Miller’s New TIG Inverters Maximize Productivity Through Advanced Waveshaping, Pulsing Controls


Both machines produce an output of 500 amps/40 V at 100 percent duty cycle, weigh 198 lbs. and feature Miller’s unique Auto-Line™ power management technology. The Dynasty 700 provides an AC/DC welding output, while the Maxstar provides a 700 DC-only output and costs slightly less.

Miller specifically designed these innovative power sources for precision metal fabrication, heavy manufacturing (high-speed and/or high-amperage), pipe and tube mills, process piping, tool and die, aerospace and automated TIG applications. They replace the Aerowave®, Syncrowave® 500 and older TIG products with more efficient, state-of-the-art inverter technology.

“The Dynasty 700 and Maxstar 700 produce an unmatched payback and return on investment when used in the right applications. For example, tube mills may be able to increase travel speed by 30 percent or more,” says John Luck, product manager, Miller Electric Mfg. Co.

Advanced AC Controls

The Dynasty 700 features advanced AC squarewave technology that enables tailoring the arc to address the need of welding aluminum and magnesium, as well as highly alloyed metals (INCOLNEL®, MONEL®, etc.) that benefit from AC “cleaning” action in severe-duty applications. Dynasty 700 capabilities include:

• Independent AC amperage control that allows independently setting the electrode negative (EN) and electrode positive (EP) amperage values. More current in EN than in EP produces deeper penetration and faster travel speeds with minimal cleaning action and less heat on the tungsten, which in turn may permit using a smaller diameter tungsten to further narrow bead profiles.

• Four AC waveshaping options to optimize arc characteristics for various applications and operator preferences. Depending on the waveform selected—advanced squarewave, soft squarewave, sine wave and triangular wave—users can tailor the arc for such characteristics as a hard, driving arc, a smooth, soft arc with good puddle control and wetting action, or a punch of peak amperage with minimized overall heat input to reduce distortion.

• AC balance control of 30 to 99 percent EN. Less EN increases cleaning action and produces a wider bead with less penetration. More EN reduces tungsten balling, helps maintain a pointed tungsten, increases penetration and minimizes cleaning lines.

• AC frequency control of 20 to 400 Hz (cycles per second). Increasing frequency to 120 Hz or more produces a narrower weld bead, which can substantially increase travel speed on fillet welds and in automated applications. [Conventional TIG technology is limited to a fixed frequency of 60 Hz.]

• Average AC amperage control, which allows adjusting the average amperage for different applications while maintaining other weld parameters.

“Achieving maximum productivity often depends on the inverter’s ability to produce a weld bead profile and characteristics that meets the application needs without over-welding, under-welding, excessive post-welding grinding or weld repair,” says Luck. “In critical or high-volume applications, only the advanced AC controls of an inverter like the Dynasty 700 provide this level of control.”

Perfecting Pulsed TIG

With the pulsed TIG process, the power source pulses between a high peak amperage and low background amperage. The Dynasty 700 and Maxstar 700 permit pulsing at DC TIG frequencies of 0.1 to 5,000 pulses per second (PPS) and AC TIG frequencies on 0.1 to 500 PPS. Further, they can control peak arc-on time from 5 to 95 percent (duration of each pulse cycle) and control background amperage from 5 to 99 percent of peak amperage.

“Applications that benefit most from pulsed TIG include automated welding, stainless steel, copper and highly-alloyed metals,” says Luck. “Good candidates for pulsed TIG include those where warping or distortion are issues, where increased puddle agitation improves grain structure and where increased arc focus can increase travel speeds.”

The Dynasty 700 and Maxstar 700 are the only inverters that permit pulsing at such extreme frequencies. In excess of 40 PPS, pulsed TIG increases puddle agitation for a better as-welded microstructure. Pulsing the current at high speeds (typically 100 to 500 PPS) also constricts and focuses the arc, which increases arc stability, penetration and travel speeds. The ability to pulse at frequencies up to 5,000 PPS further enhances arc stability and concentration potential, which is extremely beneficial in automated applications that require maximum travel speed.

A built-in sequence control allows users to pre-set the entire weld sequence for greater accuracy and repeatability, while a program memory allows storing four welding programs to minimize change-over time when switching between process and procedures.

The Dynasty 700 and Maxstar 700 feature Auto-Line technology, which enables them to accept any primary power from 208 V through 575 V (±10 percent), single- or three-phase, 50 or 60 Hz. Auto-Line can improve weld quality by compensating for voltage variations caused by large loads starting on the same line or utility “brownouts.” Other features include an automation interface kit (28-pin) for “plug and play” system integration and 115 V auxiliary power to operate a coolant system, grinder or other small power tools.

The Dynasty 700 and Maxstar 700 are covered by Miller’s True-Blue® three-year factory warranty.

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