How to Use This Vocabulary
When you read a welder’s front panel, a spool label, or a setup chart, you’re mostly translating a few core variables into what you can see and hear at the arc. For each term below, you’ll get: (1) what it means, (2) what you can observe or adjust, and (3) what it commonly looks like when it’s wrong.
| Category | Terms you’ll see on machines/labels | Terms you’ll see in weld results |
|---|---|---|
| Machine settings | Amperage, Voltage, Wire Feed Speed, Polarity, Duty Cycle | Spatter, Porosity, Undercut, Overlap |
| Technique | Travel Speed, Arc Length, Stick-out | Puddle, Fusion, Penetration |
| Consumables & gas | Electrode, Filler Metal, Contact Tip, Nozzle, Shielding Gas Flow Rate | Porosity, Spatter, Inconsistent bead |
Machine Controls and What They Really Do
Amperage (A)
Concept: Amperage is the amount of current flowing through the arc. In many setups it strongly influences how much heat is available to melt metal (especially in constant-current processes), and it affects how “forceful” the arc feels.
What you can adjust/observe: You may set amperage directly (some machines) or indirectly (e.g., via wire feed speed in many MIG setups). You can observe puddle size and how quickly edges melt.
When it’s wrong (typical symptoms):
- Too low: narrow, tall bead; poor fusion at the toes; puddle looks sluggish; arc may stutter; bead may sit “on top.”
- Too high: overly fluid puddle; edges wash away; increased spatter; risk of undercut or burn-through on thin material.
Voltage (V)
Concept: Voltage is closely tied to arc length and arc “spread.” Higher voltage generally makes a longer, wider arc; lower voltage makes a tighter, shorter arc.
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What you can adjust/observe: Set on the machine (often a knob or digital setting). Observe arc sound, bead width, and how flat the bead lays.
When it’s wrong (typical symptoms):
- Too low: harsh, tight arc; bead can be ropey and narrow; more spatter; arc may “stub” into the puddle.
- Too high: arc feels long and unstable; bead may be very wide/flat; increased spatter and risk of undercut; puddle can get hard to control.
Wire Feed Speed (WFS)
Concept: How fast the wire is pushed through the gun. In many MIG-style setups, WFS strongly affects amperage because more wire requires more current to melt it.
What you can adjust/observe: Set on the machine. Observe whether the wire smoothly melts into the puddle or repeatedly “pushes” the gun back (stubbing).
When it’s wrong (typical symptoms):
- Too low: arc can feel hissy and inconsistent; wire may burn back toward the tip; bead may be narrow with poor fill.
- Too high: wire stubs into the work; gun may chatter; excessive spatter; bead can pile up if travel speed isn’t increased.
Travel Speed
Concept: How fast you move along the joint. Travel speed controls how much heat is put into each inch/mm of weld and how much filler is deposited per length.
What you can adjust/observe: You control it with your hands. Watch the puddle size and the bead profile behind it.
When it’s wrong (typical symptoms):
- Too fast: thin, narrow bead; underfill; poor fusion; “skipping” look; toes may not tie in.
- Too slow: overly wide bead; excessive reinforcement (too tall); risk of undercut from overheating edges; burn-through on thin stock.
Duty Cycle
Concept: How long a machine can weld in a given time period at a stated output before it must cool. Often expressed like 30% @ 200A (meaning 3 minutes welding, 7 minutes cooling, at that output).
What you can adjust/observe: You don’t “turn” duty cycle up; you manage it by lowering output, welding in shorter bursts, or allowing cooling time. Observe thermal overload lights or the machine stopping output.
When it’s wrong (typical symptoms):
- Exceeding duty cycle: machine shuts down or output drops; you may notice inconsistent arc as the machine heats up; you’re forced into long pauses.
Polarity (DCEP / DCEN)
Concept: Polarity describes which terminal is positive and which is negative in DC welding. DCEP means electrode positive; DCEN means electrode negative. Polarity affects arc characteristics, penetration profile, and how stable the process feels.
What you can adjust/observe: You can swap leads inside the machine (or at the terminals) if your machine allows. Always match polarity to the wire/electrode manufacturer’s recommendation.
When it’s wrong (typical symptoms):
- Wrong polarity for the consumable: harsh, unstable arc; excessive spatter; poor penetration or poor bead shape; wire may not run smoothly.
Consumables and Front-End Parts (What’s in Your Hand)
Electrode
Concept: The electrode is what carries current to the arc. Depending on the process, it may be a wire (fed continuously) or a rod. Some electrodes also provide shielding or add alloying elements.
What you can adjust/observe: You choose the type and size. Observe arc stability and whether the electrode feeds/melts consistently.
When it’s wrong (typical symptoms):
- Wrong type/size: difficult starts; unstable arc; poor bead profile; increased spatter; inability to achieve proper fusion at reasonable settings.
Filler Metal
Concept: Filler metal is the material added to the joint to form the weld bead. In many setups the electrode is also the filler (wire/rod), but the key idea is: filler must match the base metal and the job requirements.
What you can adjust/observe: Choose filler classification and diameter. Observe whether the bead wets in smoothly and whether it cracks or looks contaminated.
