Getting in Gear with Robots: SEW-Eurodrive Case Study

Business is booming for SEW-Eurodrive, Inc., a maker of gears and pinions for industry. The demand for the company's products was beginning to outstrip the Lyman, SC-based manufacturer's ability to satisfy production goals. To meet this need, the company considered several options.

"Our choices were purchasing additional machinery or hiring more workers. People in our facility were already working six days a week," said Chuck Chandler, the plant's assistant manager. "When our production volumes reached a certain point, upper management determined that robotic automation was the best way to meet the demand." SEW-Eurodrive contacted TEC Automation, Inc. of Canton, GA, a robotic systems builder and partner of StŠubli Robotics in nearby Duncan, SC, to provide robots with the speed, precision, and reliability needed to build a cost-effective solution.

Gear Cutting
Chandler recalled the gear and pinion fabrication process used prior to the deployment of the TEC robotic systems using StŠubli robots. "Our manual process had three different steps," said Chandler. "An operator who would load both gears and pinions on their respective machines. Then the operator would remove the parts after cutting and load them on a pallet for the deburring process." Chandler said the last step was to rack the parts for heat-treating.

Chandler described the difference that robotics has made in the process. "With the robots, all of these tasks are still done within the same system and the same cycle time as the original process. While the gears are being cut, the robot is handling the deburring, palletizing, and racking."

Chandler explained the process the parts go though with the assistance of the StŠubli robots. "The robot loads and unloads a cutting machine with gear blanks and pinion blanks. The robot does all the part handling and guides the gear or pinion through the deburring process." Chandler adds that the deburring tool is fixed while the robot moves the gear or pinion around it in different planes. "The robot holds the part to the deburring tool to get the edge profile we need," Chandler said.

Force Control
The amount of pressure the robot applies while inserting the part into the gear cutting machine chuck is critical as the clearance between the part and the chuck is very tight. Chandler said the robot's end-of-arm tool adapts and adjusts to properly load and unload the machine.  The deburring tool wears as it is used. "To get the proper edge, the robot intuitively adjusts the amount of force it applies and the TEC software allows the operator to compensate for tool wear. Accurately controlling that force while precisely compensating for tool wear seems like a complex challenge but the StŠubli robot is adept at doing both."

Force control is also used in the loading process, to insert the part to a specific point in the machine. Chandler said, "The robot's force control system rigorously monitors tool pressure on the part to make sure it is positioned properly. Otherwise, the pinion gear tooth profile after the deburr process would vary."

Same Parts, Different Process
Chandler said that another benefit of the robot's flexibility stems from the fact the gears did not have to be redesigned to accommodate the automated work cell. "We are not producing just one or two different parts, but a whole family. The parts have the exact configurations as before we installed the robots," Chandler said. "The system is adaptable enough to run all the parts SEW-Eurodrive makes."

More Parts, Less Waste
Chandler noted that the volume of gear and pinion production increased significantly while the rejection rate plummeted. "Prior to investing in the StŠubli robots, our production was averaging between 75,000 and 120,000 units a year. With the robotic automation, we produced 300,000 units in 2007, and our projected growth will rise to about 500,000 units annually in the next couple of years," boasts Chandler. "SEW-Eurodrive is producing these added units with less than six percent increase in staff, about six more people," Chandler reports. "Before robotics were installed, an operator would process 65 to 85 parts a day, of which 10 to 15 were rejected, mostly due incorrect part loading," said Chandler. "With the StŠubli robots, productivity averages over 160 parts per day, with just three rejected parts. Rejects now are mostly due to a malfunction in the gear cutting machine - a dull or broken tool. The robot can discern when the part is not positioned right, or its location is wrong." Chandler goes on to say that because the robot can detect a flawed part before the cutting or deburring process, it saves time and unnecessary wear on expensive tools.

Chandler highlights another major benefit of using robotics to handle gears and pinions during the machining process were that the robots are able to correctly seat the gear blank automatically, Chandler said. "Overall, the productivity gain with the robots is at least 200 percent," claims Chandler. The machine operates during breaks and shift changes, as long as the machines have parts to run.

Using the StŠubli robots also increased quality and eliminated the need to train people in gear cutting, emphasizes Chandler. "Gear cutting is an art. We found it nearly impossible to find people off the street to learn it," Chandler contends. "Now we can maintain quality because our experienced operators monitor the robots. The robots just keep performing the same task over and over."

Encore Performance
Overall, SEW-Eurodrive is delighted with the

performance of their gear cutting work cells. "We were so pleased with the StŠubli robots that we have ordered three more from TEC Automation. Two of them are deburring pinions and utilize the TECteach Wizard path teaching software and TECell Manager PC workstation program managing software.  These also use vision-based bin picking. We are considering others. The efficiency, performance, and quality are outstanding, not to mention that StŠubli robots were the only ones on the market could hold the exacting tolerances and support the programming wizard developed by TEC we needed." said Chandler.

For more information contact:

David Arceneaux

Business Development - Marketing

StŠubli Robotics

864-486-5416

E-mail: d.arceneaux@StŠubli.com 

Jim Webb

Vice President of Sales/Marketing

TEC Automation

770-720-3333

E-mail: jwebb@tec-automation.com 

Chuck Chandler

Operations Manager

SEW-Eurodrive

864-439-8792

E-mail: cchandler@seweurodrive.com