Computerized Numerical Control (CNC) is a computerized manufacturing process in which pre-programmed software and code controls the speed and movement of the production equipment. CNC machining controls a range of complex machinery such as grinders, lathes and turning mills, which are used to cut, shape and create different parts and prototypes.
CNC machines are automated machines that play an important role in the manufacturing industry and provide more consistent, efficient, and accurate results than manual process. These machines are not only good for complex cutting and in manufacturing a wide variety of items but also in eliminating the risk of human error. CNC machines use a software programming language called G-code, which is written in straightforward and logical way. It tells the machine the exact measurement for production – specifically the feed rate, speed, location, and coordination – which allows the machine to be flexible and consistent in producing different parts. Some of the industries that use CNC machining are manufacturing, metal fabrication, automotive, electronics, agriculture, etc.
With its microprocessor-based system, a CNC machine is composed of:
- Central Processing Unit (CPU) – A CNC system is controlled in the CPU or the heart of the system. It is where the information stored in the memory as part program is received. After the data is accepted, the CPU decodes and changes this data into specific position control and velocity control signals. It also oversees the movement of the spindle or control axis to avoid actions that do not match with the programmed data or correct these actions if already taken.
- Input devices – Input devices are the devices used for putting in the part program in the CNC control. There are three input devices that are commonly used, which are the magnetic tape reader, punch tape reader, and computer via RS-232-C communication.
- Machine Control Panel – A machine Control Panel is a flat area where controlling, monitoring, or managing instruments are displayed, serving as the direct interface between the operator and the NC system. Before a program is executed, the machine should be prepared in terms of loading the system memory with the required part program, establishing a correct reference point, and other necessary command. After the preparation, the CNC then controls the axis of the motion, spindle function or tool function on the machine, following the part program stored in the memory.
- Machine Tool – There are different types of machine tools a CNC controls but what they all have in common is a slide table and a spindle to control the position and speed.
- Programmable Logic Controller (PLC) – A PLC is an industrial solid-state computer that matches the NC to the machine, which follows a pre-programmed sets of rules and carry out outputs based on inputs to control system and make logic-based decisions for the CNC machine. It is used to minimize manual operation and can survive harsh conditions such as extreme heat, cold, dust, and moisture.
- Servo Control Unit – The servo control unit is responsible for precise position control as it receives the position feedback signals for the actual movement of the machine tool axes from the feedback devices. It generates suitable signals as command values, which are interfaced with the axes and the spindle motors.
- Feedback Devices – The feedback devices, which is also referred to as the measuring system, consist of position and speed transducers that act as sensors to monitor the current position of the cutting tool at any instant.
- Display Unit – The display unit is a monitor or an interactive device between the machine and the operator which displays the present status of the programs, commands, and other necessary data of the CNC machine. It can also be useful for maintenance and installation work because it can display other important information such as machine parameters, logic diagram of the program controller, error messages, and diagnostic data.
However, CNC machinists should be knowledgeable and have the skills of a trained professional such as combining elements of mechanical design, technical drawings, mathematics and computer programming to be able to operate these machines. There are also different types of CNC machines that cater to specific purposes. For whatever purpose they are being used, it is undeniable that CNC machines have contributed tremendously to the manufacturing industry.