Certified Robotic Arc Welding (CRAW) cheat sheet

GMAW: electrode positive (DCEP) for spray/short-circuit; DCEN rarely used for special cases.

GTAW: DCEN for steel; AC for aluminum to break oxide; DCEP balling but limited thickness.

Shielding gas flow: 10-20 CFH (GMAW), 15-25 CFH (GTAW); too high causes turbulence and porosity.

Contact tip to work distance (CTWD): 1/4-1/2 in (6-13 mm) for short-circuit; 1/2-3/4 in for spray.

Wire feed speed (WFS) sets current in GMAW; voltage sets arc length; adjust one at a time.

Polarity: DCEP = electrode positive, more penetration; DCEN = electrode negative, less penetration, faster melt-off.

Gas hoses: use correct fittings (CGA); never use oil on oxygen regulators; purge lines before use.

Work clamp must be on clean bare metal, as close to weld as possible to minimize resistance.

SMAW: electrode coating provides shielding gas and slag; E6010 deep penetration, E7018 low hydrogen.

GMAW transfer modes: short-circuit (thin), globular (unstable), spray (high current, argon-rich), pulsed (controlled).

FCAW: self-shielded (no external gas) vs gas-shielded (CO2 or mix); higher deposition than SMAW.

GTAW: non-consumable tungsten electrode; filler added separately; cleanest arc, slow.

SAW: granular flux blanket; high deposition; used for thick sections; only flat/horizontal.

Plasma arc: constricted arc, higher energy density than GTAW; keyhole mode for thicker plate.

Oxy-fuel: fuel gas (acetylene, propane) + oxygen; neutral, oxidizing, carburizing flames.

Resistance welding: heat = I²Rt; pressure and current time critical; spot, seam, projection.

VT: surface defects only; requires good lighting, magnification, and trained eye.

PT: detects surface-breaking defects in nonporous materials; clean before and after.

MT: detects surface and near-surface defects in ferromagnetic materials; use AC or DC yoke.

UT: detects internal defects; requires couplant; cannot easily detect planar defects parallel to sound beam.

RT: detects internal volumetric defects; safety radiation controls; film or digital.

Acceptance criteria: compare indications to code (e.g., AWS D1.1) size and type limits.

Phased array UT and TOFD: advanced UT for better imaging and sizing.

Leak testing: bubble, pressure change, halogen, mass spectrometer; for sealed vessels.

Weld joint types: butt, lap, T, corner, edge; groove types: V, U, J, bevel.

Weld positions: 1F/1G flat, 2F/2G horizontal, 3F/3G vertical, 4F/4G overhead.

Penetration: depth of fusion into root; incomplete fusion/penetration are defects.

Heat input (J/in) = (voltage × current × 60) / travel speed (in/min).

Preheat: raises base metal temperature to slow cooling, prevent cracking.

Interpass temperature: maximum allowed between passes to avoid property loss.

Duty cycle: percentage of 10-minute period a machine can operate at rated output.

Arc blow: magnetic deflection of arc; mitigate with shorter arc, tack welds, ground position.

Reference line: horizontal line; arrow side = below line, other side = above line.

Fillet weld symbol: right triangle; size on left, length on right, pitch after length.

Groove symbols: V, bevel, U, J; included angle shown above symbol.

Supplementary symbols: weld-all-around (circle), field weld (flag), tail for process spec.

Robot path symbols: linear, circular, joint; approach and depart points.

Tool center point (TCP) must be defined; coordinate frames: base, tool, work object.

Weld symbol with number in tail: process reference (e.g., 135 = GMAW per ISO).

All-around symbol means weld continues around entire joint perimeter.

Arc eye (UV keratitis): wear ANSI Z87.1+ safety glasses and correct shade lens (e.g., shade 10-13).

Fumes: use ventilation or respirator; keep head out of plume; manganese and hexavalent chromium hazards.

Electric shock: dry gloves, insulated electrode holder, never weld in wet conditions; check ground.

Fire: 35 ft clearance from combustibles; fire watch for 30 min after hot work; hot work permit.

Compressed gas cylinders: secure upright, cap when moving, keep away from heat, no oil on oxygen.

