MIG machines come with two variable controls: wire speed and voltage. Determining the correct settings for these variables is the beginning work of a welder, and in a classroom setting best accomplished through trial and error. Have students begin by trying to draw a straight line on a steel plate with their bead. If the bead is not smooth and uniform through the line, or burns a hole into the plate, the students then need to adjust the variable controls of the machine.
While the majority of MIG welds are be straight lines, there is a simple way to help students become more used to the speed and control needed when moving their hands during a weld. Have students attempt to spell their names out in cursive on a steel plate. Not only will this give them greater control in the end, it also exposes them to the difference between a short weld and a much longer weld.
Once students have a solid grasp of what a good bead looks like and how it feels to run the machine, have them attempt to weld two pieces of steel together. This is the major concept behind MIG welding, but it will throw students for a curve once the elements of a small gap between the two pieces is added in. Suggested practice at this stage of class work is to have students lay down two sections of steel in parallel to give them ample experience with the straight line weld.
The single most common weld required from a MIG welder is the angle weld. There are numerous ways to practice this weld while using two sections of 1/2-inch-square bar. Have students position the two pieces at a 90-degree angle with each other and attempt to weld them together. This can be done with a T formation, an L formation, or any other position so long as it provides an angled weld.
After covering the basics of bead and joining work, most students will want to put their new-found knowledge to the test. Have students build a box frame out of square pipe, at least 1 inch. Not only does this project give the students a concrete goal to aim for, it provides numerous angle and straight welds.