You might be getting these results because of square waves. It may change with saw profile or sine waves. Because in some electric motor changing frequency for example increasing it increases the speed of the motor so we can say increasing sine frequency increases the power. But i guess in square wave its much more about duty cycle. But i am not sure since i am not an EE but ME.
yea agreed im more thinking it would also depend on tungsten prep as well so maby a different combination with a bit different ac balance thats the thing with these new machines so many different combos as i sit here considering an everlast unit
I have a feeling 200a on most if not all welders does not mean 200a rms, and therefore the actual power delivered is not the same between DC and the highest frequency setting on the welder. Apples to oranges. Welds looked prettier than mine though, maybe I need to involve AC and maybe some helium with my normal lift start routine
@@nicholaskruft3189 I think you are right on the money here Nicholas. the useable or functional part of ANY sine wave is its 70.7% of peak to peak voltage, or its RMS (ROOT MEAN SQUARE) value. The rms value of is a function of arc voltage and current, one is dependentvon the other. For example lets forget about amps right now. lets look ai it in terms of voltage. If we have an AC wave with a peak to peak value of 200 VAC , at rms the voltage value is 141 VAC not 200. The rms value is what everything downstream from the tungston is "seeing", not 200 volts. Ohms law says the amps (I) = e/r . r being resistance in ohms. This would be all the resistance from the metal, the tungston, any microscopic dust particles, and impurities.1.1 ohms would be good resistance in an established plasma arc. dropping e to its real world rms value of 154 VAC / 1.1 ohms value of r yeilds 140 amps not 200 at the arc. However this seems to be skewed a bit much by 60 amps? Seems to me the welder maufacturers would look at this and compensate for it, unless my math and ohms law is suddenly haywire? perhaps my math is? just thinking out loud here is all folks. lol!!
It all depends on the age of the aluminium, if it's over 40 it won't be able to hear the higher frequencies, so the higher the frequency the less it will notice.
Hey This Old Tony, tangent thing I wasn't sure you knew: I noticed your cracked nail in the video. Get some CA Glue, put a droplet on you nail and then put a tissue (facial) on the drop. Let it dry. Remove excess tissue and then get your wife's nail file or one of those lathe files you've mentioned and sand the patch smooth. It's kinda like fixing fibre glass. Source: my Mum was a nail technician for more than forty years and I suck at hammers.
@@toddsmash Pro tip, forget the tissue since you scrape most of it off, instead, put only fractionally more ca than you need and sprinkle baking powder on top {or bi carb} It'll make the ca super hard and then file down, it'll be a long while before that nail breaks again {source helicopter technicians use this to temp repair damaged blades}
I do a lot of pipe welding with an extended land bevel which is similar to the grooves you welded in. I always go high frequency on the root to prevent the puddle from spilling outside the bevel, then I go low frequency on my fill and cover pass.
The skin effect actually does appear at pretty low frequencies [1]. The skin effect at 200 Hz is as low as 4-5 mm in a plasma. With square waves there will be higher harmonics and the depth will be even smaller. Higher frequency will cause power to concentrate in the outside of the arc cone. That extra heat on the outside will dissipate a lot more before getting into the metal, and indirectly widen the arc very slightly as heat on the outside will generate a little extra plasma from the surrounding cool gas. Say you're running at 2000 Hz with a square wave and your overall skin depth is 1 mm. If the arc is 4 mm wide, the power in the center is 20x lower than the power on the very edge of the arc. At that point it might as well be off. At 200 Hz the difference will probably be closer to ~20%, but that's still a huge difference and the overall heat into the weld will be reduced a lot as well. Since power is concentrated on the outside of the cone it doesn't have an insulating later between it and outside air and it radiates faster. The reason skin effect is usually neglected at low frequencies is that the overall power dissipation doesn't change much until higher frequencies, and wires are much thinner than a GTAW arc. Electrical engineers don't care much if a wire has 10% more resistance than expected, but when you're welding a 10% change in settings can be a big problem.
the machine is most likely not producing a perfect square wave, there is a slight ramp in the cycle switch, the slower frequency allows for a longer time at max amperage while the higher frequency spends more of the overall duty cycle in the transition between positive and negative
Cory Allison this seems very likely to me too, especially given the large voltages involved the ramp times will be high. I guess the plasma also has some capacitance which will add to that.
Hey Tony! Electronic Engineer here - I think your statement at 8:35 ish might be off. I doubt it's a square wave. Probably more of a trapezoid shaped wave, with a set rise time based on the voltage you're running, humidity, quality of grounding and so on. That rise time will be the same at 20Hz and 200Hz. And probaly takes a few milliseconds. Therefore at higher frequencies instead of hitting the flat at the top of the trapezoid, it's either sloping up halfway, before sloping down again, or just spending less time at the top, so the integral yields less energy to the work. Great video as usual!
