The processing method of the roller coating machine refers to the way in which the workpiece is in contact with the bath to achieve the purpose of chemical pretreatment, including full immersion, full spray, spray immersion combination, brush coating and the like. It mainly depends on the geometry and shape of the workpiece, the site area, the investment scale, the production volume and other factors. For example, a workpiece with a complicated geometric shape is not suitable for a spray method; a fuel tank and a oil drum type workpiece are not easily sunk in a liquid, and thus are not suitable for a soaking method.

1 full immersion method

The workpiece is completely immersed in the bath, and it is taken out after a certain period of time to complete a common treatment method for degreasing or descaling and phosphating. The geometry of the workpiece is different, as long as the liquid can reach the place. It can achieve the treatment target, which is the unique advantage of the immersion method, which is unmatched by spraying and brushing. The shortcoming is that there is no auxiliary use of mechanical scouring, so the processing speed is relatively slow, and the processing time is long, especially when the workpiece is continuously suspended, except for the running time of the workpiece in the slot, and the time of the workpiece going up and down, As a result, equipment growth, site area and investment increase. For phosphating alone, at present, foreign countries tend to adopt the full immersion method. It is said that full immersion phosphating is easy to form a granular crystal phosphating film with high iron content, which has good compatibility with cathodic electrophoresis.

2 full spray method

The liquid is pressurized by a pump, and the liquid is formed into a mist at a pressure of 0.1 to 0.2 MPa, and is sprayed on the workpiece to achieve a treatment effect. Due to the mechanical scouring and liquid renewal during spraying, the processing speed is increased and the time is shortened. The length of the production line is shortened, and the site, equipment, and deficiencies of the corresponding section are that the workpieces with complicated geometric shapes, such as the inner cavity and the corners, are difficult to reach, and the treatment effect is not good, so it is only suitable for processing workpieces with simple geometric shapes. . Spraying method is also not suitable for pickling and rust removal. It will cause a series of problems such as equipment corrosion and rust between processes. Therefore, it must be very careful when choosing spray pickling. According to reports, full-spray phosphating is easy to form a phosphating film with coarse crystal grains and low iron content. It is not recommended as a pre-treatment for cathodic electrophoretic paint before use. The full spray method is mainly applied to powder coating, electrostatic painting, and anodic electrophoresis of household appliances and parts.

3 spray-soak combination

Spray-soak combination type is generally used in a certain process, the workpiece is sprayed first, then immersed in the tank, sprayed after the tank is discharged, and all sprays and immerses are the same bath. This combination means that the high efficiency of the roller coating machine is maintained, the processing speed is increased, and the soaking process is performed, so that all parts of the workpiece can be effectively treated. Therefore, the spray-soak combined pre-treatment can complete the treatment process in a short time, and the equipment occupies relatively less space, and at the same time, satisfactory treatment effects can be obtained. At present, at home and abroad, for the automotive industry with high pre-treatment requirements, it is generally preferred to adopt a spray-soak combination method.