How to Indentify Axis in CNC Milling Machine

Most of the machines have two or more slide ways, disposed at right angles to each other, along which the slides are displaced. Each slide can be fitted with a control system and for the purpose of giving commands to the control system, the axis have to be identified. The basis of axis identification is the 3-diemensional Cartesian co-ordinate system and the three axis of movement are identified as X, Y and Z axis. The possible linear and rotary movements of machine slides/ work piece have rotary movements about X, Y, and Z axis are designated as A, B and C respectively. The main axis of movement and the direction of movement along this axis are identified as follows:-

(a) Z – Axis. The Z-axis of motion is always the axis of the main spindle of the machine. It does not matter whether the spindle carries the work piece or the cutting tool. If there are several spindles on a machine, one spindle is selected as the principle spindle and its axis is then considered to be Z axis. On vertical machining centre, the Z- axis is vertical and on horizontal machining centres and turning centres, the Z- axis is horizontal Positive Z movement (+Z) is in direction that increases the distance between the work piece and the tool.

(b) X – Axis. The X axis is always horizontal and is always parallel to the work holding surface. If the Z axis is vertical, as in vertical milling machine, positive X axis (+X) movement identified as being right, when looking from the spindle towards its supporting column. If Z-axis is also horizontal as in turning centres, positive X- axis motion is to the right, when looking from the spindle towards the work piece.

(c) Y – Axis. The Y axis is always at right angles to both the x-axis and Z-axis. Positive Y axis movement (+Y) is always such as to complete the standard 3-diemensional co-ordinate system.

(d) Rotary axis. The rotary motion about the X, Y and Z axis are identified by A, B, C respectively. Clockwise rotation is designated positive movement and counter clockwise rotation as negative movement. Positive rotation looking +X, +Y and +Z direction respectively.