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Posted by Martin H. Eastburn on May 5, 2008, 8:17 pm
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Sounds like a center tap output with the center driven from one rail,
to the other or between by a control pot shifting the waveform
to be all + or all - or any area within.
Martin
Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
TSRA, Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member.
http://lufkinced.com/
Jon Danniken wrote:
> clare at snyder dot ontario dot canada> wrote:
>> On Sun, 4 May 2008 21:04:24 -0700, "Jon Danniken" wrote
>>
>>> Alrighty then, so a squarewave would be the easiest waveform to make,
>>> would
>>> that be a sufficient enough selection of waveforms, and what frequency
>>> range
>>> would be most useful?
>>>
>>> Jon
>>>
>> Square wave AC with variable duty cycle is best. More negative cleans
>> better, more positive penetrates better, from what I remember.
>
> Thanks, Clare, I appreciate it. A duty cycle control shouldn't be too hard
> to put in there, if I'm feeding them anyway.
>
> Brings up another issue though, I'm guessing the waveform will need to swing
> from positive to negative, and not just dance around above the work
> potential. Hmmm, I'll have to think about that one.
>
> Jon
>
>
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Posted by Ignoramus11115 on May 5, 2008, 12:01 am
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> Howdy,
>
> The design of my footpedal current-controlled DC TIG welder is coming along
> smoothly, but it has brought me to a crossroads.
>
> It has come to my attention that welding aluminum with DC is best to be
> avoided (I am guessing due to the need to get through the oxide layer), and
> so far I am only designing a provision for foot control of DC current (the
> current control is via a thyristor bridge after the AC transformer).
>
> Here's my question: this project will have a (low current) HF/HV arc
> starting module. If I leave this on while welding with DC, will that,
> superimposed on top of the DC current, be of any significant help with
> welding aluminum?
No. The point of AC is that the reverse polarity cleans the aluminum
oxide layer, thus achieving a good bond. HF would not help with it.
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Posted by Jon Danniken on May 5, 2008, 12:32 am
Please log in for more thread options "Ignoramus11115":> Jon Danniken wrote:
>
>> Here's my question: this project will have a (low current) HF/HV arc
>> starting module. If I leave this on while welding with DC, will that,
>> superimposed on top of the DC current, be of any significant help with
>> welding aluminum?
>
> No. The point of AC is that the reverse polarity cleans the aluminum
> oxide layer, thus achieving a good bond. HF would not help with it.
Thanks, Iggy, I appreciate it.
Jon
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Posted by on May 5, 2008, 12:07 pm
Please log in for more thread options On Sun, 4 May 2008 21:32:30 -0700, "Jon Danniken"
>"Ignoramus11115":> Jon Danniken wrote:
>>
>>> Here's my question: this project will have a (low current) HF/HV arc
>>> starting module. If I leave this on while welding with DC, will that,
>>> superimposed on top of the DC current, be of any significant help with
>>> welding aluminum?
>>
>> No. The point of AC is that the reverse polarity cleans the aluminum
>> oxide layer, thus achieving a good bond. HF would not help with it.
>
>Thanks, Iggy, I appreciate it.
>
>Jon
>
>
Greetings Jon,
Years ago I was taught how to weld aluminum with DC tig. The material
was .25 wall thickness 6061 channel. I had to clean the aluminum with
a cleaner that had hydrofluoric acid in it. Anyway, the parts were
milled first with a 45 degeree angle on each edge about 2/3 of the
material thickness. The resulting groove at the butt joint was then
about 5/16 wide. I used helium, not argon, because helium welds
hotter. I filled the groove in one pass using 1/8 rod with the welder
in the 125-300 amp range. Lots of black residue was left on the weld
but since the tops of the weld were ground off this didn't matter. Ac
is really much better and the cleaning action is remarkable.
ERS
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Posted by Gunner Asch on May 5, 2008, 12:34 pm
Please log in for more thread options On Sun, 4 May 2008 21:32:30 -0700, "Jon Danniken"
>"Ignoramus11115":> Jon Danniken wrote:
>>
>>> Here's my question: this project will have a (low current) HF/HV arc
>>> starting module. If I leave this on while welding with DC, will that,
>>> superimposed on top of the DC current, be of any significant help with
>>> welding aluminum?
>>
>> No. The point of AC is that the reverse polarity cleans the aluminum
>> oxide layer, thus achieving a good bond. HF would not help with it.
>
>Thanks, Iggy, I appreciate it.
>
>Jon
>
Most full function tig welders have this AC as an ajustable
feature...more bias one one for cleaning, the other way for more
penetration.
Personally I use more penetration by about 60/40 over cleaning most fo
the time, at about 60 hz, though I do have the option of going from
1pps to about 300.
Many plain tig welders get by just fine at 60 hz
Gunner, Dauber at Large.
Political Correctness is a doctrine fostered by a delusional,
illogical liberal minority, and rabidly promoted by an
unscrupulous mainstream media, which holds forth the
proposition that it is entirely possible to pick up a turd by the clean end.
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