Playing with the Pulser

    --Finally got to a place where I think I need the Maxstar's pulser to make a weld, so I've been playing around with the parameters. I'm trying
to weld a 3" long piece of 1/4" o.d. stainless tube to a ring of 1/2" o.d. stainless tube. Wall thickness on both is about .06". I've set the high side to 65 amps and the low side of the square wave to 20 amps, with 1 complete cycle per second. It's working; i.e. I've gone from blowing holes to successfully filling the craters I made without the pulser, but I don't think it's optimal. Suggestions appreciated!
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"Steamboat Ed" Haas : "Hold on! we're passing
Hacking the Trailing Edge! : through the moronosphere!"
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steamer wrote:

From Ernie's TIG class:
Ernie laments that no one tells the user how to actually set pulser settings for different welding situations. He says that useful information can be found at http://www.pro-fusiononline.com and cites two of their online utilities in the TIG Handbook about halfway through in the second page of the section headed "TIG Pulser".
Grant
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yeah... what he said..I said...oh whatever.
Anyway here are some basic pulser settings.
Pulser Description
A pulser is a device used to interrupt a welding arc. Mostly used on TIG, but can also be used for MIG. The idea is to cycle the arc from high amperage to low amperage. The metal melts at the high amperage and solidifies at the low amperage.
There are 3 settings for a pulser. 1. Background amperage This sets the low amperage and is usually set as a percentage of the main amperage. So if you main amperage is 100 amps, and the Background Amperage is set for 50%, then you Background Amperage is 50 amps.
2. Percentage of On time. This sets how much of each pulse cycle is spent at the high amperage and how much a the low level, once again by percentage. A setting of 50% evenly splits the cycle between low and high amperages. Less than 50% on On time gives a Spikier Pulse. Greater than 50% gives a Softer Pulse.
3. Cycles per second. This is the really confusing one, because it has the most profound effects. Older TIG pulsers only allow up to a maximum of 10, or less, Cycles Per Second (Hertz - Hz), but the newer Inverter TIGs allow much higher frequencies. My Maxstar 200DX goes up to 200hz.
The lower pulse frequencies are for traditional pulser use, where you run between 1 and 2 hz on the pulse. adding filler metal on every pulse or every other pulse as you progress across the weld.
The higher frequencies have a much different effect, in that they tend to make the metal super-liquid, allowing it to flow and wet out much smoother. These higher settings work very well with autogenous welds where no filler metal is added at all. These are also called Fusion or Flow welds. I also found these higher frequencies worked well for vertical welds in heavy Silicon Bronze.
Now the reason for all this pulsing is rather simple. Lets start with a piece of 16 ga steel. At 0.062" thick the proper amperage would be 1 amp per 0.001" of thickness or 62 amps, for a flat-butt weld, full penetration, single pass. You could easily TIG weld a seam in 16 ga Steel using a continuous 62 amps. However a spike of high amperage will melt the metal much faster than a low amperage, so you could weld faster at 80 amps than 62 amps, but at that heat you risk overheating the metal and causing undue warpage or burning of the steel, so you mix an interval of 80 amps with an interval at 40 amps. The low amperage interval allows the puddle to solidify back into steel, without allowing the arc to break. By pulsing the weld across the bead you get a very orderly row of rings, that give that distinct stack-of-dimes look to the weld bead. You adjust the exact pulse frequency to suit your style and speed of welding as well as the thickness of the metal. The other benefit is that over all, you have put less heat into the metal, so you have less distortion.
A smaller, consistent weld bead is often stronger than a larger inconsistent weld bead.
The more consistent a weld is the more the stresses apply along it's entire length. Any peak or valley in a weld becomes a stress point for failure to occur.
Whether you choose to add filler metal on every pulse, every other pulse, every third pulse or not at all is dependent upon your own welding style and the circumstances of the weld.
Where pulsers become bewildering is when you start messing with the percentage settings for the Background Amperage and percentage of On Time. The number of possible combinations is huge, and there is little or no guidance given in the welding world as to application.
Pro-Fusion has an excellent series of webpages with online calculators that allow you to punch in the overall required amperage you want and how fast you want to weld and it will generate pulser settings for you.
http://www.pro-fusiononline.com/welding/pulserate.asp http://www.pro-fusiononline.com/welding/pulseparams.asp
It still gives no guidance as to when you want a Spike pulse, or a Soft pulse, but it gives you something to play with.
50%, 50% and 1.4hz, is a setting that works for most sheet metal.
All I can say is that until somebody puts out some really authoritative research showing what pulser settings are best for what combination of weld and materiel, we will all be out there experimenting on our own.
I have searched for such a book for 5 years, and given up. Hopefully some day soon the welding engineers will decide to enlighten us lowly welders.
The guideline I can give you is that the thinner the material the more it benefits from a spikier pulse. I have yet to find a benefit to a really soft pulse.
An example of an extreme spike pulse is that you can weld a popcan at 120 amps, as long as you set your pulser to 2% On Time and 2% background amps.
Sequencer Description
What does a sequencer do? Well pretty much everything except make your coffee.
A sequencer is gods gift to repetitive welding jobs.
Any machine with a built in sequencer will have what is called a 2MT-Hold setting. This allows the sequence to be controlled by 2 button taps.
The first part of the sequence is initiated by the first button tap.
1. Preflow gas - This will purge air from the line and torch before the arc initiates.
2. Arc initiation via high frequency.
3. Initial Amperage - This is the amperage the machine starts at once the arc is initiated.
4. Up Slope - this is the amount of time the machine takes to ramp up from the initial amperage to the working amperage.
5. Working amperage - the amperage needed to weld the material.
or
5. Pulsed weld amperage.
Then a second button tap when the weld bead is complete.
6. Down Slope - the time it takes to get from the working amperage to the final amperage. A longer down slope prevents a pit from forming in the end of the weld bead.
7. Final amperage - what the machine slopes down to before terminating the arc.
8. Post flow gas - This shields the tungsten and weld area as both cool.
So all that with just 2 button taps.
To give you an idea of settings, my machine is currently set up for tack welding together stainless steel picket railings.
1/2 second preflow gas, 2 amps initial amperage, 1 second up slope, 80 amps working amperage, pulser is set to 40% on time, 50% background amperage and 1.2 pulses per second, 3 seconds of downslope to a final amperage of 3 amps and 15 seconds or postflow. I adjust the working amperage a little up or down depending on how the welds are going.
Older machines that don't have a 2MT-Hold setting require you to push and hold the button. Releasing the button starts the second half of the sequence.
The Syncrowave 351 at school doesn't have 2MT-Hold so we just use the foot pedal to trigger the sequence.
The main challenge of using a sequencer is figuring out what amperage you really NEED to weld a bead.
Trial and error can get you there.
Here are some guidelines for minimum amperages.
Start with 1 amp for each thousandth of an Inch of thickness (0.001"). So 1/8" steel or aluminum = 0.125" thick = 125 amps. Simple and easy. Now 2 complications. For inside fillet welds, increase amperage by 30% For outside fillet welds, decrease amperage by 30%
Those numbers are for Steel or Aluminum.
For stainless steel, decrease amperage by 30%. For copper, increase amperage by 100%. For bronze, decrease amperage by 50%.
Use of a pulser will skew this amperage estimate. Usually you have to increase the amperage a bit to compensate.
To hook up a control button for the sequencer you can either just buy a remote contactor control button from CK Worldwide, or make your own. I make my own because CK's is just too big to be comfortable. I use OEM replacement buttons for plasma cutter torches ($20 each). They are armored in black silicon rubber so you don't get a shock from any high freq bleed through. The wires for the switch are run along the TIG torch cables. You can just wrap electrical tape every foot or so. I use a heavy fiber sheath to encase the whole lot. The button is just electrical taped to the torch handle. I have tried making fancy brackets and electrical tape works better.
The wires hook up to the first 2 pins for your remote connector. Usually pins A and B.
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    --Wow. Lotsa info there; thanks Ernie! I'm running the pulser at a 50-50 high/low amp setting mainly because I have yet to figure out how to vary the percentage; the Miller manual's a little vague on this, heh. You mentioned doing welds with 2% high and 2% low; does that mean the arc is *off* 96% of the time? If so what reinitializes the arc each cycle, or is it the fact that the cycling rate is so high that this isn't a problem?     Much food for thought and as you say a bazillion possible combinations! I still remember watching you weld lengths of 1/16" welding rod end to end; I've yet to master that one! :-)     The thing I've noticed, after using the pulser, is that the glowing portion of metal is much larger than the one from a continuous arc but I suspect the temperature at conclusion of the weld is less than when the red area is smaller if you get my meaning. I guess what I'm saying is there's less tendency to blow holes in the joint when using the pulser (I've done it tho!)..
--
"Steamboat Ed" Haas : "Hold on! we're passing
Hacking the Trailing Edge! : through the moronosphere!"
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The pulser is controlled, by hitting the pulser button to cycle the display through the parameters. You will see the LED light up on each parameter. Use the dial to set that parameter. When you have what you want hit the large silver button to the right to kick back to the main amperage display.

