# About welding RF ignition arc-start



## graham-xrf (Dec 24, 2020)

A question about something that is the norm for TIG, but begs a whole lot of questions for one who does not know.
RF ignition, also called HF-START is the feature.
I am, of course, going to be trawling the subject until I wring out everything, but I thought to ask here first.

My welder, (yet to arrive), is basically a MIG welder that can be used in a variety of other welding methods, including one called "TIG-LIFT". I understand this means the TIG arc is started with a "scratch-lift" technique. Just thinking it through has me expecting the trick cannot be good for the tungsten point, nor for the control of the start, or re-start of a weld. I do understand the principle.

Q1. Is RF ignition a feature that could help start all the other weld methods as well?  (I mean other than TIG)

Q2. Is RF start something that can be done with an add-on technology? Could one have it in/on a TIG torch, or spool gun?

Q3. Is there something fundamentally incompatible about MIG welder's current supply, making it unsuitable for TIG?
      (Allow that polarity, and DC/AC choice is already available). Is a dedicated TIG welder, in addition to MIG, the only sensible option?

Q4. What exactly are the problems of TIG-LIFT. Can we have advice from some who have tried it? Can one get good at it?


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## jcp (Dec 24, 2020)

I have a lift start TIG machine. Most of the time it isn’t a concern. Situations do arise that would make HF much easier. Some positions are more difficult to get ‘lit up’ and not loose your arc length. It is also another coordination skill you have to develop.


Sent from my iPhone using Tapatalk


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## Lo-Fi (Dec 24, 2020)

1) not really. Stick to some degree

2) no

3) you can tig with almost any welder. How well is serious variable.

4) It encourages you to do the thing you should be aiming never to do: contact the work with the tungsten. It's perfectly usable, but at the end of the day, lift or scratch start is either old or cheap technology. The naked truth is that machines lacking HF are made to hit a price point while still claiming "it TIGs". That's not to say that they're not usable, but it's worth setting out exactly why the HF is missing.


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## graham-xrf (Dec 24, 2020)

Lo-Fi said:


> 1) not really. Stick to some degree
> 
> 2) no
> 
> ...


I have been digging. It would seem that an add-on is possible, and is done. There are YT projects on it, often along with construction of a foot switch.
The types vary a bit also. The few milliseconds of approximately 3kV of 100kHz pulse will set it off, and there are various circuits that do it.

I am getting that one cannot just add a thing like this without some caution about not hurting the welder inverter circuitry,  but the RF arc is high impedance, low energy stuff. To be sure I still know very little about it, but the bones of this trick are not yet exposed.

In the case of a simple transformer welder, there is no issue. It is those using inverters that need the care.

I agree entirely that one should seek not to contact the work with the tungsten. With HF start, it would seem that TIG is what the welder inverter does, not matter what. I was trying to tease out whether there is a fundamental difference between the power delivery aspect of TIG welders, compared to others. So far, other than the RF (HF) arc initiation, it would seem not. (OK - we get it that you need a direct cable and the MIG spool motor switched off, and pure Argon instead of 5%, 10%, 15% CO2+Ar).

[Edit]
Another thing that has become clear is that machines that offer LIFT-TIG are using a circuit that detects when the tungsten and the work are in conteact. The energy delivery is not enough to heat either the tungsten point, nor the work. As the point is lifted, it makes a tiny spark, and then the main arc gets going.


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## Lo-Fi (Dec 24, 2020)

The non dedicated machines, it's worth mentioning, are often lacking features such as ramp up/down, proportional pedal control and suchlike. They're not vital and don't stop you welding, but you're kinda missing the point of TIG, or at least some of it. This equally applies to any welding power supply user for TIG that isn't designed for it. It's why I don't bother with TIG on my multi. While it actually has HF, it's DC only and either on or off. That's it.

I've no doubt someone has hacked together an HF add-on, but you're getting into the realms of asking whether something _should_ be done just because you _can_... As a beginner, the last thing you want is to be fusting around wondering if the mod you made is working properly, or even negatively affecting machine or weld performance when you don't already know one way from the other. In my humble opinion, of course. I'd either use the TIG function as it is, or if you're dead keen buy the proper tool for the job, as it were.

