Page 42 - MetalForming July 2013

Remanufacturing
Resistance-Welding Machines
With light-duty “throw-away” industrial machinery becoming more common, many well-known brands of resistance-welding machines from the last century are well worth the cost of remanufacturing and updating to new machine specifications.
BY TOM SNOW
“They don’t build ’em like they used to” applies to resistance- welding (RW ) machines in particular because these machines con- tain a lot of expensive copper and steel to meet accepted heavy-duty welding-
machine standards.
Due to the high secondary currents
typically used in the RW process, often in the range of 30,000 A or more, many older U.S.-made brands were designed with massive water-cooled copper cast- ings that are extremely expensive to produce today. In addition, machine frames of the past, compared to those made today, typically were fabricated with heavier steel sections—more rigid, to better handle high forging forces.
Built to Standard
In the United States, the age of light- duty press-type and rocker-arm resist- ance spot- and projection-welding machines began in the 1980s, when
Tom Snow is CEO of T. J. Snow Compa- ny, Inc., Chattanooga, TN, a manufac- turer, remanufacturer and distributor of resistance-welding machinery, supplies and accessories: 423/894-6234; www.tjs- now.com.
Japanese automobile manufactur- ers and their Japanese-owned Tier 1 suppliers brought their
RW technology with them. Japanese machine designs
had proven successful in their factories for many years. But, the diminutive machines stood out in stark contrast to the larger, heavier-duty Ameri- can-made machines that conformed to the stan-
dards of the Resistance Welder Manufacturers Association (RWMA—now the Resistance Welding Manufacturing Alliance, a standing committee of the American Welding Society).
To advertise an RW machine
as meeting RWMA Standards, it
must meet certain minimum spec- ifications for weld pressure (forging force) and secondary amperage (welding heat), as published in RWMA Bulletin 16—
Resistance Welding
Equipment Standards.
These variables in machine design are important because Class A resistance spot welds of maximum strength and optimum appearance cannot be pro-
Before and after: Heavy-duty resist- ance-welding machines often are worth remanufac- turing to new condition. The veteran Taylor-Winfield press-type combination projection- and spot-welding machine shown here was originally manufactured in the 1950s. It boasts a heavy-duty steel frame and cast-copper secondary conductors that prove expensive to produce new today.
40 MetalForming/July 2013
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