1. Intuitive method:
The intuitive method is a method of diagnosing a fault by changes in morphology, sound, color, smell, and the like. It has the following methods.
A. Look carefully with the naked eye to see if there is any problem such as fuse blow, device burnout and open circuit, and observe whether the mechanical part drive shaft is bent or shaken.
B. Hear all kinds of abnormal sounds caused by faults in CNC machine tools, such as power transformers, resistors and reactors in the electrical part, because of the looseness of the core, corrosion and other causes of the vibration of the iron piece; relays, contactors, etc. Beep caused by excessive magnetic circuit gap, etc.; mechanical friction sound, vibration sound and impact sound.
C. Touch touch temperature rise, the touch of human fingers is very sensitive, can judge the abnormal temperature rise quite reliably; slight vibration can also be identified by hand; the scars and ripples that are invisible to the naked eye can be easily touched with a finger. Feel it. In addition, the virtual welding or poor contact of the CNC system can be diagnosed by gently tapping the suspicious part with the insulation and using the touch method.
D. The smell of smoke, burnt smell, etc., which are generated by violent friction or short circuit of electrical component insulation damage, can better judge the fault.
2, data analysis method Data analysis method is to find the law by looking up the technical file data to find the law, to determine the cause of the fault. The materials reviewed are mainly:
A. The numerical control system data understands the characteristics, alarm and troubleshooting methods of the numerical control system through the numerical control system data; the meaning of NC and plc machine parameter setting; the numerical control programming method; the function and operation method of each key on the panel; the performance of the spindle and the feed motor And the characteristics of the drive, etc. Focus on the structural block diagram of the CNC system, understand the function of each printed circuit board in the box, the direction of the interface, the meaning of the LED light-emitting diode lamp.
B. Electrical drawings focus on electrical components such as contactors, relays, and PLC input/output components through electrical patterns. Each country's electrical symbol is different, you should understand clearly and pay attention to the difference.
C. Mechanical, hydraulic and pneumatic partial drawings For the mechanical, hydraulic and pneumatic partial drawings of CNC milling machines, it is necessary to clarify the role of each component and to mark them one by one on the drawing. It is important to understand the parts of the electromechanical relationship that are relatively close.
D. Foreign language data, under possible conditions, try to look at the original foreign language information of imported machine tools to avoid misinformation caused by inaccurate translation.
3, failure symptom analysis method
A. Due to the limitations of industrial field test conditions and analytical techniques, the vibration method is difficult to extract and analyze some fault symptoms, and some fault symptoms are not sensitive to fault conditions. Relatively speaking, the vibration of CNC milling machine is currently recognized as the best fault symptom extraction quantity of mechanical parts. Its response to the running state is rapid, real and comprehensive, which can well reflect the nature and range of mechanical failure of most CNC milling machines. There are many advanced and effective methods to choose from, so the vibration method is the most commonly used method in the CNC milling machine failure symptom analysis method. The vibration method is divided into two categories: time domain diagnosis and frequency domain diagnosis. Frequency domain diagnosis can be divided into vibration frequency domain direct analysis method and vibration frequency domain secondary analysis method.
(1) Vibration time domain analysis method This method compares the vibration time domain signals of various fault states with the vibration time domain signals of the normal state, thereby identifying the fault condition of the numerical control milling machine. The time domain analysis method is mainly divided into time domain statistical analysis method, time domain correlation analysis method and time domain synchronization analysis method. The time domain statistical analysis method analyzes the fault conditions of the CNC milling machine by calculating various statistical parameters of the vibration signal. The time domain correlation analysis method mainly uses autocorrelation and cross correlation analysis to analyze the fault condition of the CNC milling machine. The time domain synchronization analysis method is an effective therapy for extracting periodic components in a CNC milling machine signal mixed with noise interference, also called coherent detection.
(2) Vibration frequency domain direct analysis method This method is the most commonly used method for CNC milling machine fault diagnosis. It decomposes the time domain signal with time as the abscissa into the frequency domain signal with the frequency as the abscissa by the Fourier transform, and obtains the spectrogram, and obtains the amplitude and phase information about the frequency components of the original time domain signal, thereby Get the diagnosis result.