Fellow electrical engineer here. Since the output of the welder is a (somewhat) square wave, is it possible that the higher frequency over-tones of the wave may play a role? Can the skin effect and other inductive losses come into play in higher frequencies that the fundamental frequency?
Interesting theory, although I have a feeling that because the tip of the electrode is held just over the grounded work and sparks fly (!) There must be some amount of capacitance which would account for the delay in charging up over the cycle. The plasma gap and the voltage difference effectively create a RC circuit? You could be right though, L might rear its head.
Not an electrical engineer here, so I may be way off, but here's another take on it that may also play a role in what's being observed: let's assume a perfect square or sine wave where the only difference is the frequency. At the lower frequency, electrons have more time between wave reversals to travel through the material. Therefore they travel further, causing more heat. The higher the frequency, the less far they travel before having to turn back. At the upper limit, infinite frequency, they don't move at all (at least, not as a result of the AC wave). Could this play a role in explaining why at higher frequencies you need to raise the current to get the same heat?
maybe it's because it's warming the metal for 5 ms at a time at 200 Hz and 50 ms at a time at 20 Hz; 200 Hz gives a more stable temperature, 20 Hz makes a bigger puddle
Hi Tony. In my work as a EE my experience has been that the skin effect at the frequencies you speak of is negligible. While I am no expert I believe that it is indeed the cone width that is controlling the energy density of the plasma and thereby producing a wider or more narrow weld bead. The reason the two cones looked the same in your video, regardless of the discharge frequency used, is because you are looking at the photons emitted when the electrons supplied by the welder recombine with the argon ions. However, I don't think that those photons are actually representative of the energy flow/density within the plasma beam. What you need in order to see energy flow in the plasma beam is a camera that can see electrons, or better yet heat. If you don't have either try googling "energy density in AC discharge induced plasma flows". The results of that search should have a few such heat pictures of plasma beams. What you will see is that inner cones (that can't be visually isolated based only on the light they give off) do change and that as a result the heat signature of the plasma flow changes drastically as well. The smoking gun in your experiments was not what the plasma flow looked like on the camera, but rather the characteristics of those little pits in the base metal. They were more spread out in the case of the lower frequency sample. That's because those multiple "cathode sites" formed based on the energy density of the beam. They are the tell tail sign of where the beam was the hottest, and how close or far apart they are seams to correlate well with the frequency of the plasma discharge that produced them. I have no idea if I am correct or not, so please consider my theory as just another possible explanation. Ohh, and please keep making videos! I love them, and they are very uplifting whenever I enter a bout of depression. I watch them, and then struggle out to the shop to build something and then I start to feel better. So thanks for that gift!!!!
I think the skin effect does come into play here. Look at the design of induction motor rotors. The shape of the shunt bars make a big difference in speed-torque-curves due to the skin effect. An Overview: en.wikipedia.org/wiki/Squirrel-cage_rotor
I would agree, strictly speaking the skin effect at such low freq is negligible. Total power going into the weld is some product of Hertz, Volt-Amps, and travel speed. I would bet that using a piece 1/2 - 1/4 the thickness, a nice weld could be made at 200hz with a faster travel speed. Its all a trade-off, like everything in life.
Tony, I am new to Tig welding, don't even have a tig welder but want to start. I am so appreciative of your documentation because you have managed to explain AC frequency to a chef! Damn bro, I love your style. Keep up the good work
Useful to understand this, I'm a pictures over words guy, allows me to have a useful way to tweak the knobs and pretend I know enough to be dangerous! Thanks Tony
@@weldingjunkie i know, it's my job o.O I just said that the noise produced by the ac arc at lower frequencies is annoying to me, so I use higher frequencies, between 150 and 190 generally. It may sound stupid to you, but since i have to weld alu 8/10 hours per day for the next 30 years, an annoying noise that i can avoid is more than a good reason to set frequency higher.
Experience has told me that FREQUENCY has more to do with how much energy you get into the metal. A higher frequency will take longer to heat the metal and the puddle will freeze somewhat faster. The lower the frequency, the more energy is put into the metal and the puddle is somewhat slower to freeze. The frequency is tuned to fine adjust the amount of energy put into the weld puddle. Again, this is just *my* personal experience with welding Aluminum.
