Thread: DIY TIG Welder

Hi Edd,
That is certainly an ambitious project.

I think I can see where you coming from ,in that the cost of an reliable AC/DC tig is not going to leave much change out out $7k.

In any case ,I thought your Dad had a Fronius Tig?


Alternator driven tigs are nothing new, I have seen one many years ago. The HF unit was home made and was termed a pilot arc .The arc initiates an ionised path through the argon gas shield between electrode and ground which the main current will follow- hence no need to scratch start.Lincoln used to have a kit you could buy to add to a welder to give HF.

The spark gap points can be made from a set of old fashioned points contact set which have a tungsten button diameter closer to what you need. The Miller AC/DC units had a pair of them.

Again the Miller AC/DC had a switch,a big hefty bugger between the transformer and the rectifier.

Some welders had switch which gave either cleaning or penetration but I can't remember how it worked.They were the sinusoidal wave type.It was one or the other, not a percentage like one can get with square wave.

If you go the high tech route beware of using an neon sign transformer as a basis for a HF unit.The brief read I had from an article suggested against it, as it could be fatal. Please take advice from an Australian based technician as the Yank wiring is quite different to ours.

WE shall watch your progress with eager anticipation.

Best of luck with it
Grahame

Thanks Grahame. Yeah, I do have access to a pretty fine welder, but this is more of an fun exercise for me as I love tinkering with electronics and this would be a useful project. The HF starters are hard to find now it seems, and costing around $800US. That's why I posted that link with details how to make one. Finding the parts is difficult though. For safety, I plan to ground the case on the HF starter, maybe add circuit breakers too. The result should be high enough frequency that you can touch it and only feel a tingling - not that I'm game to try.

I have heard of the tungsten spark gaps. Can't remember where it was, but someone on the net set a <1mm spark gap by fixing two TIG tungstens apart. Given that they are designed to handle high currents without burning up, they should last a lifetime at 30mA.

If anyone knows where I can get HF capacitors (doorknob/transmitting) and a high voltage (10-15kV) transformer, please post.

Probably illegal to make an electrical appliance and plug it in without some sort of certification .Cant even make a steam engine apparently or take a billy cart on the footpath or tether a cow on a disused road reserve .
They regulate ordinary people to death and let the highfliers do anything they damn well like till they destroy the whole world .

Make a machine for electrocuting politicians and bureaucrats.

good luck ---Mat

Edd
Getting back to to the points gap ting, the Millers at Tafe ( I think Cy 350 was the model number) had a plate on the top you took off and it exposed the double points.

It seemed to a happen,that we couldn't ge tHf on a machine when I ran a Cert tig class and the damm 14 machines had to be on line.

Often because of the culture of allowing students to grind in the welding bay the points gaps became filled with metallic dust.
The gap sat vertically so all that was needed was a clean with a points and re gapping.I mm seems a lot ,I remember it seemed about half that say 20 thou not 40.

As I described the points gap on the sets where about the diameter on what you commonly found on a points set from a car distributor or 2 stroke motor mower. Probably these are still available and therefore that is then one less thing you would need to cobble up, as the mechanism is mostly there.

Grahame

Yeah, I've been told 0.028", which is 0.7mm. Thanks for the tips on vertical mounting and car distribution components.

As for it being illegal, I don't think there is any regulation on private use of such things. We've built power supplies, motor controllers, etc over the years, some of which are Dick Smith kits - certainly legal. Obviously I wouldn't attempt to use this or sell it in a commercial situation, as that's where problems can occur.

Back to the HF system. From googling, it seems that to jump air requires 3kV/mm. I'm wondering if I can get away with avoiding a lot of the circuitry by using one of these. It accepts a 12V DC input and provides 7KV at 30KHz and 10mA. This would mean the frequency is high enough for the voltage to only be a tingle on human flesh, and the low current capacity is nice - in contrast a microwave oven transformer is not current limited and can very easily kill you. Another link I found showed a relative comparison of air ionisation as 0.97 and argon as 0.18. Calculating this, 7kV should allow a spark to jump 2.3mm in air or 12.5mm in argon - plenty as I'd probably start the arc at half that height.

Hi Edd,
The tingle on the flesh reminds me of what one the Miller enginneers said about HF.

Apparently it only works externally on the body parts it touches . Its the welding current that can be nasty and be routed through your body if your are dumb enough to offer it a circuit to flow through.

It only take a micro-amp to disrupt the electrical nerve signals to the heart.

We could drag the tungsten electrode across our fingernails and lift and get a tingly arc.
No one offered to try while grounded to the bench.

I talk to a electrician ( unfortunately somewhat infrequently)who does pretty much nothing else but welders including tigs. I will ask him when I next see him if he thinks it should work.

