1. What is a CNC System?

CNC (Computer Numerical Control), is a computer system that has been designed to automate equipment processing. It integrates NC (Numerical Control), machining code, interfaces, servodrives, spindle devices and other auxiliary technology. A CNC system’s primary function is to process machining information and control servo driven axes in order to complete required contour trajectories.

2. Basic Types of CNC Systems

Classification by motion trajectory:

1. Point-Control CNC System
   • The tool can be moved from one point of machining to another, without regard for the path.
   • These are common in CNC drilling machines and coordinate boring machines.
2. Linear Control CNC System:
   • The control can be used to set the exact position of the points as well as the straight line trajectory between them.
   • This allows for processing with a set feed rate. It also includes functions such as spindle speed adjustment and automatic tool change.
   • Used in simple CNC lathes, boring and milling machine.
3. Contour control CNC system
   • The software allows you to control the speed and position of multiple coordinates. This ensures that your processing is continuous.
   • Used in CNC lathes and milling machines. Also used for machining centers, special processing machines, electrical processing machines.

Classification of Machining Processes:

1. Turning and Milling CNC Systems
   • Included are CNC lathe controls and machining centers control systems.
   • They are differentiated by their ability for handling turning threads, spindle, C-axis and different coordinate systems.
2. Grinding Machines
   • Specialized for grinding machine, supporting wheel dressing, workpiece gauge access and other specific functions.
   • Non-circular grinding requires high dynamic performance, advanced curve smoothing and a high degree of precision.
3. Special Processing CNC Systems
   • Customized for specific processes such as parallel machine tools, wire-cutting, punching and gear processing.

Included are unique motion control algorithms as well as actuator controls.

Classification of Servo Systems Control Mode

1. Open Loop Control CNC System
   • Stepper motors are used to control the system when there is no feedback circuit.
   • Since the 1970s, CNC machines have been using simple and cost-effective CNC technology.
2. Semi Closed Loop Control CNC System
   • The position detection system is mounted on the motor shaft or screw shaft. It provides moderate accuracy and stability.
   • It is widely used because of its low cost and ease of use.
3. Full closed-loop control CNC system
   • The machine table is equipped with a position detection system that provides high accuracy in controlling the machine’s position.
   • Due to the presence of connecting links such as screws and nuts that can cause oscillations, it is more difficult to achieve a high gain.

Classification of Function Levels:

1. Economic CNC System
   • Simple systems using pulse string interface servodrives or stepper motors without position feedback.
   • Ideal for shapes with a simpler shape and general accuracy requirements. Typical machine positioning accuracy is 0.02mm.
2. Popular CNC System
   • Intermediate systems that support up to 4-axis controls, closed-loop, pitch-error compensation, and user developed PLC functions.
3. High-Grade CNC System:
   • Advanced systems with multiple-channel control, dual drive control, interpolation of 5 axis or above, error compensation and high static and dynamics accuracy.
   • PLC-controlled machine for complex and high-speed machining.