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Up Topic Welding Industry / Technical Discussions / HF-251 Freq. inducer
- - By Dr. D (*) Date 07-27-2005 11:58
Hey All,
I was wondering something about the miller HF-251 unit and tigging Alum.
I'm thinking about getting one for the field and it says you can tig alum, but how can one effectively do that if there's no way of adjusting your A/C balance. Your waveform would basically be set at 50/50 balance correct? And all you would really do is heat up the alum and basically clean the surface without being able to get decent penetration.
Seems like it would weld the same as if you set your machine on A/C and just scratch started it, except for the fact you wouldn't have to scratch start.
Am I missing something?
By the way I have welded Alum. using Synchrowaves, Aerowaves and Cobramatics, I haven't welded pop cans yet but I have some decent experience with Alum., just haven't used the HF-251 before.

Parent - By Lawrence (*****) Date 07-27-2005 13:40
Good Doctor.

You are correct about the wave form being a garden variety sine wave with no balance control. The superimposed HF produced from that HF 251 box will help the arc re-establish after passing through the zero point and thereby reduce the phenomena of "rectification".

Power sources such as Miller "Dial Arc" and the inappropriately named "Aircrafter" have plain sine wave AC output with high frequency. They are not high tech super machines but will do some pretty good work with aluminum if that’s all you've got. In fact they have been putting out X-ray quality work for several decades. It takes a bit more skill and theoretical understanding to get the most out of these type of machines, but one does not really need a six thousand dollar power source to get most aluminum joining accomplished if they know a few of those craftsmansip secrets :)

You may or may not get your moneys worth with that unit. Tell us a bit more about your power source and the material your trying to join. Knowing more about that will help determine if you can get by with what you have.
Parent - - By 357max (***) Date 07-27-2005 13:53
The HF box will stabilize the arc on AC. It will get the arc going to start the arc and keep it going. On AC, the positive side of the sine wave will do the cleaning. HF does nothing for cleaning. Questions; Does the welding machine you have, have the capability to remote the amperage for fine current adjustment? Does it have a contactor?
On small AC or AC/DC welders you will see something called Arc Rectification when welding aluminum and that energy goes into the welding machine's transformer as heat. This will greatly reduce its duty cycle. The 225 amp machines will be good for about 70 to 100 amps without destroying itself.
Price out a HF box and remote control device and a contactor. It may be less expensive to pay a little more and get more with a machine like a Syncrowave if aluminum gtaw is the primary need. You will than get the AC with balance control. Remember the Squarewave AC Syncrowave machines have been around 30 some years. Before that it was all sine wave AC (50/50 positive & negative) with no balance controls.
Miller used to make a square wave ac machine with no balance control called the Shopmaster and it required the HF box.
Parent - - By Dr. D (*) Date 07-29-2005 15:15
Thanks for the response gentlemen,
I was looking for something to use out in the field on my service truck. Mostly 1/8" Aluminum on up. My welder unit is a Miller Big 50. It has AC/DC and 14 pin remote so I can fine adjust the amperage with foot pedal or hand control.
My original thinking was to get an HTP 201 tig unit for the finer stuff and a cobramatic for the heavier stuff. I should be able to power the inverter type HTP tig with my welder since it has a 240V, 50A outlet.
I just figured if there were some way to adjust A/C balance with the HF box then I would use that.
By the way, I remember someone talking about tigging Alum. DCEN with helium. I tried it once with Argon just to see what kind of results I'd get. I could run an okay puddle, had to move rather fast, but the surface was pretty dirty looking afterward. I suspected because of the speed of movement(not enough gas coverage time) and lack of reverse current to help float out impurities. Does using helium give cleaner results using this method?

Thanks again
Parent - - By Lawrence (*****) Date 07-29-2005 15:46


I wouldn't suggest GTAW Aluminum DCEN+He for field work, which seems to be what your doing. To get sound welds with Helium your part preperation must be just about lab quality. Welds of the highest quality are achieved with Helium, especially on heavy sections but process control is huge and there is very little wiggle room in set up.

I would think the HTP 201(w/water cooled torch) and Cobramatic would cover just about all your bases.

Parent - - By Dr. D (*) Date 07-30-2005 08:56
Thanks Lawrence,
Yes most of my stuff would be field work, things like thin Alum. cowlings on Peterbuilts to 5/8" thick truck frames. There would be some occasional winery work which is where I thought the HTP 201 would really shine and pay for itself quickly. I really didn't think DCEN+He was such a good idea in my case either , but I had to ask someone who has experience with that process.
I did mention the machine's I've used before, but my experience with them and the shops I'd worked at only required the use of Argon. I haven't used Helium in any of the processes. When would using He help me? From my understanding, it will help to give a hotter arc thereby giving more penetration and/or allow for faster travel speeds and possibly a narrower bead. Is this it's primary use? Are there any other reasons for using He and would He have these same benefits or even work well when used in a m.i.g. process such as with the cobramatic?

Thanks again
Parent - - By Lawrence (*****) Date 07-30-2005 11:01

You have your theory down pat.

Biggest benefit from Helium comes when increased production speed turns into dollars. (not often the case in field repair) Also Helium can be a help if your GTAW powersource is at its maximum range and you appear to be a few amps short. A 50/50 Ar/He mixture can get you over the hump on a thick section or if your pre-heat begins to fade.

Helium is expensive and must be run a a much higher flow rate. Nice to have but not a requirement for most field work.
Parent - By Dr. D (*) Date 07-31-2005 04:41
Thanks for your insight Lawrence and 357MAX.
Much appreciated.

Dr. D
- By Chris Puckett Date 10-01-2019 19:12
Good day all,

I have a HF-251,
I have a question if anyone might know,

The pot that increases or decreases frequency is graduated from 0 to 100
but it really gives no indication what hz your are welding at
dose anyone know the layout?
Up Topic Welding Industry / Technical Discussions / HF-251 Freq. inducer

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