G-code Basics on Ivo's CNC Corner

Parser State

Mon, 01 Jan 0001 00:00:00 +0000

Parser State#

Before you can understand and use G-code commands you have to understand the concept of parser state.

The parser state is a table that remembers the last used command parameters so future commands can use them by default. These parameters are the unit of measurement (millimeters or inches), relative or absolute positions, movement speed (AKA “feed rate”), and more.

Deep Dive: Parser state and movement commands

Every movement command contains coordinate values like X, Y or Z. These values can be interpreted differently depending on the current parser state. It stores things like:

Basic Movement Commands

Mon, 01 Jan 0001 00:00:00 +0000

Basic Movement Commands#

Before reading about the movement commands, make sure you are familiar with the parser state. It is critical to understanding how the command parameters are interpreted.
Read about it here: Parser state

Another important concept to understand is that a movement command will only move along the specified axes. If your command only contains a Z coordinate, then it will only move up or down. If it contains only X and Y, it will only move horizontally. (G28 and G30 are exceptions, as they will move on all axes if none are listed).

Other Useful Commands

Mon, 01 Jan 0001 00:00:00 +0000

Other Useful Commands#

Pause (G4)#

G4 inserts a pause in the G-code. It is also called “dwell”.

G4 P3 - a 3-second pause
G4 P0.5 - a half-second pause

This is useful for example when you want to insert a pause in the G-code to allow the spindle to get up to speed. Make sure you don’t pause during actual cutting. If the tool spins in one place for long, it could burn the material and start a fire.