Page 56 - MetalForming Magazine June/July 2022 80th Anniversary Issue

the RW control firing the welding machine’s transformer before the appli- cation of full weld force, which causes expulsion and weak welds.
As previously noted, set weld time as short as possible. Subsequently, hold time—in sequence immediately after weld time—allows the weld to cool for a short period with the weld force still applied. Then, off time only is used if the welding machine is set to automati- cally repeat, similar to a sewing machine.
Cooling Water
As most RW machines are water- cooled, do not overlook water flow rate and temperature as key process vari- ables. RW machines are thirsty and adequate water flow typically is more important than water temperature. For example, a high flow rate of 80-deg. water will prove more effective than 45-deg. water at a low flow rate.
As the cost of using city water to cool an RW machine can be high and the incoming temperature often too
Helm Celebrates 60 Years
Founded in 1962, and a member of PMA since 1973, Helm Instrument Co. is a global leader in the design and manufacture of control systems for all types of metal and plastic forming operations, as well as weighing, packag- ing and assembly. Helm products include tonnage moni- tors, PLC input modules, machine control and automa-
Fabrication: Resistance Welding
cold, the simplest solution is to employ a closed-loop recirculating system. Beware: Some of these systems operate better than others. And, as with all things related to RW machines, con- sistency holds the key to success.
Common machine water-cooling gotchas:
• Cooling towers are not ideal for suppling RW machines, because changing ambient-air temperatures cause inconsistent cooling-water tem- perature.
• We also do not recommend the small radiator-type recirculators com- monly used with arc-welding machines, due to low flow rates and changing temperatures.
• Plant-wide water systems often provide inconsistent flow rates due to varying head pressure.
• When water systems use black-iron plumbing instead of PVC, rust will even- tually clog the welding machine’s small- diameter internal water-cooling lines.
• City and well water contain min-
ADVERTORIAL
erals that will clog water-cooling cir- cuits over time.
• The best choice: a properly sized self-contained water recirculator/ chiller. However, with these be sure to set the chiller’s water temperature above the prevailing dew point or con- densation will form. This can cause the welding machine’s transformer or weld control to become saturated and eventually short out.
$50,000 Gotcha
RW expert Don DeCorte, of RoMan Manufacturing, a global supplier of RW transformers, shares this example of an expensive gotcha:
“One of my customers, a large auto- motive plant, was experiencing high electrode-cap failure rates on several robotic spot-welding guns. I was asked to review the situation because the plant’s welding engineers were blaming the electrode-cap supplier for prema- ture failures.
“I spent an hour listening to them
HELM INSTRUMENT CO., INC.
tion systems, force transducers, signa- ture analysis, safety lights and plantwide networking software. From our strategic location in the indus- trial Midwest, we supply and support
our customers with a complete staff of representatives worldwide. Helm’s factory based service team has more than 130 years of combined experience and provides installation, calibration and machine process analysis.
Helm Instrument Co. congratulates the PMA team on its 80th anniversary.
Helm Instrument Co., Inc.
361 West Dussel Dr. Maumee, OH 43537 419/893-4356 www.helminstrument.com
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