Results 1 to 8 of 8
  1. #1
    Join Date
    Jul 2021
    Location
    South Australia
    Age
    58
    Posts
    33

    Default Metalmaster 215 Elite AC/DC TIG - current accuracy and waveforms

    In the earlier AIG TIG 200P thread here, I posted some testing I did with a good AC/DC current probe and an oscilloscope on my budget welder. The point of the testing was to see what current it 'really' puts out when the Amps knob is set, then I got a few images of the current waveforms to workout the AC frequency in AC TIG mode, and see if it was square-wave AC output or something else. It did show a couple of interesting things (to tech nerds like me anyway).

    This thread is kind of related to that one, in that I just repeated my current tests and waveform recording on a high end machine belonging to a good friend to see how it 'compared'.
    There isn't any agenda other than it's nice to see what a higher cost purely digital controlled machine looks like in this way, and share it with anyone interested.

    What started out my interest in the 'current output verses the machine setting', was a suspicion that my budget machine was a fair bit higher than it said.
    This machine however, is very very close to what the control setting says, so close in fact I'm not prepared to argue one way or the other as it's lower in apparent error than the claimed accuracy of my borrowed current probe (a Tektronics A622)

    Output current measured verses what was selected on the welders digital display.
    Metalmaster_215_Elite_DC_TIG_output_verses_selected.jpg

    A selection of waveforms captured in both DC and AC TIG modes below. In AC TIG all the 215 Elites special waveforms were captured towards the end.

    DC TIG @ 80Amps - Oscilloscope trace is 50A per division on the vertical axis. We can see about the right current on the right hand side trace image, with an amount of ripple on top.
    The left trace is a detailed view of the ripple. It shows about 8 Amps of ripple at 46Khz. I think I can deduce that the front-end inverter of the welder runs at 46Khz from this...
    MM_DC_80A.jpg MM_80A_DC_ripple-trace_8Amps P-P.jpg

    DC TIG Pulse mode at 50% duty cycle and 1 pulse per second. Very accurate. The right hand image shows a detailed view of a pulse transition. Looks very well controlled to me.
    MM_80A_Pulse-On_50%.jpg MM_80A_DC_pulse-edge_transition.jpg

    AC TIG - 60Hz AC - 30% AC Balance (normal balance on that machine). Middle image shows 10% AC Balance. The right hand image shows 50% AC Balance.
    MM_80A_AC_60Hz_30%_Bal.jpg MM_80A_AC_60Hz_10%_Bal.jpg MM_80A_AC_60Hz_50%_Bal.jpg

    AC TIG - 120Hz & 250Hz -30% AC Balance
    MM_80A_AC_120Hz_30%_Bal.jpg MM_80A_250Hz_AC.jpg

    Detailed view of 250Hz...
    MM_80A_250Hz_AC_narrow_view.jpg


    AC TIG 120Hz AC - Pulse mode at 10Hz.
    MM_80A_120Hz_AC_Pulse-10Hz.jpg

    Now the fun specialty stuff that a budget machine will never do...

    AC TIG 80A at 60Hz AC - with AC+DC HYBRID Wave Mode - You can see here a small negative DC current offset between AC pulses.
    MM_80A_60Hz_AC_in_AC+DC_Hybrid_wave.jpg



    AC TIG 80A at 60Hz AC - with Soft Square Wave mode
    MM_80A_60Hz_AC_Soft-Square_wave.jpg

    AC TIG 80A at 60Hz AC - with Triangle Wave mode
    MM_80A_60Hz_AC_Triangle_wave.jpg

    AC TIG 80A at 60Hz AC - with Sine Wave mode
    MM_80A_60Hz_AC_Sinewave.jpg

    I'm out of time tonight. See what you guys make of that. I didn't see any HF bursts during transitions in the special waveforms, but they waveforms seem to cut through the zero current transitions very fast by design (I guess).

  2. #2
    Join Date
    Dec 2018
    Location
    NSW
    Posts
    586

    Default

    Quote Originally Posted by mr.sneezy View Post

    AC TIG 80A at 60Hz AC - with Soft Square Wave mode
    MM_80A_60Hz_AC_Soft-Square_wave.jpg

    I didn't see any HF bursts during transitions in the special waveforms, but they waveforms seem to cut through the zero current transitions very fast by design (I guess).
    On this spike occurring on the wave- It would be interesting to get a focus on this as it manifests at higher and lower current levels.
    Would you anticipate this is the HF burst?
    Looking at how it handles DC pulse cleanly, this ripple seems a little out of place for what the waveform is trying to achieve.

    /no expert, but interested. Might be completely off in the weeds with this line of thought.

