What kinds of CNC machine are there?
1 Method of classifying according to the movement of the machine:
a. point control system
The so-called point control system is a process that only controls the movement of the tool from one point to another. During the movement, the cutting process is not performed, and there is no requirement for the movement track. However, there are high accuracy requirements for the coordinate position. In order to improve the production efficiency, the machine tool generally performs the positioning movement according to the highest feed speed, and decelerates or grades when approaching the positioning point, thereby reducing the positioning error caused by the inertia.
b. linear control system
The so-called linear control system controls the movement of the tool from one position to another along a direction parallel to a coordinate axis. The movement path must be parallel to the machine axis, that is, the tool can be given during the movement. The speed is cut, which differs from the point in that the moving speed and trajectory between the two points are set by the system.
c. Contour control system
The contour control system is the most versatile compared to the two control systems above. It controls two or more axes simultaneously, not only controlling the start and end coordinates of the moving parts of the machine, but also controlling the speed, direction and trajectory of the entire process. Therefore, under the contour control system, the numerical control device needs to have the function of interpolation calculation. Through the processing of the interpolation operator in the numerical control system, the cutter continuously cuts the surface of the workpiece during the movement, and can perform various straight lines, arcs, Processing of the curve. It is capable of two-coordinate or even multi-coordinate linkage control, and can also perform point and line control.
2 Classified by servo system control
a.Open loop control machine
The so-called open-loop control machine refers to a control system without feedback. There is no position feedback component in the system, and a stepper motor is usually used as the actuator. The input data is calculated by the numerical control system, and a command pulse is issued. The stepper motor is rotated through a loop distributor and a driving circuit to rotate the stepping motor through a step angle, and then the transmission mechanism drives the table to move a pulse equivalent distance. The moving speed and displacement of the moving part is determined by the frequency of the input pulse and the number of pulses.
b.Semi-closed CNC machine
An angular displacement detecting device is installed at the end of the driving motor or at the end of the driving screw, and the actual position or displacement of the executing member is indirectly measured by detecting the rotation angle of the motor or the screw, and then fed back to the numerical control system. It achieves higher precision than the open-loop system, but its displacement accuracy is lower than that of the closed-loop system, and it is easier to achieve system stability than the closed-loop system. This semi-closed-loop feed servo system is widely used in most CNC machine tools. The moving parts of the machine with large inertia are not included in the detection range.
c. Closed loop control of CNC machine tools.
The closed-loop control CNC machine tool can use DC or AC servo motors, and needs position feedback and speed feedback. It can detect the actual displacement of moving parts at any time during machining and feed back to the CNC system in time. It compares with the command signal obtained by the interpolation operation, and the difference is used as the control signal of the servo turbulence, thereby driving the displacement component to eliminate the displacement error.
3 Classified according to the functional level of the CNC system
According to the functional level of the CNC system, we usually divide the CNC system into high, medium and low third gears. Of course, this is also relative, and the criteria for division will be different in different periods. The full-function numerical control or standard numerical control is generally a medium and high-grade numerical control system, and the economical numerical control belongs to the numerical control system. The numerical control system is composed of a single-chip microcomputer and a stepping motor, and its function is relatively simple and relatively inexpensive.
4 Classified according to processing technology and machine tool use
a. Metal cutting machine tools refer to CNC machine tools that use various cutting processes such as turning, milling, length, hinge, drilling, grinding, and planing. Metal cutting machine tools can be divided into two types, one is a common type of CNC machine tools, such as CNC lathes, CNC milling machines, CNC grinding machines. The other is a machining center, such as a machining center, a turning center, a drilling center, etc. Its main feature is that it has an automatic tool change mechanism and a tool magazine, which can continuously perform various process changes and automatically change tools.
b. Metal forming machines, such as CNC presses, bending machines, bending machines, spinning machines, etc., use a CNC machine tool for extrusion, punching, pressing, and drawing.
c. Special processing categories, mainly CNC electric wire electric wire cutting machine, EDM machine, flame cutting machine, laser processing machine.