I suspect you've fallen into the trap of over thinking/reading before getting your hands dirty


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## Buffalo21 (Dec 24, 2020)

Miller has a HF-251D, add on hf unit, i still think I have one somewhere in the basement




			https://www.millerwelds.com/files/owners-manuals/O611L_MIL.pdf


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## graham-xrf (Dec 24, 2020)

Lo-Fi said:


> I suspect you've fallen into the trap of over thinking/reading before getting your hands dirty


If that be so, then I have the characteristic through my entire life  so far as my first memories, of first thinking about what I am about to do.
I have never thought it unusual to read up/learn first. Doing that has sometimes informed me enough to abandon a prospective action altogether.
I do not recognize the concept of "over" thinking anything.
I am also one of those who absolutely does RTFM first, all the way through, every time, no exceptions.
Sorry about that, I just can't shake it!


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## Twirpunky (Dec 24, 2020)

Lo-Fi said:


> ) It encourages you to do the thing you should be aiming never to do: contact the work with the tungsten. It's perfectly usable, but at the end of the day, lift or scratch start is either old or cheap technology. The naked truth is that machines lacking HF are made to hit a price point while still claiming "it TIGs". That's not to say that they're not usable, but it's worth setting out exactly why the HF is missing.



Lift arc is not old technology. In fact it is rather new technology.  Scratch start is old.  People get them confused. They are not the same.  Lift arc has a really low contact current. When the machine detects the lift of the tungsten off the work, the arc is established and the current then increases to the level needed to weld, either by foot control or a preset amp setting on your machine.  

Scratch start is full current.

D


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## Twirpunky (Dec 24, 2020)

[Edit]
Another thing that has become clear is that machines that offer LIFT-TIG are using a circuit that detects when the tungsten and the work are in conteact. The energy delivery is not enough to heat either the tungsten point, nor the work. As the point is lifted, it makes a tiny spark, and then the main arc gets going.
[/QUOTE]

Exactly. 

  For most work it is perfectly suitable.  No good for Aluminium. Really light and small parts can be problematic as they move around on the bench when you "touch" them.


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## Ulma Doctor (Dec 24, 2020)

i have a Lincoln HF unit on my Miller 250.
i generally use the machine for TIG, but i also use it when welding SMAW, the starts are great


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## Flyinfool (Dec 24, 2020)

Also look at the total package, by the time you buy the welder, and then buy whatever is needed to add HF start and you do the engineering and insulation, you might have spent less total money just getting what you really want in the first place. Then there is also the cost if you happen to blow some expensive part while doing your modifications. When it is all done will it really work as well as one designed to do HF in the first place?

For me the choice is easy, I want to be able to weld aluminum and steel (not to each other) AL like AC and steel likes DC, every AC/DC TIG welder I have looked at so far also has HF start.


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## Twirpunky (Dec 24, 2020)

Yep, gotta have AC for aluminium.


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## graham-xrf (Dec 24, 2020)

Flyinfool said:


> Also look at the total package, by the time you buy the welder, and then buy whatever is needed to add HF start and you do the engineering and insulation, you might have spent less total money just getting what you really want in the first place. Then there is also the cost if you happen to blow some expensive part while doing your modifications. When it is all done will it really work as well as one designed to do HF in the first place?
> 
> For me the choice is easy, I want to be able to weld aluminum and steel (not to each other) AL like AC and steel likes DC, every AC/DC TIG welder I have looked at so far also has HF start.


For a nut like me - not very likely!  
I already dragged a thread into the weeds on the pros and cons of various welder selections.
As it happens, I have been making little RF plasmas for years. A circuit capable of it is like a toy thing that drives a partly evacuated glass globe to get a colourful discharge display. For the arc to happen at full air pressure takes higher voltage, but so long as it is a 100kHz or more type, and high impedance, it's safe enough.


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## Mitch Alsup (Dec 24, 2020)

Q1. Is RF ignition a feature that could help start all the other weld methods as well?  (I mean other than TIG)

Not really.

Q2. Is RF start something that can be done with an add-on technology? Could one have it in/on a TIG torch, or spool gun?

Only if you have an advanced degree in electrical engineering specializing in the power electroncs side of things.

Q3. Is there something fundamentally incompatible about MIG welder's current supply, making it unsuitable for TIG?

The negitive terminal is where metal comes off of and deposits itself in the weld. You don't want the tungsten deposited, so the polarity is reversed. In MIG and Stick, the electrode IS the consumable, in tig the tungsten is not a consumable, the filler rod is.

