G-Code Overview

What is G-Code

G-Code is the programming language of 2D plotters and 3D printers. It is a lower level programming language and therefore is typically difficult to understand. Below is a snippet of code to plot a rectangle. This library aims to abstract away these instructions so that more user friendly code, such as Python, can be used instead to generate G-Code. For more information on G

G21
F10000
M3 S0
G1 X0.000 Y-50.000 F10000
M3 S1000
G04 P0.25
G1 X0.000 Y0.000 F10000
G1 X50.000 Y0.000 F10000
G1 X50.000 Y-50.000 F10000
M3 S0
G04 P0.25
M2

Library Instructions

Below are a collection of all the instructions used in this library. For a more thorough explanation, RepRap and Marlin are great (and dense) resources.

The square braces indicate a variable that can be passed to the specific G-Code instructions. For example the instruction G1 X[x] Y[y] takes in variables x and y, which could result in a G-Code instruction looking like G1 X10.0 Y5.0.

Comment

Add a comment with a line starting with ;. This instruction is not read by the plotting device.

;The following instruction lifts the pen up.
M3 S0

F

Set the movement speed f of the plotting device with F[f]. Can also be attached to individual G1 commands.

F10000

G1

Move the plotting device to the specified x and y and z coordinates at a speed of f with G1 X[x] Y[y] Z[z] F[f]. Not all of the coordinates are required.

G1 X0.000 Y0.000 F10000
G1 X50.000 F10000
G1 Z10 F10000
G1 X50.000 Y-50.000 F10000

G4

Pause for a period of time p with G4 P[p]. This command is useful in combination with a move command. A pause after moving will give the plotting device a chance to stop any vibrating that might impact the plotting quality.

; Lower plotter head
M3 S1000
; Pause for 0.25 seconds
G4 P0.25
;Point: 59.84807753012208, -48.2635182233307
G1 X59.848 Y-48.264 F10000

G20

G21

Sets the units of measurements to mm.

G21

G28

Home the plotting device. Will return the plotter to X = 0, Y = 0 and if supported, Z = 0. Not all plotting devices support this command.

G28

M2

Marks the end of the program execution.

M2

M3

For 2D plotters, used to raise and lower the plotter head. M3 S0 will raise the print and M3 S1000 will lower the plotter head.

; Raise plotter head
M3 S0
; Move to first coordinate
G1 X0.000 Y0.000 F10000
; Lower the plotter head
M3 S1000
; Draw two lines
G1 X50.000 Y0.000 F10000
G1 X50.000 Y-50.000 F10000
; Raise the plotter head on a 2D plotter, A `G1` command with `Z` height would be used here for a 3D printer.
M3 S0