3D printer m codes

G-code is a programming language for numerical control (CNC). In other words, it is the language that the computer that controls the car speaks, and it transmits all the commands necessary for movement and other actions.

Although G-code is a standard language for various desktop and industrial equipment, it can be very familiar with a 3D printer. You may not have figured this out yet, and that's okay, since 3D slicers generate G-code "automatically".

However, if you want to get a deeper understanding of 3D printing, it's important to learn the basics of G-code. This knowledge will allow you to better diagnose and control 3D printing processes, as well as configure 3D printer firmware such as RepRap or Marlin.

In this article, we'll cover the basics of G-code, including how to read, understand, and write commands, even if you're new to programming!

What is a G-code?

For those unfamiliar with programming in general, you can think of G-code as successive lines of instructions, each telling the 3D printer to perform a specific task. These lines are called commands, and the printer executes them one after the other until it reaches the end of the code.

Although the term "G-code" is used to refer to a programming language in general, it is also one of two types of commands used in 3D printing: "basic" and "auxiliary" commands.

The main command lines are responsible for the types of motion in the 3D printer. Such commands are denoted by the letter "G". In addition to controlling the three positive axes performed by the printhead, they are also responsible for the extrusion of the filament.

On the other hand, different commands make the machine perform non-geometric tasks. In 3D printing, such tasks include nozzle and bed heating commands, as well as fan control, and so on. Auxiliary commands are denoted by the letter "M".

G-code syntax

Each line of G-code commands has a specific syntax. Each line corresponds to only one command, which can lead to very long codes.

The first argument of any string is the command code itself. As you have seen, this can be a code like "G" or "M" followed by a number identifying the command. For example, "G0" corresponds to a linear movement command.

Next are the parameters that define the command more precisely. For example, for a G0 linear motion command, you can add an end position and a travel speed, also indicated in capital letters. Each command has its own set of options, which we will discuss below.

G-code comments

When you read the G-code of a command, you will see semicolons after letters and numbers that explain what the code does. Here is an example of a line with a comment to the code:

 G1 X25 Y5; I'm commenting out the code! 

Programmers often need to include plain language explanations so that other programmers can understand certain lines or sections of code. It can also happen that you forget why you wrote something in a certain way, making it hard for you to figure it out again. Code comments are used to solve this problem. Comments include everything (on the same line) after the semicolon and are completely ignored by the machine when executing G-code. As such, they are solely for the eyes of programmers.

Important 3D Printing Commands

Although there are literally hundreds of G-code commands, in the next few sections we'll cover the most basic and important ones. Once you get comfortable, you can learn other commands on your own.

G0 and G1: linear movement

The G0 and G1 commands execute linear movements. By convention, G0 is used for non-extrusion motions such as initial and idle motions, while G1 covers all linear motions with material extrusion.

Both commands work the same, however. The parameters for G0 or G1 include the end positions for all X, Y, and Z axes, the degree of extrusion performed during the move, and the speed determined by the feed rate in given units.

Example

G1 X90 Y50 Z0. 5 F3000 E1 tells the 3D printer to move in a straight line (G1) to end coordinates X = 90mm, Y = 50mm, Z = 0.5mm at a feedrate (F) of 3000mm / min. and extrusion (E) 1 mm of material in the extruder.

Most linear moves are within the same layer, which means that the Z coordinate is usually not specified on the command line.

G90 and G91: absolute and relative positioning

The G90 and G91 commands tell the machine how to interpret the coordinates used for movement. G90 sets "absolute positioning", which is normally the default, while G91 sets "relative positioning".

Neither command requires any parameters, and setting one automatically overrides the other. Positioning works quite simply, so let's get straight to the point.

Example

Let's say we want to move the print head X = 30 in a line. In absolute positioning mode it would look like this:

 G90; sets absolute positioning G0X30; moves to X = 30 

This simple move will tell the printer to move the printhead so that it is positioned at X = 30. Now, to move the relative position, we need to know where the printhead is currently located. Suppose it's X = 10:

 G90; sets relative positioning G0X20; moves +20mm in the X direction 

G91 first tells the 3D printer to interpret the coordinates relative to the current position (X = 10). Knowing this, it is enough just to move 20 mm in the positive direction of the X axis, thus reaching X = 30, as we would like.

G28 and G29: automatic zeroing and table calibration

Homing is the process of moving up to physical limits for all axes of motion. The G28 command will accomplish this task by moving the print head until the limit switches on all axes are engaged.

Moving "to zero" is important not only to orient the device, but also to prevent the printhead from running out of bounds. The G28 command is usually executed before every start of 3D printing.

A specific axis can be individually homed by including X, Y or Z as parameters. Otherwise, only G28 will provide movement to zero in all axes.

Example

 G28 X Y; only X and Y axes G28; to zero on all axes 

Another command, G29, starts the automatic table calibration sequence. There are many different methods for leveling a table before 3D printing. Usually this operation is provided by the firmware and not by the end users. For this reason, we will not go into details regarding the methods and parameters of commands. Just be aware that G29 is usually sent after automatic homing (G28). As a result, automatic table calibration should be performed, which is determined by the firmware.

G29; execute automatic bed leveling sequence

M104, M109, M140 and M190: temperature setting

These are important commands, which again are not motion related.

