Assembly In Action: Robots Weld Parts in Small Batches
August 31, 2009
Crown Equipment Corp., of Greencastle, IN, manufactures electric lift trucks for use in warehouses, distribution centers and manufacturing facilities. Unlike many assemblers, the company fabricates about 85 percent of the parts it uses. Parts are often made in small quantities-sometimes as few as one at a time-to meet real-time demand on the assembly line.
Historically, Crown Equipment welded the more than 1,500 miscellaneous parts it requires manually in nine welding stations using the MIG process. The company also employed manual welding to fabricate the four different frames it uses in its lift trucks.
A few years ago, however, the company implemented three stand-alone welding cells from welding equipment manufacturer Lincoln Electric Co. Each cell employs a six-axis robot from Fanuc Robotics America Inc. and a Lincoln Electric Power Wave 455M power source and Super Arc L-56 MIG wire.
The result has been an improvement in both weld quality and cycle times. According to Crown engineers, the cells are three to four times faster than their manual counterparts. The average weld times have dropped from five or 10 minutes to two to three minutes. Welds are also more consistent and are overall better in quality.
To facilitate the use of automation, Crown engineers created dozens of new robotic welding fixtures, all based on a standardized 24-by-36-inch or 30-by 54-inch mounting plate.
In operation, as soon as a new fixture is installed into the welding cell, the operator calls up a stored code for the part to be welded by entering a three-digit code on the cell’s control panel. This automatically loads the stored program into the robot’s teach pendent.
According to Crown, the robots are fast enough that they more than compensate for the downtime associated with changeovers, even when producing single parts. As evidence of their effectiveness, Crown cites the cells’ fast return on investment. The company’s first cell, for example, paid for itself in about four months.
“Lincoln Electric and Fanuc Robotics really helped us realize this change, and it was their experience finding these kinds of opportunities and making them work, along with the equipment design and integration, that ultimately resulted in Crown choosing Lincoln Electric and Fanuc,” says Crown senior vice president David Besser. “We have not had a single equipment failure with any of these products. We are very pleased with all the results.”
For more on automated welding, call 888-935-3878 or visit www.lincolnelectric.com/automated-solutions.
For more on robotics, call 800-iQ-ROBOT or visit www.fanucrobotics.com.