G and M are two different types of machines used in numerical control machining (CNC machining) to direct and control machine tools for different actions and functions. Here are their definitions and roles in CNC machining:
1. g**（geometric code）:
Definition: g is the one that represents geometric motion. It tells the machine how to move, including linear motion, circular motion, machining of holes, etc.
Function: G** is mainly used to define the motion trajectory of the tool and control the machine tool to cut along the specified path. Different G** means different motion modes, for example, G00 means fast positioning, G01 means straight cutting, G02 and G03 means circular cutting, etc.
2. m**（miscellaneous code）:
Definition: M is the one that represents a miscellaneous function. It is used to control some auxiliary functions of the machine tool, such as the start and stop of the coolant, the start and stop of the spindle, the tool change, etc.
Purpose: M** is mainly used to control the auxiliary functions of the machine tool, not to directly control the cutting movement. For example, M03 means start spindle rotation, M05 means stop spindle rotation, M08 means start coolant, M09 means stop coolant, M06 means tool change, etc.
In CNC machining, G and M are usually entered into the CNC system in the form of programs. Programmers write these to define the cutting path and the various functions of the machine according to the design requirements and machining process of the part. The correct use of these ** is essential to ensure the accuracy and quality of the machining of the parts. When writing CNC programs, programmers need to carefully consider factors such as cutting trajectory, tool path, cutting speed, etc., and use G** and M** reasonably to achieve the expected machining results.