/CAM systems. The company then punches out the parts using a turret press, forms the pieces, welds them together with the robot, performs a leak check and paints the part before it is shipped to customer. As a 130-employee job shop, DeWys customers range from various OEMs such as Steelcase, Herman Miller and Tennant to mailboxes for the US Postal Service. According to Hawkins, no two jobs are ever the same at the company.
The System 40 purchased by DeWys combines a FANUC ARC MateTM 100i, 6-axis robot with Lincoln's Surface Tension Transfer (STT) power source. The System 40 was chosen because it is a 'drop in place and plug in' work station. For DeWys, this meant installation was easy and the System 40's small footprint, which is forklift compatible, provides the ability to move the robot around the shop when necessary.
"With the Lincoln system, we just dropped it into place on the shop floor and it was ready to work," noted Hawkins. "We could never do that with our other robotic units as they required much installation work."
The robotic cell's power source, the Lincoln STT, uses high frequency inverter technology with advanced waveform control to produce a weld with reduced spatter and smoke. With the Lincoln STT, the electrode current is controlled during the entire gas metal arc welding (GMAW) process because electronics are used to closely monitor and control the current. The Lincoln STT is the industry's only independent current controlled wire feeding process. This process allows for controlled heat input independent of wire feed rate, which provides high production rates, especially on troublesome, thin gauge components. For DeWys this ensured the spatter-free welding needed for the hydraulic reservoir.
"We are very happy with the performance of the Lincoln STT, for us it has eliminated spatter, which was our biggest issue," said Hawkins. "We would recommend Lincoln's STT to anyone that has to make cosmetic welds on thinner material."
The robot purchased by DeWys has two identical sets of tooling, each able to hold the three, 12 gauge HRPO parts that are welded through the three phases to form one completed hydraulic reservoir at the end of the third phase. The tooling is mounted on a high-speed 180º indexing table, which means that the operator can unload and load parts while the robotic unit is simultaneously welding the next reservoir. "Each reservoir requires 10 fillet welds which the robot can complete in five minutes," notes Hawkins.
The System 40 robotic cell at DeWys utilizes Lincoln's .035" SuperArc® L-56™ MIG wire which is supplied in convenient 500 lb. drums. A shielding gas of 90 percent argon and 10 percent CO2 is used to further minimize spatter.
According to Hawkins, the programming of the robot wasn't too difficult to master, especially with the teach pendant. DeWys has three engineers on staff who handle all of the programming aspects. These are the same team members that attended a Lincoln three-day robotics training class in Cleveland. Upon their return, these employees were responsible for training the operators.
The cell also has a number of safety features including steel barriers to protect against flash and unauthorized entry, a flash screen separating the operator from the welding area, safety door interlocks, and an operator palm button that is readily accessible for quick cycling. "We have three other competitive model robots and Lincoln's is much better in terms of more options, better program protection and faster dry air movements," noted Hawkins. "The dry air movements of the System 40 robot are twice as fast as our other robots and the teach pendant allows us to lock the system so that operators can't change program settings."
Another key benefit of the system is the TorchMate, which quickly calibrates the robot. According to Hawkins, other robots in the shop may take up to 15 minutes to calibrate, while the TorchMate enables the System 40 to calibrate in only 15 seconds. And, if the torch has a collision, it has a breakaway function so that the company doesn't have to replace the entire torch.
For items that don't require the high volumes, DeWys utilizes MIG welding. The company recently purchased seven CV-300/LN-742 MIG welders from Lincoln Electric.
"We prefer to use the robots whenever possible," noted Hawkins. "With robots, there is no human factor which means we always get consistently good quality welds. Also, the robots can weld twice as fast as manual methods."
"Some of the main reasons we chose Lincoln was the service, support and reliability," claimed Hawkins. "Our older model robots don't have the support behind them, which is a real problem. Our Lincoln sales representative, Bruce Chantry, was here during our entire installation process and continues to be on call whenever we need him to answer a question or lend a hand. And, if there is something that he is not sure about, he has the support of the automation team in Cleveland behind him to call for advice."
"As our capacity increases we expect to be purchasing another Lincoln robot in the future," said Hawkins. "We are trying to convert most of our shop over to robots for a faster and smoother operation."
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Originally Written 11/19/01