dynasty and xrays

By Lawrence (*****)

Date 05-23-2007 19:46

Wililt fly

I can think of one more stumbling block that is pretty common with Aluminum. When switching from a transformer rectifier (Traditional squarewave) to an inverter like Dynasty (True Squarewave) balence control settings often become an issue. Let me explane why.

Your Dynasty can control AC dwell time on the straight polarity side of the half cycle all the way to 99% dwell on DCEN.... A transformer rectifier has balence control settings usually from 1-10. Ten being a dwell time of 68% DCEN.... New users of inverters often will try to get sufficient cleaning action with a setting that is not practical... They might set that DCEN for 80% DCEN because they set their old Synchrowave 250 or Lincoln Percision Tig to 8 (about 55% DCEN) on the balence control dial. When they do this they are actually providing much more DCEN than they imagine and usually past the point of diminishing return as far as weld quality.

Here is the whole thread from which the above text originated
http://aws.org/cgi-bin/mwf/topic_show.pl?pid=62008;hl=dynasty#pid62008

By ssbn727 (*****)

Date 05-23-2007 20:52 Edited 05-23-2007 20:58

You mean traditional "Sine Wave" when talking about a transformer rectifier power source - do'nt you Larry?
That is - unless you're talking exclusively about a Miller Synchrowave or a Lincoln Precision TIG which can produce only limited squarewave output. ;)

Respectfully,
Henry

By Lawrence (*****)

Date 05-23-2007 23:50

Henry.

I think I'm trying to say... Any transformer rectifier GTAW power supply with balence control will perform with dwell times on each side of the half cycle pretty much as as I describe... Red....Yellow, Blue, or Purple. This is "Traditional Squarewave"

A "sine wave" is produced by older/lower tech versions of transformer rectifiers, ones without any balence control...

Inverters (any brand) produce "True Squarewave".... This technology provides not only greater adjustability of dwell time on each side of the half cycle it also switches back and forth so quickly between polarities that superimposed high frequency is no longer required... This fast switching is what really distinguishes "true squarewave" in principle.

Controlable frequency is an additional benefit to true squarewave but I don't think it is applicable to the problems in this thread.

So for the purpose of this conversation we have 3 different forms of AC GTAW power delivary... sine wave.. Traditional Squarewave... and True Squarewave....

::::::Look out...... Millers new Dynasty 350 and 700 come with a thing called "Triangular-wave"... More on that in June after I have a test drive in Appleton!

By Tommyjoking (****)

Date 05-24-2007 11:47

Just a question.....you seeing any bumpy stuff on the surface of your welds? Is this t6???

Fellow aircraft welder..feeling your pain dude.

By willitfly Date 05-25-2007 06:39

tommyjoking
yes it is t6 and we weld it with 4043 to ams 1595 std. and no the welds really look good on the outside "no bumbs", We really don't do much alum. most of it is inco 718. 625, s.s.308, 17-4, 15-5, hast w, hast x.
Lots of sheet metal and castings with very tight tol. but you say you do aerospace you know what I mean.

By Tommyjoking (****)

Date 05-25-2007 06:58 Edited 05-25-2007 07:10

The reason I asked that was your commentary on the hot and fast verses (normal?) speed. I have noticed with 4043 on thinner material if the welder kept his arc and (wetted) puddle in one spot too long it causes a strange pimply looking surface on your caps/welds ...it is actually a type of porosity really a void just under the surface...it will not shoot good if you have that. Have a guy testing now that has exhibited this on his practice plates 1g. Getting him to deposit his filler and move on is solving the issue. In general your travel speed on aluminum will be much faster then on your steels and inconel. And I am sure I don't have to preach cleaning regime to you on aluminum.

In relation to the welder being the source of the headache....That balance control really does a lot to your weld....if you have a peak time control try moving it up to around 7-8 and and your balance on 6-7....I have not tried a dynasty...however a synchrowave I believe has similiar behaviours with your arc characteristics. Set incorrectly right temp or not it simply won't tie and flow properly. The synchrowave is the shiznit on aluminum at times...however I am happy just putting more hours on my old aircrafter.

Good luck with breaking those things in.....wish I had one! lol

By ssbn727 (*****)

Date 05-25-2007 08:13 Edited 05-25-2007 09:27

I know exactly what you were trying to convey Larry ;)
I just wanted you to clarify yourself so that the rest of the folks not as well versed in the specifics of how these different types of power sources work to produce the variety of arc characteristics - depending whether or not certain features are available with each type of power source as a way for those folks to better understand how these puppies really work... After all you are "Lawrence of Wulfram"!!! ;)

You'd be amazed how many folks that have a synchrowave or a precision TIG or any other brand that do not take advantage of the balance control component feature because they have'nt a clue how beneficial a properly "tuned" squarewave output can be when welding Aluminum as compared to the traditional "Sine Wave" output that was the norm in most of the latter half of the 20th century. (Now I feel old ;) )

I agree that the widespread use of inverter type power sources with adjustable squarewave output changed the playing field so to speak in the last three decades of the 20th century... The fast switching that you're talking about really started to shine when the IGBT's (Insulated Gate Bipolar Transistor) were incorporated into the inverter designs...
http://www.powerdesigners.com/InfoWeb/design_center/articles/IGBTs/igbts.shtm
http://www.irf.com/technical-info/whitepaper/choosewisely.pdf
http://www.microsemi.com/micnotes/APT0201.pdf
Got variable polarity anyone??? ;) No More High FreQ - Yey!!! ;)

Ultimately, the best way to see the differences in output between the power source designs is to play around with them with a "qualified' person that can demonstrate the distinct advantages in welding with a true squarewave inverter type power source as opposed to what I like to call a traditional transformer rectifier with limited squarewave and/or limited pulsing capability thats an accessory (not a standard feature) on some models - the pulsing controls that is... It's always amazed me how many shops have these power sources, and do'nt have a clue as to using them to their advantage and their intended purpose... Talk about buying bells & whistles without knowing how to make them play the sweet music of success!!!

They've (Miller) been working on that "triangular wave" type power source feature for years now... In fact, I remember Miller loosely talking about them back in the eighties when I went to their equipment repair course in 83. So they're finally coming out with one... Cool!!! Please let us know what you think of these new puppies! Always a pleasure conversing with ya Larry!!! ;)

Respectfully,
Henry

By Kix

Date 06-18-2007 13:19

Are you purging the back of the plate you are welding. I too have heard this problem, but on a bit thicker .1 to .125 6061-t6 with a 4043. Started out when we wern't purging and we got porosity in the welds. Started purging and then it went away. I left and i heard from a buddy the runs the weld shop that the porosity is back with these new machines they got. I don't know what kind of machines they are useing now, but i am vary curious to find out what is causeing the porosity. Yes these guys that are welding with these new machines know how to work them and understand the hole balance and freq thing. They have been welding in the aerospace IND for a long time. Proper cleaning of the test plates and filler are done and there is no moisture in the plate while welding. Weird stuff and i hate not knowing why something is happening.