If you modded your welder for TIG - TIG as an add on with inverter welders vs transfo

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It seems that a lot of inverter welders are offering a TIG option, and / or  some DIY folks have added a TIG feature to their inverter welders.  Also checked with a few resellers as to why the optional TIG torch was being offered as an accessory to only the inverter welders.  So what is known so far about the inverter welders is that they are DC, but using recitived square wave.  The transformer welders are DC using rectified sine wave.  Is the TIG function dependent on a square wave and not practical on sine wave DC.  I am aware of TIG machines that are AC/DC and assume the older ones are transformer based so they may be half wave recitified DC.Any thoughts on this especaially by folks who have modded their inverters for TIG?
Reply:Both inverter and transformer welders as long as they are constant current work fine with a scratch start TIG torch.I have seen and used both without any problems.Some MMA inverters have the additional option of lift tig when used with a TIG torch.
Reply:I'm not sure I understand your question. Define "modded for tig"? Most guys do DC tig off CC machines ( inverters or tranny units ) because you don't need anything other than a tig torch and gas set up. AC tig is possible but has a few wrinkles that also have to be addressed. Tozzi's thread on scratch start tig applies equally to inverters or tranny machines.With Ac since the polarity changes from + to - 60 times a second on 60 hz power, each time the arc crosses 0 the arc wants to extinguish. The solution to that was to use high frequency to maintain the arc when this happens. Inverters can get around this slightly because of the way they generate power and the fact they can do things with wave forms not possible with Ac based tranny units. However just about all Ac inverters are tig units, so there's no point in "modding" one. It is possible to do Ac tig off an AC only tranny using a HF box, but then you run into problem #2. That is that you have no remote ability to adjust your amps with these set ups. While a pedal is not required to do Ac tig, it's exponentially more difficult to do without one. With alum you want to get the puddle to form very fast because alum is such a great heat sink. If you attempt to go low and slow, the material sucks heat away from the weld puddle faster than you can pump it in. In that case, you heat the whole piece up. Most alum alloys heated above 300F loose all tempered hardness and loose the majority of their strength. You basically anneal the whole piece. Also the puddle becomes increasingly hard to control as the whole piece approaches the melting point. The solution is usually to up your amps above the amps needed to get the puddle to form quickly, and then back down on your amps as the piece begins to heat up. With no pedal, you are only left with arc length ( which will not cool the puddle), travel speed, and filler as your means of heat control. Go hot enough to form a puddle quickly and you have to just go faster and faster from that point making it very difficult to do. Add onto this that typically by the time you buy a HF box and an Ac stick machine, chances are you are already into the set up more than an older used industrial dedicated  AC/DC tig would run you.I thought you bought a tig capable unit just recently?.No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Originally Posted by DSWI'm not sure I understand your question. Define "modded for tig"? ?
Reply:MIG machines are constant voltage which is not suitable for the TIG process. This is the reason I suppose you see these mods.Personally I have never seen them either for sale or used.i suppose it would be cheaper to buy a basic MMA welder and use it with scratch start TIG than convert a MIG welder to weld TIG.If you do not know the difference between CC and CV machines here is a nice write up from Lincolnhttp://www.lincolnelectric.com/en-us...ge-output.aspx
Reply:Originally Posted by taz00MIG machines are constant voltage which is not suitable for the TIG process. This is the reason I suppose you see these mods.Personally I have never seen them either for sale or used.i suppose it would be cheaper to buy a basic MMA welder and use it with scratch start TIG than convert a MIG welder to weld TIG.If you do not know the difference between CC and CV machines here is a nice write up from Lincolnhttp://www.lincolnelectric.com/en-us...ge-output.aspx