Willie B
Silver Member
I too just bought a Miller Dialarc HF 250,tig and stick machine. It is a 90 amp primary transformer machine. I haven't decided whether to hard wire or buy a huge outlet and plug with cord. I bought this monster because my new Diversion 180 has too small a duty cycle. Instead of turning off it tapers off on amperage. The Dialarc has a heat exchanger in the transformer, and a water cooled torch. I should be able to weld as long as I want. The HF is said to offer high frequency. If you think of the sine wave of 60 cycle ac current a full cycle begins at 0 voltage and current. as 1/60 of a second passes voltage will rise quickly, then level out, then fall again to zero, as the polarity, or direction of flow reverses it falls below the zero voltage line and in mirror image repeats ending a cycle at zero. Lets think of voltage as electrical pressure, An arc requires electrical pressure to ionize air. Ionized air conducts electricity far more easily. In sine wave machines the current or amperes pauses 120 times a second. In the simplest of DC machines flow of current in one direction is prevented leaving a pause of 1/120 of a second. Ionization is lost quickly. The arc must re establish. High frequency machines allow less time to loose the arc making the weld smoother. My concern with this machine is: A. Is the frequency high enough to be helpful? B. Is the lack of A.C. balance control going to interfere with cleaning action in welding aluminum?
Aluminum conducts heat away at an alarming rate. A precise, well focused arc is important welding aluminum. Aluminum oxidizes instantly on contact with air. Aluminum oxide film is thin and almost invisible. Aluminum melts at around 1200 degrees Fahrenheit, aluminum oxide at 2700 degrees. As soon as you clean it oxidation begins anew. We use ac for aluminum. During the electrode positive portion of a cycle electrons leap from the work to the electrode, (tungsten). This tends to blow away the oxide layer exposing the pure aluminum. As shielding gas is used no oxidation occurs. A dab of filler rod, and a miracle happens a weld begins to grow.
If we could see lightning in slow motion, its jagged path is caused by a series of steps, voltage,(pressure) builds, air is ionized current is established. It travels until its energy is too little to conduct through un ionized air, more electrons rush in to build voltage more air is ionized, more current! The human eye isn't quick enough to see these faltering steps. We see only the jagged path it follows. If current were not interrupted, it would move in a predictable straight line. High frequency power could establish a more nearly continuous path. To us this would mean a narrow arc, concentrating its heat on a narrow point more effectively blasting away oxide, melting workpiece metal in a narrower path wasting less energy, accomplishing the weld quickly before as much heat can conduct away from the weld.
The dialarc was state of the art in its day. Very expensive new machines offer inverter technology, square wave as opposed to sign wave current, adjustable frequency, adjustable ac balance.
How much you wanna spend?
Aluminum conducts heat away at an alarming rate. A precise, well focused arc is important welding aluminum. Aluminum oxidizes instantly on contact with air. Aluminum oxide film is thin and almost invisible. Aluminum melts at around 1200 degrees Fahrenheit, aluminum oxide at 2700 degrees. As soon as you clean it oxidation begins anew. We use ac for aluminum. During the electrode positive portion of a cycle electrons leap from the work to the electrode, (tungsten). This tends to blow away the oxide layer exposing the pure aluminum. As shielding gas is used no oxidation occurs. A dab of filler rod, and a miracle happens a weld begins to grow.
If we could see lightning in slow motion, its jagged path is caused by a series of steps, voltage,(pressure) builds, air is ionized current is established. It travels until its energy is too little to conduct through un ionized air, more electrons rush in to build voltage more air is ionized, more current! The human eye isn't quick enough to see these faltering steps. We see only the jagged path it follows. If current were not interrupted, it would move in a predictable straight line. High frequency power could establish a more nearly continuous path. To us this would mean a narrow arc, concentrating its heat on a narrow point more effectively blasting away oxide, melting workpiece metal in a narrower path wasting less energy, accomplishing the weld quickly before as much heat can conduct away from the weld.
The dialarc was state of the art in its day. Very expensive new machines offer inverter technology, square wave as opposed to sign wave current, adjustable frequency, adjustable ac balance.
How much you wanna spend?