  3. #3
    Join Date
    Apr 2021
    Location
    Adelaide
    Posts
    205

    Default

    Thanks for that - very instructive.

    Quote Originally Posted by mr.sneezy View Post
    AC TIG - 60Hz AC - 30% AC Balance (normal balance on that machine). Middle image shows 10% AC Balance. The right hand image shows 50% AC Balance.
    MM_80A_AC_60Hz_30%_Bal.jpg MM_80A_AC_60Hz_10%_Bal.jpg MM_80A_AC_60Hz_50%_Bal.jpg
    Is there a standard for describing balance? These percentages are electrode positive or "cleaning" so in my mind they are inverted. I guess the reality is that you take it as it comes as the manufacturers are not consistent.


    AC TIG 80A at 60Hz AC - with Soft Square Wave mode
    MM_80A_60Hz_AC_Soft-Square_wave.jpg

    AC TIG 80A at 60Hz AC - with Triangle Wave mode
    MM_80A_60Hz_AC_Triangle_wave.jpg

    AC TIG 80A at 60Hz AC - with Sine Wave mode
    MM_80A_60Hz_AC_Sinewave.jpg

    I'm out of time tonight. See what you guys make of that. I didn't see any HF bursts during transitions in the special waveforms, but they waveforms seem to cut through the zero current transitions very fast by design (I guess).
    These are all modified waveforms - the crossover is fast so that an HF burst is not needed and the peak is shaped as described. This is what I expected to see and I hope I am not just seeing what I want to see rather than what is before me.

    Thanks for posting this - I think you should keep the current probe and visit more friends ;-)

    Regards
    Jack

  4. #4
    Join Date
    Jul 2021
    Location
    South Australia
    Age
    58
    Posts
    33

    Default

    Quote Originally Posted by Jack Ryan View Post
    Thanks for that - very instructive

    Is there a standard for describing balance? These percentages are electrode positive or "cleaning" so in my mind they are inverted. I guess the reality is that you take it as it comes as the manufacturers are not consistent.

    These are all modified waveforms - the crossover is fast so that an HF burst is not needed and the peak is shaped as described. This is what I expected to see and I hope I am not just seeing what I want to see rather than what is before me.

    Thanks for posting this - I think you should keep the current probe and visit more friends ;-)

    Regards
    Jack
    Glad you guys liked it, and I didn't waste the time laying it out (took me about an hour or so, not including the time in my friends shed).

    Re the cleaning balance.
    The oscilloscope trace is current inverted (which I should have said), which I chose to do as it made more sense to me when looking at the TIG DC EN current traces initially, after that I just stuck to that convention, EN upwards. So above the center line is actually the EN current (electrode negative) and below center line is EP (electrode positive).

    Re the standards, I gather also that there at LEAST two or three ways to describe the AC balance %.
    One is to call 30% on the positive side 'normal' and then have the dial show additional % more or less than that. So +50% dialed up would actually be 45% EP time (30%+15%).
    My TIG is sort of like that but the dial goes -5 to +5 with 0 in the middle. 0 = the 'normal' 30%.
    The Metalmaster is more direct about it, it just displays the actual EP % as delivered to the torch. So 30% is 30% EP time. 50% should therefore look like a square wave AC signal, which it seems too.
    Apparently some TIG's reverse that so 70% is 'normal' described as the EN time (USA made types I think).
    Hmm, I think the best way to think about it is like you said, there may not 'be' a standard...

    The current probe is in my work area, so I should be able to do this again. Another friend has a near new SWS brand TIG, could do a test session on that one sometime.

    One thing I took from this testing in DC is that both my budget AIG TIG and the higher cost Metalmaster both had similar amounts of primary inverter ripple on the DC mode output, which I guess means there's nothing wrong with that on my TIG. Both have similar amounts of primary inverter filtering, and it's apparently enough...

  5. #5
    Join Date
    Jul 2021
    Location
    South Australia
    Age
    58
    Posts
    33

    Default

    Quote Originally Posted by Jack Ryan View Post
    These are all modified waveforms - the crossover is fast so that an HF burst is not needed and the peak is shaped as described. This is what I expected to see and I hope I am not just seeing what I want to see rather than what is before me.
    Regards
    Jack
    I agree with that, the EN to EP transition time is so short I don't think it uses HF in between.
    Also ditto the modified waveforms, the triangle is not your classic triangular wave or the sine either , but probably how it has to be to keep the arc running.

  6. #6
    Join Date
    Apr 2021
    Location
    Adelaide
    Posts
    205

    Default

    I had a look around on the Internet so see what is said about different waveforms and most of it is very unconvincing.

