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Understanding G and M Codes for CNC Machining

CNC machining is the process of using programming code to automate machining tools. However, for that to happen, the machine must have the correct coded instructions, usually programmed. The g and m codes for cnc do this perfectly. When you use the correct codes with the proper tooling, a CNC machine can perform repeatable functions accurately. G codes for CNC comprise a letter and two numbers: most are modal, meaning they remain active unless you make changes. The m code for CNC has the same structure: a letter and two numbers.
G and M Codes for CNC Machining

What is CNC Machining?

It is a manufacturing process that uses tools to remove excess materials from production components, requiring high precision and accuracy. First, you must make a CAD design before translating it into specific codes to instruct various machine parts.

CNC machining allows the production of various components in a single process. A machine operator inputs commands in G-code and M-code, essential for a CNC machine to work effectively.  

What is G Code in CNC Machining?

Geometric code (G-code) is a CNC programming language that helps the machine interpret instructions. After interpretation, the machine passes the instructions to the specific part. One single line of g code for CNC is a block with multiple instructions. All the g-code instructions must relate to the movement of the cutting tool.

Despite what most people believe, g code for CNC is simple. All CNC machines use g-code. Every CNC machine has a microcontroller with a built-in g-code, though it’s possible to change the format in minor ways. G-codes for cnc are essential since CNC  machines don’t understand conversational language.

CNC Milling Definition, Processes, Applications

What are the Types of G Codes?

The CNC machine microcontroller already has the meaning of all the g-code commands. When you input a specific command, the microcontroller knows which instructions to send and to which CNC machine part.

While there are many g-codes for cnc, some are basic.

G00: Rapid Move Command

The rapid move command moves the tool through several points without cutting. No feed rate is necessary for this command, as the goal is to make movements at the highest speed possible.

G01: Linear Interpolation

The command moves the tool through several points with the primary purpose of making a straight line. In the command block, “F” specifies the speed rate.

Add the G01 command after a G00, G02 and G03 command. You only need the “F50” command once unless you want to change the speed rate.

G02 and G03: Circular Interpolation

The commands direct the machine to form a radius or arc in a clockwise (G02) or anticlockwise (G03) direction. After defining the radius and giving the specific command, the cutter moves straight after. You don’t need to add the feed later if it is active.

The commands G01, G02, and G03 allow you to machine any shape. These three commands are also used when cutting the material and are the foundation of the CNC g code.

G43: Tool Length Compensation

It commands the CNC controller to find the correct tool length for the tool you want to use for cutting. Often, a tool in the CNC machine will have variations in its length due to tool changes. The G43 allows you to adjust the tool position.

Adjusting a tool length is necessary to maintain its accuracy when machining. The command also helps prevent collisions between machine components. The G43 command helps maintain consistency, reducing wastage when using multiple tools.

Canned Cycle

These are repetitions of particular machine operations, such as boring, tapping, reaming, and drilling. Some of the typical canned cycle g-codes for cnc include.

  • G-73: High-speed peck drilling.
  • G-75: Quick grooving for CNC lathes.
  • G-81: Standard drilling.
  • G-84: Right-hand tapping cycle.
  • G-85: Boring or reaming cycle.

The canned cycle codes allow you to bore and drill many holes without using many lines of G code.

What are M Codes in CNC Machining?

Machine code or m code for CNC controls all the instructions that do not relate to the cutting tool movement. Most people also refer to m code as miscellaneous codes. M-codes tell the CNC machines when to commence or cease operations. G-code programming works in combination with m-code.

Different machines dictate which m codes will work. When programming, only one code is necessary per block. If there is more than one, your CNC machine will not work correctly. The CNC machine’s manufacturer spells out the m code functions and their uses.

What are the Different Types of M Codes?

Once a tool is in position after receiving instructions from g-codes, which tell it where and when to do the job, M-codes instruct the tool when to begin a movement, end a task, or end a programmed task. Below are a few of m codes for CNC.

  • M00: It directs the machine tool to stop its current function. An operator must feed another command to start the function again.
  • M02/M30: Use any of the two to end a program. The operator must give another command to restart or reset the machine.
  • M03: It commands the spindle to rotate anticlockwise.
  • M05: Use it to command the spindle to stop.
  • M06: Input it for when you require a tool change.
  • M08/M09: It directs the flood coolant to go on or off.

A CNC manufacturer can customize the m codes for each specific machine.

How do G Codes and M Codes Differ?

G code and m code for CNC perform different functions and, therefore, display specific differences.

G codeM code
The code activates the CNC machine.The code activates the CNC machine’s logic controller.
Its commands direct the function and motion of the CNC machine.Its commands only control all the operations, not involving movements.
The commands often differ on each CNC machine.M-code for CNC remains the same across all machines.
G-code for CNC deals with product design.M code relates directly to machine operations.

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The use of CNC machines has simplified manufacturing processes across all industries. However, the machines can only produce accurate and consistent parts by programming g and m codes for cnc.

Get a quote for free from Sanon China if you are looking for any services related to CNC machining and prototyping.  

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Eric Zhou

Focus on providing squeeze casting, aluminum die casting(hpdc+lpdc), mold making, CNC machining, and sheet metal fabrication solutions. If you need help, please feel free to contact us!

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