Noise: use hearing protection when >85 dBA; plasma cutting and chipping are loud.

Confined space: test atmosphere (O2 19.5-23.5%), ventilation, attendant, permit.

Robots: teach pendant in hand during programming, reduced speed, safety fence and interlocks.

Tensile test: measures ultimate strength, yield, elongation; specimen per code.

Bend test: root, face, side bends; evaluates ductility and fusion; bend radius and angle specified.

Impact test (Charpy V-notch): toughness at temperature; energy in ft-lb or J.

Hardness test: Rockwell, Brinell, Vickers; check HAZ for cracking susceptibility.

Macro etch: cross-section reveals penetration, fusion, inclusions; acid etch.

Micro etch: grain structure, phase identification; microscope.

Nick break: breaks weld to reveal internal defects; used for qualification.

Fillet weld break: fracture along throat to inspect fusion; simple shop test.

1 inch = 25.4 mm; 1 mm = 0.03937 in; 1 lb = 0.4536 kg; 1 kg = 2.2046 lb.

Heat input (kJ/in) = (V × A × 60) / (1000 × travel speed in/min).

Travel speed (in/min) = (V × A × 60) / (1000 × heat input kJ/in).

Deposition rate (lb/h) = 13.1 × (wire feed speed in/min) × (wire cross-section in²) × efficiency.

Gas flow: 1 CFH = 0.472 L/min; 1 L/min = 2.12 CFH.

Temperature: °F = (°C × 9/5) + 32; °C = (°F - 32) × 5/9.

Current density = current / electrode cross-sectional area (A/in²).

Duty cycle: allowable current = rated current × sqrt((rated duty cycle)/(desired duty cycle)).

Program structure: main routine calls subroutines; use modular programming.

Motion types: joint (fastest, not straight), linear (straight, controlled speed), circular (arc through 3 points).

I/O signals: digital (on/off), analog (0-10V or 4-20mA), group signals for handshaking.

Wait statements: wait for input, wait time, wait distance; used for synchronization.

Interlocks: prevent motion until conditions met (e.g., part present, gas on).

Program offsets: use offset function for part variation; shift frames.

Error handling: recover from arc loss, collision, or wire stick; use fault routines.

Simulation: verify reach, cycle time, and collisions before running on real robot.

WPS (Welding Procedure Specification): documents variables (process, filler, current, voltage, speed, gas).

PQR (Procedure Qualification Record): test results proving WPS produces sound weld.

Essential variables: change requires requalification (e.g., process, filler classification, polarity, thickness range).

Preheat and interpass: specified in WPS; measure with thermometer or crayon.

Root pass: often different process/consumable; ensure penetration and prevent cracking.

Post-weld heat treatment (PWHT): relieves stress, temp and time per code.

Qualification ranges: thickness, position, and diameter ranges per code (e.g., AWS D1.1).

Welder qualification: performance test; essential variables for welder differ from WPS.

Degrees of freedom (DOF): number of independent motions; 6-DOF typical for full pose.

Joint types: revolute (rotation), prismatic (linear); robot axes: J1-J6.

Forward kinematics: joint angles → Cartesian position; inverse kinematics: Cartesian → joint angles.

Singularity: configuration where robot loses DOF (e.g., wrist alignment); avoid in programming.

Workspace: reachable volume; consider tool and part orientation.

Coordinate frames: base, world, tool, user (work object); transformations between frames.

TCP (Tool Center Point): point at end of tool; define via 4-point or 6-point method.

Payload and inertia: must not exceed robot rating; affects accuracy and speed.

Robot arm: 6-axis articulated; controller; teach pendant.

Power source: synergic or pulse capable; interface to robot via I/O or bus (DeviceNet, EtherNet/IP).

Wire feeder: push-pull or push-only; mounted on robot arm or boom.

Torch: air-cooled or water-cooled; collision clutch (breakaway) to protect robot.

Gas system: regulator, flowmeter, solenoid valve, mixer for blends.

Positioner: rotates/tilts part to optimize weld position; coordinated with robot.

Safety: light curtains, fences, door interlocks, e-stops, safety-rated scanner.

Fixtures: locate and clamp parts repeatably; grounding to fixture, not robot.