1. Constant voltage method. The so-called constant voltage method is to apply an additional electrophoretic voltage between the two poles at the beginning of power on and persist until the end. Therefore, in the early stage, the pulse current is very large, forming a peak, and the film thickness increases rapidly. As the thickness of the paint film increases, the resistance value of the paint film rapidly increases, and the current quickly weakens. At this point, the increase in paint film thickness also slows down and eventually stabilizes.
The advantage of the constant voltage method is that it is relatively simple to operate during electrophoresis, but the early accumulation speed of this method is too fast, resulting in rough paint film and poor appearance after baking. Together, the constant voltage method requires a large capacity rectifier power supply due to the presence of surge currents. However, in reality, painting equipment does not require such a large capacity most of the time, resulting in wastage of power supply equipment.
2. Constant current method. The constant current method means that during the electrophoretic coating process, the current density value remains stable, that is, the current density does not change with time. In the electrophoresis process, in order to maintain a certain current density, the voltage needs to be continuously increased, so that the increase of the paint film is uniform. Experiments have shown that the constant current method can provide the best inductive effect in terms of stacking power and paint film appearance. However, the production process is slightly disorganized.
Overall, the constant voltage method and the constant current method each have their own advantages and disadvantages. From an inductive perspective, the constant current method is better, but accurately controlling the current during electrophoresis is difficult. Nowadays, painting equipment usually takes the advantage of the two, that is, using early current control method and low voltage at the beginning of electric deposition. In order to prevent excessive surge current, gradually increase the voltage to an additional value.

This article is from: http://www.zs-chsb.com/