There are many types of CNC machine tools, which can be classified from different perspectives. Different classification standards correspond to different classifications. Today, our chief engineer from Raychem Technology introduces two classification methods for each of you, that is, according to the movement method and control. Ways to classify, the specific content is as follows:
The numerical control machine tool divides according to the movement way, may divide into:
(1) Point Control System
Only the position of the tool from one point to another is controlled, but no cutting is performed during the movement, such as coordinate boring machine, drilling machine and punch press. It is required to have high positioning accuracy in the coordinate position. In order to increase the production efficiency, the positioning movement is set using the highest feed rate set by the machine tool. Grading or continuous speed reduction is performed before approaching the positioning point to approach the end point at a low speed, thereby reducing motion. Overshoot of the component's inertia and the resulting positioning error. No cutting machining is performed during the positioning movement, so there is no requirement for the movement trajectory.
(2) Linear Control System
A linear control system is a precise movement of a tool or a basic table at a certain speed, in a direction parallel to a certain coordinate axis, from one position to another. Also called a point linear movement control system.
(3) Contour control system
It controls two or more coordinate axes simultaneously (two-axis, two-axis half, three-axis, four-axis, and five-axis linkage). It not only controls the starting and end coordinates of the moving parts of the machine tool, but also controls the entire The speed, direction and displacement of each point in the machining process, ie, the trajectory of the machining process, are processed to produce the desired contour. Trajectories are straight lines, arcs, spirals, etc. with arbitrary slopes. The functions of the numerical control device of this kind of machine tool are the most complete. It can perform the control of two coordinates or even multiple coordinate linkages, and it can also perform point and line control.
The numerical control machine tool divides according to the movement way, may divide into:
(1) Open-loop CNC machine tools
Refers to the control system without feedback, there is no position feedback element in the system, usually use the stepper motor as the implementing agency. Input data through the numerical control system operation, issued a command pulse, through the ring distributor and drive circuit, so that the stepper motor rotates a step angle, and then drive the work platform to move a pulse equivalent distance. The moving speed and displacement of the moving part are determined by the frequency of the input pulse and the number of pulses.
(2) Semi-closed-loop CNC machine tools
Install the angular displacement detection device (optical encoder or inductive synchronizer) at the end of the drive motor or at the end of the drive screw, indirectly measure the actual position or displacement of the actuator by detecting the rotation angle of the motor or screw, and then feed back to the CNC system. in. Get higher accuracy than open-loop system, but its displacement accuracy is lower than that of closed-loop system. Compared with closed-loop system, it is easy to achieve system stability. Most semi-closed-loop feed servo systems are widely used in most CNC machine tools. Moving parts with larger inertia are not included in the detection range