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G-code, Axes, Planes and the E-3 CNC

Everyone who owns or is thinking about buying an E3 CNC Router/Engraver from BobsCNC will need to develop a basic understanding of G-code.  What is G-code?  G-code is the computer language used to control the movement of the E-3’s router/engraver.  The precise movement of the spindle is calculated and programmed using a system of coordinates.

There are two coordinate systems, the right hand and the left hand coordinate systems.  Hold up your right hand with your index finger sticking straight out like the barrel of a gun.  As you point the barrel away from you hold your middle finger at 90 degrees (pointing left).  Let your thumb stick straight up.  You have just created an illustration of the right hand coordinate system.  Your index finger is the Y axis, your middle finger is the X axis and your thumb is the Z axis (illustration from CNC Cookbook, CCCNCGCode).

There are 2, 3, 4 and 5 axes machine.  The E3 CNC Router/Engraver is a 3 Axes machine.

When looking at a line of G-code, coordinates are written out with the letter of the axis first followed by a number expressing a position in mm or inches.  For example, the machine home is expressed as X0Z0Y0 (it can also look like X0 Y0 Z0 with spaces added to make it easier to read). 

Two more concepts.  The coordinates are either absolute or relative.  Absolute coordinates are measured from a fixed point, usually the zero point of the work piece.  Relative coordinates are determined by their relative to the position of the spindle as it moves through the tool path. 

The last concept I want to mention is Planes.  A plane is a flat two dimensional space that is bounded by two axes.  The spoiler board and the work piece mounted on the E3 will always be in the XY plane.  The spindle travels up and down of either the XZ plane or the YZ plane.