These instructions are typically written in a language known as G-code, which consists of alphanumeric codes that represent various commands for tool movement, speed, and other machine functions. Here's an overview of key aspects of CNC programming:

CAD/CAM Software:

Designing the Part (CAD): The process begins with creating a detailed 3D model of the part using Computer-Aided Design (CAD) software.
Toolpath Generation (CAM): Computer-Aided Manufacturing (CAM) software is used to generate toolpaths based on the CAD model. Toolpaths define the routes the cutting tools will take to machine the part.
G-code and M-code:

G-code: Represents specific movements and operations, such as tool positioning, cutting speeds, and tool changes. Each CNC machine has its own set of G-codes, but there are standard codes that are widely used.
M-code: Controls auxiliary functions of the machine, such as coolant flow, spindle rotation, and tool changes.
Basic G-code Commands:

G00: Rapid positioning command.
G01: Linear interpolation for cutting.
G02/G03: Circular interpolation (clockwise/counterclockwise).
G04: Dwell or pause.
G17/G18/G19: Selection of the machining plane (XY, XZ, or YZ).

Programming Structure:

CNC programs typically follow a structured format. They include initialization commands, tool setup, workpiece setup, cutting operations, and program end.
Comments (written after a "%" or parenthesis) can be included to explain specific sections of the program.
Tool Compensation:

CNC programs must account for the size of the cutting tool. Tool radius compensation (G41/G42) is used to adjust the toolpath based on the tool's geometry.

Work and Tool Offsets:

Work Offsets (G54-G59): Define the part's origin within the machine workspace.
Tool Offsets (T): Specify the tools to be used and their respective offsets.
Variables and Parameters:

Parameters (such as feed rate and spindle speed) can be set as variables, allowing for easier modification and adaptation of the program for different machining conditions.
Simulation and Verification:

Before running the program on the CNC machine, it's common to simulate the toolpaths using software to verify that the intended operations are correct and that there are no collisions or errors.

Post-Processing:

CAM software generates a post-processed G-code specific to the CNC machine being used. This final code includes machine-specific commands and adaptations.
Editing and Debugging:

CNC programs may need adjustments or debugging, and programmers often use text editors or specialized CNC programming software for this purpose.
CNC programming requires a deep understanding of machining principles, tooling, and the specific capabilities of the CNC machine. Programmers should be familiar with G-code commands, machine setup, and the overall manufacturing process to create efficient and accurate CNC programs.