I started the unit on MIG welding this week with my Intro classes. Having taught this stuff for many a year, I've got a pretty good idea of what to expect when rookies pick up a MIG gun - a birds-nest at the feeder being one of them. The simplest explanation as to what is and what causes a birds-nest is the wire can't feed through the torch when you pull the trigger, usually because of an obstruction on the contact tip. However if you continue to pull the trigger the drive rolls are going to continue to feed the wire and it's got to go somewhere, so it will ball up like in the top photo. This one was done in some other class - I just happened to notice it while walking by.
This big old gob of wire was formed by one of my guys, however. It was much more impressive when it was all poking out from under the cover on the wire feeder. In fact, I'm thinking it might be the all time record size birds-nest of my career. There were actually another couple of pieces of wire that I had cut out before I was able to get this wad out of there. Before you say anything like maybe you should warn them about this, I told them not once, not twice, not three times, but four times: "When you're welding and the wire quits coming out, quit squeezing the trigger." Often times, it pays to heed the warnings of those with a little more experience.
Other than this one, things actually have gone pretty well. The classes in general seem to have been successful. Now that the classes are nearing completion, everyone can at least weld a little bit, I got evaluated by my supervisor and that went about like it used to in the early days at the high school - five minutes with the boss while he filled out the form and then: "Sign here. I'll flower it up a little and give you a copy." Perfect. No muss, no fuss. The students are learning and everybody's happy. Ain't life grand.