Welding Tips and Tricks

Hello. First post. Self taught while repairing bikes and cars and building custom things. Started with O/A , moved to stick then back to tig for control and versatility like a torch. They all have a place but tiggin' is purdy.

I have a weird question. DC pulse is easy to understand. AC pulse in 2D is easy to understand but some of the newer machines now include amp control on either side of the pulse and that got me wondering because sometimes I wonder too much.

Say I decide to weld at 100 amps and I set my AC frequency at 140HZ and cleaning or positive set on 25% theoretically you have 75% negative and 25% positive flicking back and forth a 140 times a second with 100 amps at each end.
Now if I go to turn on pulse and I set the frequency to 140HZ and pulse time on to 25% what is happening? Have I just split the negative and positive into two distinct controllable amperages? Meaning if I now adjust the pulse amps percent to 50% of welding amps am I getting 100 amps during the negative cycle and 50 amps during the positive cycle.
To continue with my weird question If I swapped the leads on the welder and kept the same settings would I now have 100 amps during the positive cycle and 50 amps during the negative cycle. And,,,to continue to the end I was wondering about if I turned my pulse time on to 75% would I end up with 75% negative at 50 amps and 25% positive at 100 amps.

Thanx for any input.

check out the post "taking a different approach to EN EP amperage "
in the tig welding section

Welcome to the forum.

Welcome to the forum.

As already linked. Check out that topic about "different approach to EN EP amperage". There is good write up.

Just to help a bit.
You already answered to most of your question by yourself. However on AC you don't have "pulse" settings as known on dc. Machine will switch between AC and DC currents (balance) in certain cycles (frequency) and that works as a pulse.

It was that thread about controlling EP and EN amperages that got me thinking.

I just recently (Nov.) replaced an old Squarewave 175 with an Everlast EX 250. Like a boy with a new toy for the last few months. Not the most precise settings If you like the math like I do but It sure is nice to have pedal power and arc control.
I got to say the learning curve with the new vids and forums today is so nice compared to my youth where you learned by fixing the holes you blew into dirty expansion chambers or watched your welds crack before your eyes because you never heard of cromo lol.
I've searched the 'net for info about what is really happening when pulse frequency and AC frequency are equal but nothin' yet.

I have a project in mind for my sport bike. I'd like to add daily storage in the form of small panniers but want them to look like custom expansion chambers and flow with the lines of the bike (just 'cause lol).
Originally,, I would like to use stainless (hoping to stay 30 to 40 thou. material) but finding the stainless material I need in small quantity is tough in my neighborhood. Finding aluminum in all grades is easy. With all the welds I want for the looks the aluminum will become butter unless I can control the heat.
So I was thinking along the lines of 35-40 amps for 90% EN and 70-80 amps for 10% EP. Kinda like fusion welding aluminum with a bit of 40 thou 4043 thrown in for looks and fill.

Anybody tried this setting with a digital inverter and thin aluminum? Anybody tried flippin' the leads on an analog inverter to get this effect?

motox wrote:check out the post "taking a different approach to EN EP amperage "
in the tig welding section

That does not address the question. He thinks it might be independent amplitude control ( which is what that linked thread addresses), but that is not what AC pulsing is, at all.

I'll try to sneak a drawing in here later

Thanx Oscar.

I understand I don't have the capabilities in my machine. I'm wondering if with equalizing pulse and AC frequencies if I can get the same effect of amp control then swap leads to have the ability to run a higher EP amperage.

I'll sneak back tomorrow.

geo wrote:Thanx Oscar.

I understand I don't have the capabilities in my machine. I'm wondering if with equalizing pulse and AC frequencies if I can get the same effect of amp control then swap leads to have the ability to run a higher EP amperage.

I'll sneak back tomorrow.

The short answer is: no. The absolute value of the amplitudes whether it be on the DCEN portion, or the DCEP portion, will be always be equal if you do not have Independent Amplitude Control. You can tailor the time-domain aspect of it, meaning you can dial in as much DCEP as the machine will allow, or like you said, dial in as much DCEN as you want, then switch the leads to get polarity-reversal, but the absolute value of the peak and the trough will remain identical. AC Pulsing doesn't change the absolute value of the peaks/troughs either, regardless. AC Pulsing simply digitally mimics what would normally be done by "pulsing" the foot-pedal. We all know no amount of pulsing the foot-pedal will shape the EN/EP portions of the waveform independently. Simply custom-tailoring the DCEP portion is not exactly the same as independent amplitude control, or else independent amplitude control wouldn't even be a thing. Also you can't have Pulse feature "catch" only the DCEP portion and "pump it up" while diminishing the DCEN portion to get the same effect of independent amplitude control-----it only does what your foot does on a foot-pedal, albeit in a more precise manner without human error.