When it’s wrong (typical symptoms):
- Mismatched filler: poor wetting; unusual bead appearance; cracking risk; inconsistent puddle behavior; weak joint performance.
Contact Tip
Concept: The contact tip transfers electrical current to the wire and guides it out of the gun. Tip size must match wire diameter.
What you can adjust/observe: You can replace it and ensure correct size and tightness. Observe feeding smoothness and whether the arc wanders.
When it’s wrong (typical symptoms):
- Worn/oversized tip: arc becomes inconsistent; wire may wander; spatter increases; bead becomes erratic.
- Tip too small or damaged: wire feeding problems; wire can seize; burn-back (wire fuses to tip).
Nozzle
Concept: The nozzle directs shielding gas around the arc and helps protect the puddle from the air. It also collects spatter over time.
What you can adjust/observe: You can clean or replace it. Observe gas coverage consistency and whether spatter is clogging the opening.
When it’s wrong (typical symptoms):
- Spatter-clogged nozzle: poor gas coverage; porosity; erratic arc; gas flow becomes turbulent.
- Wrong nozzle size/fit: inconsistent shielding; difficulty reaching into joints; more porosity in drafts.
Shielding Gas Flow Rate (CFH / LPM)
Concept: Shielding gas protects the molten puddle from oxygen and nitrogen in the air. Flow is commonly measured in CFH (cubic feet per hour) or LPM (liters per minute). More is not always better: too much flow can create turbulence and pull air into the shield.
What you can adjust/observe: Set on the regulator/flowmeter. Observe the sound of gas, check for leaks, and watch for porosity in the bead.
When it’s wrong (typical symptoms):
- Too low: porosity (pinholes); dull/sooty bead; unstable arc; oxidation discoloration.
- Too high: still can get porosity (turbulence); excessive gas use; arc area may feel “blown” and inconsistent in drafts.
Technique Terms That Change the Arc Immediately
Arc Length
Concept: The distance from the electrode tip/wire to the work (or puddle). Arc length influences voltage and arc stability.
What you can adjust/observe: You control it by hand position. Watch the gap and listen: a stable arc usually has a consistent sound.
When it’s wrong (typical symptoms):
- Too long: arc wanders; more spatter; wider bead; less consistent fusion; porosity risk increases.
- Too short: stubbing; wire can dip into puddle; erratic bead; possible lack of fusion if you’re constantly sticking and restarting.
Stick-out
Concept: The length of unmelted wire extending past the contact tip (for wire-fed welding). Stick-out changes electrical resistance heating of the wire and affects how the arc behaves.
What you can adjust/observe: You set it by how far the tip is from the work and how far the wire extends. Visually check the wire length before striking/starting.
When it’s wrong (typical symptoms):
- Too long: arc feels softer and less focused; more spatter; inconsistent penetration; bead can look cold and tall.
- Too short: harsh arc; increased heat at the tip; burn-back risk; contact tip overheats and wears faster.
Puddle
Concept: The puddle is the small pool of molten metal you’re controlling. Learning to “read” it is how you control bead shape and tie-in.
What you can adjust/observe: Observe puddle size, brightness, and how it wets into the edges (toes). Adjust travel speed, angle, and settings to keep it consistent.
When it’s wrong (typical symptoms):
- Puddle too small/cold: bead sits up; poor fusion; narrow bead.
- Puddle too large/hot: bead gets wide; edges wash out; undercut or burn-through risk.
Penetration
Concept: How deeply the weld melts into the base metal. Good penetration helps strength, but too much can cause burn-through on thin material.
What you can adjust/observe: Adjust heat input (amperage/voltage/WFS) and travel speed. Observe the backside (if accessible), bead profile, and how well the toes tie in.
When it’s wrong (typical symptoms):
- Too little: bead looks fine on top but can fail; toes may not blend; lack of fusion indications.
- Too much: burn-through; excessive melt-through; distortion increases.
Fusion
Concept: Fusion is the actual melting together of base metal and filler (and between passes). You can have a bead that “looks okay” but has poor fusion at the edges.
What you can adjust/observe: Watch the toes: they should blend smoothly into the base metal. Adjust travel speed, angle, and heat to ensure the edges melt and tie in.
When it’s wrong (typical symptoms):
- Lack of fusion: visible line at the toe; bead appears to sit on top; can chip off along the edge; failures often occur along the interface.
Common Weld Defects: What They Mean and What to Change
Undercut
Concept: A groove melted into the base metal alongside the weld toe that is not filled by weld metal.
What you can adjust/observe: Observe a channel along the bead edge. Adjust voltage, travel speed, and torch angle; sometimes reduce heat or slow slightly to fill the edges.
When it’s wrong (typical symptoms):
- Looks like: a sharp trench at one or both sides of the bead.
- Common causes: too hot (high voltage/amperage), too fast travel, poor angle, long arc.
Overlap (Cold Lap)
Concept: Weld metal rolls over onto the base metal without fusing properly at the toe.
