Composition of a CNC machine system


CNC Machine is now widely used in many industries and it is essential for the economy of any industrialize countries, so what is the composition of a CNC machine system or what are the basic elements to form a CNC machine system? Following is the answer for you to know.

Any CNC machine tool essentially consists of the following parts:

1)Input Device

2)Machine Control Unit

3)Machine Tool

4)Driving System

5)Feedback Devices

6)Display Unit

Input Device:

The program input device is the means for part program to be entered into the CNC control.

Five used program input devices are floppy disk drive, USB flash drive, serial communication, ethernet communication and conversational programming.

Machine Control Unit

The machine control unit (MCU) is the heart of a CNC system. There are two sub-units in the machine control unit: the Data Processing Unit(DPU) and the Control Loop Unit(CLU). It is used to perform the following functions:

To read the coded instructions.

To decode the coded instructions.

To implement interpolations (linear, circular, and helical) to generate axis motion commands.

To feed the axis motion commands to the amplifier circuits for driving the axis mechanisms.

To receive the feedback signals of position and speed for each drive axis.

To implement auxiliary control functions such as coolant or spindle on/off and tool change.

Machine Tool

CNC controls are used to control various types of machine tools. Regardless of which type of machine tool is controlled, it always has a slide table and a spindle to control of position and speed. The machine table is controlled in the X and Y axes, while the spindle runs along the Z axis.

Driving System

A driving system consists of amplifier circuits, drive motors, and ball lead-screws. The MCU feeds the control signals (position and speed) of each axis to the amplifier circuits. The control signals are augmented to actuate drive motors which in turn rotate the ball lead-screws to position the machine table. Four types of electrical motors are commonly used DC servo motor, AC servo motor, stepping motor and linear motor.

Feedback Devices

The feedback devices are also referred to as the measuring system. It uses position and speed transducers to continuously monitor the position at which the cutting tool is located at any particular instant. The MCU uses the difference between reference signals and feedback signals to generate the control signals for correcting position and speed errors.

Display Unit

The Display Unit serves as an interactive device between the machine and the operator. When the machine is running, the Display Unit displays the present status such as the position of the machine slide, the spindle RPM, the feed rate, the part programs, etc.

In an advanced CNC machine, the Display Unit can show the graphics simulation of the tool path so that part programs can be verified before the actual machining. Much other important information about the CNC system can also be displayed for maintenance and installation work such as machine parameters, logic diagram of the program controller, error messages and diagnostic data.

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