The basic principle of electrostatic powder spraying equipment coating is to use the principle of high voltage electrostatic corona electric field, high voltage is connected to the metal guide ring on the head of the spray gun, and the workpiece is grounded by spraying. A strong electrostatic field is formed between the spray gun and the aluminum profile. When the compressed air as the carrier will be supplied from the powder powder coating barrel through the spray gun of the powder tube diversion ring, due to the diversion ring connected to the high voltage corona discharge, in its vicinity produce dense negative charge, so the powder with negative charge. And into the electrostatic field with high electric field strength, under the dual action of electrostatic force and carrying gas, powder evenly fly to the grounding workpiece, and on the surface of the aluminum profile formed a layer of uniform thickness of the powder coating. After heating, it solidifies into a film with certain corrosion resistance.
Causes and solutions for the formation of coating surface defects of powder spraying equipment
1. the coating gloss is insufficient: curing time is too long; High temperature; Baking mixed with other harmful gases; The surface of the workpiece is too rough; Improper selection of pretreatment methods.
2. film color: repeated baking: furnace mixed with other gases; Over-baked during maintenance.
3. Coating surface orange peel: powder spraying equipment coating thickness is not uniform; Powder atomization degree is not good, the spray gun powder accumulation phenomenon; Low curing temperature; Wet powder, powder too coarse; The workpiece is not well grounded; Baking temperature is too high; The film is too thin.
4. the film surface produced holes: improper treatment, in addition to oil is not clean; Source pollution, compressed air oil removal, water removal is not complete; The workpiece surface is not smooth; Contaminated with dust or other impurities
5. Bubbles appear in the film: after the surface treatment of the workpiece, the water is not dry, and there is residual liquid before the treatment; Oil removal, rust removal is not complete; The bottom volatiles are not removed; The surface of the workpiece has pores; The powder coating is too thick.
6. coating film is not uniform: : spray powder is not uniform; The distance between the spray gun and the workpiece is too close; Unstable high voltage output.
7. the film impact strength and adhesion is poor: phosphating film layer is too thick; The curing temperature is too low, the time is too short, so that the curing is not complete; The bottom metal is not cleaned; Immersion of the coating reduces the adhesion of the workpiece.
8. the film produces pinholes: the air contains foreign matter, residual oil; Spray gun voltage is too high, resulting in coating breakdown; The distance between the spray gun and the workpiece is too close, resulting in the breakage of the coating of the powder spraying equipment; Coating is too thin; The film has not fully cured.
9. A small amount of sand on the film surface: powder spraying equipment is blocked or the airflow is not smooth; Spray gun atomization is not good; Powder drops into the spray chamber; Other debris contaminates the surface of the workpiece.
10. the coating off: the surface treatment of the workpiece is not good, in addition to oil rust is not complete; The output voltage of high voltage electrostatic generator is insufficient; The workpiece is not well grounded; Too high air pressure in powder form;
11. the amount of powder supply is not uniform: powder supply pipe or spray pipe blockage, powder spraying equipment glued on the nozzle harden; Insufficient air pressure, pressure instability; Air compressor mixed with oil or water; The flow of the powder feeding machine is unstable, and the powder quantity of the powder feeding machine is too small; Powder supply tube too long, powder flow resistance.
12. powder flying, adsorption performance is poor: electrostatic generator without high voltage deficiency; The workpiece is not well grounded; Excessive air pressure; Air duct of recovery unit is blocked.
13. Less dusting: insufficient wind pressure, insufficient air volume; The air pressure is too high and the proportion of air in the mixture of powder and airflow is too high; There is water vapor and oil in the air; The nozzle is partially blocked
14. powder tube blockage: due to the material of the powder tube, powder is easily attached to the wall of the powder tube; The output pipe is heated to make the powder in the pipe agglomerate; By bending, disassembling and twisting the powder tube, the powder is mixed with more granular impurities.