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What should I do if the car body cover stripes appear in the trial production process of the automobile coating production line?



During the trial production process of the automobile coating production line, it was found that a few car bodies had irregular stripes on the horizontal surface (cover, roof). With the increase in the number of passing cars, the streak phenomenon has become serious. Regardless of the vehicle type, almost 90% of the passing cars have streaks. All horizontal surfaces such as the machine cover need to be polished, which seriously affects production efficiency.

1. Description of the phenomenon of car body cover stripes appearing in the trial production process of the automobile coating production line
Abnormal body streaks occur in all vehicles that cross the line. They are irregular and almost all of them appear. In severe cases, the occurrence rate is as high as 90%. The streaks that appeared during the trial production of the automobile coating production line mainly appeared on the horizontal surface such as the engine hood and the roof, and there were also a small amount on both sides. The appearance of the stripes on the engine hood is like the traces left by the paint film being swept by a brush. The direction is not fixed, the phosphating visually has micro stripes, the electrophoretic wet film has a bumpy touch, and the stripes on both sides are similar to the stripes in the groove.

2. The reason and analysis of car body cover stripes appearing during trial production of automobile coating production line
The cause of the car body stripe defects was investigated, and the results are listed in Table 5. Experiments 2 to 6 show that the pretreatment may cause abnormal streaks. It can be seen from experiments 1 and 9 that whiteware, electrophoresis and washing after electrophoresis are less likely to cause abnormalities. Check the pre-treatment spray cycle status, and no obvious abnormality was found. By checking the pre-treatment test parameters and comparing the data of the first phase, it was found that the p H of the pre-treatment washing 3 was close to 4.0, corresponding to the old production line, the p H of the washing 3 was all> 5.0. This parameter of the new line is low. The industrial water replacement for water wash 3 will improve the stripes, indicating that water wash 3 is more likely to cause abnormal stripes.

3. Solutions to the streaks of the body cover during the trial production of the automobile coating production line
In order to ensure that the p H of wash 3 is maintained at a level> 5.0, the water supplement valve needs to be opened to replenish water overflow for wash 3 when passing the vehicle, and reverse vehicle passing verification is performed. See Table 7 for the verification of the third wash water supplement. Wash 3 After the water supply valve is closed for 10 minutes, p H gradually decreases to below 5.0, corresponding to the appearance of streaks on the body. After opening the water replenishment valve, p H rises to above 5.0, the body streaks gradually improve, and the paint surface returns to normal. It shows that the p H of the first wash after phosphating, that is, wash 3, is directly related to the car body stripes, and the p H of the washing tank liquid is controlled to be above 5.0 to ensure normal car body paint film quality.