Pulse TIG principles
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  1. #1
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    Default Pulse TIG principles

    Hello all,
    I'm looking for basic guidelines on how to setup my TIG (Invertec V160T) for pulse.

    How does one select a frequency, what effect does 20hz have on the puddle vs 200hz?

    What amount of background current is recommended? Is it based on weld joint (probably, everything is related to joint type), is it material specific?

    Or is it all just an educated guess followed by T&E?


    Thanks, Cole

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    Ugh might regret posting this but this has been my understanding through my welding career. Happy to be proven wrong. Im not a weld eng or metallurgist.

    The best welds in a technical sense which include strength and imo just as important is distortion are the welds that produce the smallest puddle but get the max penetration. Not just puddle with but whole surface area of the puddle. This is talking only about groove joints not t joints. You can have a killer looking and strong weld but the parts is warped to crap and shrank below tolerance is an utter waste.

    Metal that goes from solid to liquid then back to solid always shrink. The metal doesn't disappears but gets moved in a nonlinear fashion. Get bored a simple test can show you it. Take a 2" pipe with 1/4" thick wall about 6" long and stand it on end using a welding rotary table. Weld the edge without using wire with the bead covering the whole surface of the edge, let it cool and measure the diameter close to the edge it will be smaller by a good amount. Flip the pipe over and use a oxy/acet torch on the edge until its cherry red then let it cool and measure. It will be the same size as before or very close to it. This can also be done using pulse and the results might surprise you.

    The pulse makes the weld puddle smaller or shorter is a better way of thinking about it. Smaller puddle less distortion to the surrounding parent metal. Ive used pulse a ton on x alloy/hastalloy because its prone to cracking. The pulse doesn't stop cracks the pulse makes for a shorter puddle which in turns leaves less time for the metal to distort while the puddle is turning back to solid. Thats what makes the cracks distortion while it is in that critical stage of going back to a solid. Distortion can be replaced with movement if that helps thinking about it. If you are having issues cracking also try starting your weld right after a tack.

    My general settings are 6-7 pulses per sec 80-85 peak and 50 background. Incase you don't know what they mean which Im always shocked when a long time welder doesn't have a clue. Pulses equals one cycle of peak and background. So for a 1 pulse per second with 80 peak 50 background and welder set at 100 amps it would be for .8 sec the welder is giving 100 amps the other .3 sec the welder is producing 50 amps. Peak is a percent in time not percent of max amps. Background is a percent of max amps not time.

    Also I use pulse at times to shake the puddle with tacking if the two parent metals aren't coming together. Its liquid and like shaking a table with a water droplet on it.

    Sorry long winded but thats what Ive come to learn again if Im wrong point it out I always like learning.

    All this applies to non aluminum metal.

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    That is a good explanation. I'm sure it is a typo but in your example .3 seconds should be .2 seconds.

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    Quote Originally Posted by turnworks View Post
    Also I use pulse at times to shake the puddle with tacking if the two parent metals aren't coming together. Its liquid and like shaking a table with a water droplet on it.

    Sorry long winded but thats what Ive come to learn again if Im wrong point it out I always like learning.

    All this applies to non aluminum metal.
    I just got a Fronius Magic Wave that has that function built in. Still in the box, arrived yesterday.

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    Setting pulse functions can be all sorts of fun. I just took a quick look at the manual for that machine.
    From what I can see all you can control is the frequency and background percent/amps. This kinda limits what you can do with the pulse mode, but is easier to keep it in a "functional" range.
    Slower pulse frequencies (.5-10 hz) give you the widest range of effects on the puddle. This range can be used to provide timing for dabs of filler or a nice ripple pattern. 10-20hz lets you alter visual effects (stack of dimes vs smooth) when using positioners or high speed techniques. It is very hard to notice effect from 30-50hz and above. There might be metallurgical benefits for some alloys/applications but from behind the helmet you will be hard pressed to see any change from a non pulsed weld. From experience, 50-5000hz produced a singing noise and a slight flicker to the arc. If you could adjust frequency on the fly you could play 8bit music with it.
    Background amps will give you the biggest difference in how the puddle reacts. Changes in amps is what takes the nice algebraic heat input equation and changes it into a calculus nightmare. The lower you go, the colder the weld. At ~75% and up the puddle starts acting more like a non pulsed weld.
    When to change which setting is the hardest question, and the one that depends the most on what you're working on.
    Thin stainless fusion welds gain the most benefit from pulse. Setting the background amps to around 50% and maybe 3-6 hz depending on how fast you can smoothly move your hand will give good penetration and a nice stack of dime look. The same welds with nonpulse can be Very tricky to make look "Good" and are very sensitive to torch and hand movement.
    Using pulse when dabbing filler wire can be handy for providing timing and ripples to coverup unsteady hand movements/readjustments.
    A nice trick to pulse is laywire types of techniques. You need more amps for a given joint to melt the filler wire, but it lets you move faster offsetting the added heat. Pulse settings in this mode let you add the stack of dime look and can control puddle shape. Below 40% background can leave the puddle too cold for the filler and slow you down or can lead to lack of fusion.

