CNC equipment maintenance is a very complex, highly technical piece of work, CNC equipment and ordinary equipment has a big difference.
1.1 Using the self-diagnostic function of the CNC system
General CNC systems have a more complete self-diagnostic system, whether it is a Fanuc system or Siemens system, the CNC system on the initialization of the power supply or operation of the system can make a certain range of self-diagnostics on their own or interface. Maintenance personnel should be familiar with the system self-diagnosis of various alarm information. According to the manual to analyze to determine the scope of the fault, locate the fault components, for imported CNC systems can generally only be located to the board level, the chip-level maintenance can generally rely on the manufacturers of CNC systems after-sales service department.
1.2 Use the logic of the PLC program to find
Nowadays, the general CNC control system with a PLC controller, mostly built-in PLC control. Maintenance personnel should be based on ladder diagrams to analyze the machine control appliances, visualize the state of the CNC system I / O on the CRT. Through the logical analysis of the PLC program, it is convenient to check the problematic parts of existence, such as self-diagnostic page in the FANUC-OT system. According to the drawing PLC ladder diagram to analyze, locate the machine tool and CNC system interface failure, in order to determine the part of the fault is mechanical, electrical, hydraulic or pneumatic failure.
1.3 Fully communicate with the operator on the spot
The operator on the spot is the closest partner of the CNC machine tool, and the operator is also the first discoverer of various faults. Therefore, when the failure occurs, the maintenance staff generally do not rush hands, first with the operator to communicate fully, to carefully ask the failure occurs when the machine tool is in what working condition, the form of performance, the consequences, whether or not the misoperation, the failure can be reproduced, etc., which will help the maintenance staff to quickly analyze and determine the cause of the failure.
2 anti-interference measures for CNC machine tools
The machine tool CNC system contains both high-voltage, high-current strong electrical equipment, but also contains low-voltage, low-current control and signal processing equipment, i.e., weak electrical equipment. Strong electrical equipment generated by the strong electromagnetic interference on the normal work of weak electrical equipment constitutes
a great threat. In addition, the system is located in the production site of the electromagnetic environment is poor, the system outside the interference of various power loads, power supply system interference, electromagnetic wave interference in the atmosphere, etc. will have a serious impact on the system within the weak power equipment, due to the weak power equipment is to control the strong power equipment, so once the weak power equipment is interfered with, and ultimately will lead to the paralysis of the entire system.
Often from the following aspects to take measures to improve the ability of CNC system interference.
2.1 Reduce the power supply line and signal line interference can take the following measures
(1) CNC machine tools away from equipment with medium and high frequency power supply.
(2) CNC machine tools and high-power and frequent starting and stopping equipment with the same power supply trunk power supply.
(3) for the grid voltage for a long time under voltage, over voltage and voltage fluctuations of the occasion to install AC voltage regulator.
(4) The use of power filters. The role of the power filter is bidirectional, it can not only prevent the noise in the grid into the equipment, but also can inhibit the noise generated by the equipment to pollute the grid.
(5) The use of isolation transformers with shielding. Isolation transformer is a kind of power supply anti-interference equipment which is quite widely used, its most basic role is to realize the electrical isolation between the circuit and the circuit, and solve the interference generated between the equipment and the equipment.
(6) analog signal transmission line wiring should be as short as possible, and use shielded wire.
(7) The output signals of the photoelectric encoder, hand pulse generator, scale, etc. are connected in parallel with capacitors at the receiving circuit end to suppress high-frequency interference. The shield of the photoelectric encoder cable is grounded at both ends.
(8) The motor drive cable shield is grounded at both ends.
(9) Separate routing of power and signal lines.
(10) The control signal line is shielded twisted pair.
2.2 Reduce the interference in the machine tool electrical control system can take the following measures
(1) in the power input part of the voltage-sensitive resistor protection (surge absorber), the line transient, sharp bees and other noise suppression.
(2) Inductive loads with absorption circuitry to suppress transient noise. Inductive loads in the system, such as relays, contactors, electromagnetic Yan, motors, etc. in the shutdown will produce a strong pulse noise, affecting the normal operation of other circuits, must be installed in the inductive loads at the absorption circuit to suppress transient noise. DC inductive components (DC relay coil) in parallel with the continuity of the two pick-up tube. AC contactors, solenoid valves, relay coils in parallel with the RC resistive absorber. Three-phase AC motor armature winding parallel connection between the RC resistive absorber.
(3) to ensure good "grounding". "Grounding" is a key anti-interference technology in the installation of CNC machine tools. CNC systems and electrical cabinets in the control equipment must be in accordance with the requirements of the instruction manual for "grounding", otherwise many interfering factors in the power grid will be through the "ground" on the machine tool operation interference.