Motion
Tool Center Point (TCP)
The Tool Center Point is the reference point of the tool frame, defined as an (x, y, z) offset from the robot's mechanical interface, that the controller uses as the point being positioned and moved.
What it is
The Tool Center Point is where the robot's work actually happens: the tip of a welding torch, the center of a gripper, the point of a dispensing nozzle. It's defined as a position (x, y, z) plus an orientation (w, p, r) relative to the mechanical interface frame.
Set a TCP in a tool frame and make it effective, and the controller references that point.
How it actually works
A tool frame stores six numbers: x, y, z for the point and w, p, r for the orientation, both measured from the mechanical interface frame. You can enter them directly, or teach them. The three point method touches the tool tip to one fixed point from three different approaches to set (x, y, z), leaving orientation at the default (0, 0, 0). The six point method sets the TCP the same way, then sets the tool attitude (w, p, r) using an orientation origin, an X-direction point, and a Z-direction point.
A real filled frame looks like TOOL2 at X: 200.0, Y: 0.0, Z: 255.5, W: 90.0, P: 0.0, R: 180.0. The tool frame list shows the active tool as $MNUTOOLNUM. Setting the numbers alone leaves the frame ineffective; press SETIND and enter the frame number to make it take effect. For 4-axis robots that can't tilt the tool to the XY plane, the Two Point + Z method calculates X and Y from two approaches and takes Z from a ruler measurement typed in directly.
How it differs
- Tool frame · The TCP is the origin point (x, y, z) of the tool frame. The full tool frame also carries orientation (w, p, r) that fixes how the tool axes are rotated relative to the flange. The three point method sets the TCP alone and leaves orientation at (0, 0, 0); the six point and direct methods define the whole frame.
- User frame · A tool frame is measured from the mechanical interface and moves with the wrist. A user frame is a fixed workspace reference the TCP is positioned within. They answer different questions: the tool frame says where the tip is on the robot, the user frame says where the part sits in the cell.
Where you meet it in the field
- Set Up a User Frame with the Three Point Method · The TCP is the point you jog to teach a user frame, so an accurate tool frame comes first.
- Setting the reference position · Reference positions are taught against the active TCP, so a wrong tool frame shifts them.
- Arc welding · The TCP sits at the torch tip, which is what makes weave and path speed behave along the seam.
Common questions
- I set the tool frame numbers but the robot still moves like there's no tool. What did I miss?
- Entering the values leaves the frame ineffective until you press F5 SETIND and enter the frame number. The active tool shows as $MNUTOOLNUM.
- When should I use the three point method versus the six point method?
- Three point only solves the TCP position (x, y, z) and leaves orientation at (0, 0, 0), which is fine if you only care where the tip is. Use six point when you also need the tool's orientation (w, p, r) defined, for example when tool jog needs to align with the tool axes.
- My robot only has 4 axes and can't tilt the tool flat to the table. How do I set the TCP?
- Use the Two Point + Z method (software 7DC1/04 or later). Touch a fixed point from two different approaches to calculate X and Y, then measure Z with a ruler and type it in directly. Enter w, p, r by hand, or 0 for all three when the flange and tool directions match.
- Why does my TCP come out inaccurate after teaching it?
- Teaching error at each approach point feeds straight into the result. The four point method (7DC3/21 or later) touches a common point from four approaches and reports the deviation at each, so you can correct the outliers iteratively and tighten the TCP.