The relationship between powder coating rate and spray gun

Powder coating manufacturers are most concerned about the powder coating rate of powder coatings. The powder coating rate of powder coatings generally refers to the powder coating coverage. Under the premise of ensuring the appearance and mechanical properties of the powder coating film, the powder coating consumption per unit profile The amount affects the production cost. The powder coating rate of powder coating is not only related to the charge of powder particles, powder particle size, and coating formula, but the most easily overlooked point is that it also has a greater relationship with the spray gun.

The one-time powder feeding rate of the spray gun refers to the ratio of the amount of powder sprayed on the workpiece to the total amount of powder (including the amount of recovered powder that has not been sprayed) during spraying, which is called the deposition efficiency. The recovery amount of powder is inversely proportional to the deposition efficiency, the higher the deposition efficiency, the smaller the recovery amount of powder.

The one-time powder feeding rate of the spray gun is related to the type of spray gun, process parameters, shape of workpiece and spraying method.

For powder coating, the importance of one-time powder application rate must not be ignored. A good spray gun can reach 80% of the rated powder feeding rate, so only 20% of the powder recovery needs to be considered, which can save production costs.

Many powder coating manufacturers and customers only pay attention to the maximum powder output of the spray gun. In fact, the increase of compressed air output and air pressure can increase the powder output. However, whether the high-voltage electrostatic generator can charge this much powder is a problem.

As far as the spray gun is concerned, the dense powder will block the charging path of each other, so that the powder behind cannot be charged, or only a small charge can be charged. From the perspective of the spraying process, when the coating surface reaches electrostatic equilibrium, the powder particles coming from behind and the particles on the coating surface will repel each other, and even fall down due to the opposite motion of anti-ionization, and are recovered by the recycling equipment.

Therefore, the amount of powder output should be measured according to the charging ability of the spray gun, and more consideration should be given to whether the powder is fully charged, and it should also be determined according to the shape of the sprayed workpiece and repeated experiments.

The spray gun equipment should be cleaned and maintained regularly to reduce damage to the recovery equipment

If the spray gun is not good enough, the high pressure is not enough, or it has been used for a period of time without cleaning and maintenance in time, it will greatly reduce the powder feeding rate at one time, and also increase the burden on the recovery equipment.

The rated powder feeding rate is measured under the ideal condition that the workpiece is in the shape of a flat plate

If the workpiece is net-shaped or narrow and long, with bending, punching and other shapes, the occurrence of empty spraying will increase, and the powder feeding rate at one time will be lower.

If the workpiece has grooves, grooves, sharp corners, small holes, etc., Faraday shielding will occur, and the sprayed coating will be very thin and leak.

The reduction of the first powder coating rate, when the oversprayed powder is mixed with the new powder, will make the secondary powder coating rate and the third powder coating rate decrease in turn. After a high-voltage electrostatic charge, the molecular arrangement of the resin, curing agent or filler in the powder will change, which will reduce their chargeability, and the original charge level will not be reached during the second charge. Therefore, the "primary powder rate" of the second charge and the third charge will decrease in turn, about 5% each time.

Powder coating manufacturers should conduct experiments to determine the working voltage, output current, compressed air pressure, air outlet flow and workpiece hanging method every time they change new spraying, new shape of workpiece or change of production chain speed, so as to determine the best Process parameters to get the best powder coating rate.