Tool center point, or TCP, is a defined reference associated with the working end of a tool. In CNC and robotics, the term appears in related but not identical control functions.
| Context | TCP role | Important distinction |
|---|---|---|
| Five-axis CNC | Control accounts for tool and rotary kinematics to follow the intended tool point | Not simply a spindle RPM or feed mode |
| Industrial robot | Tool reference pose relative to the flange | Includes orientation as well as position |
| Work / part frame | Locates the job in the machine or robot environment | Not the same as the tool frame |
| Payload data | Mass and center of gravity for robot dynamics | Not defined by TCP position alone |
Why an offset matters during rotation
Imagine a tool tip 100 mm from a rotation center. Rotating the assembly changes the tip location unless the other axes compensate. A simple 1° orientation change produces an arc length of about 100 × π/180 = 1.745 mm at that radius. Real multi-axis kinematics use the full geometry and coordinate transforms, not this single-radius illustration.
A wrong tool length or pivot calibration can therefore create position errors that change with orientation. A tool that appears correct at one pose may be wrong after the axes rotate.
Calibration is a controlled procedure
For a robot, define the intended tool reference and calibrate its position and orientation using the manufacturer’s method. Enter payload and center of gravity separately. For a CNC machine, use the approved tool measurement and rotary/pivot calibration procedures. Changing a holder, extension or tool can invalidate previous assumptions.
Check several orientations and the actual working region. A single touch-off is not a complete validation of a multi-axis model. Use appropriate safe-clearance and proving procedures; never test compensation by moving near a fixture without a verified setup.
TCP is not a universal G-code
Controllers use different functions, options and commands. Tilted-work-plane programming, tool-center-point control and inverse-time feed solve different problems. Read the exact machine-builder and controller documentation, and use a validated postprocessor. This guide explains concepts and intentionally does not provide a universal executable program.
Locate the frame before interpreting a TCP number
| Quantity | Question to answer | Example of a mismatch |
|---|---|---|
| Tool relative to flange | Where is the working point on the mounted tool? | A longer extension is installed but the old tool offset remains |
| Flange relative to base | Where has the robot moved the mounting face? | Joint motion is correct, but the wrong active tool is selected |
| Part relative to base/work frame | Where is the fixture and its datum? | The fixture moved although tool calibration did not change |
| Payload | What mass and center of gravity must the system handle? | Changing TCP position is mistaken for updating payload |
Consider a simplified two-dimensional teaching example: the flange origin is at (400,100) mm, and a tool point is 100 mm along the flange’s local X axis. At a 0° flange orientation, the point is (500,100). After a 90° rotation about the unchanged flange origin, it is (400,200). If the tool grows to 110 mm but its configured offset stays at 100 mm, the unmodeled 10 mm offset rotates with the tool. This is geometry, not a simulated robot program.
Two separate verification paths
Robot: use the manufacturer’s approved TCP teaching and payload procedures. Record the active tool, reference frame and several safe orientations when checking residual position error. Universal Robots documents its actual TCP pose as position and orientation in the base frame; values without the frame definition are incomplete.
Five-axis CNC: identify the measured tool length, rotary-center calibration and controller compensation mode. Use the machine builder’s approved verification artifact and procedure. Do not substitute a robot teaching sequence for CNC pivot calibration, and do not diagnose all orientation-dependent error as a tool-length problem.
Content updated October 8, 2026. Sources and numerical examples are explained above; examples are not production test results. Editorial method · Report a correction.
References and verification
Original explanations and worked examples by MfgWorkbench. Sources below support the stated concepts or selected reference data; they do not certify every example or a production application.
- FANUC America — advanced five-axis machining concepts
- Universal Robots — deployment points, TCP and payload
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