Mechanism Analysis And Technological Controlling Of Orange Peel Of Automobile Top Coat

As the competition of automobile trade becoming more and more intensive, all the automobile manufactories are paying more attention to the quality of the automobile coating in order to be competitive. The orange peel of top coat paint is one of the most important appraising indexes because its quality remarkably affects the optic effects of the automobile. Ripples on the surface of the top coat paint are called orange peel. Orange skin phenomenon is the most common defects and very hard to control. So it has become a knotty problem to the automobile manufactories home and abroad. Combined the theoretical analysis of the form of the orange peel with the application line of our company, the defects mechanism and technological controlling of the orange peel are discussed here in detail.Theoretical analysis of the form of the orange peel is as follows:According to G. Marwede, different surface tension gives an impetus which cause the paint move from the inside small surface tension position to the outside big surface tension position. When the content of the solvent outside becomes fewer, solvent will diffuse from inside to outside. As the solvent outside volatilizing into the air, viscosity of the paint becomes larger, and the fluxional velocity becomes smaller. At the mean time, paint descends at the gravity. Then descending and ascending repeats until the viscosity becomes bigger enough to prevent the paint from moving. At this time, the difference of the surface tension outside and inside tends to disappear. The repeats of the movement produce the vortex at local position, which could hunch and when dried leads to the form of the orange peel.Technological controlling is as follows:Orange peel of the automobile top coat paint is one of the most common defects. Because there are so many factors that could affect the form of the orange peel, we have to have a control of all the coating tache. Considering the producing properties of our factory, the technological controlling is developed on such aspects below:1). Have a serious controlling of the parameter of the phosphorizing liquid.2). Strengthen the controlling of electrolyte bath liquid, adjusting the parameter reasonably.3). Increase the thickness of the primer as thicker as possible on the premise of no sags, in order to better the effects of the coating quality. Also seriously controls the application viscosity.4).The painting of top coat paint has the biggest effect on the orange peel. Decrease the film thickness as thinner as possible on the premise of enough hiding power. And increase the thickness of the clear as thicker as possible on the premise of no sags of it.5). High pressure electrostatic automatic finishing system is used on the painting line. In actual production process, we would try on all kinds of paints to find their application properties. Profitable parameters of automatic coating machine should be chosen out to the need of different paint. It needs to be find out how the adjustment amplitude of the machine affect the outlook of the automobiles. This is important to the actual application adjustment.6). Adjust the process arrangement of manual repairing position of top coat. Transfer the manual repairing position of top coat from behind the automatic finishing machine to before it so that to avoid the damnification of the dust to the automobile body.7). Be cautious to the use of the wind-power sanding tools to avoid the damage of sanding. Also to insure the flushing properties of the top coat wet film. Improvement solution and experiment on top coat painting process1. Improvement solution on top coat painting process:1). Optimize the process parameter of the electrolyte bath to decrease the film roughness2). Increase the thickness of the primer as thicker as possible on the premise of no sags, in order to better the effects of the coating quality. Increase the application viscosity to avoid the sags happening on the car body or corners. 3). Optimize the film thickness of metallic colorful paint which including metallic under coatings and clear to improve top coat painting quality and reduce the orange peel phenomena. Also the viscosity of the metallic color coat and the supplementary quantity of the slow flushing reagent are optimized to the same purpose.4). Optimize the parameter of automatic painting machine.5). Rearrange the manual repairing process of the top coat.6). Be cautious to the use of the wind-power sanding tools to avoid the damage of sanding. Also to insure the flushing properties of the top coat wet film.2. Experiments on top coat painting process: Laboratory and locale experiments are both done to go on the experimental analysis as follows:1). Analyze the effect of electro paint roughness on orange peel of top coat.2). Analyze the effect of primer thickness on orange peel of top coat.3). Analyze the effect of top coat paint thickness on orange peel of top coat.4). Optimize and adjust the parameter of the automatic painting machine. Experimentally paint on the whole car.Properties analysis and effects evaluation of the automobile top coat paint:1. Testing results of the top coat paint after being improved: 2. Evaluation of orange peel of car body after being improved(the rate of the qualified value of orange peel of body top coat) It can be seen from tables above that G value has an eligibility ratio of 73.91% and F value has an eligibility ratio of 91.3%. After being improved, G value has reached an eligibility ratio of 91.3% and G value has reached an eligibility ratio of 100%. This completely reaches the prospective purpose of no less than 90%.