pinch point injury every time a part is welded, since the gap between electrodes must be greater than ¼ in. to clear the part. One solution is to place the nuts or studs on the part prior to placing the part between the electrodes. The part can then be supported by a table and the welding machine initiated by use of dual hand buttons installed with an anti-tie-down safety circuit. If this method is not practical, use of the Soft Touch system will provide the required protection. Another highly recommended solution is to use an automated bowl feeder and placement mechanism to load the nuts or studs being welded. Projection welding machines with tooling mounted to T-slotted platens in the throat of the machine are considered to be much like a sheet metal stamping press when it comes to ensuring safety, since the parts being welded are typically loaded by hand into a locating fixture directly under the ram in the pinch point. Dual palm buttons connected to an anti-tie-down and anti-repeat circuit have long been the standard initiation means for projection welding machines, and optical touch devices are rapidly replacing the old-style palm buttons that require physical force to depress. Guarding of the welder’s pinch point with wire mesh or Plexiglas is also more prevalent than ever, and light curtains installed on the opening ensure that the operator is completely outside the work area when the machine is initiated (see Fig. 1). Zone scanners are also now available that sense if someone is inside the guarded area. Using a robot to replace the operator and manipulate a fixtured part inside the throat of a rocker arm or presstype resistance welding machine is also a good way to enhance safety. We applaud your desire to learn from this accident and to help protect your operators from similar injuries in the future. Fig. 3 — Standard spot welding machines, both vertical action and rocker arm types, can be operated safely if an operator holds the parts with both hands outside the pinch point area. Safety can be enhanced by minimizing the opening between the tips and by a control feature called Soft Touch. It is also encouraging to see that a growing number of companies are becoming proactive by adding protection systems to their spot welding machines before accidents occur. As we’ve explained, there are numerous ways to enhance the safety of resistance welding machines, but proper operator training, especially of new hires or temporary workers, should be top priority.♦ y TOM SNOW is CEO of T. J. Snow Co., Chattanooga, Tenn., a resistance welding machine manufacturer and a member of the Resistance Welding Manufacturing Alliance A STANDING COMMITTEE OF Vinoy Renaissance Resort & Golf Club, St. Petersburg, Fla. Co ommitted to advan b bro d i it WMAAnnual ncing resistance we , pr oadening its use, g elding technology, The RWMAAnnual Meeting is a three-day event filled with unparalleled networking opportunities and enlightening presentations. Renowned economist Alan Beaulieu of the Institute for Trend Research (ITR) continues to be the keynote speaker for the meeting. Additional speakers will be announced. Non-members are welcome to attend! Registration opens mid-December. For more information please contact: 26 JANUARY 2014 Keila DeMoraes at kdemoraes@aws.org or 800-443-9353, ext. 444 inoy R thre omoting its eco ti it onomic benefits. i b fit y, December rend (RWMA). Send your comments/ questions to Tom at TomSnow@ tjsnow.com, or to Tom Snow, c/o Welding Journal, 8669 NW 36th St., #130, Miami, FL 33166.
Welding Journal | January 2014
To see the actual publication please follow the link above