screw press machine continues to develop with scientific and technological progress. In recent years, with the rapid development of communication technology and sensor technology, CNC technology of screw press machine has made great progress and gradually get mature application, such as automatic die changing system, touch screen monitoring technology with perfect functions. The CNC degree of the press is improved, the accuracy of the product is improved to a large extent, and the safety and comfort of the use are further enhanced.

   However, the use of high-precision sensors and frequency converters and other electrical components, while bringing many advantages, also bring some interference problems. The internal and external interference of the control system will affect the reliable operation of the whole machine. Strong interference may even cause the screw press machine to fail to operate. Therefore, only by fully considering the anti-interference Usually, the circuit and plug-in frame in the electrical box are separated from the outside of the machine with insulation support ，just to keep good insulation between the circuit components and the casing. The grounding point of the circuit is connected to the copper plate specially set on the plug-in frame, and the control system and power equipment should be separately grounded. Special attention should be paid to avoid control system and motor, frequency converter, transformer and other power equipment series grounding.anti-interference measures in the design and installation of the peripheral circuit,  the control system can work safely and reliably.

1.Control system interference source and propagation path analysis

  Generally speaking, in addition to useful signals, all other electronic signals  are called noise, when the signal of this noise accumulated to a certain degree, it will form interference to the control system. The electrical interference of screw press machine control system involves a wide range. According to its sources, it can be roughly divided into two aspects: external lead interference source and internal interference source.

External system lead interference source

  Interference sources outside the system mainly refer to the power line interference outside the screw press machine control system, including two aspects: interference from the power supply and interference caused by the chaos of the grounding system.

  Control systems are generally powered by industrial power networks, but some large equipment in the power grid system start, stop, are likely to cause power overvoltage, undervoltage, surge, subsidence and peak interference,at the same time, the power supply system of the power cord can produce common-mode interference between the earth, and also can produce series mode interference between the power cord.All these interferences will be coupled to the control system through the internal resistance of the power supply, thus affecting the stable operation of the control system.

2.Grounding wire is often an important means to suppress noise and prevent interference.

  When using a screw press machine,a good grounding method can improve the anti-interference ability of the system to a great extent, but when the grounding wire system is chaotic, the points at each grounding point are unevenly distributed, and there is potential difference between different grounding points, which causes loop current and interferes with the normal operation of the system.

3.anti-interference scheme of power supply

  The interference of the power supply has a great influence on the system stability.Design of power anti-interference scheme and increasing the anti-interference ability of power circuit can greatly weaken the disadvantages of interferenceIt is required that the ac voltage regulator has no self-excitation phenomenon, and the ripple is as small as possible, so that it can avoid external interference and self-interference.

4.Anti-interference scheme of grounding system

  For the screw press machine, the correct grounding method can not only suppress the influence of electromagnetic interference, but also suppress the electromagnetic interference sent out by the equipment. Therefore, the power grid and the chassis can be co-grounded, and the circuit can be floating. That is, the grounding point of the chassis is connected to the grounding point of the power grid, and the grounding point of the circuit is independent to avoid interference from the earth potential and grounding circuit.Usually, the circuit and plug-in frame in the electrical box are separated from the outside of the machine with insulation support ，just to keep good insulation between the circuit components and the casing. The grounding point of the circuit is connected to the copper plate specially set on the plug-in frame, and the control system and power equipment should be separately grounded. Special attention should be paid to avoid control system and motor, frequency converter, transformer and other power equipment series grounding.