SETTING THE CURRENT IN MIG WELDING MACHINE
MIG Welding Machine, proper safety protection, and one piece of mild steel plate approximately 12 in. (305 mm) long x 1/4 in. (6 mm) thick, you will change current setting and observe the effect on MIG Welding.
On a scale of 0 to 10, set the wire feed speed control dial at 5, or halfway between the low and high setting of the unit. The voltage is also set at a point halfway between the low and high settings. The shielding gas can be CO2, argon, or a mixture. The gas flow should be adjusted to a rate of 35 chf 916 L/min).
Hold the welding gun at a comfortable angle, lower your welding hood, and pull the trigger. As the wire feeds and contacts the pate, the weld will begin. Move the gun slowly along the plate. Note the following welding conditions as the weld progresses: voltage, amperage, weld direction, metal transfer, spatter, molten weld pool size, and penetration.
Reduce the voltage somewhat and make another weld, keeping all other weld variables (travel speed, sickout, direction, amperage) the same. Observe the weld and upon stopping record the results. Repeat this procedure until the voltage has been lowered to the minimum value indicated on the machine. Near the lower end the wire may stick, jump, or simply no longer weld.
Return the voltage indicator to the original starting position and make a short test weld. Stop and compare the results to those first observed. Then slightly increase the voltage setting and make another weld. Repeat the procedure of observing and recording the results as the voltage is increased in steps until the maximum machine capability is obtained. Near the maximum setting the spatter may become excessive if CO2 shielding gas is used. Care must be taken to prevent the wire from fusing to the current tube.
Return the voltage indicator again to the original starting position and make a short test weld. Compare the results observed with those previously obtained.
Lower the wire feed speed setting slightly and uses the same procedure as before. First lower and then raise the voltage through a complete range and record your observations. After a complete set of test results is obtained from this amperage setting, again lower the wire feed speed for a new series of tests. Repeat this procedure until the amperage is at the minimum setting shown o the machine. At low-amperage and high-voltage setting, the wire may tend to pop violently as a result of uncontrolled arc.
Experienced welders will follow a much shorter version of this type of procedure any time they are starting to work on a new machine or testing for a new job. This experiment can be repeated using different types of wire, wire sizes, shielding gas, and weld directions. Turnoff the welding machine and shielding gas and clean up your work area when you are finished welding.