What is powder coating?
In the coating industry, powder coating is a widely used basic process type.What we usually call powder spraying or coating powder spraying generally refers to electrostatic powder spraying. This process is a new type of coating process that has developed rapidly in recent decades. The raw material used is plastic powder.It uses the corona discharge phenomenon to make the powder coating adsorb on the workpiece.The basic process of powder electrostatic spraying is: the powder spray gun is connected to the negative electrode, the workpiece is grounded (positive electrode), the powder coating is sent to the spray gun by the powder supply system through the compressed air gas, and the high voltage generated by the high-voltage electrostatic generator is added to the front of the spray gun. Discharge generates a dense charge near it. When the powder is ejected from the nozzle, it forms a circuit to form charged paint particles. It is attracted by the electrostatic force to the workpiece with the opposite polarity. As the amount of powder sprayed increases , the more the charge accumulates, when it reaches a certain thickness, due to the electrostatic repulsion, it will not continue to adsorb, so that the entire workpiece can obtain a certain thickness of powder coating, and then the powder is melted and leveled after high-temperature baking, and finally used The powder coating is cured, that is, a hard coating film is formed on the surface of the workpiece.
Powder Coatings
In addition to thermosetting epoxy, polyester and acrylic powder coatings, a large number of thermoplastic grease-resistant materials can also be used as powder coatings, such as polyethylene, polypropylene, polystyrene, fluorinated polyether, nylon, polycarbonate and various Fluorine resin, etc.With the development of science and technology and industry, powder coatings have been widely used in the automotive industry, electrical insulation, corrosion-resistant chemical pumps, valves, cylinders, pipes, outdoor steel components, steel furniture, castings and other surfaces.
Powder electrostatic spraying equipment
Powder electrostatic spraying equipment mainly includes: powder spraying room, high-voltage electrostatic generator, electrostatic spraying gun, powder supply device, powder recovery device, etc.
The powder spray booth is one of the main equipment for powder electrostatic coating.During operation, the dust content in the spray booth should be controlled so that it is lower than the explosion limit (generally set at 10g/m³).The powder spraying room should be easy to clean, so that the powder is not easy to deposit in the room, so as to change the color of the powder, and the room should have enough light to facilitate the coating work.
Electrostatic spray gun
Classification: Spray guns can be divided into portable powder spray guns, fixed automatic powder spray guns, disc spray guns, etc. according to their uses; according to the charging form, they can be divided into internal charged electric guns and external charged electric guns; according to their diffusion mechanism, they can be divided into conflict Type guns, rebound guns, secondary air inlet guns, centrifugal rotary cup guns, etc.
Spraying efficiency: The charging mechanism form of the powder spraying gun is a key factor to improve the spraying efficiency.Generally speaking, the core of powder spraying equipment is the spray gun and charging system.As far as the current market is concerned, corona spray guns account for a huge proportion, because the biggest advantage of using high-voltage corona discharge to charge the powder is that it can spray all kinds of thermosetting powder coatings today, and Can get very good results.Its advantages are mainly manifested in excellent stability, high powdering rate and fast powdering speed.
Powder supply system
The powder supply system is to continuously and evenly transport the coated powder material from the powder container to the powder spray gun for spraying.
The powder supply system is composed of air compressor, oil-water separator, air dryer, regulating valve, compressed air pipeline, electromagnetic control valve, powder supply device, powder delivery pipeline, etc.
The form of the powder supply
In the powder supply system of powder electrostatic spraying, there are many types of powder feeders used, which can usually be divided into: pressure vessel type, mechanical conveying type of screw or turntable, and Venturi air suction type.
Powder Recovery Unit
Powder recovery can be divided into wet method and dry method.
The wet method is to filter the airflow with the powder through the liquid container to achieve purification, and the powder with the liquid is dried and reused.
Dry powder recovery is to collect powder particles in the powder airflow discharged from the powder spraying room.The types of dry powder recovery include gravity sedimentation, inertial separation, cyclone separation, sintered plate separation, etc. In actual production, multi-stage recovery devices are often used to achieve better separation effects.
