http://www.instructables.com/files/deriv/FTW/1PYJ/FAKC0MSF/FTW1PYJFAKC0MSF.MEDIUM.jpg

I was surfing youtube and found several videos about it, and in turn this good instructables page (http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/) detailing how to build your own.
If you search "welder microwave transformers" on google theres a lot of pages with very similar instructions so it seems fairly legit, but I'd still like to hear someone else's opinion.

Will the transformers last long enough to make it worthwhile, or will they be burned out after like 15 minutes of arc production? If you enclose it all in a box do you need a fan blowing through to cool the components?

do I need to get microwaves with an output of atleast X watts, or will I have enough current even if theyre on the smaller side? I would be using it for a variety of sizes and forms, but mostly 1/8" steel plate so i don't need something capable of repairing tractors and real heavy shit.

The last thing im unsure about is the heavy wire that this project calls for. According to charts ive looked at, 10 gauge wire (which is what you need) has a conductor diameter of 2.58826mm. Does that refer to a single 2.588mm thick wire, or the multi-strand stuff that we more typically think of when hearing the word? I'm assuming its for multi-strand but I don't actually know. If that's the case, do I just find some copper wire that's 2.588mm thick and call it good?


I'm pretty sure I am getting 1 of the 2 microwaves I need in the next couple days, so hopefully someone can give their 2 cents on this before I hunt too much for the second one.


Thanks for the help,
-Jon

one more thing about rewiring the secondary spools on the transformers...

on that instructables page, steps 3 through 5 talk about how to do this correctly.
http://www.instructables.com/files/deriv/FRT/CV8Z/FAQDX2E3/FRTCV8ZFAQDX2E3.MEDIUM.gif
he said they used about 20 foot of wire on each transformer doing it. since wiring has atleast 2 actual wires in it, (+) and (-) and sometimes a ground, does that mean you only need 20 feet of wire to do that part? cause you'll take off the outer protective cover to separate em, so cant you just use the (+) for one of em and the (-) for the other?

hope that makes sense... atleast thats how it looks in his schematic, like you gotta redo the secondaries with this 10AWG but you get to leave the primaries alone.

I've been thinking about doing this a while and even have a few transformers already, I'm trying to get at least 4 though.
I know (the almighty) lifejunkie has built one so we'll have to wait for him to get here.
since wiring has atleast 2 actual wires in itNot all wiring has two wires, only "2 conductor" power cable. I was planning on using power wire from some old amp kits.

I would think that the electrical characteristics of braided v/s non- would be the same. I think you'll want to use braided since it's more flexible and will be easier to wind and get tighter coils with.

The power rating is what both the primary and secondary coils can handle individually, so you'd want to get as big of transformers as possible in order to be able to get the most power out of them without frying them. The bigger the transformer the longer the periods of time you'll be able to weld.


I don't think you should be too concerned with sticking to the exact numbers he uses in that instructable. Your transformers will likely be different sizes and so you'll need different lengths of wire to get the proper amount of windings.
If you're far enough into your engineering classes that you're starting to think like an engineer about stuff like this, like me :(, then there is a systematic approach you can take to doing all of this rather than just shooting from the hip. I could elaborate more on this if you'd like.

I've been thinking about doing this a while and even have a few transformers already, I'm trying to get at least 4 though.
I know (the almighty) lifejunkie has built one so we'll have to wait for him to get here.
Not all wiring has two wires, only "2 conductor" power cable. I was planning on using power wire from some old amp kits.

I would think that the electrical characteristics of braided v/s non- would be the same. I think you'll want to use braided since it's more flexible and will be easier to wind and get tighter coils with.

The power rating is what both the primary and secondary coils can handle individually, so you'd want to get as big of transformers as possible in order to be able to get the most power out of them without frying them. The bigger the transformer the longer the periods of time you'll be able to weld.


I don't think you should be too concerned with sticking to the exact numbers he uses in that instructable. Your transformers will likely be different sizes and so you'll need different lengths of wire to get the proper amount of windings.
If you're far enough into your engineering classes that you're starting to think like an engineer about stuff like this, like me :(, then there is a systematic approach you can take to doing all of this rather than just shooting from the hip. I could elaborate more on this if you'd like.

lifejunkie quit, man. A god among men, he was. :(

Anyway, the stranded versus nonstranded is only a factor where high frequencies are involved and where you will be flexing the wire alot. For wrapping the transformer, high frequency impedance is not important and the wire will not be moved once it's in the core. The only factor to be considered is cost. (That is, assuming you crimp a stranded wire to the solid wire for the wand.) I recently had to help a welder roll up his leads. They were about 30, 40 feet long and were about 3/4" in diameter. Of course, he was using high-powered straight DC with a generator as it's power source.

Here are the DC wire charts: http://www.windsun.com/Hardware/Wire_Table.htm For AC, you would divide the power rating by the square root of 2 to get the RMS rating.

Personally, I don't like the fact that it is AC only with these. If I were doing it, I would experiment with diodes on the AC side. I'd see what half-wave and full-wave would do. (Of course full wave is going to be about twice the power of half, but you gotta look at how hot your transformers get and all.)

Household wall sockets are rated for 120VAC @ 15A. It shows two, but I doubt most people doing this project will realize that you have to plug the sockets into two separate circuits in order for the two-socket thing to work right. As a safety precaution and since it is a better idea, don't use the two-plug method. Get a proper high-power cord and plug and power the welder with a single socket.

For ventilation, I would definitely recommend using some sort of fan until you know how hot it's going to get while you use it.