Symbols - Welding & Robotics
Symbols for welding and robotics tests whether you read a drawing correctly the first time, because a misread symbol on a robotic cell becomes a wrong program and a rejected part. The governing standard is AWS A2.4, with ISO 2553 in international work; the two differ in enough places to matter.
Anatomy of the symbol
- The arrow points to the joint; the arrow side is the side the arrow touches, the other side is opposite.
- The reference line carries the symbol; the tail carries process, procedure, or specification references such as GMAW and a WPS number.
- A circle at the junction means weld all around. A flag means field weld. Backing and spacer symbols sit above or below the reference line as required.
- Groove symbols show shape: V, bevel, U, J, flare-V, square. For a V groove the angle shown is the included groove angle; for a single bevel it is the included angle between the bevel face and the square face.
- Fillet symbols carry size to the left and length and pitch to the right, for example 1/4 with 6-12, meaning a 6 in weld on a 12 in pitch.
Reading order
- Arrow side or other side?
- Which symbol, and what size?
- Continuous or intermittent; length and pitch.
- Supplementary: all around, field, backing, contour.
- Tail: process, procedure, or note.
Robot-specific annotation
Robotic drawings often add information a standard symbol cannot carry: work angle, travel angle, push or drag direction, weave width and dwell, TCP reference, seam tracking requirement, and the robot job number in the tail. Treat those as binding requirements, not advisory notes.
Worked example
A symbol shows a fillet on the arrow side with size 5/16, length 8, pitch 16, a circle at the junction, and a tail reading GMAW, WPS-114. That reads as 5/16 in intermittent fillet welds, 8 in long on a 16 in pitch, arrow side, welded all around the part, by gas metal arc welding to that procedure. The robot program must therefore build a stitch pattern with matching on and off distances, not a continuous pass.