Flow coating is a method in which the paint is sprayed by a paint liquid circulation pump through a nozzle and forms a curtain to fall on the surface of the object to be coated. In the past, it was mostly used for manual operation to perform flow coating on small batches of coated objects, and now it is often used for large batches of coated objects.
During the flow coating, the workpiece passes along the horizontal direction at a certain speed, while the paint liquid is sprayed in the shape of a curtain and falls vertically and contacts the workpiece. This coating method has the advantages of high production efficiency, low labor intensity, and is suitable for assembly line production. Since the paint liquid can be recycled, if the operating environment is sealed, the effect of less solvent volatilization loss and less coating loss can be obtained.
Curve coating is a coating method between dip coating and spray coating. Curve coating and dip coating are the same in that they both use excess paint to wet and adhere to the surface of the object to be coated. However, due to the mechanical and gravity effects of spraying added to the flow coating, the coating effect is better, and the paint used in the flow coating is also recycled and the total demand is less than that of the dip coating. Due to the high fluidity of the coating and the larger contact surface with the air during curtain coating, the solvent consumption in the coating is relatively large, so the stability of the coating is required to be high, and the thickness of the formed coating film is not easy to be uniform. Disadvantages of shower coating.
The difference from the spraying method is that the paint liquid is not sprayed out in the form of spraying in the form of mist, but sprayed out in the form of a liquid curtain, so a thicker coating can be quickly formed on the surface of the object to be coated.
The flow coating equipment is divided into two types: intermittent type and continuous type. The intermittent type is a fixed equipment suitable for small batches of manual operations, and the continuous type is a pass-through equipment suitable for large batches of automatic operations.
Continuous coating equipment is generally composed of a coating tank, a solvent tank, a spray device, a paint pump, a ventilation and fire prevention device, and a transmission device. Among them, the shower coating room is the main equipment for completing the shower coating operation.
The shower coating room is divided into four sections: the entrance area, the spray area, the excess paint removal area, and the exit area. After the workpiece enters the entrance area, it is sprayed in the spray area, and then enters the excess paint removal area to remove the excess paint. After being sent out from the exit area, it is dried.
① paint. For curtain coating, slow drying and good leveling properties should be selected.
② paint viscosity. Since the paint is in the spray state during the flow coating, the solvent in the paint evaporates quickly, and the paint will thicken quickly, so it is very important to control the viscosity of the flow coating. In order to control the viscosity of the coating, the solvent should be replenished in time, and an automatic detection device for the viscosity of the coating should be equipped to adjust the viscosity of the coating in time.
③ Select the appropriate nozzle diameter and spray pressure. In order to obtain a good effect of shower coating, the suitable nozzle diameter and spray pressure should be selected according to the shape and other characteristics of the object to be coated.
④ Clean the equipment in time. In order to ensure that the spray system is unimpeded, the pipelines, nozzles and other equipment should be cleaned in time after the operation is completed.