Didn't see anyone else mention this so thought I would chime in with a thought: electric pixies aside, if you apply an oscillatory heat source to an object, the extent to which that heat penetrates the material will depend on the frequency. Think of it as a thermal-skin effect. For flat plates this decay goes as exp(-d * sqrt(pi*f/a)) where d is the distance from the surface, f is frequency, and a is the thermal diffusivity. I'm getting skin depths on the order of a few mm so I think this makes sense. The key here is that it matches intuition, higher frequencies, smaller boundary effect. Not saying there aren't other physics, but I bet this is a piece of it. *Correction* I think this is complimenting Sharky's explanation
Good stuff Tony, very helpful....would like to see more...thumbs up from me...excellent explanation. 6061 his welding is the Mona lisa of welding....he turns his welds into an art form.
Soooo...like the lower frequency gives u a wider puddle with less penetration down and slightly lower crown, but more penetration sideways (cause of the wider puddle/arc); while a higher frequency gives you a tighter puddle and more penetration down with a slightly higher crown. In simple terms one might even just say that a lower frequency gives you a wider arc, while a higher frequency gives you a tighter arc...like you know...99% of all welding videos on RU-vid regarding AC aluminum welding. I love TOT, but this was 😆🤣 Though I gotta say, some of the best actual puddle footage on RU-vid, something so many can’t get right. I loved the previous video on general Tig advice, that slow-mo footage of the puddle moving around while the torch was still, and pointing straight down, was priceless.
Electrical Engineer here, with experience in RF, high voltage, and power transmission. Induction heaters for very large pieces of metal often are run down into the audio range, 1kHz or even less, to get sufficiently deep penetration of the work piece. There very well may be some merit to the skin effect theory, or at least should definitely not be ruled out on account of the low frequency. The shape of the electrode tip will strongly impact the electric field gradient, causing breakdown at lower voltage for sharper tips, and probably impacts the way current circulates within the plasma. What this means in practical terms, I have no idea. I'm not a welder :-)
"Blood plasma is a yellowish liquid component of blood that normally holds the blood cells in whole blood in suspension. In other words, it is the liquid part of the blood that carries cells and proteins throughout the body." ~Wikipedia
Hopefully most people got this and just didn't comment on the pun. I got it and I'm an EE that knows almost nothing about biology or any field of study that defines what people are made of and how it works.
@@hotdogandahayride9823 yeah I'm a physics guy mostly and only did a bit of biology in highschool (besides what my mum taught me, she's a biology and chemistry teacher)
Just want say I agree with your experience. When I was welding aluminum regularly at my old job we would bump up the frequency to get the best penetration we could into the roots of our corner joints and more control on edges.
@8:00 it clicked in my head. As I'm listening to your description, i'm thinking about my experiences with high power audio. Low frequency sound penetrates walls, while high frequencies reflect off the surface of the wall. Eureka! Of course this principal would extend to the frequency of the AC current, and it's ability to penetrate through or reflect off the skin of our materials. Great video as always! Thanks.
Hay tony, I started watching your videos only the other month. The ones about making a chainsaw go cart and now I'm bloody hooked! They are just so enjoyably good! Keep making them and I'll keep watching thanks!
Skin depth is a completely reasonable explanation for heat penetration with thicker materials like your test sample. Skin depth in aluminum at 20Hz (sine wave) is about 18mm and at 200Hz is about 6mm. it should be noted that a square wave (or a squarish wave) has frequency components on every odd harmonic above the base frequency that account for maybe a 10th or so of the total power of the signal which would tend to flow shallower.
At that depth its still ~40% current. This does not explain the differences in these "thin" pieces. Also, the welding puddle is very shallow. In order for this to play a significant role the aluminium would have to be much worse at conducting heat and u would still have to heat the first cm to its melting point to see the effect. And maybe even then you would be unable to see it, as the current is not focused. As soon as its in the aluminium it spreads out (inverse square law). By the time its 1cm deep it will be spread out to ~6x the area (from a 1cm² arc), so resistive heating will already be minimal (in the order of the welding cable itself or less).
That would be in 6mm depth at 200Hz. With the current density (current per area) already more than halfed due to the increase in area. The lower temperature will also reduce heating compared to the welding puddle. Also... we dont have a rod/wire with the current going threw its lenght, we manually inject the current at the side. So the skin effect will be even lower. I think the higher frequency doesnt alow the arc to wander around as much (less time to move around). And thus its a more narrow area.
I do know that you're absolutely correct about the shape of the tip part. Electrical charge likes to collect to a point. Perhaps it's something like this: The higher the frequency, the less time each pulse has to travel through the material. So it doesn't heat it as deeply on a higher frequency.
Think of it as a very fast stitch weld setup. If your MIG has stitch settings, you can duplicate the results. The longer the on time, the hotter the individual event. That happens because you are putting heat in faster than it is carried away. Because of this, longer on time results in higher local temperatures and larger puddle size. As the frequency goes up the shorter heating period no longer 'gets ahead' of the cooling period (as far, and eventually, not at all). Also the arc kernel is what generates the heat, not material resistance, so the surface shape and size effects heat flow (both in and out) My 2 cents. Thanks for all your videos, great insight - always learning, and having fun too.
