Certified Robotic Arc Welding (CRAW) key terms

The percentage of a ten-minute period during which a welding power source can operate at a rated output without overheating. Exceeding it causes thermal protection to trip or shortens equipment life.

A power supply that holds amperage nearly steady while voltage varies with arc length. Used for stick and TIG welding, where the welder controls arc length manually.

A supply that maintains a set voltage while current changes with wire feed speed and arc length. This self-regulating behavior makes it standard for GMAW.

The volume of shielding gas delivered per unit time, usually set in cubic feet per hour or liters per minute. Too low allows atmospheric contamination; too high causes turbulence that draws air into the arc.

The distance from the end of the GMAW contact tip to the workpiece surface. It affects current, penetration, and arc stability, so it is held consistent in a qualified procedure.

The consumable copper-alloy tube at the end of a GMAW gun that transfers welding current to the electrode wire as it passes through. Wear enlarges the bore and degrades current transfer.

The rate at which filler wire is pushed into the arc, expressed in inches or meters per minute. On a constant voltage system it primarily determines welding current and deposition rate.

An arc process using a continuously fed consumable electrode wire shielded by an externally supplied gas. Often called MIG welding in shop practice.

A GMAW transfer mode in which the electrode touches the puddle, extinguishing the arc, then pinches off metal and re-establishes it. Produces low heat input, suited to thin sheet.

A high-current GMAW transfer mode in which fine molten droplets are propelled axially across the arc without shorting. Requires argon-rich gas and produces deep penetration with high heat input.

An arc process using a nonconsumable tungsten electrode with separately supplied filler and an inert shielding gas. Gives precise control on thin material and is common on aluminum and stainless.

The gap between the electrode tip and the molten weld pool. It governs arc voltage, arc width, and penetration, and must be held within the range set by the welding procedure.

The electrical potential across the welding arc, measured in volts. It varies with arc length and, in GMAW, is set on the machine to control bead shape and width.

The depth to which the weld metal extends into the base metal or a previous pass, measured from the original surface. It is a key fusion quality judged by examination.

A discontinuity in which weld metal fails to bond to base metal or to an earlier pass. Often caused by low heat input, poor angle, or travel speed that outruns the puddle.

Cavities formed by gas trapped in solidifying weld metal, appearing as rounded internal or surface voids. Causes include moisture, oil, drafts, and inadequate shielding gas coverage.

Sectioning a weld, polishing the cut face, and etching it to reveal the fusion boundary, penetration, and internal discontinuities at low magnification. A standard destructive test for procedure qualification.

A destructive test pulling a specimen until it fractures, reporting yield and ultimate strength and location of failure. Used to confirm a weld meets specified strength requirements.

A destructive test bending a specimen around a specified radius to reveal ductility and near-surface defects on the tension side. Root and face bends are typical qualification tests.

Energy delivered per unit length of weld, calculated as voltage times current times a process efficiency factor divided by travel speed. It strongly influences cooling rate and mechanical properties.

The rate at which the arc moves along the joint, expressed in inches or millimeters per minute. It affects bead size, penetration, and heat input per unit length.

The mass of filler metal deposited per unit time, commonly given in pounds or kilograms per hour. It rises with current and wire feed speed and drives productivity planning.

Heating the base metal to a specified temperature before welding to slow cooling, reduce hydrogen cracking risk, and improve fusion. Minimum values are set by the welding procedure.

A written document giving the ranges of variables such as process, current, voltage, travel speed, and preheat that a welder must follow to produce a compliant weld.

The record of actual variables used and test results obtained when qualifying a welding procedure. It supports the welding procedure specification and is retained as objective evidence.

A welding parameter that, if changed beyond the permitted range, requires requalification of the procedure because it can affect mechanical properties or soundness. Examples include process and heat input.

Welding a test coupon to the proposed parameters and subjecting it to destructive tests to prove the procedure produces sound welds meeting code requirements.

The point on a robot, usually the welding wire tip, whose position and orientation the controller coordinates. All programmed frames are defined relative to it.

A coordinate system defined by the programmer relative to the workpiece or fixture, letting positions be taught in part coordinates rather than robot base coordinates.

A motion type in which each robot axis moves to its target independently, producing a fast but non-straight-line path. Used for travel between weld zones, not during welding.

A motion type that moves the tool center point along a straight path at controlled speed. It is the standard choice for welding a straight seam.

A programmed side-to-side oscillation of the torch across the joint during travel, used to fill wider gaps and control bead shape. Amplitude and frequency are set in the weld schedule.

The orientation of the welding gun relative to the joint, described as work and travel angles. It affects penetration, bead profile, and shielding gas coverage.

The number of independent motions a robot axis or manipulator can perform. A six-axis arm can position and orient the tool arbitrarily within its reach.

The three-dimensional volume the robot can reach with its tool center point. Parts and fixtures must be placed so every weld is inside it with acceptable orientation.

A robot configuration where two or more axes align, causing unpredictable or excessively fast axis motion near the path. Weld paths should be programmed to avoid passing through it.

Connecting the workpiece and equipment to earth to provide a safe return path for current. A poor work lead connection causes stray current, arcing, and shock hazard.

Local exhaust ventilation that captures welding smoke near the arc before it enters the welder's breathing zone. Required where ventilation alone cannot keep exposure below limits.

The cable connecting the welding power source to the workpiece, completing the circuit. It must be clamped close to the weld to prevent current traveling through fixtures or bearings.