No pictures on this update, but I did find a very large fan for the triac, and some emi suppression caps for adding HV. Also bought four 70 amp diodes, which will do until i can find some stud mounted ones on ebay. All together, less than $20.
Since someone asked for it, here's my project log of building a TIG welder from the ground up (not from a stick welder). Three transformers provide 20 volts each, at probably 50 amps each. I'm going to need to install a 240 volt outlet if I really want some power, the power factor on the transformers (rewound microwave oven transformers) is pretty bad. So far I've tried the transformers and the HF/HV starter, but not together (need a cap for a low pass filter to prevent HV entering the transformers. Power control is provided by a phase angle control, two anti-parallel SCR's (while essentially a triac, triacs have problems with inductive loads, sometimes they dont turn off at zero crossing). Pictured is a triac, although im going to the surplus store tomorrow for the biggest scr's they have. Tig torch is WP17V, with valve.
Some pictures
MT1 broke off the triac
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No pictures on this update, but I did find a very large fan for the triac, and some emi suppression caps for adding HV. Also bought four 70 amp diodes, which will do until i can find some stud mounted ones on ebay. All together, less than $20.
Do you have a wiring schematic for this. I bet I could scrounge up most of this.
If it's not nailed down, it's mine.
If I can pry it loose, it's not nailed down.
Very interesting !
I'd like to see a bead you've layed with it.
When I do start welding, I don't think it will be pretty. I've never welded tig or even OA, so don't expect anything great.Originally Posted by sanddrag
Schematics are in pdf and dxf
Wheres the thread on your DIY Plasma Cutter?
Some new pictures. Sorry people on dialup (~2mb)
24-The welder on a prototype case. The "case" is pretty much non existant until I get the plasma cutter working (tin snips are painful)
25-The arc starter, only the transformer has been mounted. It's a 9kv/30ma unit, so it probably needs a seperate circuit from the welder (rated 240va)
26-The front plate, incl. circuit breaker and current adjustment pot (which is unconnected)
27-HF suppression caps, to prevent the power stage from being destroyed by the arc starter
28-A large 120 vac fan
29-The starter tank mmc, aren't those caps familiar?
30-Adjustable Spark gap, a 10-32 screw will clamp the electrodes (tungsten) in place
33-Poor man's HV wire, just some clear plastic tubing around a 600v rated wire
34-Heat sink compound
35-Triac next to triggering diac on top of a big heatsink
Does anyone have an suggestions on how to flatten aluminum sheet? It's bent out of shape from the tin snips, and I can't seem to get it flat again.
I am also very interested in your work. It would be nice if you could put some size and values of the components in your pdf file. With the rewound transformers the voltage and wire guage also would help.
Thanks, John
The HF suppression caps are rated .047uf 1600 vdc, 900 vac with 5 parallel sets of two in series, giving a .235 uf 1800 vac bank of capacitors. Secondaries are ~22 volts, using around 20 turns of 16 ga plastic insulated (non magnet wire, much cheaper) wire. The tank cap is around 30 of the same .047uf caps in series.
I'm pretty sure I need a better power control circuit than what I have, so the details on that will come later.
Great work. Its certainly coming together.
I finally had a chance to run both the arc starter and welder, and am slightly disappointed. There's two issues:
First, the plastic holding the spark gap pretty much caught on fire. There is a fairly easy fix, move the gap to the exact center, and if necessary, add a fan (would also provide some arc quenching=better performance)
Second, and more importantly, the arc would not sustain full power. Without a capable amp meter, I can only guess the cause. I have a feeling the transformer (I'm running only a single transformer to prevent tripping the house breaker), is saturating. The HV arc would stay on the entire time, but the high current arc would only be sporadic, despite the arc distance. I'm going to run it again tomorrow with the second transformer running off a different branch via an extension cord, and see if I can't get an arc to sustain. But it was definately a welding arc.
Edit:
After some reading, I realized saturating a transformer is impossible by excess secondary current draw (it's dependent on voltage and frequency only ) I guess my next option is the second transformer, maybe in series.
Last edited by js530; 07-24-2006 at 01:32 AM.
Sorry for the long wait, but there's some good news....
