Content of process design
It mainly includes: processing method, processing time, process flow and so on.
1 processing mode is to refer to the way that the workpiece is in contact with the bath liquid to achieve the purpose of chemical pretreatment, including full immersion, full spray, spray soaking combination, brush coating and so on. It mainly depends on the geometric size and shape of the workpiece, site area, investment scale, production volume and other factors. For example, the workpiece with complex geometrical dimensions is not suitable for spraying. The oil tank and oil drum are not easy to sink in the liquid, so they are not suitable for immersion.
1.1 all soaking methods completely soak the workpiece in the bath liquid. After a period of treatment, a common treatment method, such as removing oil or removing rust and phosphating, is carried out. The geometry of the workpiece is simple and varied. As long as the liquid can reach the place, it can achieve the treatment target. This is the unique advantage of the immersion method, and it is a spray. The brush can not be compared. The disadvantage is that there is no auxiliary use of mechanical scour, so the processing speed is relatively slow and the processing time is long, especially when the workpiece is suspended and conveyed, except the working time of the workpiece in the slot, and the time of the work piece up and down, so that the equipment increases, the area of the site and the investment increase. Only for phosphating, the foreign comparison tends to adopt the full immersion method. It is said that the full soaking phosphating is easy to form a granular crystalline phosphating film with high iron content, which has good compatibility with the cathodic electrophoresis.
1.2 the full spray method pressurized the liquid with the pump, and made the liquid form fog shape with the pressure of 0.1 ~ 0.2Mpa, and spray on the workpiece to achieve the treatment effect. Because of the mechanical scour and liquid renewal, the processing speed is accelerated and the time is shortened. The length of the production line is shortened, and the corresponding section of the site, equipment and shortcomings is that the complex workpiece, such as the inner cavity and corner, is not easy to reach, and the treatment effect is not good, so it is only suitable for the work of simple geometry. Spraying method is not suitable for acid cleaning, it will bring about a series of problems such as corrosion of equipment and rust between processes, so it must be very careful when choosing spray acid washing. It is reported that the whole spray phosphating is easy to form a phosphating film with a large dendritic shape and a low iron content. The whole spray method is mainly applied to powder coating, electrostatic painting and anodic electrophoresis of household appliances and parts.
1.3 spray - soak combined spray - soak combination, generally in a certain process, the workpiece is first spray, then soaked into the trough, and then spray after the trough, all spray, soak are the same slots. This combination means keeping the high efficiency of spraying, improving the processing speed and soaking process, so that all parts of the workpiece can be effectively treated. Therefore, the spray soaking combined pretreatment can complete the treatment process in a short time, and the equipment occupying site is relatively less, and the satisfactory treatment effect can be obtained at the same time. At home and abroad, the automobile industry with higher requirements for pre processing tends to adopt spray immersion combination.
The 1.4 brush coating method directly brushes the treatment liquid to the surface of the workpiece by hand to achieve the purpose of chemical treatment. This method is generally not easy to get good treatment effect and is less used in the factory. For some large and simple workpieces, this method can be considered.