Great video - I really appreciate the upfront honesty. I really learned something: Not to trust people who seem too confident in their non-explainable beliefs about welding especially. I never understood people who are just learning stuff by heart but have no clue why or how they are working. It's like remembering every single outcome of every single equation without ever doing actual calculations. That just feels wrong and dumb to me.
Come for the shop tips and education and stay for the Dad Jokes. I heartily pressed the picture of the clenched fist with thumb extending upward, indicating my approval.
Great video! Under the same exact conditions, such a small change in frequency should have little effect on arc. When you start getting into orders of magnitude of frequency change then you will start to see a small difference but at that point you have a device that will not pass rf noise emission standards for certain communications bands. From an emag perspective, changing the sharpness of the tip will have a significant impact on arc width. In terms of power delivered at different frequencies, again, a change in frequency should have no effect. I and most of your commenters agree that your output wave will have more distortion at higher frequencies but there are probably other non-ideal components within your machine causing less power delivery. This is kind of difficult to measure because you would have to measure the power close to the tip. Just the tip, and only for a minute, mind. However, because the currents we are dealing with are relatively high, electromagnetic effects come into play and so the current "paths" through the material after the arc can be significantly different at higher frequencies.
Tony, I'll take a stab at this. I'm going to guess puddle width is driven by the amount of time the AC freq is in the negative or positive position. At 20 Hz, the 'wave' cycle time is 1/20 of a sec, or .05 sec. The neg or pos duration would be half of that, so .025 sec. Electron and Ion travel direction are driven by the polarity of the electrode. So when using 20 Hz, the Electron/Ions are being 'pushed' (or pulled if you prefer) for ~.025 seconds in one direction before the polarity changes and reverses the direction. For 200 Hz, the wave/cycle during is 1/200 of a sec (10 times shorter) thus the electrons/ions are pushed (pulled) away (towards) from the electrode 1/10th the amount of time as with 20 Hz. This decreased time is witnessed with your (TOT's) test as the Higher Freq (200 Hz) bead profile is obviously a lot narrower due to the shorter amount of time that electrons/ions can 'fan out' from the shortest/direct path to the work piece. I'd try to explain myself better here but i'm probably already too wordy so i'll leave it at that. Tony, thanks for all your efforts and great videos!
Also, if you have the chance to look at a capacitive coupled (AC) plasma in a vacuum, in an environment with pressure around 5 Torr and 100% Argon gas (doesn't everyone have that opportunity? ;)-if the plasma is struck with 350 KHz, the plasma area will extend not only between cathode and anode, but it will radiate out in a circular fashion. The amount the plasma extends outward is extremely affected by the frequency used to strike/run/drive the plasma. If you use 13.56 MHz (~40X faster freq), the plasma 'ball' is very notably smaller in circumference, this phenomenon has been studied at length and is driven by the duration of polarity (as i was trying to explain above). Ok, off to mow the grass. Be well.
this is the way I am leaning, thinking there are simply too many variables that even in a carefully controlled "lab" with the best of circumstances would not arrive at truly definitive answers...in the same breath wonderfully simple, in, "what do you want to have happen?"
Here are some notes that may not clarify things to many people, but I need to try anyway. The reason for AC in TIG welding has been to clean the surface oxide of the aluminum (and sometimes some other reactive metals) by a couple of different phenomena. The first one is the ion bombardment during the reverse (=Electrode Positive) phase. The normal Straight polarity (=Electrode Negative) mode sends electrons out of the tungsten. As TIG welding functions with controlled, "fixed" current, the arc voltage settles freely according to arc length and gas composition and typically is 8 to 10 V for good DC welds in argon or near 14 V in pure helium. But what happens, when the polarity is changed? At reverse polarity, the voltage becomes quite erratic and varies from about 25 V to beyond 35 V, using argon. Now, let's talk about the heat. The POWER equals Current times Voltage. As the current is kept constant (although two different polarities), it is obvious that the power during the reverse cycle is maybe triple that of the straight polarity cycle. As already mentioned, there is ion (argon or helium, or both) bombardment of the aluminum surface during reverse polarity. Unlike electrons, these heavy ions "kick" oxides loose from the surface and thereby produce cleaning. However, the ions actually seek surface oxide spots. That means after the near area has been cleaned, the ions bombard wider and wider! That actually shows in this video - there are two hue cones, an outer one somewhat colored and a narrower one inside that appears bright white. As the camera frame rate is not extremely high, it is not obvious, but I would say the inner arc cone is that of straight polarity and the outer one comes from the reverse polarity times. There is a patent (by Rod Rohrberg et al.) claiming another mechanism for removing the surface oxides. The patent description points out that the thermal expansion coefficient of molten - or melting - aluminum is many times higher than that of aluminum oxide. Thereby producing very rapid heat pulses even with DC pulsing will cause a mechanical push-out of the surface oxides. As crazy as it may sound, it actually worked in practice. Merrick Engineering built a number of welders utilizing fast pulses of 150 A over a background of 15 A, all straight polarity. The overall heat was controlled by the pulse duty cycle, which typically varied from 15% to 18%. The pulse rise time was a few tens of microseconds. Nowadays both operating principles are by default combined in VP (Variable Polarity) welding systems by Liburdi Pulsweld. In those power supplies, the reverse polarity represents some 5 to 20 % duty cycle and the rise time in each direction is in 100 microsecond domain. The power supplies are used in aerospace industry, where controls and repeatability justify a higher price than the old AC welders (with their fixed 50 % pulse duty cycle) ask for. Using a minimum necessary duty cycle for the reverse polarity keeps the unnecessary cleaning spread at bay and allows better puddle control. And a narrow seam.
