Page 37 - MetalForming March 2015

on the complete dynamic model of the robot that resides within the robot con- troller. QuickMove optimizes accelera- tion to enable the robot to reach its programmed positions in the shortest possible time, in turn optimizing cycle times beyond applications that depend solely on robot-axis speed.
In addition, the IRC5 robot con- troller features the ABB TrueMove func- tion designed to ensure that the robot follows the prescribed motion path regardless of its speed.
Expulsion Expelled
Resistance welding galvanized steel, and certainly aluminized hot-stamped material, requires a high level of welding expertise, and Richards has two welding engineers on staff to ensure sound weld- procedure development. “And we use ABB as a resource as well,” Richards says. “For example, we’re working hard at per- fecting our non-expulsion process param- eters (including industry-recognized solu- tions such as pulsed welding and heat-energy slope control) in our resist- ance-welding operations, and ABB has helped a great deal here. As part of this process, we’re performing much more tip dressing than we used to. Along with perfecting our weld procedures, this has greatly reduced expulsion and resulted in reduced maintenance and cleanup costs, while extending tip life.”
Along with the emphasis on eliminat- ing weld expulsion, Wellington has begun to focus on avoiding cold welds. Here, again with ABB’s help, it has been installing poka-yoke devices to check weld current after each tip dressing. The robots bring their weld tips over to these current-check stations where they send current through a puck, or blank, of steel.
“Before we implemented the poka- yoke current checks,” shares Richards, “periodically a cold weld or two during a shift would require us to inspect an entire shift’s worth of assemblies. On the welding cells where we’ve added the poka-yokes, we’ve completely elimi- nated cold welds. And, we’ve been able to, with the increased confidence in our process, reduce the frequency of weld testing by 15 to 20 percent.”
Yet another resistance-welding pro- ductivity boost came in 2010 when the firm began to switch from pneumatic welding guns to servo guns. “The servo guns are very accurate, and the welding process becomes much more repeat- able,” Richards explains. “With pneu- matic guns the list of process variables impacting weld quality and consisten- cy is long, including ambient air tem- perature and humidity, and the quali-
ty of the air coming from the compres- sor. In many cases we would have to over-pressurize the pneumatic guns to make up for process variables.
“With servo guns (Wellington uses guns from Centerline and Milco), this issue goes away,” Richards continues. “We get extremely consistent weld pres- sure and quality. That consistency has resulted in a 20 to 30 percent increase in weld-cap life.” MF
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