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Greetings,
I've seen the videos of tig welding razor blades, thin sheet, coke cans, etc. and in every instance where the ppm is mentioned the range is from about 30 to 150. So what circumstances would require the ppm of 200 to 500 that some of these machines are designed to produce?
Also, the pulse frequency spec. is shown as .5-20hz. or .2-500hz., why not .5-20ppm or .2-500ppm.? Am I reading it wrong?
Thanks, Richard
Richard,
Frequency,particularly any thing to do with electricity is always referred to as Hertz, or a measurement number of complete cycles per second. PPM or pulses per minute is not correct. It really is the wrong choice of words,as it does not refer to the completed cycle between pulse and welding current and back again. Second it is not pulses per minute you are concerned with, it is number of completed pulse cycles per second. If You are simply referring to the number of Pulses per second, it is less accurate than referring to hertz. Practically does it make a difference? Lets take the setting of .5 hertz. If you have 1/2 of a pulse per second, that would mean that you are only measuring the actual Pulse part of the cycle. So it would take 2 seconds to complete the pulse stage of the cycle, or 4 seconds (if balance is set 50/50) to complete the entire cycle.
So with .5 hertz, the pulse cycle is actually completed in 2 seconds, and both low and high components of the pulse cycle have been accounted for.
hz (hertz) is cycles per second, which in a pulsing frequency context would be 60 times smaller than ppm (pulses per minute, or cycles per minute.)
My machine (an older Mosfet-based Everlast "Super200P") goes up to 300 hz pulsing frequency. the 300Hz pulsing is helpful for constricting, focusing or "stiffening" the arc, and making it penetrate more deeply and not having the heat spread out as wide.
But a skilled welder can accomplish similar effect without using pulsing at all, by simply holding a tighter arc length (holding the tungsten electrode closer to the work.) So, its best to learn to weld without pulsing, to develop manual heat control before experimenting with pulsing.
Super high frequency pulsing (as high as 10 kilohertz or more) has been found to increase arc pressure. This article has some other interesting facts about high frequency pulsing.
http://www.thefabricator.com/article...tube-producers
I can tell you that in actual use, high frequency pulsing (300Hz) has an effect in DC welding that is helpful to keep the arc more directional and focused. It can be helpful to prevent the arc from melting a nearby edge. (See attached pictures, showing 1/8" 1018 steel flatbar I welded with 300Hz pulsing, close to an edge without melting the edge.)
My machine, which lacks adjustable A/C frequency (its pre-set at 60Hz), also benefits on low amp aluminum welding in some joints from the 300Hz high frequency pulsing as well. I feel the 300Hz pulsing setting helps focus the AC arc and perhaps partially makes up for the machine not having adjustable A/C frequency.
The adjustment on my pulsing frequency knob is kind of funny in that its not very linear, so its hard to set anything other than the minimum or maximum pulsing frequency. Most other knob settings seem to be just a small bit above minimum. However, I basically just use it maxxed out (300Hz) or at minimum (of perhaps 1.5 pulses per second) and I don't feel not being able to vary in between those two settings is holding back my welding abilities very much. I'd say having both a relatively high frequency pulse setting, and a relatively low frequency setting is useful, however. They are useful in different scenarios.
Low frequency pulsing can be helpful for limiting heat input, for example, if you are welding thin sheetmetal and want to minimize distortion. Whereas I usually use high frequency pulsing more when I want to make the arc more directional, contricted, and "focused".