My new 325 amp TIG machine will go up to 300HZ. I stay at 130HZ. I control the arc by shaping the electrode. Blunt for wide arc, sharp for narrow arc. If I increase the HZ it requires a higher amp setting. If I pulse, it needs the amps increased with increasing the pulses per second. Raising the frequency out of site is only for entertainment. I love that high whine 😛
I think the most likely explanation has been touched on in a few comments: This probably has more to do with the time it takes to re-establish the arc each time the current reverses than skin effect or wave shape or other such factors that are only significant at much higher frequencies. Given a fixed delay between when the current direction reverses and when the new arc is established and at full temp, a lower frequency arc would spend more time generating heat per second. This would also place a limit on how high you can push the frequency while still getting enough heat at max available current.
There was a comment made in the video that really resonated with me. "if 'I don´t know why, I`ll never remember it". I´ve been aware of that "feature" of my personality for many years, and it´s caused me a lot of headache in learning-environments. It seems at though learning in school never really is a matter of understanding.-It´s more a matter of remembering and being able to recite something for an exam, and then forget about it. But i like understanding. It´s the reason why i later in life learned so much about all things in life (like why AC frequency does what it does). I just wish teachers would recognize that some people really need a level of understanding instead of just remembering, and that the two might be causally linked.
I recommend anybody who is welding make sure you put earplugs in so you can actually pay attention to the weld characteristics and the flow of everything instead of the sound. And this goes for Arc, mig welding, or Tig welding.! Sometimes the sound of the arc can cause you to do things you wouldn't normally do. Like speed up or slow down.
I think one of the Easiest ways to describe the differences in high and low and why they do what they do is that higher frequencies are smaller waves and therefore fit in between and go through the materials actual molecular structure better giving that more direct property, more "penetration"
I never welded anything in my live and I didn't understand a thing. But nevertheless I watched the whole dam video just because it is sooooo fucking funny and well made. Props to you mate.
If you haven't checked out "skin effect" on Wikipedia, it's good read. Note, near the bottom, the curves with the caption "Skin depth vs. frequency for some materials at room temperature..." At TIG frequencies, it's pretty shallow for a wide range of metals -- generally less than 1 mm. So, Tony, I agree that skin effect is a good way of thinking about it and it's not what's at work. The effect whereby lower frequencies seem to correlate with deeper weld penetration is one example of a propagation phenomenon you see with waves of any kind (e.g., EM (electro-magnetic) and Mechanical (e.g., acoustic, seismic, ultrasound...)). Bottom line: most media (the materials the wave is propagating through) exhibit a "low-pass" or "high-cut" property whereby they attenuation higher frequencies more than lower ones. Here's a familiar example: you're at a commuter airport, where you have to walk off of the flight line to get into the terminal, having just landed in a commuter plane that was piloted by two teenagers with 150 hours between them. You hear the scream of the jet engines, and it hurts. A lot. But as soon as you walk into the terminal, mostly what you hear is the low rumble of the bigger jets taking off. Well that screaming sound from the engines on the flight line has a LOT of high frequency content in it that you don't hear inside the terminal. Why? Because the building materials (brick, steel, glass, sheetrock) all attenuate higher frequencies more than they do lower ones. Put another way, the lower frequencies *** penetrate deeper*** into those attenuating (a.k.a. "lossy") media (again, the building materials) than the higher frequencies do. That's why, once you're inside the terminal, all you hear are the powerful, low frequencies: they propagate through (i.e., penetrate) the building material medium, whereas all those higher frequencies don't. Well, it's the same principle at work with AC TIG: lower frequencies penetrate deeper into the medium (your base metal) than higher ones do. In case other readers are engineers or physicists: yes --- I'm leaving out a bunch more wave propagation stuff, like wave reflections owing to abrupt changes in the impedances of layered media, dispersion, blah blah blah.
