1. Powder coating spraying construction technology
The powder spraying construction process is to use the principle of high-voltage electrostatic corona electric field. A high voltage negative electrode is connected to the metal diversion mark of the spray gun head, and the sprayed workpiece is grounded to form a positive electrode, so that a strong electrostatic electric field is formed between the spray gun and the workpiece. When the compressed air used as the carrier gas sends the powder paint from the powder supply tank to the guide rod of the spray gun through the powder tube, the corona discharge generated by the guide rod connected to the high voltage negative electrode generates a dense negative charge near it , So that the powder is negatively charged and enters the electrostatic field with high electric field strength. Under the dual action of electrostatic force and carrier gas, the powder uniformly flies to the surface of the grounded workpiece to form a uniform thickness of powder layer, and then heat and solidify into Durable coating film.
Powder coating construction process: pre-treatment-drying to remove water-spraying-inspection-baking-inspection-finished product.
Two, powder coating spraying construction requirements
1. General powder spraying construction requirements
(1) In order to give full play to the characteristics of powder coating and prolong the service life of the coating film, the surface of the broken coating must first be treated with strict surface pretreatment.
(2) When spraying, the object to be coated must be completely grounded to increase the spraying efficiency of powder coating.
(3) For coated objects with large surface defects, conductive putty should be applied to ensure the smoothness and smoothness of the coating film.
(4) After spraying, the objects need to be heated and cured. The curing conditions are subject to the technical indicators of the powder product, but the curing temperature and time must be fully guaranteed to avoid quality accidents caused by insufficient curing.
(5) Check immediately after powder spraying. If defects are found, they should be dealt with in time. If defects are found after curing, their range is small and only partial and does not affect the surface decoration of the coated object. The same color powder can be diluted with acetone and repaired. If the range is large It also affects the surface quality, after sanding with sandpaper, spray again or use paint remover to remove the coating, and then powder again.
(6) The recycled powder must be screened to remove impurities, and then mixed with new powder in a certain proportion.
(7) The powder supply barrel, powder spray room and recovery system should avoid the pollution of other powders of different colors, so it must be cleaned every time the color is changed.
2. Art-type powder spraying construction requirements: Art-type powder has the characteristics of beautiful appearance, strong three-dimensional effect, and decorative effects, but its construction process requirements are strict:
(1) When spraying powder, the input air pressure should not be too large, generally it is better to control it at 0.5～1.5kg/cm2. Too much air pressure will cause poor pattern definition or some pitting. The electrostatic voltage should not be too high, generally controlled at about 60-70Kv. If the voltage is too high, the powder attached to the surface of the workpiece will rebound and cause pitting. Defects such as poor leveling.
(2) When spraying powder, pay attention to ensuring the thickness of the coating film. Generally, it can be controlled between 70-100μm to help form obvious patterns and larger patterns. If the coating film is thin, the pattern is not obvious, and the pattern is also small. Defects such as pitting and bottoming appear.
(3) It must be baked at the specified temperature and time during curing. If the temperature is too low and the time is too short, the powder will not form a pattern, and the mechanical properties will be greatly reduced due to incomplete curing.
In addition, due to the particularity of the art pattern powder production process, after spraying with the recycled powder, the pattern will become smaller or insignificant. Therefore, it is generally recommended not to use the recycled powder of the art pattern powder. It must be tested to use. From the above point of view, although the construction requirements are strict, I believe that as long as the above factors are better grasped in the coating process, the ideal and satisfactory results will be achieved.