Q4. What exactly are the problems of TIG-LIFT. Can we have advice from some who have tried it? Can one get good at it?

THe major problem is tungsten contamination where the tungsten picks up tiny pieces of the metal being welded (remember the negative stuff from before) and this leads to porocity and pinholes in the weld beads.

Lift start is better than scratch start, HF start is better than either.


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## Ulma Doctor (Dec 24, 2020)

Twirpunky said:


> Yep, gotta have AC for aluminium.


not exactly
Mig welders are DC machines{generally speaking} (except for the very inexpensive HF units)
the is a lot of mig welding aluminum DC reverse polarity in production


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## Twirpunky (Dec 24, 2020)

In reality it depends in what you want to do with the welder.   Usually two separate machines are need if you want to "Do it all"   

1. Dedicated MIG welder. This is a Constant Voltage machine designed for wire fed semi-automatic welding.  
2.  A dedicated AC/DC  Constant current machine with HF.

  Multi process machines try to fit both 1 & 2 into the same machine.  Limited results.  You don't get AC or HF with a Multi-process.   You do get DC CC for stick and lift arc Tig and DC CV for MIG.   

For the money, I go with two separate machines.   

   Miller just released a new welder this year that does "Do it all"  It has AC/DC HF CC and CV MIG.   I have not used one yet so I cannot say if it the real deal or not.    Seems like it was around $3000. 

For the same $$ you could have two dedicated welders.

D


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## Lo-Fi (Dec 24, 2020)

Ulma Doctor said:


> the is a lot of mig welding aluminum DC reverse polarity in production


 
Not at the gauges hobbyists regularly work in, I'll wager. Boat hull, maybe. Ali fuel tank, not so much.


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## Twirpunky (Dec 24, 2020)

Ulma Doctor said:


> not exactly
> Mig welders are DC machines{generally speaking} (except for the very inexpensive HF units)
> the is a lot of mig welding aluminum DC reverse polarity in production


  I was reference to TIG.  Yes, a lot of aluminium is done with a spool gun CVDC and industrial wire fed machines.  Not really what the OP was looking for.

D


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## Lo-Fi (Dec 24, 2020)

I have a mate who's a shipwright, he says they use MIG and spool guns all the time on Ali hulls. We're talking thick gauge plate, fat wire, lots of amps and get the job done because time is money. Right tool for the job, and all that! TIG in that situation would take many times longer for no better result. 

I've often pondered messing with hybrid TIG, though. Think standard TIG torch with auto feed wire in from the side from a MIG feed. Amperage on right foot, pedal to tap on the left for wire feed or something like that. Sorry, off topic! Lol

Wasn't a dig, Graham. I fall into that place myself quite often!


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## Cooter Brown (Dec 24, 2020)

You will think welding is impossible at 1st when you try to use that lift arc machine.......

If you are just trying to learn a DC machine is good enough but If you want to make money with it I would highly recommend getting one with AC most people I encounter that need something welded need aluminum....


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## Ulma Doctor (Dec 24, 2020)

Twirpunky said:


> I was reference to TIG.  Yes, a lot of aluminium is done with a spool gun CVDC and industrial wire fed machines.  Not really what the OP was looking for.
> 
> D


i didn't mean to step on your ego


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## Twirpunky (Dec 24, 2020)

i didn't mean to step on your ego 


Didn't take it that way.

D


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## Chewy (Dec 24, 2020)

On Topic and Off.  High Freq has been around for years.  I had it 30 + yeras ago in my truck shop for stick welding.  A Century AC-DC welder with add-on High Freq box.  I used it for welding on farmers' S--t spredding tractors.  Tractors that only scrapped the holding lots while the cows waited to be milked. As you can expect, there was not a lot of clean metal on the machines and implements.  I burned 6011 or 6013 rods as best I could on patches and repairs.  Sometimes I couldn't get them started.  The high freq was a godsend UNTIL one day in the summer. It was 100 degrees with 100 percent humidity and I was soaking wet. Crawled under a John Deere to repair a blade and that *&*$# high freq traveled down my gloves and clothes and LIT ME UP!!  Never turned it on again.  No problem with it for TIG or using it under controlled circumstances.  But if you are thinking about using in general, beware.


