waveshapes??

[Mid Wales welder]

Hi all! I have been doing some ali tig welding useing a lincoln v205t ac/dc which i have found to be a very good machine. Anyway i was reading the stats about it the other day and noticed that it said it has adjustable waveshapes on this machine. Now, i know about differant waveshapes and what they are used for but i just cant seem to find out how to adjust them and even if they are something that can be adjusted, as in how do you go from square to sine to triangle? Is it as simple as pulse is a certain wave and adjusting the frequency and balance is part of it to?
I hope people reading this get the jist of my question, lol have allways been rubish at explaining things.
I have been tig welding for quite a while now, its just been a long time sinse doing all the theory at college and i find it alot more interesting now than i did back then lol.

Kind regards

Dave.

 

[chevy2]

Go onto the Miller site as they explain different ac welding waves,
Look at the spec of the dynasty 200 as that machine has wave adjustment,
Edit, just read your post again,
Hears the manual incase you dont have it that shows how to adjust the wave pattern.
(page 21 will take you staight to the setup menu)
http://www.lincolnelectric.com/assets/servicenavigator-public/lincoln3/im937.pdf

 

[hotrodder]

Waveform selection is in the 'hidden menu' along with a bunch of other stuff. To make sense of the menu you'll need a user manual applicable to the YEAR of the machine as they changed things on the later ones, or at least the 'facelifted' ones which offer 2 stick modes instead of just the one. FWIW on mine (2000 ish) it's parameter 5. To access the menu you hold down the parameter while switching it on and instead of going through it's start up routine (everything lights up and the software version is displayed) the display will show 0 and the amperage dial lets you cycle up and down through the various parameters

ETA Chevy edited his post to include a link to a manual while i was posting. If the machine your using is older (doesn't offer soft and crisp arc modes) then the hidden menu is almost certainly laid out differently

 

[Mid Wales welder]

Thanks very much for both your replys, very helpfull!! i checked the link chevy2 posted and yes that was for the newer model (with soft and crisp arc), but i foud the operators manual for the older model (everything was differant) that i am useing so i now know how to change the waveshapes and i will try them out
Still not sure exactly how waveshapes work, are the differant shapes just to do with how it switches between DCEN and DCEP and also how much heat is input both into the material in EN and the tungsten in EP?

Thanks again for the replies!

 

[hotrodder]

Yeah, it's the way they switch polarity. AC out of the wall is a sine wave, it spends most of it's time transitioning between the peak to peak value* which was improved with the introduction of squarewave which as a graph of the waveform suggests spends more time at the peaks. Inverters take this a bit further than transformer machines in that they use witchcraft to chop up the electricity and rebuild it. They switch a lot faster than transformer based kit which is why continuous HF is no longer necessary on most (all?) inverters- when continuous HF is needed it's to stop the arc going out/to reignite it as it crosses from -ve to +ve. Triangular wave is kinda the opposite thinking to square wave... spends less time at peak but maintains the fast switching

If AC balance and frequency remain the same then for a given amperage squarewave puts more heat into both the tungsten and work than a sinewave and triangular less. You wouldn't leave (at least) the balance the same though... more time spent at peak = more EP and EN. Don't need all that EP time so you bias the balance to EN which is more efficient from both the tungsten and the works POV. Combine that with changes to AC frequency and the arc can be 'shaped', higher frequencies narrow the arc cone resulting in a narrower weldpool and stiffen it some making it more stable. This make it easier to alter weld size and profile on fillets and outside corners respectively. Lower frequencies are more efficient at putting heat into the work

Triangular wave is designed more for thin materials (the v205t won't kick out it's full 200A in triangular wave and frequency is restriced at amperages above 170A, maybe for kinda the same reasons) which makes it a more natural partner with higher AC frequencies. Inverter squarewave is typically 'harsher' and louder than the smoothness that is transformers. Triangular waveforms are even harsher IMO and (especially at higher Hz) noisy. Mine gets left in squarewave for everything using frequency to fine tune weld size/profile. Note that the max EN% that the work will tolerate varies a little with waveform and frequency

Note that none of the above bells and whistles let me do anything that can't be done with basic kit. It's let me weld faster, makes some jobs a bit easier and gives more options... take an outside corner that's gonna be linished out for example, at higher frequencies it makes it easier to produce a small weld with good pen so less time with a grinder if you want a crisp corner. If you want a nice radius then lower frequencies produce a wider, softer arc

As Chevy said Millerwelds have loads of stuff on AC waveforms including effects of balance and frequency and (applicable to the poshest/lastest kit) fully assymetric AC where the amperage of both the EN and EP phases are independently adjustable (the origional Aerowave and the bigger Dynasty's if looking at owners manuals, they'll be articles/stuff in the resources section too).


*mains voltages are RMS values, peak to peak of 230V is something like 320V for example

 

[Mid Wales welder]

Thanks hotrodder, I couldn't have asked for a better explanation!! It's all very complicated, but very interesting!

Kind regards

Dave.

 

[hotrodder]

Cheers. Best way to get to grips with it is to weld a bunch of coupons varying one parameter at a time... say an outside corner at 60 / 90 / 120 /150Hz and same deal with fillets. Balance settings anywhere between 65 and 75% EN should be in the ball park as long as the material isn't manky/was brushed. If you're pushing balance as far towards EN as the material will tolerate for whatever reason then higher frequencies typically call for a small reduction in %EN... running a series of short beads is usually enough to see the difference say upping the balance in 5% steps from 65 - max @ 60Hz and then repeating at different frequencies.
Triangular wave is unlikely to offer anything other more noise unless we're talking stuff thinner than 1.2mm IMO