All About CNC Machining: Process, Materials, Applications, and Cost

The overall CNC machining process consists of four main steps, as listed below:

1. Designing the CAD Model

A CAD (Computer Aided Design) 3D model is developed by an engineer or designer. This part is designed according to specific CNC design principles, which are included in the overall DFM (Design for Manufacturing) philosophy. DFM ensures that the part can be efficiently manufactured on a CNC machine. For CNC parts, it is not strictly necessary to create 2D drawings of the part, since the machine instructions are created using CAM software which generates machine instructions. However, 2D drawings are often generated to indicate key dimensions for quality control purposes. 

2. Converting the CAD File to a CNC Program

The CAD file is exported to a CAM (Computer Aided Manufacturing) software package that contains a range of tools to convert the 3D model into a set of instructions that can be understood by the CNC machine. CAM software is normally used by CNC machine operators to generate G-code. At the end of the process, a G-code file is saved to the machine. This file contains all the relevant instructions required to manufacture the part. 

3. Preparing the CNC Machine

Preparing the machine to fabricate a new part number starts with setting up the required fixturing to hold the raw stock material in place while the cutting tool removes material. Alternatively, the raw stock is fixed in a spindle and stationary cutting tools are presented to the rotating stock piece to remove material. The required tooling must be checked for wear or chips and placed into the machine. More advanced CNC machines have automatic tool changers and tool libraries that allow the machine to automatically select the relevant tool needed to machine a specific feature without having to wait for the operator to swap out tools.

4. Executing the Machining Operation

When the material is securely clamped into the machine, the correct tooling is selected and the G-code is loaded, the actual machining can commence. Once the cycle-start button is pressed the machine will select the appropriate tool, move to the workpiece and begin removing material as per the G-code instructions and will continue until the part is complete. For operations that require machining with more than one type of tool, or with the part in more than one orientation, some CNC machines may require the operator to reposition the in-process work material between operations.