13.2 CAC-A Equipment and Setup
Stephanie Oostman
Components
The information included in this section is generalized, and you should check with the operating manual and/or manufacture of your specific equipment on set up procedures, limitations, and safety considerations.
In section 13.2.1 Basics of the Process we read what CAC-A does, and a few notes on specifications on the equipment. Most welding machines that are capable of SMAW can also be used to perform CAC-A with a few additional pieces of equipment. To set up a welding machine for manual CAC-A you will need the following:
- A constant current (CC) welding machine capable of at least 28V output.
- A CAC-A Electrode holder. See image above
- A ground clamp.
- Carbon arc electrodes capable of the polarity you need.
- compressed air that can be supplied at at least 80-100 psi.
- Air Hose for compressed air.
The power source can be either AC or DCEP, however the carbon arc cutting process requires higher output than some welding machines produce, making them an ineffective choice for this process. Running a machine at the higher output needed for CAC may cause the machine to over extend its duty cycle unless the machine is a heavy industrial type capable of 100% duty cycle, to avoid overloading your welding machine take breaks and consult the manufacturer for the machine’s duty cycle.
The electrode type and diameter, and the material to be cut, may also impact which polarity to select. Minimum electrode diameters, polarity, amperage and air pressure settings will all be dictated by what the material is and how thick. This is no different than most welding procedures. A ¼” electrode on DCEP has a range of 200-400 amps for example, and can be used to cut carbon steel, stainless, copper and nickel alloys, aluminum and cast iron.
Air supplied should be 80-100 psi nominal. While you can use higher than 100 psi, it does not make the removal of molten metal more effective. The air line needs to have at least an inner diameter of ⅜”, and the air compressor must meet the needed capacity to adequately produce a clean effective cut. For lighter duty work, these recommendations can vary with air pressure as low as 40 psi and an airline inner diameter of ¼”. If the air pressure is not sufficient, the operator will not be able to produce a smooth, uniform cut. This can also happen if the diameter of the air hose used is too small, as it will create a constriction of air flow to the electrode holder.
Note: Oxygen should never be used in place of compressed air in the CAC-A process.
The modern day CAC-A torch is designed to bring both the electrical cutting power of the process together with the blasting power for compressed air.
Refer to the pictures in this section. Both the upper and lower jaws are insulted and the lower jaw has a head with holes to allow compressed air through. The head can be rotated allowing for different angles or positions and both jaws only have one groove that can accept multitude o