The tool center point is the exact spot on a robot's tool that it actually controls and moves — the tip of the welding torch or the center of the gripper — and defining it correctly is fundamental to making a robot go precisely where you mean.
The tool center point is the working tip of whatever tool a robot is holding — the end of the glue nozzle, the center of the gripper's grasp. It's the point the robot's commands actually refer to, so it must be defined accurately.
When you tell a robot to "move to this point," which part of it goes there? Not the base, not the wrist — the working tip of its tool. That point is the tool center point, and getting it right is a quiet fundamental of every robot program.
What it is
The tool center point (TCP) is the reference frame at the functional tip of the end-effector — the tip of a welding torch, the nozzle of a dispenser, the center of a gripper's grasp, the point of a probe. It's defined relative to the robot's wrist flange. Every motion command, taught point, and path the robot follows is expressed in terms of where the TCP should be and how it should be oriented — not the arm's joints or flange.
The point the robot actually controls
Forward kinematics gives the flange pose; adding the tool's offset gives the TCP — the point paths and commands are really about.
Why defining it correctly matters
Accuracy. If the TCP is set wrong (wrong offset from the flange), the robot puts the tool tip in the wrong place — the weld misses the seam, the glue lands off-target. Even a few millimeters of error ruins precision work.
Reorientation about the tip. A correct TCP lets the robot rotate the tool about its working point — e.g. tilt a welding torch while keeping the tip on the seam. With a wrong TCP, rotating swings the tip away.
Path programming. Paths (a weld line, a glue bead, a cutting contour) are defined for the TCP, so it must correspond to the real tool tip.
Setting it up
Defining a TCP means measuring the tool's offset and orientation from the flange. This is often done by calibration: touch the tool tip to a single fixed point from several different arm orientations, and the robot solves for the offset that keeps that tip stationary (the "4-point" or "N-point" method). The TCP is then stored and used for all motion.
Why it matters
The tool center point is the bridge between a robot's mechanics and the task — it's the point the whole system is really trying to control. Defining and calibrating it accurately is a basic, essential step in deploying any robot that uses a tool, from welding to dispensing to assembly.
