In the process of using the CNC system of economical machine tools, it is necessary to improve its anti-interference ability. The common methods include: restraining noise source, blocking noise transmission path, and improving the core of CNC system. Practice has proved that in processing, using these methods flexibly according to the specific situation can effectively improve the anti-interference ability of the NC system of the economic lathe.
1、 Suppress noise source interference
The noise sources of CNC system mainly include internal noise and external noise. For internal noise, try to eliminate it; External noise cannot be eliminated directly, but it can be avoided as much as possible. In production, the measures to eliminate internal and external noise mainly include the following:
1. Eliminate switching sensibility
Switching inductive loads such as relays, contactors and motors will produce high surge voltage, and its pulse power is likely to damage semiconductor devices. This situation can be suppressed by using parallel diodes or connecting RC absorption circuit. The DC relay coils of the machine tool main motor and the electric tool rest motor are connected in parallel with diodes, and the RC absorption circuit is connected in parallel with the contactor coil and the motor winding. Practice has proved that the inhibition effect of this method is still very obvious. In addition, thyristor zero crossing switch can be used to replace AC contactor, which can completely eliminate transient noise.
2. Eliminate DC power supply noise
The power supply of most economical lathe CNC system computers is composed of three terminal integrated voltage regulators. The circuit is simple and reliable, but the ability to suppress the power supply noise from the external AC power grid is very weak. To suppress the interference of noise sources, multi-stage filter circuit can be considered to strengthen filtering. Connecting a line filter at the input of AC power supply can not only suppress the generation of common mode noise and normal mode noise, but also be effective for external power supply noise.
2、 Optimize circuit design
Most economical CNC systems use single-chip computers, which need to expand some peripheral interface circuits. The input port of single-chip computers should be added with pull resistors, especially the interrupt port should be added with integral and shaping circuits, and the output port should be added with current drivers to enhance the anti-interference ability of input and output ports.