Cleanliness control that cannot be ignored in product quality
Guide
In everyone’s impression, a new car needs a longer running-in period before it can be used normally. Nowadays, many car companies do not deliberately remind the new car of the running-in period when customers pick up the car. The reason is that on the one hand, the machining accuracy and assembly accuracy have been improved, and on the other hand, the cleanliness index of the parts has been greatly improved, which avoids engine failures caused by abnormal early engine wear. This is the most life-like feeling brought by cleanliness.
In the military industry, the impact of cleanliness is particularly prominent. In the Chinese and foreign aerospace delivery projects, there are countless launch failures caused by redundant materials. At the same time, it has been found in the research process of other products in the military industry that cleanliness control is an important factor in product life and efficiency.
Comparison of cleanliness control before and after
Product failures caused by product cleanliness often occur during the use of various types of products.
BearingWear Cylinder wear
Oil pump wear Valve wear
Cleanliness control failure case
●Case One
For the casing produced by a certain engine company, the runner is formed by casting. The runner is like a winding road. So far, there is no way to thoroughly clean the sand in the runner. The particles flowing out of the casing flow channel directly enter the bearing, and a bearing of about 150,000 yuan will be broken within a few hours.
●Case Two
The thermal barrier material coated in the middle of the imported engine casing of a fighter engine company is of good quality, but the quality can no longer be guaranteed after overhaul. When an airplane flies over an inland area, it will fall off after flying several times, and it will fall off once it flies over the sea.
●Case Three
An aviation control system company sent two types of hydraulic control valve bodies for inspection. The test results of small valve bodies showed that there were 336 particles of 150 to 200 microns, including 161 metal particles; 369 particles of 200 to 1000 microns, and 369 particles larger than 1000 microns. There are 20 particles. The test results of the large valve body showed that there were 1,164 particles of 150 to 200 microns, of which 640 were metal particles; 1,687 were particles above 200 to 1,000 microns, and 71 were particles larger than 1,000 microns.
●Case Four
A bearing company of Hangfa has sent for inspection of 3 types of bearings. The bearing test results show that there are 342 particles of 150 to 200 microns, of which 30 are metal particles; there are 312 particles of 200 to 1000 microns, and there are 20 particles larger than 1000 microns. A.
Current Status-Comparison of Technical Cleanliness Standards
Under the irradiation of ultraviolet light, the pollutant particles on the surface will fluoresce. Because the energy of ultraviolet rays is absorbed by the dirt, the electrons of the dirt particles are excited and jump to the high-level electron layer. The unstable electrons at the high-energy level will then return to the original low-level electron layer. In the process, the original absorbed energy is It is released in the form of heat and light-fluorescence. The frequency of this activation release is thousands of times per second, so the fluorescence under ultraviolet light is not flickering but continuous and stable. According to the fluorescence, the position of the dirt on the surface of the part can be visually detected. The fluorescence intensity can also be used with signal detection equipment. The measurement thus indicates the degree of contamination of the surface. But if you want to identify the composition and other characteristics of the pollutants, you must rely on other analysis methods.
This is a new trend in the determination of parts cleanliness. The basic principle is that the surface to be detected and the pollutant particles have different light absorption or scattering rates. The test method is to clean a certain number of parts under certain conditions, fully filter the filter membrane through which the cleaning liquid passes, and collect the dirt on the surface of the filter membrane, then dry the filter membrane and use a microscope (the best equipment is with Image recognition and analysis equipment with shooting function) is detected under light irradiation, and the dirt particles are counted according to the particle size and quantity, and the result of solid particle contamination of the measured object parts can be obtained. This is a cleanliness detection method suitable for quantification of precision cleaning, especially for detecting tiny particles.
Limit value of particle size quantity method: For parts of specific specifications, when a certain sample number, inspection frequency, cleaning medium, cleaning parameters and operation process are specified, the particles are counted according to size, and each size range specifies the maximum allowable particle Quantity, as long as one item exceeds the standard, the test conclusion is unqualified.
In some occasions, the cleaning solution sampling method is often used to evaluate the product cleanliness index. The basic principle is to use the sampling method to count the particle size in all the cleaning solutions, so as to calculate the number of particles in all the cleaning solutions. The cleanliness of the product.This method is a simplified method of the particle size quantitative method. Due to the uncertainty of the sampling method, this detection method is suitable for certain requirements on the particle size of the product parts, but it is not an exclusive indicator for the particle size and size. Case.
The gravimetric method is the most commonly used method for measuring cleanliness in industrial production and testing. The measurement principle is to clean a certain number of samples under certain conditions, and then fully filter the cleaned liquid through the filter membrane. The dirt is collected on the surface of the dried filter membrane, and the filter membrane is fully dried again. According to the analysis The balance weighs out the mass of the dried filter membrane before and after the filtration and cleaning, and calculates the added value to be the mass of the solid particle contaminants on the test sample.
Typical limit of gravimetric method: For parts of specific specifications, the maximum allowable weight of residual dirt under certain sample quantity, inspection frequency, cleaning medium, cleaning and filtration methods, and the unit is mg or ug.
Aerospace Intelligent Manufacturing has always been committed to the process research and expansion of the intelligent manufacturing industry. It currently involves a series of process processes such as machining, assembly, welding, logistics, and automated warehouses. It has been used in aviation, aerospace, military, automotive, high-speed rail, construction machinery, and wind power. And other industries have achieved a high degree of recognition. It is precisely because of the analysis and research of various production processes that it is found that cleanliness is irreplaceable for product quality. Combining the technical reserves of aerospace fluid technology, the company has developed a combination of high-pressure water jet technology, ultrasonic technology, and robot flexibility. Ability of different cleanliness control solutions.
