| With China's rapid economic development, the dream of cars entering ordinary families has become reality. Correspondingly, car makers start all-round competition. It covers all aspects: quality, price, environmental protection, after-sales service and so on. As far as economy car is concerned, reducing costs to demonstrate price advantage is the most important factor for market share, in addition to a guarantee of high level of quality. In the field of automotive painting, undoubtedly, it is one of the most effective ways to reduce costs by optimizing technology on the premise of quality guarantee. This thesis seeks to improve the process of painting on the inner surface of the car to minimize the use of paint, on the premise of a guarantee of that use of vehicles will not be affected, by analysis on painting process of the inner surface, in consideration of the requirements of coatings all parts of the body. It can be improved in all aspects: cost, environmental protection, labor intensity.1. Analysis of the process flows of primer painting and top paintingThe graph below is a typical"three painting two baking"metallic paint process flows of painting. There may be miner difference in different painting workshops.As difference between the functions of the outer surface and the inner surface, the requirements for coating performance are different outer surface and inner surface. The outer surface requires bright color and gloss to deal with the harsh environment outdoor. It demands be provided with good performances ---water-resistant, acid-resistant, alkali-resistant, solvent-resistant. At the same time, it needs good performances, such as good resistance of stoning, salt-resistant.The requirements for coating performance of the inner surface is different from the outer surface, for it doesn't suffer from strong sunlight, rain ,snow and the severe changes in temperature. The main considerations are its appearance, adhesion and the environment of it.The typical process flows of painting above ensure that the coating of the body is protective and decorative, but less considerations on economy.For the purpose of lowering the cost of painting, we can make rational optimization on the processes based on different requirements for coating performances of different partss of the car body, on the premise of a guarantee of that coating performance will not be affected.We should not make big changes on the process flows of spray- painting on the outer surface, for the requirements for coating performance of the outer surface are high and it is through the automatic spray-painting machine, the place and the amount of spit of spray-painting have been carefully designed. Therefore, the optimization of the process focuses on the parts spray-painted by hand on the inner surface.2. Analysis and improvement program of paintting process on the inner surface2.1In the painting process on the inner surface of the four doors, doorframes and pillars, they are the main considerations--- whether there are any painting defects, for examples, running, empty, particles, cratering, etc, whether there is any obvious color difference from outside board, whether or not up to standard of hardness and adhesion. In addition, corrosion resistance and water-resistant must be taken into account.2.2 There are special requirements for coating on the inner surface of the fuel tank lid and around the fuel tank import. In addition to color difference, the main considerations are corrosion resistance and resistance of gasoline.2.3 There is no a clear requirement except protective requirement for the coating appearance on engine room. There are three kinds of situation.2.3.1The inner surface of the hood: no obvious defects such as running, empty spray and color difference, and they can be taken into consideration---corrosion resistance, heat resistance and resistance of gasoline.2.3.2The upper sides of the engine room that can be seen (including the radiator support, etc.): the requirements are no color difference, corrosion resistance, heat resistance, and resistance of gasoline.2.3.3The lower sides of the engine room: the region can not be seen and the electro deposition coating can meet the requirements.2.4 There is no a clear requirement except protective requirement for the coating appearance on luggage box. There are three kinds of situation.2.4.1The inner surface of the luggage box lid: no obvious defects such as running, empty spray and color difference and be provided with a certain degree of corrosion resistance.2.4.2The inner surface of the luggage box: completely covered by interior parts. Generally, only the corrosion-resistant of coatings can be considered, the electro deposition coating can meet the requirements.2.4.3Luggage box frame: no obvious appearance defects such as running, empty spray and color difference and be provided with a certain degree of corrosion resistance.To sum up, we have made specific improved program of painting technology on inner surface, as follows: 3. Experimental verification and effect evaluation of the improved programThe experimental verification of