Wave Shape

Date 06-11-2014 01:18

Hello Blaster, we have 2 of the Dynasty 350's and along with these we received the "Dynasty Quick Reference". Do you have this information? I'll link it here(hopefully) if you don't.

I wish that I could say that I have spent hours and hours figuring out what each one of these waveforms accomplishes or the differences from one to the other that might be noted, can't say that though, nor can I give you any wondrous suggestions. I have probably spent more time using the default waveform and altering the HZ settings and the AC balance. Love the machines so far, just haven't gotten to mess with them as much as I would like. As to the "triangle wave", from the little that I have read it is supposed to aid in puddle control on thin materials, don't have personal experience either way at this point.

I look forward to hearing from others who "have" experience with those features and others. So much to learn, so little time. Best regards, Allan

http://www.millerwelds.com/pdf/DynastyQuickRef.pdf

By Lawrence (*****)

Date 06-11-2014 12:16

I've been working with Asymmetric GTAW since the mid 1990's and have posted on uncouted threads here in the forum about advantages, disadvantages and techniques. A little searching will produce quite a bit of fact and opinion about that :)

The advent of new power supplies and inverter GTAW wave forms are for the most part based on the same theory and reasoning as why men climb mountains and dogs lick themselves... Because they can.

Down and dirty distillation:

1. GTAW aluminum with AC frequencies above 220 Hz ............ Will only trigger migranes.

2. High frequency AC GTAW (kiloHz) stirring the weld pool.......... = Bullshyt

3. 95% of all aluminum GTAW done today to X-ray standards can be accomplished within the parameter range that can be attained by any transformer (synchrowave ) style power supply.

4. AC balence control in excess of about 72% EN will require special surface preparation of aluminum in order to see any benefit of reduced "cleaning action"

5. (related to 4) Penetration and cannot occur on aluminum alloys if the oxide coating is not fully removed... Waveforms/Balence/FancyCrap will not alter this fact.

6. Pointed Electrodes are not just for inverters... better fillet performance occurs with sharpened electrodes with AC GTAW... Just don't overheat the tungsten... It's really that simple.

7. (Related to 6) Do not use pure (green) tungsten electrodes for GTAW ever.

By aevald

Date 06-11-2014 14:33

Thank you Lawrence, as always, to the point. When I have a bit more time I will likely pick your brain additionally with regard to some of these points. Best regards, Allan

By js55

Date 06-11-2014 14:55

Lawrence,
I believe you are allowing your experience and knowledge to interfere with the latest and greatest technological snake oil. :grin:

By Lawrence (*****)

Date 06-11-2014 15:24

Don't get me wrong.

The coin has a shiny side.

Inverters are small, they draw less current.

If you are welding on sections thicker than 1/4 inch or on castings... Asymmetric AC can be a big benefit.

If you need to make small fillets or increase travel speeds on thin materials, Asymmetric AC can be a benefit.

The frequency control available with inverter AC GTAW power supplies will allow a number of benefits that are pretty cool.

If you view an Asymmetric inverter GTAW power supply as *two power supplies and a computer* one power supply being DCEN and the other being DCEP, with the computer controlling how that current is metered out on each side of the AC half cycle, the possibilities are almost endless for creativity in producing welds on aluminum....

We even did some trials on Pratt Whitney and GE oxidized Inconel 718 Hot sections...... 99% DCEN with the one percent of DCEP being at an outrageously high current value in order to give an assist in oxide removal in situations where common surface prep was impossible.... The results were pretty cool.

So it's not like I have no use for the new toys... I actually like them.... But the sales folk just do not usually give a real analysis of benefits when they talk about products/technology

By js55

Date 06-11-2014 15:44

Lawrence,
What you describe has of course always been the problem. They come up with a remarkable technology and then the marketers take over and over sell it.
Virtually all of these new technologies have some extraordinary abilities in limited applications.
Short circuiting, pulsing, solid state, inverters, flux cored wire, etc.

By 46.00

Date 06-12-2014 06:46

Lawrence, what is your take on welding Aluminum with DC- (or using straight polarity) for GTAW using inverter technology?

By Lawrence (*****)

Date 06-12-2014 11:33

Hey 46

I would say GTAW with DCEN (DC-) is a process typically used for relatively thicker sections of Aluminum base metal and is also typically done with Helium gas.

I really don't see one tiny speck of difference between DCEN produced with an inverter vs a transformer type power supply.

My question back to you would be; If the GTAW operation was on that relatively thicker base metal; Why are we discussing GTAW at all. Why not use GMAW ?

By 46.00

Date 06-12-2014 11:49

I was actually referring to it's use on mainly thin wall Aluminium pipe and yes, with Helium gas. Have you come across this?

By Lawrence (*****)

Date 06-12-2014 12:28

Even with thin wall pipe... The only difference between an inverter and a transformer might be the arc starting mechinisim. The current is the current is the current.. (in my opinion)

Some inverters use a capacitor discharge type system rather than a high frequency arc starting system.... Both can do work of the highest quality as long as a good process control regimine is in place.

By Metarinka (****)

Date 06-11-2014 02:57

I can't speak too much to waveshape, but in my experience balance followed by frequency are the two biggest settings to dial in. Also it's beneficial to increase the frequency as high as you can but I've never seen a commercial power supply that can actually keep anything close to a stable waveform above 300Hz. I recommend 100Hz minimum and then adjust your balance. I would stay away from that wave shape garbage, square wave has always worked fine for me and in truth it will always be clipped. I spent a good amount of time and resources looking at GTAW waveshapes and pulse welding and found that most of it makes very little difference on the end product.

By welderbrent (*****)

Date 06-11-2014 19:35

Man, and here all this time I thought he was referring to the different wave patterns of the princesses and queens riding on the floats at the Rose Parade :confused:

Really though, some good insights Lawrence, thank you.

And I will jump on the wagon of sales reps overselling. Yes, there are a good many machines available today that can limit your total equipment expense if set up properly, especially for smaller shops with a wide range of applications.

BUT, there will never be a one size fits all, one machine can do it all, this snake oil will cure all of man's ills, welder. And so many of the new toys are just that, toys. Most hobby welders and small shops don't have the time to play and find all the advantages. The supplier won't keep coming around to make sure he knows how to use every function every time they set up for a new job. After a short time the machine gets pushed into some back corner with other tools stacked all over it relegated to tool stand status. And if you want the machine to make your welds good because you can't weld, forget it.

They really need to be careful about their marketing of new items. And customers need to be careful about their buying practices. Don't be hoodwinked.

Now, that doesn't mean that schools and companies that could really benefit from the new research and development should stay away. But they too need to be careful how they spend their money and then have to train people to use the equipment. But our students deserve to be exposed to as much as possible, both old and new equipment. It goes both ways. Teach them nothing but the newest and they make fools of themselves in a lot of tests because they haven't got a clue how to set up the older machines. Or, teach them nothing but new...same story, only reversed.

Just my two tin pennies worth.

He Is In Control, Have a Great Day, Brent