Introduction: CNC (computer numerical control) machine tool is a kind of automatic machine tool equipped with program control system, which can directly process and produce parts with complex structure, precision, small batch and multiple CNC machining. There are many types of machine tool numerical control system, this paper will mainly introduce the knowledge of machine tool numerical control system.
The numerical control system can be defined as a system, in which the machine can be controlled by a certain format of alphanumeric and symbolic data. This format is called part program.
To change the operation program of the early CNC system needs to change the hardware of the machine itself. In 1970's, CNC system controlled by special microcomputer or microcomputer was developed to make machine tool adapt to different work easily by changing control program or software.
Types of machine tool numerical control system
1. Control system
According to the control system, CNC system can be divided into two categories. They are: open loop CNC system and closed loop CNC system
Open loop NC system: open loop NC system is a system whose output is independent of input. This means that the output of the machine / process is not compared with the given input. In addition, the open-loop CNC system also has the following characteristics: simple construction and work, lower cost, low accuracy, no use of sensors.
What are the advantages of CNC system
Closed loop numerical control system: in closed loop numerical control system, the output depends on the input. This means that the output of the machine / process is compared to a given input. The closed-loop CNC system also has the following characteristics: building and construction complex, expensive, high precision, using sensors.
2. Motion control
On the basis of motion control, machine tool numerical control system can be classified into point-to-point numerical control system, direct cutting numerical control system and contour numerical control system.
Point to point NC system: in the point to point NC system, the machine tool moves from one point to another at a predefined speed and passes through a shortest path (the shortest path between two points is a straight line). PTP NC system has the following functions: tool speed and path are predefined, low cost, for discrete manufacturing processes, such as drilling, spot welding, etc.
Direct cutting CNC system: the direct cutting CNC system has the ability to move the machine along / parallel to any spindle under controlled feed and speed. The direct cutting CNC system has the following characteristics: the tool feed, speed and path (only along / parallel to any spindle) can be changed according to the requirements; it is more expensive than PTP – CNC system; it can be used in milling, turning and other continuous manufacturing processes; the functions of PTP – NC system can also be performed by linear cutting NC system.
Contour CNC system: contour CNC system has the ability to move the machine along / parallel to any complex path. Contour NC system has the following characteristics: tool feed, speed and path can be changed according to requirements, more expensive than PTP and NC system, used in milling, turning and other continuous manufacturing process, PTP and NC system functions can also be implemented through NC system.
3. Number of axes
According to the number of axes, the CNC system can be divided into five groups: 2-axis machine tool, 2.5-Axis machine tool, 3-axis machine tool, 4-axis machine tool and 5-axis machine tool.
2-axis CNC machine tool: like lathe machine tool, the machine tool can only access two axes, and the tool moves in two directions (such as X and z).
What are the advantages of CNC system
2.5-Axis CNC machine tool: it is also a 3-axis system, but the movement is not three-dimensional. The X and Y axes move to this position first, and then the third axis starts to work, such as drilling and tapping machines.
Three axis CNC machine tool: three axes (x, y and z) move simultaneously in three dimensions, which is the most widely used machine tool, can achieve high precision and high precision, and can be used for automatic / interactive operation, slot milling, drilling and cutting sharp edges.
4-axis CNC machine tool: 3-axis machine tool rotates one more turn on a-axis or b-axis. The common example is vertical machine tool or horizontal machine tool. In 4-axis machining, milling is performed on the additional axis, while the operations on X, y and Z are the same as those on the 3-axis system, and the rotation on a or b axis revolves around X.
5-axis CNC machine tool: the 3-axis machine tool rotates additionally in two directions (Y and z) on the a-axis and b-axis, and the rotation is given by the bed and spindle motion (pivot point) respectively. 5-axis machine tool is an advanced CNC machine tool. Its multi-dimensional rotation and tool movement functions make undercutting and deep groove entry more convenient, and unparalleled smoothness and speed can be realized. Therefore, it can create precise and complex parts, which are usually used for advanced applications such as aerospace parts, titanium sheets, oil and gas equipment parts, military products, etc.
This paper explains in detail the CNC system of machine tools. Browsing the article, you can understand that CNC machine tools are automatic machine tools equipped with program control system, which can achieve the purpose of complex, precise, small batch and multiple CNC machining parts processing and production. There are many types of machine tool numerical control system, which can be classified according to the control system, motion control and axis number.
Automatic manipulator "ekthink" for machining motor shaft with CNC cylindrical grinder
Using cylindrical grinder to grind motor rotor of truss manipulator
CNC lathe processing drawings why processing drawings is very important
Copyright ©SHENYI MACHINE TOOL IMPORT AND EXPORT CO., LTD.