It works!!!!!
The 25 amp circuit breaker (the one on the aluminum front panel) kept tripping, which might be a good thing depending on how you look at it (3kw of power...). It would start an arc at about 1/2" away from the workpiece, which caught me by suprise a few times. I could weld for about 5 seconds before the breaker tripped, which may explain why the puddle just looks like a blob of metal. I also think the shielding gas flow rate was too slow, or the electrode was too far out of the cup.
Tomorrow I might try using two seperate 20 amp outlets with an extension cord, and without the 25 amp breaker.
Now does anyone have some 100+amp diodes?
A few more pictures
It seems the filler doesn't really want to stick to the aluminum. Is this caused by surface oxidation? The duty cycle is fairly low, even with a fairly large fan on it. I'm going to see if some secondary side ballasting can help limit current.
I'd really like to see how it compares to a real tig welder. The closest to a bead I could get was the bottom of the first picture. As soon as the puddle develops, the surrounding aluminum starts melting. I'll try again tomorrow. I only tried to lay a bead on aluminum because I don't have big enough diodes for steel.
(The switch on the torch controls a relay which controls the HF starter)
What shield gas are you using and what type of tungstun?
Straight argon and pure tungsten (green). HF was on the entire time, aluminum is unknown extrusion alloy. Filler is 4043.Originally Posted by lwill
all that is good but it looks like you could use a little cleaning on the aluminum.
Aluminum to get a good weld must be very clean. And depending on the amperage/voltage used you might have to preheat the metal to get a good weld started.
If youve never welded before aluminum isn't the best thing to start on and definitely not on a rigged up welder.
just my 2cents
thanks
Michael T.
"If you don't stand for something, chances are, you'll fall for anything!"
The oxidation on the AL can definately be a problem, ANY contamination on AL make it more difficult. Best thing to do is wire brush it just before you weld with a stainless steel brush. (normal steel one will leave residue as well) Even with it very clean, starting a bead is tuff if you have never done it. You will see the surface turn dull, this is the remaining oxide on the surface of the molten puddle. You have to stick the filler rod into the puddle to break this surface. Once that is done the bead will form much easier because the fresh metal is inside the sheld gas area and will not oxidize as fast. Another thing that can cause problems is the fact that AL conducts heat so well that if is laying on a steel table it could be soaking up the heat. It looks like you are useing a very thin piece so this may be to your advantage to keep from mealting the whole thing. Very large peices of AL you need to preheat before welding to get a good joint.
I failed to pay attention to your earlier posts, are you using AC or DC? AL needs AC if you are using argon or argon/helium mix to help "scrub" the oxide away. If you are using DC you can use pure helium I am told. (never tried it myself) Steel needs to be welded using DC with ground on the work peice. 2% thoriated(sp?) "red" tungsten will give you a better weld and last alot longer on steel but will contaminate aluminum.
I hope this info helps, good luck! Keep on posting!
I'm using AC, which is why I tried aluminum. I also tried to tack weld two ~14 ga pieces of aluminum sheet. I noticed it seemed to only heat one at a time, and both failed to stick together. There was a slight gap between the plates, but it wasn't more than 1 mm. I didn't brush the surface, so that might have something to do with it.Originally Posted by lwill
I've welded aluminum with my mig welder, but that was an excercise in frustration. I probably should've used a teflon gun liner, but never bought one.
I definately need a better way to cool the transformers. Oil cooling would be an option, except the whole flammability issue.
You definately have to use filler rod with aluminum to break the surface and get them to stick. You cannot "tack" or fuse aluminum together like steel. Once the puddle starts on one piece it will help the heat flow to the other, sort of like tinning a soldering iron. The heat flows with the arc and both will take the path of least resistance. Once the puddle starts you can help control how hot it gets (since it looks like the variable peddle is a bit in the future for you! )by adding rod faster or slower.
I am far from a pro at TIG, but fake it pretty good and have been lucky to use good Miller and Lincoln machines (and had good teachers). I feel for you learning on a machine when you are not even sure if is working right. If you get a chance, try out a real machine so you can tell better what is wrong. I'll give what advice I can if you ask.