To start, the M104 command sets the target temperature that the hot end must reach and holds it until otherwise specified.

Some of the parameters include actual temperature value (S) and print head (T) for heating.

Example

 M104 S210; set target temperature for hot end to 210 degrees 

This command line tells the 3D printer to heat the hot end to 210°C.

Alternatively, if we want to wait until this target is reached before moving on to the next line, we can use the M109 command.

 M109 S210; set the hot end target temperature to 210 degrees and do nothing until it is reached 

Setting the table temperature is very similar, but instead set using the M140 and M190 commands:

 M140 S110; set target table temperature to 110 degrees M190S110; set the target bed temperature to 110 degrees and do nothing until it is reached 

M106 and M107: Fan control

Another important command for 3D printers, the M106 and M107 commands provide fan control.

M106 turns on the fan and sets its speed. This is especially useful for the part cooling fan, as during the 3D printing process, different speeds are required during the printing of the first layer and the web.

The speed parameter must be between 0 and 255. A value of 255 provides 100% power, and any number in this range will indicate the appropriate percentage.

Example

 M106; turn on the fan at maximum (100%) speed M106 S128; turn on the fan and set it to 50% power 

Multiple variable speed fans can be identified using the index (P) parameters since each fan is assigned an index by the firmware.

Finally, the M107 command will turn off the specified fan. If the index parameter is not specified, the partial cooling fan is usually disabled.

Program structure

Now we have a good opportunity to look at the actual code snippet that is used for 3D printing. As we will see later, G-code programs can be divided into three distinct sections.

It is worth noting that if you use a text editor to open a G-code file created with a 3D slicer, it may not immediately start with G- or M-commands. For example, a slicer like Cura or Simplify3D runs the code, including some of the print process parameters defined earlier in the comments. These lines do not affect the print, but instead are a quick guide to parameters such as layer height.

Stage 1: Initialization

The first section of any program includes the preparatory tasks necessary to start printing a 3D model. Below are the first six lines of G-code initialization commands from the actual 3D print job.

 G90 M82 M140 S80 M104 S200 G28 G29 

As we now know, the first line tells the move to use absolute positioning, and the second line tells the extruder to also interpret the extrusion in absolute units.

The third and fourth lines start heating the bed and the nozzle to the set temperatures. Note that it will not wait for the target temperature to be reached, meaning the printer will automatically reset and level the table when heated.

Some initialization routines (such as the one used by the PrusaSlicer) include a nozzle cleaning process or printing a single straight line before moving on to the 3D printing process.

Stage 2: 3D printing

This is where the magic begins. If you look at the layered G-code file, you realize that it's really impossible to understand what a nozzle actually does.

3D printing is a layer-by-layer process, so you'll find that this step involves a lot of movement in the XY plane when printing a single layer. Once this is done, one tiny movement in the Z direction will define the beginning of the next layer.

Here is an example of what G-code commands might look like in 3D printing:

 G1 X103.505 Y153.291 E4.5648; movement and extrusion in the XY plane G1 X103.291 Y153.505 E4.5804; movement and extrusion in the XY plane G1 Z0.600 F3000; change layer G1 X104.025 Y154.025 F9000; movement in the XY plane G1 X95.975 Y154.025 E0.4133 F1397; moving and extruding in the XY plane 

Step 3: Reloading the 3D Printer

Finally, when the 3D print is complete, some last lines of the G-code commands reset the printer to its default state.

For example, the nozzle may move to a predetermined position, the hot end and table heaters are turned off, and the motors are turned off.

 M107; turn off the fan G1Z10; move the nozzle away from the print M104S0; turn off hot end heating M140S0; turn off bed heating M84; turn off the motors 

Data input and output via the terminal

So far we have only talked about the fact that the computer sends G-code commands to the 3D printer (usually transmitted via an SD card). However, this is not the only way to communicate.

Some 3D printer control software, such as Pronterface and OctoPrint, allows you to interact directly with the 3D printer, in which case you can enter commands manually.

For obvious reasons, it would be impractical to print anything by sending code lines individually. But sometimes this method of communication is required for other purposes, such as obtaining valuable information for calibration or when the 3D printer does not have a display.

For example, an M105 "report temperatures" command will retrieve the current nozzle and bed temperatures (which can then be displayed by something like OctoPrint).

This link is also very useful for viewing and changing EEPROM settings that are hardcoded at the firmware level. Parameters such as motor steps / mm, maximum feedrate or PID controller can be visualized with M503 ("report settings"), changed manually and then saved with M500 ("save settings").

Writing G-code

By now you should be able to read and understand G-code much better. We recommend looking towards the following options to deepen your knowledge:

• online G-code visualization is a great tool to test your skills as you can write G-code commands and simulate them accordingly. It's actually a lot of fun!
• looking at exported G-code files from slicers should also give you some idea of ​​how G-code works for 3D printing.
• You can use the information from the official Marlin website as a command reference.

Compatible

We hope that with your understanding of the G-code commands, you will become a more advanced 3D printer user. Although G-code is not the most complex computer language, it still requires practice and learning.

Before we wrap up this article, it might be worth talking a little about G-code compatibility.

There are many types of 3D printing firmware, and each can have a different "variant" of G-code. This can lead to serious compatibility issues, as commands that work on one machine may not work on another.

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