Tig Welding of Alum. upgrade

Welding Techniques, Theory, Machines and Questions.

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hammermill
Posts: 2938
Joined: Sun Jun 27, 2010 10:43 pm
Location: pendleton or

Re: Tig Welding of Alum. upgrade

Post by hammermill »

others may disagree and i may be wrong but i seem to remenber the frequency is controled by the distance of the gap. really doesnt matter just makes it easier to get a arc started.
Wanna-Be
Posts: 461
Joined: Mon Nov 14, 2005 9:17 am
Location: Brady, WA

Re: Tig Welding of Alum. upgrade

Post by Wanna-Be »

I just talked with an old machinist/hobist friend who happens to have a lot of practical electrial savy. He has the same Miller Econo Twin HF machine and it was him and friend that helped me get this machine 13 years ago.
Here are some his comments about it. Fine machine except that there isn't way to "soften the arc" at the end the weld pass and this is critical on aluminum. This doesn't have anything to do with HF but with the amperage. As built, all you can do is set the machine to what is going to work for getting the arc started and when at the end of the weld pass, have another piece of scrap metal or copper to run the arc off onto. Failing this, you will always have an ugly arc crater, etc..

The other short coming is the 160 amp or so current that limits you to about 1/8" aluminum or pre-heat of thicker pieces or larger fabrications. I have found this problem with mig on aluminum and resort to a small propane torch until the fabrication has some heat retained from previous weld passes.

To over come the lack of in process control over the amp. setting and especially rapid reduction of current at the end of the weld pass I looked at the manual and found there wasn't anything apparent in the basic circuitry, circa '70s. However looking at the mechanical break down, it seen very good detail about how the inticial current is adjusted with a crank and screw pushing or drawing a shunt (choke) between the Primary and Secondary windings in an E core.

Being more mechanically inclined, I'm thinking of replacing the captured nut in the yoke of the shunt frame with a sleeve that is treaded inside for the crank lead screw/shaft. This sleeve would have a sprocket on the outer end that would be driven by a small reversable motor, controlled from a switch on the tig torch. Not only could you adjust the current while welding but could reduce it for a softer arc at the end of the pass.

Here are some scans of there related pages from the manual. (I Will find a place to upload the manual and let you all know later)

Miller Econo Twin HF007.pdf
(46.86 KiB) Downloaded 455 times
A good exploded view of the unit
Miller Econo Twin HF006.pdf
(48.04 KiB) Downloaded 429 times
Here you can see the Shunt yoke break down in detail. I plan to replace that 'captured' square lead nut with a sleeve that is internally threaded for the crank lead screw. This sleeve will have a sprocket or gear, driven by a motor and rotate inside the yoke assembly while adjusting the shunt in or out of the transformer core. The crank will still have primary adjusting control over the shunt by the internal threads. Still have to finger out the motor and limit switches.

Steve
Jet vert Mill, Champion 12X30 lathe, Amer. Mach. Tool radial drill, 24X60 LeBlond lathe, Scharmann 3" Hrz Brg Mill, Steptoe 18" Shaper, S/B Shaper,B&S (No.4 36") Gear Cutting Mach., Verson 22.5T Press Brake, Enco 12" hrz. saw, McEnglevan foundry furnace, Rockwell 14X42 lathe, K&T 2H univ horz. mill,DoAll 16-2 Vrt. bandsaw,Canedy-Otto drill press,Buffalo Iron Worker
hammermill
Posts: 2938
Joined: Sun Jun 27, 2010 10:43 pm
Location: pendleton or

Re: Tig Welding of Alum. upgrade

Post by hammermill »

does one dare ask about duty cycle on the welder, i know it is easy to get beyond a 10 or 29% duty cycle.
Wanna-Be
Posts: 461
Joined: Mon Nov 14, 2005 9:17 am
Location: Brady, WA

Re: Tig Welding of Alum. upgrade

Post by Wanna-Be »

The duty cycle is 50% as show in the attached spec sheet.
Miller Econo Twin HF008.pdf
(64.16 KiB) Downloaded 384 times
Steve
Jet vert Mill, Champion 12X30 lathe, Amer. Mach. Tool radial drill, 24X60 LeBlond lathe, Scharmann 3" Hrz Brg Mill, Steptoe 18" Shaper, S/B Shaper,B&S (No.4 36") Gear Cutting Mach., Verson 22.5T Press Brake, Enco 12" hrz. saw, McEnglevan foundry furnace, Rockwell 14X42 lathe, K&T 2H univ horz. mill,DoAll 16-2 Vrt. bandsaw,Canedy-Otto drill press,Buffalo Iron Worker
awake
Posts: 70
Joined: Fri Jan 29, 2010 5:07 pm
Location: Angier, NC

Re: Tig Welding of Alum. upgrade

Post by awake »

Don't know if you are still working on this ...

I am sure that the mechanical amperage adjustment that you are proposing will work better than none, but from my experience with TIG, I would say that it will not be nearly as helpful as a true pedal-control machine. The ability to change the amperage INSTANTLY is extremely helpful when it comes to TIG.

If you were prepared to spend some money before you realized you had the Econo-TIG on hand, you might consider the possibility of selling the Econo-TIG and using the money to help defray the cost of an inverter machine. I have had extremely good results with my Everlast multi-process TIG-Stick-Plasma machine (www.everlastgenerators.com), and Jody Collier on Welding Tips & Tricks has run some of the TIG-only units through their paces and seems to think they do a very good job. The analog TIG units are considerably less expensive than the digital ones; IIRC, their 185-amp AC/DC Tig unit is less than $1000, and that will include foot pedal, TIG torch, stick holder, and argon gas regulator. I have no connection with the company other than being a satisfied customer.
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