FAQ - Push-Pull Systems
Cobramatic® MIG Welding Wire Feed System
Q. What is Push-Pull and how does it work?
The Cobramatic® wire feed system is based on a push-pull principle with a "slave" motor in the wire feed cabinet and a drive motor in the welding gun. The slave motor is an AC motor which runs at a higher speed, but lower torque, than the gun motor. The gun motor is a DC motor with lower speed than the slave motor, but higher torque and is controlled by a solid state full bridge rectifier control located in the wire feed cabinet.
The slave motor has a two torque position switch allowing the system to operate all soft wires from .030" (0.8mm) to 1/16" (1.6mm) and hard wires from .030" (0.8mm) to .045" (1.2mm). The maximum inches per minute capability of the slave motor is 1200. However, when the torque switch is in the ".030" - .035" Aluminum Only" position, it has a torque of 1 to 1-1/2 pound inches. When this switch is placed in the "All Other Wires" position, the torque is increased to 4 pound inches.
The gun motor has a high torque output over a wire feed range of 300 to 900 inches per minute with a torque of 10 pound inches. Thus, the slave motor is always trying to overdrive the gun motor, but since the gun motor is controlling the wire feed, the column strength of the wire literally slows the slave motor. As a result, the Cobramatic® system can feed at distances between the motors to a maximum of 50 ft. (15.2m). Also, only the contact tip need be changed to go from one wire size to another.