Electronics > Mechanical & Automation Engineering

limits of function generators and welders

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coppercone2:
I fixed my welder after replacing some chips

I think I want to break it again by doing pulser experiments. I have a old miller dynasty 200 (non DX) without pulser or waveform settings (i.e. sine)

I see its possible to buy a device that plugs into the foot pedal to basically simulate a potentiometer output.


So long I maintain a reasonable amplitude level, does anyone see any problems with waveshape inputs into the machine, within reason (i.e. no more then audio band)? Do you think I can break something by going too fast on frequency, if I make sure amplitude is within reason?

I am curious about looking at the arc under different conditions.


I imagine its related to maximum slew, the machine in the DX form, has a maximum setting for 400 PPS, or 400Hz PWM.


They sell this thing, which does most of what I want to see, but its limited to 40PPS
https://jattus.com/shop/tig-perfect

I was also curious if I could put a higher frequency then the manufacturer limits for experimental reasons (i.e. 1KHz)


I wanted to use a old wavetek function generator with DC offset and PWM capability. This function generator is acceptable to damage


Then I can look at things like DC offset and sine, triangle, sawtooth, pwm and shaped functions. If I go to like 2KHz, is it possible for a inverter to go boom?

And its related to probing plasma experiments etc

The function generator has a external trigger, which I can plug into a switch, to make some automated welding machine too


My hunch is that a low pass filter protects the thing from crazy inputs, so long I don't try to make it into a RF generator



I bought
97-3106A-20-27P
97-3057-1012-1

from amphenol (not knockoffs, I take my bootleg hacks very seriously).


I am just wondering if there might be a ground loop problem with the FG. So I will use a HP 8904A with the isolation turned on



I m doing some research, basically it says the arc constricts as frequency increases, and it stiffens, which I guess is another way of saying arc pressure increases. Weld pressure is a interesting observation of the arc, it seems to be related to observations about the weld pool penetration, or that high current welds seem to "push" the weld puddle down into the metal, similar to how you can quantify mechanical pressure denting something..



https://www.everlastgenerators.com/forums/showthread.php/1032-Pulse-per-minute(ppm)



Trying to figure out what it will do or why the pulse setting helps is confusing, but I realized I can experiment with high speed welding by using a linear rail, where I can quickly slide the torch along a corner weld or such
I think that 400 Hz DC should bring the arc pressure up substantially.


I wonder if this means you can do a lighter bevel on a deeper weld (sharp angle), it could mean less filing


I also wonder if there is.. relevant information about this, when it comes to ion thruster power source design

Njk:
Where's the image came from? It was published in a trade magazine, which is actually a yellow press so it's not possible to trace the origin. Perhaps it does not show the whole picture. According to a more reputable research papers, e.g. "Effects of current pulsation at ultra-high frequency on physical aspects of the arc and its implications in the weld bead morphology in the GTAW process", by Tiago Vieira da Cunha & Carlos Enrique Niño Bohórquez, Oct 2020 (available for fair use at sci-hub), the effect has its first and most profound peak at 20 kHz pulse frequency while the first minimum is at 40 kHz. Moreover, the phenomenon also depends on the pulse current magnitude.

Anyway, I don't think it'll be easy to reproduce that using a home welding machine. Most of them still use a plain old PWM-controlled bridge invertor with switching frequency just above 20 kHz. Perhaps a frequency-controlled resonant inverter (LLC, LCC, etc.) where the switching frequency can reach above 40 kHz would be a bit better, but that machines are still rare, expensive and I'm afraid in that machines the inverter startup time is longer because of its resonant nature. Can be too long for a tens of kHz current pulse frequencies.

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