Tool centre point (TCP): the point a robot actually controls

From flange to working point

Every arm ends in a mechanical interface, the tool flange, where the end effector is bolted on. The flange pattern is standardised: Universal Robots lists EN ISO 9409-1-50-4-M6 for UR5e and ABB lists ISO 9409-1-50 for GoFa 5. The tool centre point is a point defined relative to that flange, usually where the tool does its work, together with an orientation.

When a program asks for a straight-line move or a rotation about a point, the controller plans that motion for the TCP. If the TCP is defined at a gripper’s fingertips, rotating the tool turns it about the fingertips rather than about the flange.

Why a wrong TCP causes errors

If the defined TCP does not match the real tool, linear moves and reorientations happen about the wrong point. A tool that should pivot around its tip swings the tip through an arc instead, and taught positions stop matching when the tool changes. Defining and checking the TCP after every tool change prevents a common class of errors.

Controllers generally provide a way to measure the TCP by touching a fixed point from several orientations, or to enter it from the tool drawing.

Reading “maximum TCP speed”

Maximum TCP speed is the fastest the tool point can move under the manufacturer’s conditions. ABB notes that GoFa’s safe collaborative speed is lower than its maximum and depends on the application. In a collaborative cell the risk assessment sets the speed, so a higher datasheet ceiling matters mainly for fenced or mode-switching operation.

• UR5e full specifications
• ABB GoFa 5 full specifications
• UR5e vs ABB GoFa 5, compared row by row