Don't make this mistake...
Posted: Sun Jan 15, 2017 3:15 pm
I repaired our MM252 yesterday. The idler roller hinge in the wire feeder had snapped off. Here's why:
Someone had overtightened the roller tensioner. I know who, and he no longer works there (attendance problem). This guy was trying the "fake it 'til you make it" approach. He had obviously MIG welded before, but knew nothing about the machine. Before I go further, I'm not implying anyone here is stupid enough to do what he did for the reason he did, but it brought up something to be aware of that I'll get to at the end. This guy apparently thought you loosen the tensioner to change the wire, then tighten it all the way when you're done, like a lock nut. Tightened all the way, the wire will bird's nest before it will slip if you get sticking at the tip. Sure enough, it did, and two revolutions later fed the wire into the gears between the rollers. With no give left in the tensioner, the hinge snapped, and the machine was down for four hours as I fixed it.
The point this brings up: Some wires require more tension to push than others. For example, 308 has a hard slick surface, so the tension should be set higher to drive it reliably. One should always make sure there are a few turns of the tensioner left so there is "give" in the event the wire snarls like this. A good test when setting tension is to stop the wire at the gun with your hand and make sure the rollers slip on the wire rather than drive it around the rollers.
Someone had overtightened the roller tensioner. I know who, and he no longer works there (attendance problem). This guy was trying the "fake it 'til you make it" approach. He had obviously MIG welded before, but knew nothing about the machine. Before I go further, I'm not implying anyone here is stupid enough to do what he did for the reason he did, but it brought up something to be aware of that I'll get to at the end. This guy apparently thought you loosen the tensioner to change the wire, then tighten it all the way when you're done, like a lock nut. Tightened all the way, the wire will bird's nest before it will slip if you get sticking at the tip. Sure enough, it did, and two revolutions later fed the wire into the gears between the rollers. With no give left in the tensioner, the hinge snapped, and the machine was down for four hours as I fixed it.
The point this brings up: Some wires require more tension to push than others. For example, 308 has a hard slick surface, so the tension should be set higher to drive it reliably. One should always make sure there are a few turns of the tensioner left so there is "give" in the event the wire snarls like this. A good test when setting tension is to stop the wire at the gun with your hand and make sure the rollers slip on the wire rather than drive it around the rollers.