    Here is one video comparing different waveforms. The drawn waveforms are not accurate as on inverter machines, they are generally based on a square wave to get fast zero crossings.

    https://www.youtube.com/watch?v=OYO1GKVLS2s

    I think there is very little difference between the different waveforms. The "cold" triangle wave, for example, is cold because it is cold - the RMS current was less than for the square wave. The current was set at 100 amps for each waveform but that was the peak current, not the RMS current. The RMS value of a triangle wave is a bit over half that of a square wave. Maximum heat comes from an (advanced) square wave. Minimum heat comes from a triangle wave - or you could turn the square wave current down to match it.

    Miller has this to say about different waveforms:

    Someinverters also bring control over the waveform itself to meet a specificrequirement or operator preference. Some of the waveforms include:

    • Advanced Squarewave, which gives fast transitions for a responsive, dynamic and focused arc for better directional control.
    • Soft Squarewave, which provides a smoother, softer arc with a more fluid puddle than the squarewave.
    • Sine wave, which gives the soft-arc feel of a conventional power source, while using square transitions to eliminate the need for continuous HF.
    • Triangular wave, which combines the effect of peak amperage while reducing overall heat input. Leads to quick puddle formation and, because of lowered heat input, reduced weld distortion, especially on thin material.

    I don't know if that was written by the engineering department or the publicity department.

    By the way, an advanced square wave is just a square wave - there is nothing advanced about it.

    Has anyone tried different waveforms? What do you think?

    Jack

  7. #7
    Join Date
    Jul 2021
    Location
    South Australia
    Age
    58
    Posts
    33

    Default

    Hey Jack I think you're right, these features may well have been dreamed up by a marketing department. It will be interesting to see if anyone here has found a big difference in modes while welding ?
    Going by what he said in the video, my $650 AIG 200P has 'Advanced Square Wave' as well, as it's only AC waveform

    I agree with the RMS current thought too. Isn't real heating power into the metal going to be all about the RMS current rather than a fancy shape of it...
    (Perhaps these machines should actually display RMS current rather than peak current to compare apples with apples between waveforms).

    I suspect if we do the same current probe and oscilloscope test runs on the Everlast, that the actual current waveforms will look very like the Metalmasters (in fact the controls on the Everlast look to be very similar with maybe a different button layout).
    Cheers,
    Martin

  8. #8
    Join Date
    Apr 2021
    Location
    Adelaide
    Posts
    205

    Default

    Martin,

    I think I have found the purpose of the different waveforms - as least so far as Fronius is concerned. Here is what they have to say:
    Welding current sources suitable for AC have an inverter for generating alternating current. Many welding systems offer various settings for specifying how the current alternating between plus and minus should behave. Users can select between different half-wave forms.
    For example, the current can flow first in the positive range and then in the negative range at a constant strength—this results in a hard rectangle. Using this setting, the arc is extremely stable, but the extremely loud operating noise is unpleasant for the welder; it may even be necessary for them to work wearing hearing protectors. Smooth, sinusoidal waves are also possible. The arc is then unstable, but the welding noise is pleasantly quiet. In most aluminum applications, a combination of the two is the best choice; a rectangle with rounded corners for the negative half-wave and a sine wave for the positive half-wave.

    It looks like Fronius also mis-draws the waveforms although it doesn't have an advanced square wave - it has a hard rectangle instead.

    Perhaps Fronius doesn't update their WEB site very often. I found this while I was there:
    When purchased, the end of the tungsten electrode is flat. The electrode is sharpened before use with direct current. For a stable arc in alternating current welding, however, the end of the tungsten electrode has to be semicircular, so that the arc can be effectively controlled. The rounded end is also referred to as a “cap”.

    More often referred to as a "ball" and as far as I know, not needed since inverters came on the scene.

    Regards
    Jack
    Attached Images Attached Images

Similar Threads

  1. Elite AR5E T&C grinder
    By C-47 in forum METALWORK GENERAL
    Replies: 8
    Last Post: 1st Aug 2021, 06:12 PM
  2. First welds with the Metalmaster 215
    By Stustoys in forum WELDING
    Replies: 26
    Last Post: 15th Feb 2021, 10:12 PM
  3. Metalmaster AL330A Owners
    By NedsHead in forum METALWORK GENERAL
    Replies: 53
    Last Post: 27th Jan 2020, 09:02 AM
  4. Generator waveforms
    By .RC. in forum ELECTRICALS
    Replies: 13
    Last Post: 1st May 2019, 10:08 PM
  5. Smootharc Elite TIG 230 ACDC update, parts
    By blouis79 in forum WELDING
    Replies: 0
    Last Post: 29th Oct 2013, 01:29 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •