The welding engineer's objective is to keep the electrode at a constant distance from the part surface with a sufficient gap to avoid stubbing out. As a rule of thumb, an arc length of 0.10 inch acts as a base. Half the weld penetration required, expressed in thousandths of an inch, is added to the base measurement to give the arc length for a given amperage. The weld speed, which is the speed of travel of the torch over the part or the part under the torch, is dependent on the flow rate of the material to be welded and the material thickness. The objective is to weld as quickly as possible while still yielding a quality output.
Weld speed is a predominant factor in defining the production output of a welding system.
The welding current corresponds to the amount of heat applied to the part to effect the weld, and it depends on the material to be welded, material thickness, welding speed, and shield gas. The objective is the achieve defect-free welds with the required penetration. Free arc pulsation software, available on the Internet, precalculates a variety of arc pulsation parameters. The welder should start by using 1 amp of welding current for every 0.001 inch of material thickness and for each 10-IPM weld speed increment if the material is stainless steel. Thus, for a 0.030 inch material thickness, the average weld current would be 30 amps in the first level with average weld speeds.