The most interesting discussions are the ones we have with ourselves 🤓 Me and myself believe the following… AC= DCEN + DCEP + DCEN + DCEP + … in a sine or square wave. Assumption: Energy input DCEN = DCEP DCEN = good penetration and therefore more energy is transferred into the workpiece DCEP = oxide cleaning action and very little penetration and therefore more energy is lost to the surroundings (measurable?). Flat stock → little difference between low and high frequency because the surroundings (air and or argon) can dissipate the excess heat easy. Corners → heat build up because the amount of excess energy is not lost (or not as fast) to the surroundings (air or argon). High frequency (to me) is like setting a local fire and then quickly blowing it out before it can do much damage. Low frequency is like setting a fire and watching it burn for a while. My reasoning for what it's worth 🤔
i was always under the understanding that higher frequency allows to run your tungsten sharper without it balling up thus creating a more precise and controlled arc. my welder does not have adjustable frequency, would like to try one. good video!
Your critique of other Tubers' weld comparisons was almost "fightin' words" until you called out Jody in particular for not being full of ish. He's the one who really pulled me into welding as a hobby.
With some divices you can also variate your zero line of the sinus. The minus cleans the material and the plus makes it burn into the material/puts in the heat. So if your material is dirty, or highly oxidated, you pull the sinus down, so that minus curve is longer and lower/deeper. With a low frequency you stretch out your sinus and with a high frequency you compress your sinus.
6:09 I thought blunt tip will narrow the arc for greater penetration and pointy will be wider. Some videos say the electrons leave the material perpendicularly (@welding academy). The longer electrons travels, the more energy it looses. With a blunt tip, the electrons have shorter distance to travel, making the puddle deeper.
So... reading through the comments, my brain shit its pants! I guess i should have doped up on adderall while i was in school to stay focused. Instead, my pubescent mind would just wonder anywhere in from what my buddy ate for dinner based on the smell of expelled gasses from his mud vein, to what circus act I'll perform with my unpredictable yogurt slinger before the parents get home. I always thought welding much like i do... IT WAS PORK CHOPS!! Really though, great videos! Getting smart and giggling like a girl! Much appreciation to your knowledge, willingness to share, and knee slappers TOT! You help guys like me figure out a way to make it through a conundrum!
Always enjoy your videos... I want to put my 2 cents in it's about your cup set up nothing wrong running a screen but in my time I really don't use them on aluminum. a stander diffuser #4 or #5 cup. there are time I have used a screen or larger cup but not often. In your test I would use the #4 it does have an effect on the etching zone. also you can run less gas 10 CFH. there are many variables in AC welding. wave form, AC balance, frequency and independent amperage. all play a roll ( causing complete Chaos ) ;-) Cheers
full disclosure, i know little to nothing about tig welding. however, i know about how hertz works, and about heat transfer. i agree that its not the skin effect that's doing this at all, what i believe is happening is solely heat transfer. a lower frequency means that the arc switches less often (obviously) which means each "switch" lasts longer on the surface you're welding to. You're giving it "more time" to heat the part, essentially. This means it will take a shorter time to "melt the puddle" so to speak, because you get hotter faster. a higher frequency is the opposite. each switch lasts a shorter amount of time, so it takes longer to get up to heat. inside a corner, as you showed, there's nowhere for the heat to go except up. And because of the lower frequency, there isn't a lot of heat management. its not centered on the part or the bead. it goes everywhere. higher frequency has a lot better heat management because you're heating it more often, for shorter times, and thus seems to make a tighter bead. a good example of this is cooking something in the microwave. cooking something for 5 seconds at a time, then letting it sit for 5 seconds, etc, (.2Hz) cooks the food slower but more precisely than cooking it for 50 seconds, then letting it sit for 50 seconds (.02 Hz) which will spread the heat out everywhere as it cooks outside of a corner or small area, the heat dissipates faster than inside, so , as you said, it doesn't make a lot of difference. just my two cents
As a electrician (is that spelled right? Well iam ELEKTRIKER) higher frequency forced the current to run more towards the surface (because the changing current is inducing a magnetic field). Thou your right and thats what iam seeing as well. You get more heat INTO the area that you are welding. Maybe towards higher frequencies the current travels off of your weldpuddle into the surrounding... Just a theory here :) You can touch the arcs of powerfull teslacoils (with like more than a few mA output) and dont get killed because the current is just running over your skin (because of kHz to Mhz of frequency!) This video is older and maybe nobody reads this but HEY thanks for your very good videos, YOU LIVE MY DREAM. Id like to have that kind of equiptment ;)
