Orange peel is a common and difficult leveling problem in the powder coating process, which greatly affect the flatness of the coating film, and has a large influence on the decorative appearance of the product. There are many factors to this problem. The orange peel in powder coatings is inseparable from the characteristics of the powder coating itself and the influence of the equipment in the coating spray and the control of the process parameters during the powder coating spray process. We find the corresponding solution to avoid orange peel for different reasons.
Orange Peel in Powder Coating │ Powder Material
It is difficult to level the powder coating with low resin content, which is easy to cause orange peel. Therefore, selecting a powder coating with a high resin content is advantageous for improving the leveling performance of the powder coating.
Powder Particle Size Distribution
When the proportion of the powder having a particle diameter(> 75um) is too high, the leveling property of the coating film is deteriorated, and the orange peel is likely to occur.
The stability of the powder coating refers to the phenomenon that the powder coating crosslinks under the storage conditions. The more intense the crosslinking reaction, the larger the molecular weight becomes, and the higher the viscosity of the powder at the curing temperature, the lower the leveling property, and the orange peel is likely to occur.
For these reasons, powder coating manufacturers need to consider the choice of raw materials to solve the orange peel caused by powder coating material.
Orange Peel in Powder Coating │ Coating Spray Devices
Due to the normal wear of the nozzle of the spray gun, the atomization of the spray gun is poor, so that the thickness of the powder adsorbed on the surface of the bow and arrow is different, and the leveling is difficult, and the orange peel is easily generated.
A small amount of powder particles foul in the nozzle, causing nozzle clogging, and the ejection pressure is insufficient, so that the powder unit discharge amount is lowered compared with other spray guns, resulting in a decrease in the surface powder thickness of the workpiece, which causes an orange peel.
If the hang has deformation, the workpiece will deflect with the shape of the hanger, so that the surface of the workpiece is not perpendicular to the spray gun, and the film is too thin from the spray gun, the flow film is poor, and the orange peel is serious.
These reasons require the manufacturer to clean the gun nozzle in time, improve the atomization performance of the spray gun, and replace the twisted and deformed hanger in time.
Orange Peel in Powder Coating │ Coating Process
The leveling time is too short and the powder has not yet leveled.
If the heating rate is too fast, the ripples on the vertical surface increase, the leveling is not good, and the orange peel occurs.
During the spraying process, due to excessive ventilation, the air flow rate in the powder spraying chamber is too fast, so that the powder particles sprayed from the spray gun are affected by the external wind, and the movement mode of the powder changes. This causes the thickness of the powder adsorbed on the surface of the workpiece to be uneven, affecting the leveling and producing orange peel.
The phosphating film is rough and uneven, and the orange peel phenomenon is likely to occur after dusting.
For these reasons, paint manufacturers need to improve production management to ensure that each production process meets the standards.
In combination with these factors, in order to reduce and eliminate the orange peel problem, it is necessary for the powder coating production manufacturer and the coating spray manufacturer to work together to solve it. Manufacturers can adjust the powder coating formulation to improve the self-leveling performance of the powder coating; powder coating spray manufacturers need to strengthen the management and maintenance of the equipment, while improving the spraying process. These solutions can effectively control the orange peel problem and achieve the decorative appearance of the powder coating.
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