Machine Setup: Polarity, AC Balance Concepts, and Amperage Ranges for Beginners

What the Machine Is Really Controlling

Your TIG machine mainly controls where the heat goes (polarity and AC settings) and how much heat you deliver (amperage). Everything else you do—torch angle, travel speed, filler timing—works best when these two are set in a sensible starting zone.

Polarity and Heat Distribution (Why It Matters)

In TIG, the direction of current flow changes how heat is split between the tungsten and the workpiece. Think of polarity as choosing whether the workpiece gets the majority of the heat (good for penetration and tungsten life) or whether more heat is forced toward the tungsten (which can reduce penetration and overheat the electrode).

• DCEN (Direct Current Electrode Negative): most heat goes into the workpiece. This is the default for steel and stainless because it provides strong penetration and keeps the tungsten cooler and stable.
• AC (Alternating Current): current alternates direction. This is the default for aluminum because it can provide both penetration and a surface “cleaning” effect that helps deal with aluminum oxide during welding.

Practical takeaway: if you choose the wrong polarity, you can get symptoms like a wandering arc, a tungsten that overheats or balls unpredictably, or a puddle that won’t form the way you expect—even if your torch technique is decent.

DCEN Setup for Steel and Stainless (Beginner Focus)

Why DCEN Works Well Here

Steel and stainless do not require the same oxide-cleaning action that aluminum does. With DCEN, you get a tight, controllable arc and efficient heating of the base metal—useful for learning puddle control without fighting unnecessary variables.

Amperage: Your Primary Heat Input Knob

Amperage is the main control for how quickly you can establish and maintain a weld puddle. More amps generally means:

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• Faster puddle formation
• More penetration potential
• Higher risk of burn-through on thin material
• More distortion and a wider heat-affected zone if you linger

Less amps generally means:

• Slower puddle formation (you may feel like you’re “waiting”)
• Less penetration
• Higher chance of a tall, ropey bead if travel speed is too slow
• More sensitivity to poor fit-up (gaps become harder to bridge)

Starting Amperage Ranges (DCEN Steel/Stainless)

Use these as starting points, not rules. Joint type (butt vs fillet), edge prep, fit-up, and how much heat is sinking away (large plate vs small coupon) can shift your needed amperage significantly.

Caveat examples:

• A tight, well-fit butt joint on 1.6 mm may weld nicely at 50–60 A, while the same thickness with a visible gap may need higher peak amps (and better technique) to avoid underfill.
• A small coupon heats up quickly; on a long bead you may need to reduce amperage as the part gets hotter.

AC Setup for Aluminum (Beginner Focus)

Why Aluminum Usually Uses AC

Aluminum forms a tough oxide layer that melts at a much higher temperature than the aluminum underneath. AC helps by alternating between:

• Penetration-focused heating (driving heat into the base metal)
• Surface cleaning action (helping disrupt/remove oxide so the puddle wets out)

Beginner goal: set AC so the puddle forms smoothly and wets the toes without looking dirty or “scummy,” while still achieving enough penetration for the joint.

AC Balance (Concept and Outcomes)

AC balance adjusts the proportion of the AC cycle that favors cleaning action versus penetration. Different machines display this differently (percent cleaning, percent electrode negative, etc.), but the practical effects are consistent:

• More cleaning: better oxide disruption and a more visibly “etched” zone next to the bead, but typically less penetration and more heat stress on the tungsten.
• More penetration: tighter, hotter puddle into the base metal with less cleaning action; if set too far this way, the puddle may look dirty and resist wetting.

Beginner-friendly approach: start near a middle setting recommended by your machine’s default AC program, then adjust based on what you see:

• If the puddle looks contaminated, grainy, or refuses to wet out at the edges despite good cleaning and gas coverage, increase cleaning slightly.
• If the tungsten is overheating or the bead is wide and shallow, reduce cleaning (favor penetration) slightly.

AC Frequency (Concept and Outcomes)

AC frequency changes how often the current alternates per second. You don’t need the electrical theory to use it effectively; focus on arc shape and control:

• Lower frequency: a wider, softer arc. This can feel more forgiving on broader joints but may reduce precision.
• Higher frequency: a tighter, more focused arc. This can improve control on corners, fillets, and thin edges, and can help direct heat more precisely.