Geo,

I guess I'm confused by what you are trying to accomplish now that I've read through here. In the beginning your first post, you are mistaking AC frequency with pulse frequency. When adjusting EN/EP balance, you are adjusting the duty cycle of each half of the square wave. So for every full wave, or 1 cycle if you will, you have EN 75% of the time EP 25% of the time. When you start bumping the frequency up, you change the number of times that the AC cycle happens per second, but you get full amperage on both sides of 'zero.'

Pulsing is a completely different concept. When pulsing, you are adjusting the machine to directly vary amperage based on the parameters you set. With your machine (I have the same one, as do a few others) the "Pulse Low" (or pulse 1, its been a while since I used it) is used to control pulse from 0-25hz (cycles per second) while the other is used to control from 26-500hz (250 is the max on AC I believe.) The control is logarithmic, not linear, so the more you turn the knob, the higher the jump in frequency is.

Background current as a percentage is what the low side of the pulse is, with peak obviously being the high. It does this without regard for what you have the balance of the machine set at. 90/10, 10/90, 75/25, it doesn't matter, the machine will pulse the same way. I guess I'm not sure what you are trying to accomplish with flipping the torch leads around. The only thing gaining EP will do is make you go to a bigger tungsten size by about triple.

I have thought about this exact question as well. Matching the AC frequency with the pulse frequency creates an interesting situation. It seems to me that *if* the cycle starts on the high side of the pulse and EN side of the AC wave and everything is synced up, you would be welding at 100 amps EN for 75% of the cycle and 50 amps EP for 25% of the cycle using your numbers.

Welding amps - 100 amps
AC frequency - 140 Hz
Balance - 75% EN
Pulse frequency - 140 pps (Hz)
% peak Time - 75%
Background current - 50%

So, say you start at 100 amps (high pulse) and EN, it will stay there for 75% of the cycle, then switch to EP and low pulse at the exact same time for the remaining 25% of the cycle. Seems to make sense to me.

The problems would be if the cycles were not perfectly synced and/or it starts on the high side of the pulse and EP side of the AC wave. Then it would be a mess.

Anyway, it' a good brain twister.

Thanx for understanding Zank.

Grain time, I'm trying to see if I can run a higher EP amperage (for more cleaning) over a much smaller than normal % of the AC cycle (or frequency) with our machine.
Why? to see if I can run lower EN amps to lessen HAZ on my project which will require 3 sides of about a 3 to 4 in. by 7 to 10 in. strips of 60 or 100 thou (I'd like to stick with 60) 6061 T6 that have been formed into a sort of half round shapes with different radius on each piece which will make it difficult to apply a heat absorbing backer.
It would be real simple with steel and may end up that way but I godda try.

The EX250 is kinda vague (just dials and not linear as Grain Time mentioned) for sure and I'll never know the exact numbers but I have some pretty good settings for myself with different joints in aluminum.
Other machines have actual read out of these setting and I thought some one may have tried equalizing AC frequency and pulse frequency to see the effect. Whether they line up or not, who knows, but there is only a few ways to skin a cat with chip technology.

I did try this (without the lead swap) before posting and something happens on the EP side I think.
Parameters: -Cracked a beer and cut a couple of 3x10" 6061 T6 1/8th aluminum coupons. Didn't brush off oxide but cleaned with acetone. No extra effort on fit up just tack and go.
- Set torch and machine to the way I do 1/8th" aluminum butt joints; FL3 head, gas lens, #7 cup, 14-15 CFM, 1/16th E3, ground 3 to 1 then tip flattened to 2 to1, 130 amps on display and SCC pedal does the rest (ususally once welding display shows 90-95ish), AC frequency 50 HZ (this is what I like on butts, just me), EP about 25%, 3/32 5356 in the tig pen.
- Fired an arc and welded an inch. Needed a bit more cleaning and turned it up a touch (thinking 30 ish%) and did another inch. Now I had a 1/16 of etching. Turned on pulse (first time on AC because I have not felt the need) set PPS to 50 ish, on time to 30ish%, pulse amps to 50 ish. Weld and inch, needs more pedal, longer to get going, and etching is almost gone but bead is clean (should try it with 4043). Try another inch with some more pedal and speed and same. Turn up AC frequency to 120ish (not touching pulse settings) and etching is back and wider. Return to 50HZ and etching is gone. Turn off pulse and etching is back.
Cooled the machine and started on the beer. Hmmm.

I know each set-up requires slight tweeks to the rest but this Is why I posted the question.
-

Like the part about the beer
The rest is very interesting!!!!!

Why not just use a huge tungsten and weld it with EP as high as you can stand? I guess I don't know what 'look' you are trying to achieve by using EP more than EN in a given wave form.

What is the purpose of balance if you are not putting a limit on how much of each cycle you are in a given polarity? I better understand what you guys are talking about after having read zank's reply, I just don't understand what the practical application would be aside from education and experimentation.