The layout and wiring inside the electrical control cabinet is very important. Good layout and wiring are not only convenient for production and maintenance, but also improve the reliability of the CNC system.
1. Handling of 220V power supply line for electrical cabinets Precautions for high-power equipment will cause serious pollution of the power grid, causing large fluctuations and surges in the grid voltage. Due to the high pressure in China
(220V), high internal resistance power grid, serious pollution of the power grid. Although the system uses voltage regulation measures, the grid noise will still break into the system. According to statistics, the short-circuit, under-voltage, over-voltage and noise intrusion of the power supply cause CPU malfunction and data loss account for more than 90% of various interferences. Therefore, in the anti-interference design, power supply interference should be considered. The main points are as follows:
1) The power cord should be away from any other cable in the system, and the filter should be installed near the entrance to ensure that interference on the external power supply network enters the cabinet; 
Figure 1 External 220V power line processing method
2) The filter should be installed as close as possible to the power input socket. The incoming and outgoing lines should be routed close to the ground. The two must be separated and not paralleled. It is better to have 180° difference, and the power line of the filter should be far away from the filter. Enter the power cords, don't let them have a chance to get close together, otherwise the interference has a chance to recouple to the power line; 
Figure 2 Filter input and output should not be too close
3) Important components such as the AC power supply of the CNC system should use a low-pass filter to reduce high-frequency interference signals on the power frequency power supply. If there are conditions, the power supply for the servo motor driver, inverter, computer and control circuit inside the CNC system can use three filters respectively, which can not only suppress the external power supply interference, but also suppress the mutual interference between the parts. But it is important to note that at point 2 above, the filter output and input line must be clearly defined, otherwise the filter may not be useful. 
Figure 3 Power supply for important equipment is filtered by filters
4) Pay attention to the wiring in the control cabinet. Do not route the strong electric signal line and the weak electric signal line in one slot, and do not rely too close. 
Figure 4 Strong and weak signal signal lines should be separated
2. Grounding and shielding precautions Good grounding can effectively change the path of interference and conduction, and vent it into the control cabinet or large metal plane to protect sensitive equipment from being affected. However, the wrong grounding position and method can not only protect the circuit well, but may introduce interference into the sensitive device, which is worse than before processing. Shielding protects the internal circuit and allows interference to be conducted through the shield to the ground. Therefore, it is very important to shield the grounding of the shield. It is required to make the surface overlap between the shield and the ground to reduce the impedance. The following are considerations for grounding and shielding:
1) The electrical control cabinet should be made of conductive metal plates. In order to ensure the electromagnetic consistency of the control cabinet, a one-piece structure or welding should be used.
2) The mounting plate of the control cabinet is made of conductive metal plate to improve the grounding performance of the system. 
Figure 5 Installing the baffle with bakelite, grounding through a slender wire, can not guarantee reliable connection
3) The outer casing of the high-voltage equipment such as filters, inverters, switching power supplies, and motor drives is mounted on a metal plate and attached to it, as shown in Figure 4.
4) Each shielded cable enters the entrance of the control cabinet. The shield should be grounded. The grounding method of the shield is shown in Figure 6. 
Figure 6 Shield metal layer is not grounded 
Figure 7 How the cable shield is grounded
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