Every professional powder coating gun has a built-in delivery system which features a feed section. Powder coating feed systems avail powder to the pump. The role of the delivery system is to store, prepare, and maintain a steady flow of the powder to the gun. The powder is stored in a hoper or a box. Compressed air forces the powder out of the hopper or box and delivers it to the venturi pump.
Like other powder coating equipment, there are many delivery systems in the market. The operator needs to know the system that will work best for him/her.
The most common feed systems are hopper and box-fed. Selecting a gun with the right feed system can improve the quality of your products.
Guns with box-fed systems: This type of gun delivers the powder to the pump directly from the box that came with the powder. The box is placed on a stand below the gun, tilted at an angle to ensure efficient flow. The powder is delivered to the gun through a powder pick-up tube that is inserted into the tilted box. In most cases, the pick-up tube has compressed air in it to break up compacted powder. This facilitates delivery of uniform powder to the gun. When the powder gets into the gun, it is directed to the venturi pump by the pick-up tube. The pump routes the powder out of the gun and onto the surface being coated.
During the application process, the box holding the powder vibrates constantly. The vibration causes the powder in the box to shift constantly, and it replaces the powder that has been sucked into the pick-up tube. This movement of the powder ensures a continuous flow of the powder, thus uniform coating. If the box doesn’t vibrate, the powder that is sucked into the pick-up tube will not be replaced, and this would lead to the development of rat holes. As a result, the powder will be delivered in surges, thus degrading the quality of the coat.
Using a gun with a box-fed system has several advantages which include quick color change, flexible as it weighs less, low initial investment, and it is fast to set up and start operations. Some of the demerits associated with box-fed systems include consistency problems when working with special effect powders such as those with certain particle sizes and it is affected by humidity.
This type of powder coating feed system is best suited for single color powder, coaters who use different powders for different instances, and operators who coat a few parts.
Guns with hopper-fed systems: The powder is placed into a fastened container which features a perforated plastic casing on the base. The casing has numerous tiny holes that allow compressed air to pass into the container and fluff the coating powder making it flow inside the hopper. This process is known as fluidization.
The flow of the compressed air into the hopper is regulated to minimize powder wastage due to over-pressurization or excessive agitation of the container. If your system has a reclamation unit that is running as you spray, it is advisable to regulate the intake of compressed air to minimize powder loss.
Some of the advantages of using a gun with the hopper-fed system include reduced chances of powder contamination as the hopper is sealed, fluidization mixes the powder thoroughly, fluidization eliminates moisture from the air thus maintaining the condition of the powder, and the powder is delivered uniformly as it is well-conditioned.
The disadvantages associated with this type of feed systems include reduced throughput, increased coating time, and it is costly especially if you buy several hoppers to store all your powders.
This type of feed system is best suited for operation in areas with humidity issues, systems with a reclamation unit, operators who use have a limited color application, and in applications that demand special effects.
Recent and current innovations in the powder coating industry have significantly reduced the effort, time, and charges associated with color changes. Numerous efforts to streamline powder delivery systems, increase application efficiency, and redesign the powder booths have contributed to the speeding up of the color changing process. A well-designed, controlled and maintained system could change colors within minutes.
Recently, the industry has witnessed the emergence of various features which have helped reduce the period for color change operation to around ten minutes or less. Some of these features include:
– Powder booths that feature plastic walls which repel instead of attract the powder.
– Booths with curved walls which discourage powder accumulation.
– Powerful discharge of air through the guns and pumps to clean the system.
– The automated sweeper as well as belts which sweep powder particles lying on the floor to the recovery systems.