Definition, Components, and Machining Process of CNC Machine Tools
(Source: International Metalworking Network)
Definition of CNC Machine Tools
CNC (Computer Numerical Control) machine tools are automated machine tools equipped with a programmable control system. This system can logically process programs specified by control codes or symbolic instructions, decode them, and control the machine to perform various machining operations. The CNC unit is the “brain” of the machine, handling all control and operation functions.
Advantages of CNC Machine Tools
- High machining accuracy with consistent and stable quality.
- Multi-axis linkage is possible, allowing the machining of complex-shaped parts.
- Easy to adapt to new parts: modifying the CNC program is usually sufficient, saving preparation time.
- High precision and rigidity of the machine tool itself allow for optimized cutting parameters, improving productivity (typically 3–5 times higher than conventional machines).
- High degree of automation, reducing operator labor intensity.
- Higher skill requirements for operators and even more for maintenance personnel.
Main Components of CNC Machine Tools
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The Machine Body
The main mechanical structure, including the bed, column, spindle, and feed system. This is responsible for performing cutting operations. -
The CNC Unit
The core of the system, including hardware (PCBs, CRT displays, keyboards, tape readers, etc.) and software. It receives and stores part programs, performs data processing, interpolation, and executes various control functions. -
Drive System
Includes spindle drive units, feed drive units, spindle motors, and feed motors. Controlled by the CNC unit through electric or electro-hydraulic servo systems, it drives the spindle and feeds. Multi-axis linkage enables machining of complex geometries such as curves and surfaces. -
Auxiliary Devices
Essential supporting systems for machine operation, such as cooling, chip removal, lubrication, lighting, and monitoring. This includes hydraulic/pneumatic systems, tool changers, CNC rotary tables, indexing heads, tool monitoring, and inspection devices. -
Programming and Peripheral Devices
External equipment used for program creation and storage outside the machine (e.g., CAD/CAM workstations or DNC systems).
Machining Process of CNC Machine Tools
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CAD (Computer-Aided Design)
Used to design 2D drawings or 3D models of the part to be machined. -
CAM (Computer-Aided Manufacturing)
CAM software generates the G-code (machining program) based on the CAD model. -
CNC
The CNC controller reads the G-code and drives the machine accordingly to perform the machining.
CNC Program Structure Explanation
CNC programs are generally divided into:
- Main Programs
- Subprograms – Used for repetitive machining features to simplify the main program.
The structure follows:
Characters (numeric values) → Words → Blocks → Program
Programs can be edited using basic tools like Windows Notepad, and simulation software can be used to verify the program before execution.
