Coordinate System

In this first lesson, we talk about Coordinate System. Every workpiece that we machine must have a workpiece coordinate system (WPC) and is defined using G54. There are 3 axes on every coordinate system, one is X axis, running left-right along the machine, one is Y axis, running towards-away from the operator, one is Z axis, running up and down vertically. Once we have this coordinate system, any point or line can be fully described using their corresponding X, Y and Z values. If the points are always defined with reference to the workpiece zero point, it is called absolute position programming (G90). If the points are defined with reference to the current position, it is called incremental position programming (G91).



For every points in the diagram above, write down their respective X and Y values using G90 method, followed by using G91 method.

To machine the workpiece based on the coordinate system, we need to instruct the machine how to cut, from where to where. These instructions are called progamming codes. Every program comprises of blocks, words and addresses.

To instruct the machine simply to move from one point to another, we use the command G0. When we move in air, we can move very fast, making use of the maximum feed rate as provided by the machine builder. To instruct the machine to cut into the workpiece (removing metals along the way), we use the command G1. In this case, however, we need to tell the machine how fast it can move. This is to be defined using the F word. This value depends on what material we are cutting and what kind of tool we are using.

We also need to define the spindle rotation using the S word.

An example program for Mazak machine is as follows:

G0 G90 G40 G94 G21 G17
T1 M6
G90 G54 S597 M3
G0 Z100.0
G0 X-30.0 Y-30.0
G0 Z10.0
G1 Z-20.0 F119
G1 X0.0 Y-30.0
Y110.0
X57.0
Y147.0
X155.0
Y65.0
X42.42 Y0.
X-30.0
Y-30.0
G0 Z50.0
M2

Based on the program given above, can you draw the shape of the workpiece on a piece of paper as an additional exercise?