This Article takes an In-depth look at the M-Code Plain Text Language
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Computer numerical control (CNC) is a fundamental part of modern manufacturing. The majority of machines operate using instructions and guidelines that have been downloaded using a CNC program controller. For a machine to interpret the commands from CNC, the commands have to be entered using G and M codes. CNC operators are required to know the appropriate codes and instructions as well as how to use them. Both types of coding are necessary for the system of a CNC device to perform correctly.
M-code is a part of the language that AutoCAD and CAM, computer aided manufacturing, use to input instructions into CNC machines. G-codes and M-codes work in unison for positioning a workpiece and guiding the machine‘s actions. M-codes, miscellaneous or machine codes, control the operations of the equipment telling it when to operate or cease operation. While the G-code can direct a machine to move in a line or arc, once the tool is positioned, it won‘t know to stop, change tools, add coolant, or complete any other actions, which are provided by M-codes. Instructions for a tool to turn on or off is part of the M-code language.
The use of M-codes varies depending on the machine. During programming, one M-code is required per code block giving the commands for a tool to turn on or off and activate other operations. Having more than one M-code in a code block can cause problems. The definition of M-code functions and their uses is spelled out by the machine‘s manufacturer.
Operators use M-codes to tell a machine to change tools, turn on the spindle, load coolant, or open and close a door. There are several M-codes that operators need to know for a machine to perform properly. Also, each machine has a different method for downloading the M-codes. One controller may require a zero between the M and the number while others don‘t need the zero. The particular method for a machine is clearly laid out in the instructions from the manufacturer.
M-codes are an important component of the operation of a CNC machine. While G-codes describe the positioning for an operation, M-codes provide data for a machine‘s actions. For the proper functioning of a CNC machine, G and M codes have to be entered. They work in tandem and together to instruct, guide, and program the responses of a CNC device. As with any computer, CNC machines have a controller for data input. Though most computer languages are built on C or C++, there are variations for each type of controller.
Fanuc manufactures robotic controllers that use M-codes for commands for CNC machines. Their controllers use the M zero number form of M-codes. Below are several of the Fanuc controller M-codes.
M commands are part of an information group that determines how and when a machine should start or stop an action. Beginning with M00 they continue in an arithmetic progression to M99, which ends the program. How an M-code is used differs between vendors and producers. In many cases, not every M-code is programmed into the machine. Knowing the codes and how they make the machine function is critical. In some cases, when a code is not used or programmed, the definition of the code is left to the discretion of the user.
Examples of the programmable codes for a lathe and milling operation are listed below. Table 1 has codes for a lathe while table 2 has the M-codes for a milling operation. Both tables are examples of M-codes for Fanuc controllers.
| M code | Description |
|---|---|
| M00 | Program stop |
| M01 | Optional program stop |
| M02 | End of program |
| M03 | Spindle start forward CW |
| M04 | Spindle start reverse CCW |
| M05 | Spindle stop |
| M08 | Coolant on |
| M09 | Coolant off |
| M29 | Rigid tap mode |
| M30 | End of program reset |
| M40 | Spindle gear at middle |
| M41 | Low Gear Select |
| M42 | High Gear Select |
| M68 | Hydraulic chuck close |
| M69 | Hydraulic chuck open |
| M78 | Tailstock advancing |
| M79 | Tailstock reversing |
| M94 | Mirrorimage cancel |
| M95 | Mirrorimage of X axis |
| M98 | Subprogram call |
| M99 | End of subprogram |
| M code | Description |
|---|---|
| M00 | Program stop |
| M01 | Optional program stop |
| M02 | End of program |
| M03 | Spindle start forward CW |
| M04 | Spindle start reverse CCW |
| M05 | Spindle stop |
| M06 | Tool change |
| M07 | Coolant ON – Mist coolant/Coolant thru spindle |
| M08 | Coolant ON – Flood coolant |
| M09 | Coolant OFF |
| M19 | Spindle orientation |
| M28 | Return to origin |
| M29 | Rigid tap |
| M30 | End of program (Reset) |
| M41 | Low gear select |
| M42 | High gear select |
| M94 | Cancel mirrorimage |
| M95 | Mirrorimage of X axis |
| M96 | Mirrorimage of Y axis |
| M98 | Subprogram call |
| M99 | End of subprogram |
There may be some confusion regarding the codes for CNC machines since some operators refer to all codes as being G-codes even though they input both G and M codes. To avoid misinformation and misunderstandings, it is important to know that every code block has to have one M-code to begin and end a function. The G-code tells the machine where and when to do a job. M-codes stop an operation, end a programmed task, or begin a movement after the tool has been positioned.
