Orientation

CNC machines are based around the Cartesian coordinate system, sometimes called rectangular coordinates. The three axes can be identified on a vertical milling machine, for example, by the right-hand rule. In placing one’s right-hand palm up on the machine’s table and extending thumb, forefinger and middle finger so they create three axes, the positive X-axis points in the direction of the thumb; the positive Y-axis, in the direction of the forefinger; and the positive Z-axis, in the direction of the middle finger. Similarly applied, the right-hand rule helps to identify axes on other CNC machines. Positive motions refer to the cutter relative to the workpiece. For instance, if the table was moved left while the tool remained stationary, this would still produce a positive machining action.

The intersection of these three axes marks the machine’s home position. Homing the machine will bring the three axes to this X0, Y0, Z0 position. The zero position can be moved to find, for instance, the corner of a workpiece.