Introduction of commonly used instruments in the fault detection of CNC machine tools

In the fault detection process of CNC machine tools, it is necessary to use some necessary instruments. The instruments can directly reflect the status of the fault point from the perspective of quantitative analysis and play a decisive role.

1. Vibration measuring instrument

Vibration meter is the most commonly used and most basic instrument in vibration testing. It amplifies, transforms, integrates, and detects the weak signal output by the vibration sensor, and then directly displays the vibration of the device under test on the instrument or display Value size. In order to meet the requirements of on-site testing, vibrometers are generally made into portable and pen-type vibrometers. The appearance of the vibrometer is shown in Figure 1-18.

Vibrometer is used to measure the operation of CNC machine tool spindle, the operation of the motor, and even the operation of the whole machine. It can be determined according to the required parameters, vibration frequency and dynamic range, sensor installation conditions, and machine tool bearings. For factors such as type (rolling bearing or sliding bearing), different types of sensors are selected respectively. Commonly used sensors are eddy current displacement sensors, magnetoelectric speed sensors and piezoelectric acceleration sensors. Is also effective, these dedicated

Currently commonly used vibration measuring instruments include the TK-81 from Bentley, USA, the VIBROMETER-20 from Schenck, Germany, the VM-63 from RI-0N, Japan, and some domestically made instruments.

Generally speaking, the most convenient to use in the field is the absolute judgment standard, which is formulated for various typical objects, such as the international general standards ISO2372 and ISO3945.

The relative judgment standard is applicable to the same equipment. When the change of the vibration value reaches 4dB, it can be considered that the state of the equipment has changed. Therefore, for low frequency vibration, usually when the measured value reaches 1.5 to 2 times the original value, it is the attention zone, and when it is about 4 times, it is the abnormal area; for high frequency vibration, 3 times the original value is set as the attention zone, and when it is about 6 times It is an abnormal area. Practice has shown that the more accurate and reliable way to evaluate the state of the machine is to use relative standards.

Two, infrared thermometer

Infrared temperature measurement uses the principle of infrared radiation to convert the measurement of the surface temperature of an object into a measurement of its radiation power. The infrared detector and the corresponding optical system are used to receive the invisible infrared radiation energy of the measured object, and It becomes other energy forms that are convenient for detection to be displayed and recorded. The appearance of the infrared thermometer is shown in Figure 1-19.

According to the different response forms of infrared radiation, it is divided into two types: photoelectric detector and thermal detector. Infrared thermometers are used to detect parts of CNC machine tools that are prone to heat, such as power modules, wire contacts, spindle bearings, etc. The main manufacturers include HcW series from Kunming Institute of Physics in China, HCW-1 and HCW-2 from Northwest Optical Instrument Factory of China, IR series from Shenzhen Jiangyangguang Company, and CYCLOPS and SOLD models from LAND Company of the United States.

Infrared thermal televisions, photo-mechanical scanning thermal imaging cameras and focal plane thermal imaging cameras are also used to measure temperature using infrared principles. The judgment of infrared diagnosis mainly includes temperature judgment method, similar comparison method, file analysis method, relative temperature difference method and thermal image abnormality method.

Three, laser interferometer

Laser interferometer can perform high-precision (position and geometric) accuracy correction on machine tools, three measuring machines and various positioning devices, and can complete the measurement of various parameters, such as linear position accuracy, repeat positioning accuracy, angle, straight line Degree, perpendicularity, parallelism and flatness, etc. Secondly, it also has some optional functions, such as automatic pitch error compensation (applicable to most control systems), machine tool dynamic characteristics measurement and evaluation, rotary coordinate indexing accuracy calibration, trigger pulse input and output functions, etc.