Most parts and products produced by CNC machines are programmed using CAD or CAM software that give directions for CNC machines using alphanumeric programming. Even though engineers are fluent in those two forms of software, it is still important for them to have an understanding of how G and M codes direct a CNC machine.
CNC machining is an electromechanical process that controls tools across three to five axes with high precision and accuracy, removing excess material to create parts and components. Designs for CNC machining are first developed using CAD software, which is then converted into CNC codes to guide the tools in the CNC machine.
CNC machining delivers high-quality finishes on turned components through a diverse range of applications, accommodating both vertical and horizontal machining needs.
The multitasking ability of CNC machines allows for the completion of a component or part in a single operation, with ease and efficiency. The types of applications performed by CNC machines include bushings, collars, fasteners, fittings, inserts, machined components, machined washers, pins, nuts, spacers, spindles, standoffs, drive shafts, and splined shafts to name a few.
M-code simulators are software tools designed to emulate the behavior of M-codes, which are machine instructions used in numerical control systems. These simulators are crucial for verifying and optimizing machine tool programs before they are executed in real-world operations. Various companies develop and offer M-code simulators tailored for different industries and applications. Below, we review some of the leading M-code simulators and their developers.
Predator Virtual CNC is an extensive CNC machine simulation software that supports M-Code simulation. It delivers a highly realistic 3D simulation environment, allowing users to accurately test and evaluate CNC programs.
environment, enabling users to preview and validate CNC programs before they are executed on physical machines.
Founded in 1994, Predator Software is the developer of the Predator Virtual CNC simulator. The company specializes in manufacturing software solutions, including CNC programming, machine monitoring, and shop floor automation.
Vericut is a prominent M-Code simulator known for its advanced features in CNC program verification and optimization. It provides a comprehensive simulation of the entire machining process, including material removal and tool movement, to help detect errors, collisions, and inefficiencies within the program.
Created by CGTech, which was founded in 1988, Vericut is a leading software in CNC simulation, verification, and optimization. CGTech is a global company that serves various industries, including aerospace, automotive, and defense.
Cimco DNC-Max is a versatile software suite offering both DNC (Direct Numerical Control) and M-Code simulation features. It allows users to manage and transfer CNC programs to machines while providing simulation capabilities to validate programs and identify potential issues.
CIMCO A/S, established in 1991, is the developer behind Cimco DNC-Max. As a leading provider of DNC and CNC communication software solutions, CIMCO offers a variety of products designed for CNC machine tool management and data transfer.
Mastercam is a well-known CAD/CAM software for CNC programming, featuring an integrated M-Code simulation tool. The Mastercam Simulator enables users to visualize and test their CNC programs, ensuring accuracy and efficiency before actual machining.
Developed by CNC Software, Inc., which was established in 1983, Mastercam is a leading CAD/CAM software for CNC machine programming. Its built-in simulator allows users to preview and validate toolpaths prior to executing them on physical machines.
Fusion 360, developed by Autodesk, is a comprehensive product development software that integrates CAD, CAM, and CNC machining functionalities. It offers a robust simulation environment for testing and verifying M-Code programs, ensuring they are free of errors and optimized for machining processes.
Autodesk, founded in 1982, is the creator of Fusion 360. This all-in-one tool provides extensive 3D CAD, CAM, and CAE capabilities, including integrated M-Code simulation. It is widely adopted across various industries for product design and manufacturing tasks.
