How CNC Machine Works? Learn with Diagram

What is a CNC Machine?

CNC stands for Computer Numerical Control. The machine or whole system where a computer is used to control Numerical Control(NC) machine tools such as lathe machines, mills, slotter machines, shapers, etc is called a CNC Machine. For example when the cutting operation is performed by the CNC system then it is called CNC Machining. CNC machines are helpful for removing layers from stock grinding and it is suitable for a wide range of materials such as metal plastics, wood, glass, foam, etc. The main purpose of using CNC is precision. During the cutting and drilling, all the measurements and operations are controlled by the computer rather than by hand, so there is almost no chance of human error. This will give a very good shape of the materials, low wastage, and a very less time operation.

CNC Machine Block Diagram

Here, you can see the block diagram of CNC machine so it will help you to better understand about the CNC machine.

Important parts of a CNC Machine

A CNC machine has the following important parts,

1. Input Devices
2. Machine Control Unit(MCU)
3. Machine Tool
4. Driving System
5. Feedback System
6. Display Device

Input Devices

The input devices for a CNC machine can be classified into three major parts - 1. Manual Input 2. Readers/Sensors 3. External Input

The manual input is that through which we can give manual input to the system such as a keyboard. CNC machines have some sensors/readers as input devices to measure or read the tapes so they can cut the metal according to this measurement. External is provided to the system through different ports. This may be used to store programs or software.

Machine Control Unit(MCU)

It is the main part of the CNC Machine that takes all the inputs, processes data and controls all the operations for the machine. It reads, decodes, and executes data after receiving it from the input devices, and feedback systems. After executing the programs it generates the appropriate output signal to control the machine tools.

The main thread in a CNC machine is to properly set up the machine tools with the proper axis so the cutting, drilling, or designing operation happens with exact precision. So, the MCU helps a lot to implement the interpolation(linear, circular, or helical) to generate the axis. Also, it generates the axis motion commands and feeds them to the amplifier circuit to drive the axis mechanisms.

Machine Tools

Machine tools are positioned and placed at the actual place where the cutting or drilling operation is to be done. Generally, most CNC machines are built with some common machine tools such as a sliding table and spindle to control the position and speed. Generally, the sliding table is controlled in X-axis and Y-axis directions whereas the spindle is controlled in the Z-axis direction.

Driving System

The driving system of the CNC machine is built with amplifier circuits, driver motors, ball lead screws, etc. The amplifier takes separate inputs for a separate axis. The MCU feeds the speed and positioning signal to the amplifier for each axis. The signals from the MCU are amplified by the amplifier so it can drive the heavy driver motors and other parts. So, these driver motors rotate the ball lead screws to position the machine table.

Feedback System

The feedback system in a CNC machine consists of speed and position-measuring sensors or transducers. So the system continuously monitors the speed and positions of the machine tools during cutting. The feedback signal sends the feedback signal to the MCU. So the MCU makes the difference between the feedback signal and reference signal to generate the control signal to correct the position and speed errors.

Display Unit

The display unit(such as a screen) shows the data and information to the user.

CNC Machine Working Procedure

1. First of all the required programs, software and are installed in the MCU unit.

2. Input or instruction is provided to the MCU through manual input or other input systems.

3. The MCU starts executing programs according to the instruction given and it generates an output common signal and fed to the driver circuit.

4. Once the driver circuit receives the command signals from the MCU it starts the actual machine operation.

5. The feedback system continuously measures and monitors the machine operation and provides the feedback signal to the MCU.

6. The MCU again generates the command signals to eliminate the error by comparing the reference signal with the feedback signal.

7 In the display unit user can see all the commands, actions, information, and data regarding the machine's operation.

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