View Full Version : Building a Tig weld set.

dr pepper
04-07-2010, 05:17 AM
Because of the silly prices of tig sets, I thought I'd put together a diy set, and maybe do another for portable use on my 4x4 driven off the alty.
The unit is powered by 2 commercial microwave transformers and has hf start, this being provided by a car ignition coil and a simple radio freq osc using spark gaps made from hard drill bits.
The transformers give 200a at 24v, and will burn a 4mm arc welding rod, so I'd be able to do tig on around 1/4" thick material.
The obstacle I need to get over at the moment is synchronising the hf to the mains, maybe I should just power the coil from the mains via a motor start capacitor rather than designing the req electronics.
Heres some photos, the transformer is just a roughout for now, the arc is the hf start in operation, the aim of it is to start the arc at lower current levels:

04-07-2010, 05:21 AM
Extremely interesting, keep us posted!!

04-07-2010, 07:30 AM
I started building a TIG set based on the Miller Synchrowave patents, but then I found I could buy an inverter based 200 Amp AC/DC TIG for 500 ($750 at current exchange) with much better performance.

I still have the 250 Amp controlled bridge sitting on the bench gathering dust.

dr pepper
04-07-2010, 07:38 AM
500 notes, couldnt justify that.
My totall so far is a few quid, most of the stuff is salvage or scrap bin.
I might be ineterested in your bridge, allthough a straight bridge is really what I'd be looking for and you can get cheap russion diodes on ebay these days, and russion doesnt mean poxy they are sposed to be high quality.

04-07-2010, 10:18 AM
A couple of DIY tig builds that you might find interesting...




dr pepper
04-07-2010, 07:25 PM
seen those, the first one supplied me with some ideas for my 4x4 on board welder, I even got in touch with the author of the site.
The second one is interesting, allthough in my opinion uneccessarily complicated, the only time I've seen that kind of adjustment is on automated process machines, which maybe what the author had in mind.

John Stevenson
04-07-2010, 07:53 PM
I started building a TIG set based on the Miller Synchrowave patents, but then I found I could buy an inverter based 200 Amp AC/DC TIG for 500 ($750 at current exchange) with much better performance.

I bought one of those machines, awesome.

At 200 amps they have a 60% duty cycle which is far better than a lot of the dearer brands.

I reckon it's correct as well because I was welding the side board on a dump truck the other day and ran about 20 1/8" ali rods one after the other with it set at 170 amps.

Mind you i still have to work out what all the knobs are for :D


04-07-2010, 08:27 PM
A cheap way of getting arc ignition is to use a piezoelectric gas lighter. The multistrike ones are best. Connect wires to the earth and the power cable. Rigged up as a foot control, with a ferrite torroid on the power cable to protect any electronics, you should be able to get a 1/4 ins spark in argon.

Been there, done that, worked for me.


04-07-2010, 09:44 PM
Many people use an arc welder for a tig welder conversion. I have a miller thunderbolt 240 arc barely used that I can't get anyone to come get even for $100.

04-07-2010, 09:46 PM
How close to chicago are you vpt? I have to go to chicago in May and would gladly give ya $100 for it! (can't seem to find a buzzbox for a similar price, just to power a tig line on occasion)

04-08-2010, 05:16 AM
Instead of the ignition coil, a microwave transformer secondary is about right for feeding a Cockroft-Walton multiplier to supply the spark gaps and the output will automatically be in phase with the output current.

The Miller Syncrowave pattent is US 4,038,515


You can download a copy of the Syncrowave manual that contains a circuit diagram (at least of the power stage) from http://www.millerwelds.com/om/o360j_mil.pdf

John Stevenson
04-08-2010, 05:17 AM
Years ago when I was doing vintage racing bikes I wanted a TiG set for welding on the sheet metal NSU frames.

With nothing to loose I hung a big diode pack onto an Oxford 110 amp oil cooled welder to get DC.

Borrowed a small TiG torch and a bottle of argon to try it and after a scratch start it was away, will only do steel and stainless but it worked quite well, in fact a friend still has it after I upgraded to a larger AC/DC set

dr pepper
04-08-2010, 06:09 AM
Thats sounds like my kind of technique.
A micro tranny original would probably do, allthough safety is a consideration, a micro tranny produces loads of power, a limit resistor would work but if it shorted you'd have a very dangerous situation, a little fiat punto ignition coil is a lot safer, and I could connect the coil to a standard 240v lamp dimmer type circuit, and connect the coil to it through a motor start capacitor, the reactance of the cap dropping the volts enough for the coil, and the spark energy would be reasonable in phase (but not the volts and amps).
My use of micro trannys is rewind the secondary to produce 24v then wire 2 in series to give the req 50v, my first design ended up a volcano, I used 7 strand 10awg cable it melted and blew up, I now have some fibre glass high temp 8 awg stuff which will take a little longer to cook.