The basic components of CNC machine tools include processing programs, input devices, CNC systems, servo systems, auxiliary control devices, feedback systems and machine tool bodies. The machining program can be written manually (such as when machining simple workpieces by lathe CNC system), and complex machining requirements can be drawn on the computer (such as when milling machines and machining centers are machining curved workpieces), and then generate machining programs. The input of the program can be manually input by the panel of the numerical control system, or transmitted through the communication port of the computer with a cable, and can also be transmitted with the USB interface of the computer.
The following analysis is made from two aspects of CNC system and drive unit:
1. Selection of CNC system
The numerical control system is the "brain" of the numerical control machine tool, which operates and processes the control information of the machine tool. According to the principle of numerical control system, it can be divided into two categories: economical numerical control system and standard numerical control system.
1.1 Economical CNC system
From the point of view of control method, economical CNC system generally refers to open-loop CNC system, which has the advantages of simple structure, low cost, convenient maintenance and debugging, and low operation and maintenance cost. The torque is restricted by each other, and the improvement of performance is limited. Therefore, economical CNC systems are often used in CNC wire cutting and some economical CNC lathes and milling machines that do not require high speed and precision, and are also widely used in the CNC transformation of ordinary machine tools.
The open-loop numerical control system means that the index control system itself does not have a position detection device. The numerical control system sends a certain number and frequency of command pulses, and the drive unit performs the machine tool positioning. When the open-loop system is affected by external factors, the machine tool does not move or does not move in place, but when the system has reached the designated position, the machining accuracy of the machine tool will be greatly reduced. However, because of its simple structure, rapid response, stable and reliable operation, convenient debugging and maintenance, and very low price, it still has the largest market in China.