    Pulse modes overall can let you have a much finer control over the weld puddle. Its almost like adding a micrometer dial to the amp control of the machine. Some machines let you control the pulse width/on time of the main amps setting. You can also adjust your self right into uselessness if applied wrong. Play around with it on some scrap to get a feel for what setting does what. If you are setting up for something tricky, make a mock up part and try it out.
    I can add more rambling details if needed.

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    I build a lot of different thin stainless steel items so pulse is a must have in my work. I have been learning pulse since I got a dynasty 200 12 years ago, and tomorrow i will learn more. I use a few standard pps, .5 to 3.5, 35, 60, 120, 180, 300. Each pps allows me to do something else good. For example, I use 300pps to "solder weld" certain components.

    Learning to set it up will be a continuing effort for anyone. Learning to turn your pps down .1 is totally different then turning your amps up 5. And changing your bg up 10% can add a 5-7 amp for better puddle flow.

    I even have pulse programs for doing sanitary tube when I need to stand on an I beam hanging over the edge, holding a mirror, with a pipe to wall gap that's like 4". It allows me to go S L O W so I can deal with footing issues

    Now all that said, no one can tell you how to set up pulse for you situation. Pulse can be set for a number of reasons and sitting there playing with it is the only way to "understand" it.


    Sent from my SM-G960U using Tapatalk

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    Thanks for the replies guys! I guess I'll just have to experiment with some welds and parameters.

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    As soon as you have any sort of consistent results from playing start writing down what you set, what you did and what the results were like.

    Never a truer statement than what PlasmaOnTheBrain said "You can also adjust your self right into uselessness if applied wrong".

    When it comes to raw settings there are a lot of ways of getting to functionally equivalent weld pool and metal fusion behaviour. How you exploit the more advanced settings is very dependant on your particular welding style and what you have learned on. Of course when the going gets tricky you need the really clever stuff but don't get into the habit of endless small changes. Most of which you will promptly tune out by technique variations. Often you need a, relatively speaking, big change to clearly see what is actually going on.

    If you have reasonably advanced machine with lots of variables there is much to be said for initially treating it like a good quality, but less controllable, machine such as the aforementioned Fronius Magic Wave. With good brand you can be sure that the more limited range of control covers a good set of useful capability and that all reasonable settings for what you are doing will "work". You are much better off learning to get the maximum use out of a more limited sub-set of control settings before trying to get to grips with the really clever stuff.

    Clive

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    Quote Originally Posted by Clive603 View Post
    With good brand you can be sure that the more limited range of control covers a good set of useful capability and that all reasonable settings for what you are doing will "work". You are much better off learning to get the maximum use out of a more limited sub-set of control settings before trying to get to grips with the really clever stuff.

    Clive
    On this machine I'm limited to freq (0.2Hz to 300HZ) and background current (10-90%) manipulation. No super fancy stuff here.

    I think I'll begin experimentation like this-
    1/8" mild steel coupons, 1/16" er70 wire, flat stringers
    100% pedal = 1A/.001" wt, mild steel
    50% BG current limitation
    various Hz

    repeat sampling with fillet welds of same material

    That should give me a level playing field on a familiar material and joint type.

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    I bought the Fronius because it can run on 110/220 single phase. Went with air cooled and control button on the torch. Got the wireless foot pedal too. Also because my accountant told me to buy a few machines before years end. New Dynasty 280 arrived too. Currently using a Dynasty 350 water cooled. In a few weeks I will call my LWS and have the Miller hot shoe come by again. Continuing education.

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    Save your self some filler wire, just play with fusion welds for the first few minutes and see what each end of the dial does.
    I do believe in writing down settings that work but when you're approaching something new with welding with all of the variables and controls that are NOT the same from machine to machine and brand to brand, its better to just spin the dials and calibrate what it's doing to your eyes and hands.

    Take a 1/4" or thicker bit of stainless, clean it nice, and just run a bunch of fusion welds at 100-150 amps. Toy with each pulse setting just by spinning the dial from min to max and seeing what it does, before you worry about writing down each 1/4 turn of the dial's difference. Once you have a nice visual and tactile feel for what the pulse is doing, then you start narrowing down materials, filler, settings ect ect...

    The Fun part about pulse tig is that as long as you have a big enough tungsten, you cant hurt the machine/consumables any no matter what settings you tweak *bashing the filler wire or planting the tungsten excluded*

    I've gone through more than a few contact tips when applying the same idea's to Mig/Pulsed mig.......

    DO take pictures and post them on this thread, its a lot easier to explain with pics.


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