(3) Vibration frequency domain secondary analysis method This method further processes the information provided by the spectrogram to improve the accuracy of fault diagnosis. It needs to transmit the measured spectrum map to the microcomputer and analyze it with dedicated software. The secondary analysis method mainly includes power spectrum analysis method, cepstrum analysis method, frequency refinement analysis method and wavelet analysis method.
B. Noise spectrum analysis method This method introduces less disturbance in the near-field measurement, and its analysis result is very close to the vibration measurement. For example, after the gear of the CNC milling machine wears out, the sound pressure level of the gear running noise is obviously increased due to the involute tooth profile distortion, which is generally ten decibels larger than the normal gear noise level difference. The frequency of the noise is generally high, but the corresponding vibration amplitude may not be large. If the vibration source component is a moving component, it is not easy to set the sensor, and noise spectrum analysis can be considered. Noise measurement has the characteristics of rich information, convenient testing and non-contact, but should try to solve the interference problem of environmental noise.
C. Oil Analysis Method This method diagnoses the wear failure of CNC milling machines by monitoring the distribution of wear debris in the lubricating oil and the degree of contamination of the lubricating oil. The specific methods used are:
(1) Magnetic plug inspection method A magnetic probe (magnetic plug) is inserted into the oil passage system of the numerical control milling machine to collect the ferromagnetic abrasive grains in the oil, and periodically observe to judge the wear state of the numerical control milling machine.
(2) Particle counter method The photoelectric particle size is used to automatically count and analyze the particle size in the oil sample.
(3) Oil sample spectrometry method According to the spectrum of specific wavelength emitted by various metal abrasive grains in the oil sample when excited under the ion state, the type and content of the metal in the oil sample are detected, thereby diagnosing the fault.
(4) Oil sample iron spectrum analysis method It is a method of separating the abrasive grains generated by the friction pair of the numerical control milling machine from the oil sample under the action of high gradient strong magnetic field, and arranging and sedimenting to a transparent glass base according to the particle size. On-chip, then use various means to observe or measure to obtain various information of the wear process, thereby analyzing the wear mechanism and an analysis method for judging the wear state of the equipment.
4, expert system law expert system should generally include the following parts: knowledge base, inference engine, dialogue part, knowledge acquisition part and explanation help part, the most important part is the knowledge base. There are many ways to build a knowledge base. At present, there is a fault tree method that is more commonly used for CNC milling machines. The fault phenomenon of the CNC milling machine can be divided into mechanical part, feed drive part, cNC part and spindle servo control part according to its occurrence. Each part can also be divided into finer subsystems according to the complexity of the fault, such as CN (: part can be divided into power control part and display part, etc. Each subsystem can represent its fault by fault tree. Firstly, the system fault is analyzed. The event is called the top event. The top event is actually some fault phenomenon, such as "the Manual Pulse Generator does not work", "the feed direction is opposite to the mark", etc., which will lead to the direct cause of the event, including hardware failure. Listed by human factors and environmental factors, and connected with fault events by appropriate logic gates, called intermediate events. The causes of fault events are gradually expanded, that is, the root causes of these phenomena, such as trigger damage, the main The faulty node of the printed circuit board is called fault node. According to this method, the fault tree of each subsystem can be established. After a large number of fault trees are established, it can be converted into the basic data model of the machine to establish a database. The expert system also has a neural network-based CNC milling machine fault diagnosis expert system, which utilizes the high power of the neural network.
Absolute rotary Encoder measure actual position by generating unique digital codes or bits (instead of pulses) that represent the encoder`s actual position. Single turn absolute encoders output codes that are repeated every full revolution and do not output data to indicate how many revolutions have been made. Multi-turn absolute encoders output a unique code for each shaft position through every rotation, up to 4096 revolutions. Unlike incremental encoders, absolute encoders will retain correct position even if power fails without homing at startup.
Absolute Encoder,Through Hollow Encoder,Absolute Encoder 13 Bit,14 Bit Optical Rotary Encoder
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