Requirements for Sensor Use on CNC (Automated) Machine Tools

What is a CNC machine tool?

A CNC (Computer Numerical Control) machine tool is a machining device controlled by computer programs. It uses numeric codes to represent control information in the machining process and inputs this information into the control system. The CNC system sends control signals to the machine to produce parts with the shapes and dimensions specified in the drawings. CNC machines address complexity, precision, small-batch and multi-variety part machining with flexibility and efficiency, and they represent the modern direction of machine tool control technology.

Components of a CNC machine tool:

CNC machines consist of program carriers, CNC controllers, servo drive units, the machine body and other auxiliary devices. Below is a summary of the basic working principles of each part.

CNC machines move and machine parts according to programmed instructions. They integrate mechanical systems, automation, computing and measurement electronics and use various sensors. Sensors commonly used on CNC machines include photoelectric encoders, linear grating rulers, proximity switches, temperature sensors, Hall sensors, current sensors, voltage sensors, pressure sensors, liquid level sensors, resolver/transducers and speed sensors. These devices are mainly used to detect position, linear displacement, angular displacement, speed, pressure and temperature.

CNC machines place high demands on sensors:

1) High reliability and strong anti-interference capability;

2) Meet equipment accuracy and speed requirements;

3) Easy maintenance and suitability for the machine environment;

4) Low cost of ownership.

Different types of CNC machines have different sensor requirements. Generally, large machines need fast response; mid- and high-precision CNC machines require high accuracy. Displacement detection for machine components is strict: small CNC machines often require very high accuracy and use optical grating rulers, while large CNC machines with longer travel commonly use magnetic grating rulers.