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Powder coating booth production is a core and critical process in the entire powder coating production process. The quality of the powder coating on the profile surface directly depends on the precise control of various process parameters during the spraying process, and also relies on strict control of details. Among them, powder output and atomizing air are two core technical indicators, and their adjustment precision directly affects the uniformity and adhesion of the coating. Before the formal powder coating operation, multiple test sprays and adjustments are required: operators can visually observe the amount of powder output at both ends of the spray booth while focusing on checking the uniformity of powder distribution. From a technical principle perspective, powder travels in a straight line within 10cm-15cm of the spray gun tip, while beyond this range it forms an atomized powder state. It is this atomized powder that ultimately effectively adheres to the profile surface. Therefore, whether a stable atomization effect is formed is the core standard for judging and controlling the distance between the spray gun and the profile – too close a distance will lead to powder accumulation, while too far a distance will result in insufficient atomization and a decrease in adsorption rate. Besides the control of core process parameters, many small operational steps in spray booth production are equally important, as these details directly affect the stability and consistency of the coating quality.
The installation position and arrangement of the spray guns are fundamental to ensuring uniform powder coverage, directly affecting the thickness consistency and flatness of the coating on the profile surface. In terms of installation angle, the spray guns should maintain a certain tilt, and the tilt direction should be biased towards the profile's running direction. This angle design allows the atomized powder to adhere more smoothly to the profile surface, avoiding powder shedding or accumulation due to airflow interference. In terms of arrangement, all spray guns must be vertically parallel, and the gun tips must be on the same straight line to ensure seamless spraying. At the same time, the spacing between spray guns must be reasonably set, and overlapping spraying areas are strictly prohibited—overlapping areas will cause powder accumulation, resulting in uneven coating thickness; while excessive spacing will create spraying blind spots, resulting in some areas without powder coverage. The height of the upper and lower spray guns needs to be precisely adjusted according to the width and height of the profile, ensuring that the powder completely covers the upper and lower edges and sides of the profile, leaving no area untouched.
The fluidized bed is an important component of the powder coating spraying system. Its core function is to use airflow to create a stable fluidized state for the powder coating—that is, the powder exhibits a smooth, liquid-like flow. This state ensures that the powder is smoothly drawn into the duct and forms a uniform atomization effect under the action of the accelerating airflow. The practical method for judging whether fluidization is sufficient is simple and intuitive: the operator can gently stir the powder in the fluidized bed with their hand or a clean stick. If no obvious resistance is felt and the powder flows smoothly with the stirring action, it indicates sufficient fluidization; if there is resistance when stirring, or if the powder clumps or separates, it indicates insufficient fluidization. Controlling the fluidizing air pressure is crucial: insufficient pressure prevents the airflow from effectively carrying the powder, causing it to settle at the bottom of the fluidized bed and preventing it from being smoothly drawn into the duct, resulting in unstable powder output. Excessive pressure causes the airflow to over-impact the powder, leading to powder splashing, which also disrupts fluidization stability and affects atomization. Therefore, the optimal fluidizing air pressure must be determined through multiple adjustments before production. During production, the pressure gauge readings must be checked regularly to ensure they remain within a stable range, preventing pressure fluctuations from affecting coating quality.
In powder coating, material utilization is a critical factor in production economics. Actual production data shows that only about one-third of the powder adsorbed onto the profile surface and ultimately forms an effective coating accounts for the total powder output from all spray guns; the majority of the remaining powder is scattered inside the spray booth. Therefore, timely powder recycling and proper reuse not only reduce raw material loss and control production costs but also reduce waste emissions, aligning with green production principles. The use of recycled powder must follow scientific mixing principles: Recycled powder must never be used alone; it must be mixed with newly added virgin powder in an appropriate ratio before use. A reasonable mixing ratio ensures that the fluidization properties and electrical properties of the powder are essentially the same as the virgin powder, thus guaranteeing the stability of the coating quality. If the proportion of recycled powder is too high, problems such as powder particle wear and decreased electrical properties will lead to reduced coating adhesion and uneven gloss; if the proportion is too low, the economic value of the recycled powder cannot be fully realized. Generally, the mixing ratio of recycled powder to new powder is recommended to be controlled between 1:1 and 1:2. The specific ratio can be fine-tuned according to factors such as the cleanliness and storage time of the recycled powder. At the same time, the recycling system needs to be cleaned regularly to prevent dust, impurities, or powders of different colors from mixing into the recycled powder, causing cross-contamination and affecting the spraying effect.
