Parts inspection is an important link in the processing of parts. Mechanical parts are checked to determine their technical status and the quality of the technological measures taken. So what are the inspection contents and what are the inspection methods? Let us take you to understand!
Main contents of parts inspection
In the quality inspection process, parts are generally inspected one by one, and its main contents can be divided into the following aspects:
Inspection of geometric accuracy of parts
Geometric accuracy includes dimensional accuracy and shape position accuracy, but sometimes maintenance work does not pursue the geometric size of a single part, but requires relative matching accuracy, which is often an important part of the inspection work.
The shape and position accuracy commonly used in maintenance include roundness, cylindricity, concentricity, coaxiality, parallelism and perpendicularity.
Inspection of Surface Quality
The inspection of the surface quality of the parts in the maintenance work is not limited to the inspection of the surface finish, but the inspection of the surface of the used parts for scratches, burns and roughness.
Inspection of mechanical properties
According to the characteristics of quality inspection, except for the hardness of the mechanical properties of the part material, other indicators are generally not checked, but some properties encountered in the process of part manufacturing and overhaul, such as balance status and spring stiffness Wait, it cannot be ignored.
Inspection of Hidden Defects
During the manufacturing process of parts, there may be original defects such as slag inclusions and cavities inside, and microscopic cracks may occur during use. These defects cannot be found directly from general observation and measurement, but it may have serious consequences on the machinery. Therefore, in the quality inspection, some parts must be purposefully inspected comprehensively.
Method of parts inspection
There are many methods of parts inspection, and new inspection technologies are advancing with each passing day. However, starting from the reality of quality inspection work, it can be summarized as follows:
Sensory test
This is a method to identify the technical condition of parts only by the inspector’s intuitive feeling without checking the equipment. This method is simple, and in the quality inspection, it is also easier to distinguish the defects of a large number of disassembled parts, so this method is still useful. However, this method cannot be used to inspect parts with high precision requirements, and requires inspectors to have rich experience. Generally start from the following aspects:
Visual inspection
The main content of sensory inspection during visual inspection, such as fractures and macro cracks of parts, obvious bending and distortion, burns and abrasions on the surface of parts, severe wear, etc., can usually be directly identified with the naked eye. In order to improve the accuracy of visual inspection, it can also be carried out with the help of a magnifying glass in some cases. In order to make up for the lack of visual inspection of some walls, it can also be inspected by means of an endoscope with optical fiber as light transmission.
Hearing test
The method of judging whether mechanical parts are defective by relying on the auditory ability of the human ear is a long-standing inspection method. This method has been used for decades in the daily inspection of railway vehicles. Knock the inspected workpiece during the inspection. When the parts are not defective, the sound is clear and crisp, but when there are internal shrinkage cavities, the sound is low. If there are cracks inside, the sound is hoarse. Therefore, according to different sounds, the parts can be judged With or without defects.
Tactile check
By touching the surface of a part with your hands, you can feel its surface condition. Shake the fittings relative to each other to feel their fit. The machine in operation can feel its heating condition by touching its parts, so as to judge its mechanism condition.
Instrument and tool inspection method
A lot of inspection work is carried out with instruments and tools. Due to the different principles and types of instruments and tools, they can be divided into general measuring tools, special measuring tools, mechanical instruments and meters, optical instruments, electronic instruments, etc.
Physical inspection
This is a method to detect the technical status of parts by using physical quantities such as electricity, magnetism, light, sound, heat, etc. through changes caused by workpieces. The realization of this method is also combined with the instrument and tool inspection method. This method is usually used to check the hidden defects inside the part without damaging the part itself, and it is generally called non-destructive testing. Non-destructive testing technology is developing day by day in recent years, and magnetic particle method, infiltration method, ultrasonic and ray method are widely used in production now.
Hope the above content can help you!
