- TIG
Understanding the Advanced AC & DC TIG Programs on UNIMIG Machines
Sarah Mazlin
10 October 2022
Not every TIG welder is the same. Some have only lift arc DC TIG with the most basic functionality. Others are high-frequency AC/DC TIG machines that come filled with advanced programs that can be used to customise a weld.
UNIMIG have a range of TIG welders that include basic lift arc to professional grade, packed full of these specialty features. Each program allows for specific and unique control over a weld, so you have complete control.
Speed Start (DC only)
The Speed Start program speeds up the formation of the weld puddle. When turned on, it applies a synergic pulse program to the beginning of the weld. It can be set to run between 0 seconds to 60 seconds. When the time runs out, the machine will switch back to the standard parameters set for your TIG weld.
The initial pulse that is set works to create the weld pool much faster than a standard start, as the vibration of the pulse speeds up the melting of the joint edges for quicker puddle formation.
It can be used to make faster tacks, or it can be used when stitch welding on thinner materials, as it reduces the heat in the metal, so you can stitch for longer. It is recommended for use on sheet metal and fit ups with small gaps.
It is called SpotPlus on the RAZOR MULTI 230 AC/DC.
Steady Arc (DC only)
The Steady Arc program automatically adjusts the welding amperage based on the arc voltage, which corresponds to the arc length. As the distance between the torch and the workpiece changes, so does the voltage.
If the arc length (and therefore voltage) decreases, the machine increases the amperage, and if the arc length (and voltage) increases, the machine decreases the amperage.
When welding, holding a short arc length will provide a narrow weld pool. Adjusting the arc length to be longer will widen the weld pool, which increases your heat input into the base plate.
With Steady Arc, when the length of the arc changes and the voltage fluctuates, the amperage is adjusted accordingly. That means the size of the weld puddle remains the same, as does the heat input, which impacts the weld penetration.
When the torch is held close to the workpiece, the voltage decreases. Steady Arc increases the amperage, ensuring the heat input remains sufficient to maintain penetration.
When the torch is held further away from the workpiece, the voltage increases. Steady Arc decreases the amperage to prevent excessive heat input in the weld.
By adjusting the amperage according to the fluctuations in voltage, you get a consistent weld puddle, a sharper and more stable arc, and a constant heat input. It also means you have more control over the weld when in awkward positions, and maintaining a consistent arc length is difficult.
It also lets you weld with a very short arc. The closer the tungsten gets to the workpiece, the more it increases the amperage, which prevents contact between the two and stops the tungsten from sticking or becoming contaminated.
You can set how sensitive the machine is to changes in arc voltage, for example, from 1A to 50A. This means you can set it so that for every 1-volt variation, the machine changes the welding amperage anywhere from 1A to 50A.
If you set the sensitivity to 50A per 1 volt, this means that if the arc voltage drops by 1 volt, the welding current will increase by 50A.
Setting the sensitivity higher means there will be bigger changes in the amperage with each change in voltage. Even small adjustments in the torch position and arc length will result in changes to the welding amperage, and the arc is more responsive to changes.
Setting the sensitivity lower means there will be smaller changes in the amperage with each change in voltage. Adjustments in the torch position and arc length will result in more subtle changes to the welding amperage, and the arc is less responsive to minor variations.
It is called ArcPlus on the RAZOR MULTI 230 AC/DC.
TackPlus (DC only)
The TackPlus program is a tack welding program with a preset weld time and adjustable frequency (0-6Hz) to create evenly spaced and sized fusion tack welds along a joint with minimal heat input.
You can adjust how often the tacks will occur, and the program will run until the torch trigger is released. The set amount of time for each tack means a filler rod can’t be used with this program, so it is mostly recommended for thin sheet metal. It minimises warping and other plate distortion that can occur on thin materials.
Amplitude Control (AC only)
The Amplitude Control program allows for a more penetrative weld in AC. It works by adjusting the percentage of the AC waveform that is on the negative side. Here, zero is a 50/50% AC waveform with equal amounts of EN and EP—a standard AC weld cycle.
By increasing the percentage of electrode negative, more heat is transferred to the base plate, allowing for greater penetration, a narrower arc and less cleaning (or ‘pickling’) around a weld. The increased EN percentage also allows for faster weld speeds and metal deposition.
By decreasing the electrode positive percentage, the amount of heat in the tungsten is reduced, so your tungsten won’t ball up or deform as quickly. You’ll also be able to use smaller-sized tungsten electrodes for the same job, as the heat is off the tungsten and is precisely directed into the weld.
The narrower arc and greater penetration that the Amplitude Control provides means that you can weld on thinner materials with ease. However, it’s not recommended on thicker materials as the reduction of the EP percentage won’t provide enough cleaning of the oxide layer during a weld.
It is called FusionPlus on the RAZOR MULTI 230 AC/DC.
Mixed AC/DC TIG
Mixed AC/DC welding is the combination of AC TIG and DC- TIG in one weld. There are two periods during a mixed weld. The first is the AC period, where the oxide film is broken, and surface impurities are flushed out. The second, the DC- period, is where the arc becomes narrower and penetrative, with higher heat inputs.
It allows for enhanced control over the welding process, particularly when welding materials that require both cleaning and deep penetration, such as aluminium.
There are quite a few benefits from this type of weld, including higher welding speeds and penetration, so you can weld on thicker materials and a faster weld puddle on cold workpieces.
For example, if you’re trying to weld 10mm thick aluminium. This can be difficult with a standard 200A machine as there’s not enough penetration with limited heat input.
Using the Mixed AC/DC feature would allow you to weld these thicker materials effectively without needing to purchase a helium gas mixture.
You can adjust the percentage of AC compared to the DC- during a full cycle from 0-80%. By adjusting this to 70%, you’ll spend 70% of the complete cycle in the AC period and 30% in the DC- period.
It’s a good idea not to have more than 50% DC-, as it could reduce the cleaning of the oxide layer by too much.
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