These M-Code simulators are invaluable tools in numerical control systems, allowing users to verify and fine-tune their machine tool programs prior to actual execution. The companies behind these solutions have established themselves as leaders in M-Code simulation, offering software that enhances CNC programming, minimizes errors, and boosts overall efficiency in manufacturing.
CNC, or Computer Numerical Control, machining is a systematic process aimed at efficiently producing parts. This technique involves computer-controlled machines that execute tasks based on pre-programmed instructions, starting from a 2D or 3D design rendered on a computer.
After the design file is input and coded, the CNC machine carries out each operation in line with the specified design parameters.
The key distinction between CNC machining and other manufacturing methods is that CNC machining is a subtractive process. It involves removing layers of material to achieve the desired shape, as opposed to additive or formative manufacturing techniques.
The success of CNC manufacturing largely depends on the initial programming. The software must be precisely coded with accurate instructions, ensuring the machine operates within its specified limitations. The effectiveness of CNC processes is directly influenced by the quality of the instructions provided. Careful attention is given during the programming phase to minimize errors and prevent production delays.
CAD-CAM refers to the software used for both designing and machining parts with CNC machines. CAD (Computer-Aided Design) software is utilized to create, draw, and model parts using geometric shapes and constructs. CAM (Computer-Aided Manufacturing) software then converts the CAD data into machine language, known as G-Code.
Before converting the CAD model into machine instructions, CAM software determines the toolpaths required to remove excess material from the workpiece. Together, CAD and CAM provide the CNC machine with precise instructions needed for accurate and efficient cutting operations.
Before uploading the CAD-CAM program to the CNC machine, it is essential to prepare the correct cutting tools. One approach involves manually selecting tools from a tool cart and installing them into the machine.
Alternatively, an Automatic Tool Changer (ATC) can streamline this process. The ATC system holds tools on a rotating drum or chain and automatically swaps them out as needed. This method is designed to enhance efficiency and minimize downtime.
Another crucial setup step is defining the gage point, which determines the distance from the tool tip to a reference point. Proper calibration of this measurement ensures that the tool cuts at the desired depth. Additionally, testing the coolant or lubricant system is vital. Coolant can be applied via air, mist, flood, or high-pressure methods. Accurate pressure settings are necessary to prevent tool damage and protect the machine.
Common setup mistakes include neglecting to check the coolant quality, which may result in unpleasant odors, inadequate levels, low concentration, or insufficient filtration.
Work holding devices are used to secure, support, and position the workpiece during machining operations. Also known as CNC fixtures, these tools ensure precision, consistency, and smooth operation by stabilizing the workpiece. Unlike jigs, which guide tools, work holding devices primarily focus on securing and supporting the workpiece itself.
Similar to CNC tools, work holding fixtures come in various types, each suited for specific operations such as turning, milling, drilling, boring, and grinding.
G-codes are widely recognized as the standard language for CNC machining. While there are universal G-codes applicable to all CNC machines, manufacturers often customize these codes to fit their specific equipment. Each G-code corresponds to a particular movement or function of the cutting tools in a CNC machine.
G-codes can be generated by various software programs from a CAD design, but they can also be manually written or created through conversational programming, which does not rely on CAD designs. These codes can be transferred to a CNC machine via a USB drive, directly from a CAM computer, or programmed directly into the machine itself.
Program proofing is the last step before executing the actual cuts. It aims to verify the accuracy of the program and ensure the CNC machine setup is correct, preventing potential issues with the G-code.
This step is crucial for detecting any errors in the G-code. Proofing can be done by running the machine through the cutting process without engaging the workpiece, known as "cutting air," which, while effective, is time-consuming and occupies the machine. Alternatively, a G-code simulator can be used, providing a virtual simulation of the CNC process to identify any problems.
Once all preparations are finalized, the next step is to insert the workpiece and begin the cutting process. The initial workpiece should be closely monitored as it undergoes machining. This prototype serves as a benchmark for all subsequent parts and will provide valuable insights into the effectiveness of the programming and setup.
After completing the setup and testing phases, the CNC machine is ready for production. CNC machining enables manufacturers to produce parts quickly, efficiently, and safely, with each part being an exact replica of the original design.
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