Cheers
Grahame

Update. I have worked out how to build the entire project:

Power Supply:
BOC Smootharc 130 or 170 $300/$400

Gas:
12V, 1A solenoid that I found in the shed - $0
Will have to adapt the 3/16" fittings to 3/8" using hexagonal brass stock OR just buying the adaptors $0 - $10?
12V Regulated power supply @ 2.2A. Just happened to have that in the shed from an old hard drive enclosure - $0
Microswitch for the torch to turn gas on/off - $0

HF start
12V triggered relay with 240V contact for primary side of the HV transformer (found in shed too) - $0
Mains switch (240V/10A) - $0
Spark plugs x 4 - $20
Aluminium flatbar to mount spark plugs onto - $0
HV transformer (Should be high enough at 9kV) - $120 delivered
Tank capacitor = 6 x Cap Cer 3kV Z5U 10mm LS .01 uF - $11.70 from DSE
Suppression capacitor bank = 10 x Cap Mains Sup 275V DX2 0.047uF - $8.00 from DSE

TIG Stuff and Hardware:
TIG Torch with 25mm male dinse connector and separate gas fitting. - $120
2 x Male Dinse fitting - $16.76
2 x Female Panel dinse - $22.50
5m of 25mm2 welding cable - $45

Total and comments:
Total is about $665 for a 130A TIG welder or $765 for 170A. Allowing for the fact that these projects ALWAYS cost more than anticipated, it will still be well under $1000, even if $800 or $900.
Let's compare this to a Fronius Transpocket, costing $2500 (just for kicks and only because we used to have one).
• Both are switched-mode power supplies (inverters) and DC only
• Weight and volume will be about twice as much, as there are two boxes (power and HF start)
• This will not have pulse, while the Fronius does
• This has HF start, Fronius has lift-arc
• Both have solenoid valve
• Fronius is a 150A welder, this is either 130 or 170.
• Fronius costs more than three times as much.
• Being modest about my abilities, the quality of the finely engineered, Austrian Fronius is higher, but I understand the circuitry of this one and can repair it myself (the TIG side of things, not the MMAW power source).

Questions:
• The TIG torch is rated at 150A AC. Is this okay for the maximum current of 178A DC from the welder? It would be very minimal use at this current of course.
• 9kV is surely enough for the HF unit, right? I'm pretty sure it is, but confirmation would be nice

Hi Edd.

Given you stick to light work at lower amps your 150 amp torch should be ok .

Sustained work around 150 is getting close to a water cooled torch rating and that will open an extra bucket of worms for you.

Grahame

Hoping to have this finished early January (won't start until after xmas when I have the Smootharc 170)

I have the 9kV transformer and bought my spark plugs - champion gold for $2 each on ebay - about $13 delivered for 4.

Wow Edd, I'm looking forward to see how this works out for you. I looked at going the exact same thing quite a while back. I finally put it in the too hard/expensive bucket along with most of my other plans

If its going to cost you over a K for a dc only unit, would it not be better to simply buy one of the basic dc tig's advertised on ebay, you can get a better unit than what you would be constructing for around 600 bucks total, or go a basic ac/dc for K.

a) Shouldn't be over a k. No such thing as a quality 200A inverter TIG unit for $600 with HF start and Solenoid - at least not one I've ever seen. The cheapest *decent* AC/DC machine I've seen is Token Tools for $2350. I think I'd sooner burn my money than buy a $1000 POS.
b) The fun is in the project.

After I get a chance to play with my Smootharc 170, I will start building this. Hmm need to find a suitable case.

Okay no problems, at work I have unitigs etc and have no idea on there price, here at home my personal tig cost me 7k.

I have no idea as to the quality or duty cycle on the cheapos, but would still imagine they would do better than the proposed one in your project.

That being said if your doing it for the physical and mental challenge then go for it, nothing equates to knowledge gained

Good luck and keep the forum updated on the project as it progresses if you could

Thanks.

Originally Posted by simso

That being said if your doing it for the physical and mental challenge then go for it, nothing equates to knowledge gained.

Yep. It all comes down to what you like doing as a hobby. One step back is "Why not just buy a welder?" and a step back again is "Why weld? Just buy what you need already welded or pay someone to do it?". There are people who are quite content with a drill as their only power tool.

Part of the reason I chose this instead of a cheapo is that the power supply (BOC Smootharc) has a 16 month warranty and I have a BOC shop down the road from where I live. I am adding the solenoid and HF start without modifying it at all. Therefore I am hoping overall it will be better quality than the eBay TIGs.

$7k? Sounds like a Fronius MagicWave 2200.