Beginner-friendly approach: start with a moderate frequency. If you struggle to keep the arc from washing too wide, increase frequency. If the arc feels overly narrow and you’re not getting good sidewall wetting, reduce frequency.

Starting Amperage Ranges (AC Aluminum)

Aluminum often needs more amperage than steel at the same thickness because it conducts heat away quickly. Use these as starting points and be ready to adjust for part size (heat sink), joint type, and preheating practices (if used in your shop).

Caveat examples:

• A small 1.6 mm aluminum coupon may weld at 80–90 A, but a large 1.6 mm panel can feel like it “won’t puddle” until you increase amperage because the panel pulls heat away.
• A fillet weld on aluminum often needs more amperage than a butt joint on the same thickness because you’re heating two members at once.

Practical Step-by-Step: A Beginner Machine Setup Workflow

Use this checklist each time you start a new practice session. It keeps you from chasing problems that are actually setup-related.

Step 1: Identify the Material and Thickness

• Confirm whether you’re welding steel/stainless or aluminum.
• Measure thickness (calipers are ideal). If you can’t measure, compare to known samples.
• Note joint type: butt, lap, or fillet. (Fillets and laps usually need more heat.)

Step 2: Choose Polarity / Mode

• Steel/Stainless: set to DCEN.
• Aluminum: set to AC.

Step 3: Choose a Conservative Starting Amperage

• Pick a value from the tables above based on thickness.
• If the joint is a fillet/lap, start toward the higher end of the range.
• If fit-up is poor (gap), expect to adjust and consider improving fit-up rather than only adding amps.

Step 4: AC-Only Adjustments (Aluminum)

• AC balance: start near the middle/default. Increase cleaning only if the puddle won’t wet out cleanly; decrease cleaning if tungsten is overheating or bead is wide/shallow.
• AC frequency: start moderate. Increase for a tighter, more precise arc; decrease for a wider arc if you need broader coverage.

Step 5: Select Tungsten Size (Rule-of-Thumb)

Choose tungsten size based on the amperage you expect to use. Oversizing is usually safer for beginners (less overheating), but too large can make it harder to focus heat on very thin work.

• Up to ~70 A: small tungsten (commonly 1.6 mm / 1/16 in)
• ~70–150 A: medium tungsten (commonly 2.4 mm / 3/32 in)
• Above ~150 A: larger tungsten may be needed depending on your setup

Keep in mind: tungsten preparation and type were covered elsewhere; here you’re simply matching size to expected heat load.

Step 6: Cup Selection (Coverage vs Access)

Choose a cup that provides adequate shielding coverage while still fitting the joint access:

• Larger cup: more forgiving shielding coverage, helpful on open joints and practice beads.
• Smaller cup: better access in tight corners, but less forgiving if your torch angle or stickout varies.

If you’re learning, start with a medium-to-larger cup that fits the joint comfortably, then downsize only when access demands it.

Step 7: Set Gas Flow (Quick Starting Targets)

Use a stable, moderate flow that matches cup size and draft conditions. As a practical starting point:

• Typical indoor practice: about 12–18 CFH (or roughly 6–9 L/min)
• If you use a larger cup or have more stickout, you may need slightly more flow.
• If you hear turbulence or see inconsistent shielding symptoms, reduce flow slightly and verify torch angle and stickout.

Shielding gas principles were covered earlier; this is simply a reusable starting target for setup.

Reusable Setup Template (Fill This In Before You Strike an Arc)

Material: ____________________________  (steel / stainless / aluminum)  Thickness: ____________  Joint: ____________ (butt/fillet/lap) Polarity / Mode: _____________________  (DCEN for steel/stainless, AC for aluminum) Tungsten size: _______________________  (match to expected amps) Cup size: ____________________________  (coverage vs access) Gas flow: ____________________________  (start ~12–18 CFH / 6–9 L/min indoors) Initial amperage: _____________________  (use thickness table; adjust for joint & heat sink) AC only (aluminum):   AC balance: ________________________  (start mid/default; tune for cleaning vs penetration)   AC frequency: _______________________  (start moderate; tune for arc width/precision) Notes (fit-up, heat sink, clamp mass): _____________________________________________