Depending on the welding machine, the frequency may be set as low as 20 Hz and as high as 250 Hz. The lower setting produces a much less focused arc and the higher setting provides a much more concentrated, stiffer, and more focused arc. Most welding is preformed with a setting between 100 Hz and 120 Hz. Higher frequencies are often used for machine or automated GTA welding, for which higher travel speeds are possible. The higher the frequency, the stiffer and more focused the arc is, which is particularly helpful in fillet welds, where the edge of one plate is being heated and the middle of the base plate is not, Figure 16-37. The stiffer and more focused arc will allow the welder to direct the heat on the base plate because it will take more heat to melt due to its thermal mass -- Welding Principles and Applications Eighth Edition Larry Jeffus
Interesting phrase, that. Fits right in with this channel. Think of the dam as the mold against which you cast tin for a repair to a tin pot. You dam it up with whatever you have handy, and the dam itself is worthless junk. : A tinker's dam is a temporary patch to repair a hole in a metal vessel such as a pot or a pan. It was used by tinkers and was usually made of mud or clay, or sometimes other materials at hand, such as wet paper. The material was built up around the outside of the hole, so as to plug it. Molten solder was then poured on the inside of the hole. The solder cooled and solidified against the dam and bonded with the metal wall. The dam was then brushed away. The remaining solder was then rasped and smoothed down by the tinker.[6][7] In the Practical Dictionary of Mechanics of 1877, Edward Knight gives this definition: "Tinker's-dam: a wall of dough raised around a place which a plumber desires to flood with a coat of solder. The material can be but once used; being consequently thrown away as worthless"
You definitely got me thinking.. Skin effect may be what concentrates the current at the focal point of the plasma.. It essentially keeps the current from spreading into the part and heat stays closer to the surface. This means that the current has to be carried away from the weld area on the surface of the part. A lower frequency will allow the current to penetrate. For reference look here.. en.wikipedia.org/wiki/Skin_effect In the examples there is a graph that shows what is considered the depth of AC currents in some different metals. For aluminum the depth would be about 6 mm at 200 Hz and 20 mm at 20 Hz if I read the graph correctly. I would suspect that the skin effect is significant enough to make a difference in how the current penetrates the part you choose. It's also good to remember that square wave are really the sum of odd higher frequencies at lower levels also. Not all of the power is at the primary frequency. (Fourier Series). I should had that the current in the surface of the part simply radiates away the heat..
I think one of the best examples of how higher AC frequency can be advantageous is in a T joint, when executing a fillet weld. At 75% EN, 25% EP, you will see increased travel speeds, and more efficient heat transfer. But, to truly see the difference between say 50Hz and 200HZ, macro-etch testing can be doe to see the difference in penetration profile. Visual observations can be misleading, objective testing is the best way to truly test the benefits.
Well your theory does make a lot of sense.. The skin effect can be very prominent at frequencies above 60Hz. And Induction motors have to deal with that "problem" on each start ( consider a direct start....) Its hard, without other tests, to be sure if the diference is caused by the skin effect, but based on electrical engineering theories, the skin effect is definally plaing it's part on the game. The interesting part is that, on electrical wires, the skin effect is the cause of power loss by heating. The reason is that the wire has only a part of its area conducting electricity. So, to me, your theory is on the right direction.
Tony, I think your explanation is spot on. You probably know this by now, or someone else mentioned it in the comments below, but just in case, here is what I found... The skin depth at lower frequencies is negligible for small conductors at these frequencies, (20 to 200hz). But, for large conductors it is very relevant. See: en.wikipedia.org/wiki/Skin_effect#Examples According to the graph there, the skin depth @ 200hz is 6mm, while @ 20hz it's 11mm. That's a big difference in the depth of current flow. The more resistive a material is, the larger the skin depth. As always, thanks for the videos!
Before going wild with physics theory... I would use a clamp Amps meter and see if the current is really the same in each frequency. I would do the welds again with someone watching the meter telling me where I'm at when at full pedal. Then if the results are different I would do it again trying to match the current by controlling with the foot pedal. If I had a welder I would be testing this right now. Very interesting. Thank you for all the great work.
