Importance of AC frequency?

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I already know I'm going to get crapped on by everyone here after this post is over but.... What is the importance of AC frequency control. I see that HTP, Miller, and Lincoln all have controls ranging from 20-200Hz. My cheap chinese AC/DC pulse tig, stick, plasma  ... seems to only output at 60Hz but has a crap load of other settings that I have yet to fully grasp the importance of.They include: Pre/Post flow, Pulse Frequency (Hz) apparently only usable in DC, Pulse Duty (%), Basic Current (%) no clue about this one.. another DC only function, Slope (s), Current, and AC Cleaning Width (%)Apart from not setting this machine up, how important is it really to have adjustable AC frequency control. I have a little understanding that it broadens or sharpens your arc dependent on setting. How much do you guys use it?I only bought this machine because it was cheap and allowed myself to get my feet wet with AC tig. Its only a temporary thing. I have yet to plug it in.
Reply:Well, my old transformer machine doesn't have it. We didn't have it years ago and never heard of it so did a fine job without it. I haven't much aluminum experience but they tell me all the dodads just make for a finer, easier to run weld. There are applications where it would be required (exotics and such). A lot of the new weld procedures have only been made possible due to advances in the welder machines. I'm just stubborn I guess, never tuned a motor with a laptop and don't need a computer in my welder...lol.Sorry I couldn't help, just tried to post something positive because you're probably correct...you're going to get crapped on...lol.Anything worth doing is worth doing RIGHT
Reply:As you said, AC frequency has the effect of making the arc broad and soft at low frequency, and narrow and stiff at higher frequency.  Not really very important since everyone got alone fine without it untill it came out a few years ago.  Would be nice to have, IMO a more constricted/concentrated arc is helpful in getting a puddle started, especially on a tight aluminum joint.  I cannot think of any practical reason for wanting a broader/softer arc.AC cleaning is the % of time that the AC wave form is electrode positve (EP).  In EP, the electrons leaving the surface of the metal, flowing to the elctrode, cause surface oxide to break down, thus "cleaning" the aluminum.  EP also causes much more heating of the electrode and limits the current that can be run.  Adust to produce a narrow "frosted" band along side the aluminum weld.Preflow:  time setting to start gas before the arc, to purge the line, only need a second.Postflow:  time setting to continue gas after the arc, to protect tungsten and weld ffrom oxidation or a few seconds while cooling.Slope:  Time to transition (slope) from start current to weld current on starting the weld, or the time to slope from weld current to zero current on stopping the weld.  Don't know if you have upslope and downslope or what, but upslope IMO is never needed, while downslope is very helpful in slowly filling the crater at the end of a weld to prevent shrinkage/crater cracks.  Same thing can be done manually with a foot pedal/current control.Pulsing:  Alternating between a high current pulse and a low current pulse.  Idea is to melt, then cool, melt, cool.  Primarily helpful in out of position welding, like vertical up, overhead, arcound a pipe/tube.  Also benificial for full penetration fusion (no wire) tubing welds, helps prevent burn through.Pulse freq.:  Number of high/low pulses per second, cycles per second, Hz.Pulse duty %:  The % of a pulse cycle time that is high current.Basic current:  The amount of low pulse current, also called background current.Current:  The high pulse current setting.To make the "stack of dimes" look, you essentially produce overlapping spot welds by setting a short high pulse to melt a spot, and longer low pulse to cool, and a slow frequency of maybe 1 pps.
Reply:An inverter produces a square wave that can be shaped by the weldor. Some more technical than others, but its a great advantage once you use one and get to know it. I set my arcmaster on 25 Hz AC when welding 1/4" Aluminum lap welds. Much more and I don't have enough heat to keep a puddle. On deep grooves or fine stuff I turn the Hz up to 150 (as high as it goes) to make the arc more concentrated. I really don't use pulse much.  It helps more on the lower amp settings.I just posted this answer in another thread.David Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Thank you for your detailed reply pulser. I sort of already knew most of that stuff but its good to have it documented so that I can refer to it later.The welder has a down slope that I had no idea how to use until your info. I am also hearing conflicting information in that the AC frequency can or cannot be adjusted. I know the welder can adjust in DC mode but why would it not in AC?It is a "square wave inverter machine" if that means much. David... how would one shape this output? I assume your machine must have an AC freq. adjust?
Reply:An AC wave is 50% + and 50% - .  With an inverter you can change those percentages usually from 15% + wave 85% - wave.  This makes the arc "hotter" because its - more of the time.  65% + wave helps clean the aluminum.  It puts MUCH more heat into the tungsten.  Cleans crappy aluminum quite well.  I clean my aluminum first so it can be at around 25% + wave 75% - wave.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:This is all very interesting..I never knew HOW they worked..I just know how to MAKE them work.. ...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:From what I have read, An inverter takes 60 hertz and chops it up into smaller pieces to like 20,000 Hz.  Then it goes to the transformer to be reduced to welding voltage and current.  It takes a much smaller transformer at 20K hz than at 60 Hz.  So now its smaller.  When it comes out of the transformer, the inverter can switch on and off to manipulate the wave.  An Ac inverter is really two inverters, one for + and one for -.Lincoln started with a similar thing called chopper technology.  My ranger 250 runs at 19Khz DC.  Lincoln also claims they can make an identical (emulate is the word they use) wave to the one an SA200 produces.  I have not used that setting much at all.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:I don't know if it applys in an inverter or the newer machines, but the high frequency is necessary to help establish and arc path in older regular AC machines.SA200,Ranger8,Trailblazer251NT,MM250,Dayton225AC,T  D-XL75,SpoolMate3545SGA100C,HF-15-1  RFCS-14 When I stick it, it stays stuck!
Reply:Originally Posted by yellowI am also hearing conflicting information in that the AC frequency can or cannot be adjusted. I know the welder can adjust in DC mode but why would it not in AC?It is a "square wave inverter machine" if that means much. David... how would one shape this output? I assume your machine must have an AC freq. adjust?
Reply:Originally Posted by hotrodderfrom what you said here i think you may be confusing AC frequency with pulse frequency. DC has no frequency (it's direct current) so if you can adjust the frequency when set to DC it must be the pulse frequency.
Reply:Originally Posted by yellowI already know I'm going to get crapped on by everyone here after this post is over but.... What is the importance of AC frequency control. I see that HTP, Miller, and Lincoln all have controls ranging from 20-200Hz.
Reply:Originally Posted by yellowYea... exactly what I was thinking!! Its the damn wording in the manual that has me all confused.  Tomorrow I'll post a pic of the front panel and what the manual literally says about the knobs. Its a real brain teaser trying to figure out what the hell they are saying.