Robot Programming and Logic
Robot Programming and Logic covers how motion, weld control, and cell logic combine in a robotic arc program. Items ask about motion types, point termination, frames, offsets, and the I/O handshake that actually starts and stops the arc.
Motion and points
- Joint interpolation moves all axes to a point without controlling the path; it is for air moves, not welding.
- Linear interpolation holds a straight TCP path; circular interpolation needs three points. Weld segments are almost always linear or circular.
- Termination, or zone, decides how closely the robot passes through a point. Fine termination stops at the point and is used where geometry matters; a coarse zone rounds the corner and shortens cycle time but changes path and heat input at that corner.
- Speed is programmed as TCP speed on linear and circular moves.
Frames and offsets
- The tool frame defines the TCP. Change the torch or contact tip position and every welding point moves.
- The user or work object frame defines the part. A fixture shift is corrected with a frame update or an offset, not by retouching dozens of points.
Weld start and stop logic
A typical sequence: gas pre-flow, wire feed start, arc establish with a start delay to build the puddle, motion, crater fill, burn-back, wire cut or retract, gas post-flow. Interlocks confirm gas flow, wire present, and no arc fault before motion is allowed. Arc recovery logic retries after a lost arc, and a retry limit prevents welding repeatedly over a bad start.
Worked example
A fixture is rebuilt and every part now sits 2 mm high. The program welds at a 12 mm CTWD and the arc starts stubbing. The height error is a frame error, so the fix is to update the work object or apply a Z offset to the weld routine; touching up each point fixes this batch and breaks the next. If the offset pushes CTWD outside the qualified range, the WPS is affected and the offset must be limited.
Traps
Welding with joint moves; a coarse zone at a corner that must stay sharp; forgetting that a tool frame change shifts every point; assuming program override changes weld parameters when it actually changes travel speed and therefore heat input.