The machine will do it's magic on every pulse.

The pulser will give you more consistent welds since it acts as a metronome, timing your filler metal...tap, tap, tap...
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    --Ooooookay I think I've got it now. Looks like I hadn't figured out the manual exactly right; i.e. I wasn't using the percent function correctly. (You could earn a respectable living rewriting the manual!)     Here's my 'current' (ha-ha) setup for welding 1/16" wall stainless tube (attaching 1/4" o.d. to side of 1/2" tube):     -Peak current: 65 A     -Low current: 20 A     -Portion at peak: 30%     -Pulse frequency: 30PPS     -Tungsten is 3/32" dia, 1.5% lanthanated (what I had)     --Now here I've learned something: unless the pulse frequency is down around 1 or 2 to allow dipping rod in the puddle with some sort of rhythm, the next number that doesn't drive my eyes nuts is around 30; i.e. equivalent to the 'frames per second' on TV, so 30 it is for now.     Anyway this seems to produce adequate results and I'm no longer blowing holes in the material. The pulsing action melts filler rod plenty fast enough for my skill level so I'll stick with this for a spell.     Have tried to use the spreadsheets at pro-fusiononline.com but they're a little over my head, heh. Think I'll stick with the trial-and-error method a while longer..
--
"Steamboat Ed" Haas : "Hold on! we're passing
Hacking the Trailing Edge! : through the moronosphere!"
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