Simple Safeguarding to Prevent Resistance Welding Injuries

According to the Bureau of Labor Statistics, more than 5,000 American manufacturing workers suffer injuries involving amputation or limb loss every single year. In all, amputations rank in OSHA’s top three serious workplace injuries. These devastating, life-altering injuries are typically avoidable with the right safety equipment in place. For example, our Detect-A-Finger® drop-probe device is designed to prevent a press-type resistance welder from cycling if it encounters fingers in the point-of-operation area, therefore preventing contact between the operator and dangerous moving parts.

Simplicity is the key to the success of this device, which consists of two components: the control box (mounted on the frame of the welder) and the drop-probe assembly (mounted on the upper arm). The control box provides interface of the device to the spot welder’s control system. If the drop-probe unit is never allowed to complete its preset downward travel, the welder will not start its stroke. Insulated mounting hardware for the probe unit is also included. Whenever an operator initiates a machine cycle, typically through an electric foot switch, the sensing probe in the system is automatically released, ensuring that safeguarding cannot be deactivated or overlooked by the operator. If the probe detects anything more than the material thickness, it halts the machine from cycling. However, if an operator’s fingers or hands have not entered the point-of-operation area, the sensing probe will drop into its preset position, and the control unit will allow the machine to cycle to maintain ongoing machine productivity and performance.

Designed exclusively for welders, the RKC-500 Detect-A-Finger device has a unique, compact sensing probe module that allows it to be attached to a welder arm, whether it is fixed or moving. The drop-probe stroke is 1-5/8 in. Each unit is furnished with two plain 18 in aluminum drop-probe rods. These rods are to be shaped by the user to specific requirements. To prevent welding splash, additional lightweight clear plastic shielding can be attached to the rod. Depending on the type of welder, a single-stage or a two-stage foot switch may be required. This foot switch is protected from unintentional operation. A die-cast cover protects the top and both sides and the front is protected by a hinged flap. The flap must be lifted with the toe before the foot may enter the switch. The electrical contact arrangement is 1 NO and 1 NC.

With its compact design, this safety device easily mounts on most machines, regardless of brand, providing fabricators with an invaluable way to enhance both safety and productivity. Depending on space and preference, the drop probe assembly can be mounted on either the left or right side of a machine, while the head and control unit are normally mounted on the machine frame or custom-fabricated brackets. The aluminum probe rod is shaped to fit around the tooling, allowing parts to be formed safely at high speed to achieve maximum output.

This safety device may also be applied to mechanical foot pedal-type welders, although the mechanical pedal must be removed and replaced with an air cylinder to operate the arm and foot switch. The cylinder bore and stroke (push- or pull-type) can be determined from actual machine measurements, and the method and location of attachment to the welder linkage. The air cylinder can be controlled by a three-way, normally closed 115V AC solenoid air valve. Adjustable flow control valves may be employed to smooth the welder arm movement, and an air filter-regulator-lubricator assembly may also be required.

The RKC-500 device is available for $1,053. There is also a premium DAF-100 device for welders that features an adjustable stroke up to 4 in and comes with the control box, drop-probe assembly, aluminum sensing probes, and other necessary components. This premium version is available for $1,998. All of these resistance welding safety devices are designed for compliance with OSHA 29 CFR, Subpart 0, 1910.212 general requirements for all machines.