Assembly in Action: Checker Verifies Weld Quality on Motorcycles
Indian Motorcycle Corp. (IMCGilroy, CA) was formed in 1998 to relaunch an American icon. The original Indian Motorcycle Co., which built the first American-made motorcycle in 1901, was a leading motorcycle manufacturer for almost 50 years. Even though it was out of production from 1953 to 1999, the Indian brand is still well known to motorcycle enthusiasts.
Holding true to the brand’s reputation for quality, IMC has built a state-of-the-art manufacturing facility in Gilroy. To ensure consistent process quality, the company uses Unitek Miyachi Corp.’s (Monrovia, CA) MM-360 weld checker to diagnose problem areas and optimize welding processes to manufacture the 2002 Indian Chief motorcycle.
IMC uses a Miyachi STA-100 control on a 50 kilovolt-ampere (KVA) press welder that joins a nut to the backbone frame of the motorcycle. The same welding platform had been delivering high-quality welds for other models already in production, but the welding operation for the 2002 Chief was showing an unacceptable number of cold welds.
"We had made a few tooling modifications for the new Chief model and were having problems getting the weld nugget to stick. When we asked Miyachi for help with analyzing the problem, they offered to come out and take a look at it firsthand. They were at our site within a week and had us up and running in less than a day," says Dennis Dibala, machine repair technician.
Weld parameters, including current and force, were monitored and analyzed with the MM-360. The conduction angle was found to be maxed out at 180 degrees, indicating that the 50 KVA transformer was delivering maximum current to the load. However, the current measured at the electrodes was only 8 kilo-amperes (KA), instead of the 14 KA needed for an acceptable weld.
Further analysis revealed that the tooling modifications had increased the resistance of the secondary circuit to the point that the transformer voltage was insufficient to drive the required current to the electrodes. Eliminating excess resistance allowed the transformer to deliver 14 KA at the electrodes with a conductance angle of only 130 degrees, producing good welds.
The MM-360 was also used to measure force and current to verify squeeze time. These measurements revealed that the current was firing before the force curve had completely stabilized. This contributed to expulsion during the weld and inconsistent positioning of the nut being welded. By making additional adjustments, the squeeze time was optimized and expulsion was eliminated, resulting in consistent set-down of the nut against the motorcycle frame.
"The Miyachi support staff not only analyzed and fixed the problems in real-time, they also took the time to show us exactly what the root causes were and how to avoid them in the future. The bottom line for us is a more consistent process that measures up to IMC’s stringent quality standards, backed up by a higher level of knowledge and understanding that will help us to keep the process operating well within required margins," says Dibala.
For more information on weld checkers, call 626-930-8560 or visit http://www.unitekmiyachi.com
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