Coordinates
World Frame: World Coordinate System
The world frame is a standard Cartesian coordinate system fixed in the robot's work space, and it's the reference that user and jog frames are built on top of.
What it is
The world frame is a Cartesian coordinate system fixed in the work space, at a position determined by the robot. It's one of the seven coordinate systems a FANUC controller uses to describe where the robot is and how the tool is oriented.
It matters because it's the base reference for other frames. User frames and jog frames are both specified on top of the world frame, and when either of those isn't defined, the world frame stands in for it. Position data and the instructions that act on that data are expressed relative to the world frame.
How it actually works
A Cartesian position is given as (x, y, z) for location and (w, p, r) for orientation, where w, p, and r are angular displacements about the X, Y, and Z axes. The world frame is the fixed reference used for specifying position data and executing the corresponding instructions.
The origin of the world frame is fixed at a spot determined by the robot model (FANUC documents its exact location under the world frame origin reference). Because the frame doesn't move, it's also the anchor for larger constructs: the cell coordinate system, for instance, is defined by the position of the world frame origin (x, y, z) and its rotation angles (w, p, r) within the cell, which is how multiple robots in one cell get related to each other.
How it differs
- User Frame · A user frame is defined by the user for a particular work space and is specified relative to the world frame. The world frame is the fixed default; if no user frame is defined, the world frame substitutes for it. So a user frame is a shifted, application-specific reference sitting on top of the world frame.
- Tool Frame · The tool frame moves with the wrist and defines the TCP and tool attitude relative to the mechanical interface (flange). The world frame is fixed in the work space and doesn't move with the arm. World tells you where in the cell; tool tells you where on the end-effector.
- Jog Frame · A jog frame is a user-defined frame used only to make jog feed convenient, and its origin doesn't have to be tracked carefully. The world frame is a permanent structural reference for position data and instructions, holding whether or not you're jogging.
Where you meet it in the field
- 3-point user frame setup · User frames are taught relative to the world frame, so understanding the world reference is the starting point before you define a user frame.
- Setting the reference position · Recorded positions live in a frame; knowing which frame is the underlying reference matters when you set and verify a reference position.
Common questions
- If I never set up a user frame, what frame are my positions in?
- The world frame. When a user frame isn't defined, the world frame substitutes for it, and the same goes for the jog frame. So your taught positions are still referenced to something fixed even if you never explicitly configured a user frame.
- Can I move the world frame origin to a convenient spot on my fixture?
- No. The world frame origin is fixed at a position determined by the robot. If you want a reference tied to your fixture or workpiece, that's what a user frame is for, and it gets defined relative to the world frame.
- Is the world frame the same as the cell frame when I run multiple robots?
- They're related. The cell coordinate system is defined by placing each robot's world frame origin within the cell frame, including its rotation angles. That's how robots sharing a cell get positioned relative to one another in the 4D graphics function.
- If I re-teach or change a frame after programming, do my points still work?
- Changing the tool or user coordinate system after teaching means the programmed points and ranges need to be reset, otherwise you risk damaging equipment. The world frame is the fixed backstop, but shifting the frames built on it invalidates positions taught against the old frame.
Sources
- FANUC B-83284EN/09 (Operator's Manual, Basic Function) · 3.9 Setting Coordinate Systems / World coordinate system