Hi, thanks for your very interesting video and your views regarding TIG welding quality problems. Back in the '60s I was an electrical engineer with one of England's foremost specialist metal fabricators, to the aerospace, petrochemical and nuclear industries. Part of my job was to resolve any problems of welding quality, particularly with TIG and MIG systems. Hopefully, some of the following may be of help in your research. Please forgive me if some of this is 'teaching granny how to suck eggs'! In the UK at that time, most TIG setups were made by British Oxygen and consisted of a 440v, 250 or 500 amp oil-filled transformer (across 2 phases) with switchable output current selection and outputs of 80/100v. The transformer output was then series connected to a bank of large capacitors, followed by an HV/HF spark unit to induce the HV/HF onto the welding circuit. In AC TIG welding, this HV/HF superimposition produces: ionisation of the argon shielding gas, clean starting and smooth, stable, wave balancing to sustain the welding arc. Welding metals such as aluminium and its alloys requires a well balanced AC waveform but, unfortunately, any oxide film present on the molten welding pool causes 'partial arc rectification' (i.e. it acts like a diode). These unwanted DC components unbalance the AC waveform, producing a reduction of the positive half-cycle duration - and the duration of the positive half-cycle is very important for successful welding of metals such as aluminium. The large series capacitor bank between the transformer and the HV/HF unit was intended to correct and block the effects of these additional DC components added to the AC welding waveform. This capacitive solution worked very well but the initial cost and ongoing maintenance of such a unit was considerable. In the mid 60s we purchased several American made Union Carbide 440v three phase, air cooled, self-contained transformer welding sets but, as well built as they were, the design used a large, series INDUCTOR as a solution to reshaping the AC waveform, rather than using a capacitive one. This did provide a significant reduction in unit cost, and it worked, but most of the higher skilled welders complained that the weld quality had a noticeably inferior 'feel' to that produced by a system using a capacitor bank. As an aside, we also went through a widespread phase of poor weld quality that looked very similar to that caused by the DC wave component problem. Nevertheless, this one was finally tracked down to a cost cutting exercise by the purchasing department, who had changed suppliers of the tungsten electrodes. I never quite got to the bottom of that one but it appeared that the cheaper tungsten probably contained more impurities. Reversion to the original 'expensive' supplier provided an instant solution! Cheers, Chris
@@impactodelsurenterprise2440 Thanks for your kind response - it even amazes me how much technical junk is still rocking around amongst the few remaining brain cells after all these years - don't get me started on the original Union Carbide hand-held plasma cutter - scary or what! Talk about James Bond and that laser beam approaching his goolies😀
Higher frequency simply focuses the puddle and the oscillation maintains the puddle size better than the lower frequency which tends to allow the puddle to wander.
Idk but I would think of the freq like a pulse. The higher the frequency the less time spent on the penitration side of the cycle. So if I was pulsing in DC on say carbon. The higher the pulse the higher the amperage required to penitrate the same as no pulse. Thanks for the videos. Always good stuff.
its the switching losses of the mosfets. that square wave isnt really square, but takes a few microseconds to switch from + to - . at higher frequencys (more switching) those losses get higher. also since puddle heats up only on - and cools down on +, when power is used for cleaning, high ac results in a puddle that heats up more consistent. if u imagine that heat up cool down as a triangle wave, on high freq the ripples get smaller. maybe that affects welding aswell. thats my theorys, what could cause the effect you demonstated. also i doubt the skin effect would affect anything below gigaherz frequencys :) great video as always, i know im a little late, haha
Hmmmmmm Yeeeeeees...............i did not hear a word you said,after that cool looking CK water cooled torch and leather cover was on screen.But it was another awesome video with cool arc shots.
i want to try tig welding... i am an old guy and have been welding smaw, gmaw, fcmaw, dual shielded fcmaw, old school oxy acetylene welding and brazing and even just plain old soldering with a torch or an iron for years, when you referenced Jody from welding tips and tricks.. had to subscribe... kudos dude.. btw Jody rocks and so does weld.com
I did the same video on the HTP invertig 221 with the freq changing only before you did this and I had the same results as you. This is less of a gimmick then the wave forms at least. The wave forms don’t do anything at all it’s a scam. This was spot on with frequency great info.
The skin effect "depth" is (put simply) a measurement where the current is about a third as dense as the surface; and given Aluminium's fantastic heat conductivity - I think that supports your theory of the effects you've witnessed; at least partially. We must remember that it's the heat of the plasma that melts the metal, not the current (though the plasma's output is somewhat proportional to current) - I would assert that because more electrons are near the surface of the material from this effect, that the resistance is increased, and thus the total current is decreased - leading to the "cooler" result. Depth (m) ~= 503*SQRT(P/(R*f)) Where: P = Resistivity of medium (Al = 2.7e-8; some tweaks to do here if you take temp into account) R = Relative permeability of medium (Al = ~1.0) f = Frequency of current @ 20Hz, Al = ~19mm @ 200Hz, Al = ~6mm