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## Buffalo21 (Dec 24, 2020)

You can TIG weld aluminum with DC current, NASA  and the aerospace industry (because of weld quality) does it all the time, using AC is easier and more forgiving, why almost everyone else uses it.


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## graham-xrf (Dec 24, 2020)

From what I am finding, there are some (very) homebrew solutions, usually involving one of those cheap little high voltage generators from eBay, and a spark plug to make low frequency splat sparks. Activated with a foot switch. Unsurprisingly, a high voltage "spark" will disrupt the TIG main inverter control circuitry, and that protagonist avoided the direct connection by having another spark gap in the handle, which by then sports an add-on wire.
This, of course, is all very crude, but it confirms the principle I was trying to get articulated.

I value what @Mitch Alsup was saying. @Chewy  experienced a spark-plug style shock from a very crude kind of spark starter. Not the same as true RF. There is irony here about needing the electronics degree. 

The property of HF voltages, by which I mean a (RF) Radio Frequency alternating high voltage is that you do not get any shocks. It is a different circuit to the common electronic ignition sparks maker. To be sure, you can get burns from the hot ionized air, but the RF current travels mostly over you than through. The guys who have played with Tesla coils (including me) can attest that it is easy to place one's hand on 60,000Volts of 500kHz RF, while holding a screwdriver, and see  foot-long sparks and corona leaping from the thing while one's hair steadily rises and spreads out. I used to check if a 10kW transmitter for 300kHz ADF air navigation was switched on by touching a 9mm screwdriver to the antenna connection outside the building, and drawing away about 6" of reddish noisy arc. My hand would be firmly gripping the screwdriver shaft, so that only the end of the screwdriver suffered the hot air. That RF current was using my body as the counterpoise to the antenna, still transmitting. One does not feel anything unusual, and I have lived the greater part of my life since.

*WARNING: These Tesla coil things are deadly if not operated with care - not from the high voltage, but instead from the "low" voltage 240V AC power cables. Those who know carefully have them battery operated, and taken out well away from anything with a power line, including street lamps. A RF arc is a ionized gas almost zero ohms conductor. The plasma, finding a mains line, connects you to it as if it had the wire stripped and wrapped around your ankle. DO NOT !!! AC mains electric shock kills. 60kV of 500kHz RF does not.*

That all said, (with disclaimer), the principle seems straightforward. The cost of add-on parts in home-brew style HF-Start project seems to be about $30 - $40, plus about 3 weekends.

This does not mean I am advocating using these. There is perhaps a sound reason why they are not on every welder by now. Only - I have not seen it convincingly spelled out yet. Sure the whole world welds. I am just after removing the mystery to the point I understand it, right down to the on/off switch.


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## graham-xrf (Dec 24, 2020)

It seems the feature required by inverter-type TIG supplies is a low-pass filter choke and capacitors arrangement to block the HF start voltages from hurting the electronics. Adding on HF start boxes risks this damage unless one includes the RF choke, and such a thing is not so easy when it has to pass 200A or more at the lower frequency. Adding such a RF thing to (say) the cheap Harbor Freight TIG will likely damage it.

You can add one without problems to any transformer-based buzz-box.

So far, all the circuits I have seen use a high frequency transformer coupler component to add the RF voltage in series with the welder output. Of course, one set of coils is wound in the thick high current welder wire, and there is the possibility of shunting the RF from getting back into the welder.

Still researching this..


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## MikeInOr (Dec 25, 2020)

removed


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## rwm (Dec 25, 2020)

I have a Miller Dynasty 200 and I have used lift arc a lot. I use it when welding out of position and I can't physically use a pedal. I'm pretty sure that lift-arc on mine initiates the high frequency start for a split second to establish the arc. It is not at all like scratch start where there is current flowing. It does not damage the tungsten if done right. As an alternative you can put a dial control or mini switch on the torch head and use this to initiate the HF. I have never been shocked by the HF and I find it works incredibly well if you have a good ground. When it fails, there is usually a weak ground.
The comments on DC for aluminum are interesting. I need to try that.
I have always wondered if a Piezo starter from a BBQ could be used to start the arc?!
Robert


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## graham-xrf (Dec 25, 2020)

rwm said:


> I have always wondered if a Piezo starter from a BBQ could be used to start the arc?!
> Robert


Re: a piezo spark start, or come to that, an anything-at-all spark start can kill your inverter semiconductors. If it was that easy, everybody would be doing it. To get a welder to maintain an arc is done at a relatively low voltage. Not so to get a voltage to break down the air gap and jump a spark. That is about 30kV/cm, or 3kV/mm if you like.

