IBM EGX-400 - Manual (Page 106)

102 Chapter 6 - Detailed Description of Functions
6-1. Coordinate Systems and Origin Points
Workpiece Coordinates and Machine Coordinates
This machine uses coordinate values for the X, Y, and Z axes to indicate the position and height of the spindle head. The
display's top screen displays coordinate values that indicate the position of the spindle head. The coordinates displayed
here are a type of relative coordinates that take the "workpiece origin point" as the reference point.
You can freely change the location of the workpiece origin point. If the location of the origin point is altered, the dis-
played coordinate values also change, even if the actual position of the spindle head remains the same. Such coordinates
are called "workpiece coordinates."
The position at the machine's mechanical operating limits, that is, all the way to the left along the X axis, all the way to
the front along the Y axis, and all the way to the top along the Z axis, is called the "machine origin point." Coordinates
that take this as the reference point are called "machine coordinates."
The location of the machine origin point is determined mechanically and cannot be changed. Machine coordinates indi-
cate the absolute position of the spindle head. The location of a workpiece origin point that can be freely changed can
only be indicated by machine coordinates. For this reason, the X/Y-axis origin-point setting menu and the Z-axis origin-
point setting menu display only machine coordinates.
The Machine's Workpiece Origin Point
With this machine, a reference to just "the origin point" or "the origin" signifies the workpiece origin point. You can also
divide the location of the workpiece origin point into two parts, an X- and Y-coordinate origin and a Z-coordinate origin,
and set these separately. With this machine, the X- and Y-coordinate workpiece origin point is called the "home position,"
and the Z-coordinate workpiece origin point is called the "Z0 position."
The home position serves as a reference point that determines where on the table cutting is performed. Also, the tool-
down and tool-up positions are determined with reference to the Z0 position. These may be considered as indicating the
number of millimeters to lower or rise from the Z0 position.
Changing the home position or the Z0 position also makes the location of cutting or the cutting-in depth change, even
when the commands from the computer are exactly the same.
Unit of Measurement for Coordinate Values
One coordinate unit is 0.01 mm (0.00039 in.). An increase of 100 in a coordinate value produces 1 mm of movement.