Pinch-Point Safety System for Resistance Welding

Resistance (spot) welding is essential in the fast-paced manufacturing of aerospace, marine, railcar and automotive components. Unfortunately, pinch point accidents involving these machines are all-too-common when welding electrodes are driven together at forces up to 12,000 psi while an operator’s hands are pinched between them, leading to mangled, crushed or severed fingers. According to OSHA, hand injuries account for nearly one-third of the thousands of disabling on-the-job accidents that occur each year. Most of these hand injuries – up to 80 percent – are caused by pinch point accidents, which is why installing viable pinch-point safety on resistance welders is so important. The Unitrol SOFT TOUCH Pinch-Point Safety System from Rockford Systems, LLC (Rockford, IL) is the first and only fully passive safeguarding system that prevents a spot welder from applying full force if it detects fingers in the machine’s point-of-operation area.

SOFT TOUCH automatically compensates for any changes in transformer tap switch position or line voltage shifts to prevent production from being abruptly stopped. If any of the system sensor wires become shortened or disconnected, it will lock out and prevent the electrodes from closing or the welding sequence from continuing. If the system sensor board detects electrode continuity before the foot switch or hand switches are closed, it will lock out and not allow any electrode movement. Workers cannot remove, circumvent or tamper with any part of the system. There are no operator set components, and no user adjustments or calibration is required when new setups are made. The continuity system cannot be overridden and is in place at all times that the welding machine is under power.

SOFT TOUCH can be used as the primary pinch-point safety system because it is fully passive. All inputs and outputs require closure of both electro-mechanical and solid-state redundant components for fail safe operation. Self-monitors output relay to prevent any operation if a fault in the output contacts is detected. When welding a C-shaped part that is not fully closed and requires electrode force to push the parts together, a limit switch can be added to the welder and adjusted to close when the space between the electrodes is less than ¼ in. In this case, two actions are required before the electrode force increases and the weld sequence begins. The system works with and is available for all resistance welders, including spot welders, projection welders, seam welders and transgun welders; 1Ø AC, 1Ø DC secondary, 3Ø frequency converters, 3Ø DC rectified secondary, and MFDC (inverters). The system includes a five-year prorated warranty that is determined using the date of the new control from the original ship date.

Rockford Systems, LLC, 4620 Hydraulic Road, Rockford, IL 61109, 815-874-7891, Fax: 815-874-6144, sales@rockfordsystems.com, www.rockfordsystems.com.