Okay-
If it's not one thing it's the other...my classrooms Miller Spot welder LMSW52 is doing scary things. I haven't done much trouble shooting on them before, and as usual the booklet doesn't cover my trouble to be shot.
When the tongs (12" standard) come together, the electricity doesn't seem to be reaching the tips. No normal hum (it's quiet) , and the nut and bolt you can see just behind where the wire braid is, seems to be heating up to a lovely shade of orange (if I hold it long enough...which I probably shouldn't do and will stop now). Needless to say it is not creating a weld, and is not totally consistant as to when it does this, but now that school is starting it probably will be constant:). We tend to weld galvanized thin gage (26g) sheet metal, or mild sheet steel also @ 26g. My supervisor has suggested that the zinc from the galvanized metal coats some of the inside workings...does this sound feasible? I tend to be skeptical, assuming these machines are made partially for galvanized sheet metal, and if they are plated by doing so, it's a lame design.
Any advice is appreciated. I will contact Miller, but everyone at this website is so much more fun, and quite honestly, usually much more helpful.
Thanks...Alison
I will go talk to some of the guys that do lots of spot welding on galvonized steel. I am not sure if you are saying it does not preform on mild steel. Have you tried filing the tips or even replacing them. Is your work piece lead in a good location? Wait, it must be if the cable that conects to the tongs is getting hot. Let me go see the spot weldor guru's and I will get back to you hopefully today.
Mike
Ok, just got back from the production floor. I talked with a gentleman that is now 76 years old and has worked here, in production resistance welding since hw was 17 years old. He ran several tests pieces for me using 14 ga. 16 ga. and 26 ga. galvonized sheet metal. Every one was of superior quality. We pulled 2 of them and they each had a very nice nugget. This rules out the zinc coating issue. I think the porblem is in your tongs. How is the pressure to the tips on the tongs applied, hand, pneuhmatic, hydralic? Ensure that your contact tips have pressure applied before the current is energized. Make sure the contacts are free from carbon and do not have arcs on them. Make sure your connections are good. The fact that your cable is glowing orange tells me you have a problem with your connections or tips. Other than these suggestions, I cannot offer you any more suggestions.
Mike
For it to heat its own parts like that indicates considerable current flow. Lack of welding indicates leakage of current. Look for broken insulators- probably in the area of the pivots the tongs move on.
Good luck
Bill
The tips are fine...fairly new, clean, aligned, right pressure etc. Yesterday when I cleaned the tips, it worked fine. Today...after no use in-between...when I went to demo to the students, nothing (Murphy's law). Miller suggested tightening the braid, which seemed to be tight when I took it apart. The braid however has widened a bit where the bend is...but no fraying or anything like that. I've cleaned the ends of the tongs (which weren't dirty), the insulators appear to be in one piece. It's apart right now, so I don't know if the act of taking it apart, cleaning, and reassembling will make a difference (just wanted to see more AWS advice before I reassembled).
The tongs come together from hand pressure (actually foot pressure through a foot peddle...it's on a stand).
Help!
Also I'll let you know if it's okay after it's "check-up".
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