improved program of coating technology on inner surface can be divided into three parts: laboratory determination, workshop on-site verification, and survey on the user feedback. The performance of the coating of improved program as follows:3.1 Laboratory determination of improved program3.1.1Corrosion resistance:According to the experimental results, both the coating of ED coat+ metallic coat +Clear coat, and of ED coat + metallic coat and a separate ED coat, Will be able to reach more than 1000 hours in the neutral salt spray test. Corrosion resistance by ED coat is reassuring.3.1.2 Water-resistant: the coating of ED coat + metallic coat + clear coat varnished through 240 hours in the water-resistant test, the results showed it was qualified.3.1.3 Gasoline-resistant: the coating of ED coat + metallic coat + clear coat soaked in gasoline through 30-minutes, the experiment results showed it was qualified.3.1.4 Physical properties (hardness, adhesion): the pencil thickness of the coating of ED coat + metallic coat + clear coat is F, the adhesion is zero by determination through cross-cut test. So did the standard coating process.3.1.5 Color difference: From the results, compared with the standard test, the coating of ED coat + metallic coat + clear coat has no obvious color difference by naked eyes, there is no obvious change in gloss by naked eyes, and further determination by color difference meter,â–³E is qualified. The coating of ED coat + metallic coat, compared with standard test board the by naked eyes, that gloss is reduced can be ignored.3.1.6 Appearance: By fresh determination of the coating of ED coat + clear varnish, compared with the standard coating process, although G value is slightly higher, F value is slightly lower (less bright young), still, they are qualified in board standards. Laboratory results qualified, in coatings corrosion-resistant, water- resistant, adhesion-resistant, and gasoline-resistant, the experimental data is ideal.3.2 Painting workshop on-site verification of the improved the program Painting workshop on-site verification is aimed at inspection whether there is any obvious color difference the appearance of the coating between the within and outside the board, the improved process compared with the standards process, and inspection actual operation of the program.3.2.1Color difference: Compare with the coating of the outer surface, the coating on the inner surface of the door, door, in the column, the inner surface of the tank and around fuel tanks mouth and outside the board had no obvious difference by observed and measured. There is no obvious change in gloss by naked eyes. and further determination by color difference meter,â–³E is qualified. But it is the slight increase compared with laboratory test results, mainly due to non-uniform film thickness, so need to strengthen operator skills training. The inner surface of the engine cover, on both sides of the upper part of the engine room, the inner surface of the luggage, the mouth parts of the luggage, there is no color difference compared with the outer surface by naked eyes., that gloss is reduced can be ignored because the requirements for coat gloss are not too high.3.2.2 Appearance: the inner surface of the door, door and the door pillar need to ensure that the coating has a decorative, its appearance have a certain influence on sales of products, compared with other parts. It must be focused on detection and analysis in the vehicle test to comparison to the standard process. Test results show: the G value of the color coating is slightly higher, the F value is slightly lower (on the map, data mobile to the upper left corner), as a relevant result appearance effect is slightly lower, but overall remain in the range of qualified. Taking into account the internal surface of the decorative coating not as strict as the outer surface, it is imperceptible only observation by naked eye in natural light.3.2.3 Hardness: the pencil thickness is F, determinate the coating on the inner surface of the door, door, the column, the inner surface of the fuel tank and around the mouth of the fuel tank. And it is the same to the determination of the laboratory results.3.2.4 Operability: As the manual spraying to reduce the size and in the process of spray-painting, the number of the door switch and fuel tank covered reduce, the spray-painting efficiency is improved.The results showed that the improved process improved the efficiency of the coating on the premise of quality guarantee.3.3 User feedback survey After the market confirmed that the user didn't reflect badly.4. Comprehensive evaluation of the improved program.After implementation of the improved program, the primer paint saved is about 0.5 kg / Tai, the metallic paint saved is about 0.5 kg / Tai, the clear paint saved is about 0.5 kg / Tai, Total saved cost is about 42 yuan every car. Economic benefit is significant. By comprehensive evaluation in protect, decorative, operability, economy and sales, the scientific and practical program achieved the target of the subject.
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