Page 64 - MetalForming October 2011

Stamper Sold on Three-Phase
Mid-Frequency Resistance Welding
Metrican Stamping Corp. retrofits a single-phase AC resistance-welding machine with three-phase mid-frequency DC inverter technology. ROI is based on savings in cycle time, consumable life and power consumption.
BY TOM SNOW
Although three-phase mid-fre- quency direct current (MFDC) inverter-type technology is fast becoming the norm when purchasing new resistance-welding machines, con- verting existing single-phase resist- ance-welding machines to MFDC tech- nology has been relatively slow to take hold. However, savings in cycle time, consumables and power usage can combine for a successful and cost- effective conversion of older equip- ment, as evidenced by Metrican Stamp- ing Corp., Dickson, TN.
Early in 2009, Metrican mainte- nance personnel focused attention on problems with a specially designed automated dial-index welder that had come from its Canadian plant. Equipped with a 150-KVA single-phase AC trans- former, the machine had proved mar- ginal for the application. A single-gun machine with a rotary table, the setup was tasked with welding two critical
Tom Snow is CEO of T. J. Snow Com- pany, Inc., Chattanooga, TN, a manu- facturer and distributor of resistance- welding machinery, supplies and accessories: 423/894-6234; www.tj- snow.com.
Metrican Stamping retrofitted this automated dial-index welding machine with MFDC technology, which delivers more energy to the welds and allowed the machine’s cycle time to be reduced from 9.5 sec. to 7.5 sec., increasing production rate by 101 parts/hr.
nuts with ring projections to a Gener- al Motors seat component, and had been running at maximum capacity for several years.
Blinking Lights, Grunting Machine
Despite being connected to a large
primary electrical service, the aging single-phase welding machine grunted and lights blinked when it fired. In addition, weld quality was not consis- tent and electrode life short. Excessive weld times were necessary to com- pensate for the borderline welding
62 MetalForming/October 2011
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