Consider if your welder output was the secondary coil of a straightforward transformer buzz box. A piezo would be in parallel with it. The coil would effectively short-circuit the piezo. When the output is not a transformer winding, but instead the output stage of bipolar transistor switcher electronics, other mayhem might ensue. I am not yet familiar with the inverter stage electronics, but I do know that a IGBT transistor, tough as it may be, is not going to survive a 30kV voltage excursion on it's junction.


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## graham-xrf (Dec 25, 2020)

*HF-Start - Some notes on how it works*
What I mean is - what I have understood of it so far.

Even without being an electronics expert, consider the following typical circuit fragments. I will try a general explanation, but if electronics is not your thing, suffice to say that one circuit is all about stopping HF-start stuff from getting back and hurting the inverter electronics. Both circuits show the way HF start is added in series with whatever the welder produces, and only does it's thing briefly.







In both cases, just notice the connections to the torch, and follow one lead back. See how it encounter's a thing with _coils_.
That RF coil, part of an RF transformer, is made from big fat conductors, and is the way to introduce the high frequency start _in series_ with the the welder voltage. It is only effectively there briefly. When not introducing radio frequency voltages, the RF coil looks like a bit of fat cable coiled up, not affecting the regular weld currents in any way.

Here is a picture of the bits..



Notice two white wires going into the coupling coil. They are for the RF resonant oscillator generating the radio-frequency voltage.
It might be air-cored, or it might have a ferrite rod up it - I can't tell.
- - - - - - - - - -
Many RF generators are the crudest possible, made exactly like the early Marconi spark transmitters for ships, using a spark gap with an induction coil. Many DIY designs just use a spark plug to provide the gap. Every splat sets the circuit ringing at radio frequency, which dies out, until the next spark. The spark seems continuous, while HF start is on, but it is really a series of separate sparks.

Notice the first circuit HF Arc Starter. All the bits to the top left are not the whole inverter, but a chunk of circuit devoted only to stopping RF and overly high voltages getting back into the inverter. D3 and D4 together will limit anything across them to 100V. Varister RV2 will short out anything over 100V.

The capacitors and inductor L1 form a low pass filter, blocking any RF. L1 needs to be made of thick stuff. The whole act is repeated upstream of L1, limiting voltage to 100V, with a belt-n-braces D1 with D2, at 200V, just in case the other fails.

The entire circuit fragment shows an extremely determined and elaborate provision to absolutely stop any high voltage shenanigans introduced by the HF coil transformer T2 from getting back into the inverter. It is a huge and deliberate protection circuit.
- - - - - - - - -

The second circuit is a "buzz box" welder circuit in it's entirety. No high tech IGBT switcher pulsed and arc current controlled waveforms here. It's just a transformer! OK then - it also has a bridge diode rectifier to deliver a DC option. The choke inductor "Z" blocks radio frequency energy getting back to hurt the bridge rectifier 4 diodes silicon rectifier "SR". Capacitors C1-C4 shunt any remaining RF.  VR1 is a overvoltage protection device. C7, R2, and R3 are a snubber circuit, also to damp unwanted ringing. T3 is the gadget we are looking for. It's the series coupling RF transformer. Notice the spark gap G, and the step-up transformer T2. When the AC voltage is high enough to cause the spark to jump, the spark completes the circuit C6 and the inductance of T3, which rings at radio frequency.

So - anyone contemplating "adding" a HF start needs at least to understand exactly what they are doing, and how it works. That said, the bits are pretty cheap, perhaps amounting to 5% of a whole welder cost. I am unimpressed by all versions of "spark plug gap" oscillator I have seen so far. Those featuring a proper RF oscillator will interest me more.

In at least one YT video, the guy adds a sparkplug version to the welder, which initially messes it up, though it survives. He says it "seems to cancel" the welder. He "gets it to work" by introducing another spark gap in the lead in his handle add-on. Actually, it was "working" after a fashion, perhaps from a single little spark at the electrode. I DO NOT advise attempting anything like this. It's still too easy to damage a $800 welder this way.


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