What you can adjust/observe: Look for a rounded “lip” at the edge that doesn’t blend in. Adjust travel speed and heat; ensure you’re directing the arc to the leading edge of the puddle.
When it’s wrong (typical symptoms):
- Looks like: bead edge sitting on top with a visible line/shadow underneath.
- Common causes: too slow travel with insufficient heat for tie-in, wrong angle, puddle too big and pushing ahead.
Porosity
Concept: Gas pockets trapped in the solidifying weld. Often caused by poor shielding, contamination, or drafts.
What you can adjust/observe: Observe pinholes on the surface or worm tracks. Adjust gas flow, check nozzle cleanliness, reduce arc length, and ensure the joint is clean and dry.
When it’s wrong (typical symptoms):
- Looks like: small holes, craters, or pitted bead surface.
- Common causes: low/unstable gas flow, leaks, clogged nozzle, too long arc, dirty base metal, wind/drafts.
Spatter
Concept: Small droplets of molten metal that scatter and stick around the weld.
What you can adjust/observe: Observe BB-like dots around the bead and on the nozzle. Adjust voltage/WFS balance, arc length, stick-out, and ensure correct polarity and clean consumables.
When it’s wrong (typical symptoms):
- Looks like: lots of scattered metal droplets; noisy, harsh arc.
- Common causes: voltage too low for the WFS, long arc, wrong polarity, poor grounding, inconsistent stick-out.
Practical Step-by-Step: A Simple “Read the Bead” Check
Step 1: Set a baseline and run a short bead
- Choose a flat practice piece and run a bead long enough to see a pattern (not just a tack).
- Hold a consistent stick-out and arc length while you move at a steady travel speed.
Step 2: Inspect three zones
- Bead face: Is it smooth or full of spatter and pits (porosity)?
- Toes (edges): Do they blend in (good fusion) or show a groove (undercut) or a rolled lip (overlap)?
- Profile: Is it tall and ropey (often cold/fast) or very wide/flat (often hot/slow)?
Step 3: Make one change at a time
- If the bead is tall and narrow with poor tie-in: slightly increase heat input (amperage/WFS or voltage depending on your machine) or slow travel a bit.
- If the bead is washing out edges: reduce heat input or increase travel speed slightly.
- If you see porosity: verify gas flow rate, nozzle condition, and reduce arc length.
Mini-Exercises (Quick Checks)
Exercise 1: Match the symptom to the term
Match each symptom (A–H) to the correct term.
- A. A trench along the bead edge
- B. Rounded lip of metal sitting on the plate edge without blending
- C. Pinholes scattered on the bead surface
- D. BB-like metal dots around the weld
- E. Bead looks fine but chips off along the toe line
- F. Arc wanders and gets noisy when your hand lifts away
- G. Wire keeps “pushing” into the puddle and the gun chatters
- H. Machine stops output after a few minutes at high setting
Terms: undercut, overlap, porosity, spatter, lack of fusion (fusion), arc length, wire feed speed, duty cycle
Exercise 2: Pick the most likely adjustment
For each defect, choose the most likely first adjustment (you can have more than one correct, but pick the best first move).
| Defect you see | Best first adjustment | What you’re changing |
|---|---|---|
| Porosity starts suddenly mid-bead | Check nozzle for spatter blockage; verify gas flow rate | Nozzle / shielding gas flow rate |
| Excessive spatter with harsh arc | Shorten arc length; verify voltage/WFS balance | Arc length / voltage / WFS |
| Undercut on both sides | Slightly reduce voltage or slow down just enough to fill toes | Voltage / travel speed |
| Overlap (cold lap) at the toes | Increase travel speed slightly or increase heat to improve tie-in | Travel speed / amperage-WFS / voltage |
| Wire burn-back into the tip | Increase WFS slightly and/or increase stick-out consistency; replace tip if damaged | WFS / stick-out / contact tip |
| Arc is unstable and bead is inconsistent after a lot of welding | Pause to cool or reduce output | Duty cycle management |
Exercise 3: Two-setting diagnosis (voltage vs WFS)
You run a bead and get a lot of spatter plus frequent stubbing. Which is more likely: (1) WFS too high for the voltage, or (2) voltage too high for the WFS? Write your guess, then test by making one small change: either reduce WFS slightly or increase voltage slightly. Re-run a short bead and note whether the arc becomes smoother and the spatter decreases.
Quick Reference: What You Can Change vs What You See
| If you can change… | You’re mainly influencing… | Watch for… |
|---|---|---|
| Voltage | Arc length feel, bead width/flatness | Undercut (too high), ropey bead/spatter (too low) |
| WFS (often amps) | Deposition rate and heat demand | Stubbing/spatter (too high), burn-back/weak bead (too low) |
| Travel speed | Heat per length and bead size | Overlap (too slow), lack of fusion/undercut (too fast or too hot) |
| Gas flow rate | Shielding quality | Porosity (too low or turbulent too high) |
| Arc length & stick-out | Stability, spatter, penetration consistency | Wandering arc/spatter (too long), stubbing/burn-back (too short) |
| Polarity | Arc behavior and penetration profile | Harsh arc, spatter, poor penetration if incorrect |
