Something I haven't done much with yet is welding/brazing to fabricate items. I've done a lot of soldering, which is pretty similar to brazing so that doesn't present much of a challenge (so he sez). Welding is a different story, and looks to be a very handy skill to have. I started looking into inexpensive learning-level welders and found some info about modifying cheap Harbor Freight welders, from pretty crappy AC to sort-of-OK DC current welders.
The basic approach is to take your HF alternating-current welder and turn it into a DC welder, using a high current diode bridge and large-value electrolytic capacitor. This requires some serious mod work, cutting wires and installing the rectifier/capacitor inside the welder. I bought the rectifier and capacitor on ebay (BTW, this type of modification is described on a number of web sites so I don't think it is necessary to go into much detail here).
I also got some 10 gauge multi stranded wire and spade type connectors to match, to make sure the connectors and wire would not limit the current available for welding. Wire this size is pretty stiff so it is necessary to think about the physical arrangement of the wires/diode bridge/capacitor so you are not exposing the device terminals to excess stress.
I finally completed the mods but was not totally confident that everything was wired up correctly. To verify the wiring I performed an incremental power-up test. I began by using an external 40V power supply. I used it to bias up the capacitor and (hopefully) back-bias the diode bridge (it should look like an open circuit). Everything looked OK so I plugged the welder power cord in, took a deep breath and flicked the power switch. Nothing, nada. Well, not all bad -- no smoke. But not great, either. So I cussed and opened the welder back up, and discovered I had not reconnected a connector on the controller board. Well, that's better than an egregious wiring error I guess.
After plugging the connector back in, the welder powered up OK. Some trial runs produced results that clearly showed I need some practice making a good bead -- not too surprising there, but I got some good metal puddles that show promise.
I started out with the slowest wire feed rate and just got "bangs" as the capacitor charged up and blew out the welding wire. Now I'm up to about the halfway point on the feed-rate dial (whatever that means in physical terms) and get a more or less continuous arc. I ran some beads across the surface of some iron plate I had for the testing. The next thing to try: gluing some metal pieces together to see how well this metal glue gun works.
Fun stuff.
By the way, while doing the welding tests I wore protective gear, including a welding helmet with eye protection. The ultraviolet light from arc welding is hazardous! Heed all warnings that come with your welder.
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