A powder coating machine is a device that applies protective coatings on metal parts similar in finish to conventional liquid paint. The main difference between the two processes is the method by which the coating is applied. In the case of powder coating, a stream of positively charged powder is applied to a grounded or negatively charged metal surface. This electrostatic method creates a better coating to metal bond than is possible with conventional paints as well as offering several other benefits not possible with liquid coatings. There are several different powder coating machine types in general use with the most common being the corona and tribo spray gun variants.
Powder coating is the process of coating metal items with layers of powdered thermoplastic or thermoset polymer. The process is an efficient and highly effective method of coating a wide variety of consumer products ranging from domestic appliances to garden furniture. These finishes are applied with several different powder coating machine types including spraying, electrostatic disc, electrostatic magnetic brush, and fluidized bed systems. Of these, the spray types are the most widely found in most commercial applications. The corona and tribo spray coating machines see the most use.
The corona gun powder coating machine consists of a powder dispenser, a high voltage generator, a corona spray gun with powder feed hoses, and a negative or ground connection. To operate the corona gun system, the ground connection is attached to the workpiece and suitable powder coating material is loaded into the machine's dispenser. The high voltage generator energizes an electrode in the gun, thereby imparting a powerful positive charge in the powder and creating a high energy electrical field between it and the workpiece. This electric field serves as a motivating agent which draws the positively charged powder to the surface of the workpiece. Upon contact, the powdered coating bonds to the metal surface, thus forming an even layer.
The tribo type powder coating machine also relies on a electrical field to bond the powder to the metal surface but uses compressed air to transport it through a Teflon® tube and nozzle towards the workpiece. The positive electric charge in the powder is imparted by friction between it and the surface of the Teflon® tube and bonds the layer of powder to the metal in the same way as the corona gun method. After coating with both systems, the workpiece is often heated to allow the plastic coating to spread out more evenly and complete the bonding and curing process.