What should I do if the car body roughness is abnormal during the trial production process of the automobile coating production line?
During the debugging of the automobile coating production line, the roughness of the electrophoretic paint film on the engine hood, rear door and other parts of the two models produced by the new production line was measured to be relatively high (Ra=2.5> 0.30 μm). Most of the vertical surface and ceiling roughness such as four doors can meet the standard requirements. The electrophoresis roughness of the hood, fenders, roof and other parts of the body of another model is unstable.
1. Description of the abnormal phenomenon of car body roughness during the trial production of the automobile coating production line
Through the on-line hanging board and polishing test, the reasons for the abnormality of the body roughness are investigated, as listed in the following table. The on-line hanging board and white parts polishing test shows that the abnormality of roughness Ra is less related to the pre-treatment electrophoresis; combined with the comparison test of 1~3 white body polishing, it can be seen that the abnormality of the engine hood roughness Ra is more related to the body panel .
Serial number verification factor verification method verification result
1 Engine cover Ra The upper part of the front cover is pasted on the car body plate → rotate 90° before electrophoresis. There is no obvious streak on the whiteboard and after electrophoresis, the whiteboard Ra=1.18 μm; after phosphating Ra=1.13 μm; electrophoresis Ra=0.25 μm
2 Engine cover Ra. Before electrophoresis, the horizontal plane of the engine cover is pasted with ACT standard test plate. There is no obvious streak after electrophoresis; phosphating test plate Ra=0.65 μm; electrophoresis Ra=0.22 μm
3 Engine cover Ra The upper part of the front white part of the body cover is grounded with sandpaper on the horizontal surface. The stripes in the polished area basically disappear; the polished area electrophoresis Ra=0.22 μm; the unpolished area electrophoresis Ra=0.31 μm
4 Phosphate polished before electrophoresis of engine cover Ra=0.27 μm electrophoresis in the polished area; electrophoresis Ra=0.24 μm in the polished area; electrophoresis Ra=0.27 μm in the unpolished area
5 Fender Ra The front fender facade of the upper part is pasted with the body sheet → rotate 90° before electrophoresis, the test board has no obvious stripes, the white board Ra=1.12 μm; electrophoresis Ra=0.24 μm
2. Cause analysis of abnormal body roughness during trial production of automobile coating production line
In order to further prove the influence of white parts on electrophoresis roughness, the white parts of the same part of different car models and the electrophoretic roughness were compared. The results are shown in Figures 1 and 2.
It can be seen from Figures 1~2 that the Ra value trends of white parts and electrophoretic coating films are similar for the two models in the same body part, indicating that the Ra values of white parts and electrophoretic coating films are highly correlated. The roughness of white parts Ra is 2.5, which is close to or> 1.20 μm, the electrophoresis roughness basically exceeds the 0.3 μm standard. Combined with the instructions of the onboard wall and the polishing test, the abnormality of the roughness Ra of the electrophoretic coating film of the two models is related to the white body.
3. Measures to solve the abnormal phenomenon of car body roughness during trial production of automobile coating production line
After polishing the white parts, the roughness of the white parts is obviously reduced, and the effect of using 240# and 400# sandpaper on the white parts is better than 800# sandpaper. At the same time, hang the board along with the line to explore whether the repair of the white parts by phosphating can reduce the influence of the quality of the white parts on the electrophoretic roughness.
Phosphating can slightly improve the roughness of white parts, and the roughness of white parts, after phosphating and after electrophoresis basically shows a corresponding relationship. Therefore, to ensure that the electrophoresis roughness is improved, it is necessary to start with the improvement of the white parts to completely solve the problem. The roughness requirement is added to the white parts purchase standard, which can be controlled from the source and the effect is more significant.