Powder coatings have extremely strong adsorption properties and are easily contaminated by suspended particles in the air, such as dust, fibers, and oil particles. If these contaminants enter the spray booth, they will mix with the atomized powder and adhere to the surface of the profiles, causing defects such as flocculent material, particle spots, or pinholes on the powder-coated surface. These defects will be further solidified after high-temperature baking and cannot be eliminated by subsequent treatments, severely affecting the smoothness and decorative effect of the profile surface. Therefore, the spray booth must adopt strict sealing measures to create a closed production environment. Specific requirements include: the doors and windows of the spray booth must be fitted with sealing strips to ensure no gaps when closed; the ventilation system must be equipped with high-efficiency filters to prevent contaminants from the outside air from entering; an air curtain or transition area should be set up at the entrance of the spray booth to prevent dust from being brought in by personnel entering and exiting; and it is strictly forbidden to open the observation windows, maintenance doors, or other openings of the spray booth at will during the production process. At the same time, the interior of the spray booth must be cleaned regularly to remove powder and dust deposited on the walls, floors, and equipment surfaces, maintaining the cleanliness of the internal environment of the spray booth and preventing spraying defects caused by contaminants from the source.
The air pipes of the spraying system are the channels for powder transport, and their internal cleanliness directly affects the smoothness of powder dispensing. During production, some powder adheres to the inner wall of the air pipes. If not cleaned for a long time, this residual powder will clump due to moisture, compression, etc. When used again, the clumped powder will be sprayed out with the airflow, resulting in a "powder spitting" phenomenon—that is, the powder is sprayed out in granular form instead of a uniform atomization. This will cause a grainy texture on the profile surface and an uneven coating, seriously affecting the spraying quality. Therefore, regular cleaning and maintenance of the air pipes is crucial. Specific maintenance requirements: After each day's production, the air source must be shut off, the connection interfaces at both ends of the air pipe must be disconnected, and compressed air must be used to blow from one end to the other to thoroughly remove any residual powder from the inner wall. If the powder color or type is changed during production, the air pipe must be thoroughly cleaned beforehand to avoid cross-contamination between powders of different colors and formulations. For spraying equipment that will not be used for a long time, the powder inside the air pipe must be completely blown out before shutdown, and both ends of the air pipe must be sealed to prevent dust from entering or powder from becoming damp and clumping.
Spare powder tanks are important auxiliary equipment for improving powder changing efficiency in spray booth production. Their main function is to allow for quick switching when changing powder color or type, avoiding production stoppages caused by cleaning the original powder tank and waiting for powder to be prepared, effectively improving labor efficiency. The management and maintenance of spare powder cans should focus on two key aspects: dust prevention and moisture control. First, spare powder cans must be placed in a dry, clean environment, with the opening sealed to prevent dust and debris from entering and contaminating the powder. Second, the relative humidity of the storage environment must be controlled below 60% to prevent the powder from becoming damp and clumping, which would affect its fluidization and electrical properties. Simultaneously, the remaining powder in the spare powder can should be clearly labeled with its color, type, production batch, and storage time for quick identification and reconstitution in subsequent use. Before using the spare powder can, the state of the powder inside must be checked. If clumping or dampness is found, it must be crushed and dried before use to ensure the powder quality meets production requirements.
Powder replenishment is a crucial step in filling spraying blind spots and ensuring comprehensive coverage of the profiles. Even after all technical parameters have been adjusted before production, continuous monitoring of the profiles is still necessary during production. Operators must observe the powder coating process of the profiles in real time through the powder replenishment window of the spray booth, paying particular attention to areas prone to thin coating, such as edges, corners, and grooves. If shallow powder coverage or blank areas with unadsorbed powder are found, powder replenishment must be carried out promptly using a manual spray gun. Since the powder output of a manual spray gun is usually greater than that of an automatic gun, the operator can appropriately increase the hand swing speed during powder replenishment to avoid localized powder accumulation and uneven coating thickness due to excessive powder output. It is particularly important to note that some profiles, due to their structural design limitations, may create dead zones during powder coating that cannot be remedied by powder replenishment. These areas are often deep and narrow grooves, mostly located on the non-decorative surfaces of the profiles. The core reason for this phenomenon is the "Faraday shielding effect": two opposing surfaces in a groove are on the same electrode and are too close together, forming a repulsive electric field that hinders powder adsorption within the groove. For these areas, indiscriminate powder replenishment should be avoided, as it can lead to excessive powder accumulation, resulting in defects such as excessively thick coatings and sagging. This affects both the surface quality of the profile and wastes powder. If these dead corners are located on non-decorative surfaces and have little impact on the overall appearance of the profile, powder replenishment can be omitted, prioritizing the coating quality of the decorative surfaces.
The core of powder coating booth production lies in "precise parameter control and meticulous attention to detail." Adjusting the powder output and atomizing air is fundamental to ensuring coating quality, while seven key details—spray gun position, fluidizing air pressure, powder recovery, booth sealing, air pipe maintenance, spare powder bin management, and replenishment operations—are crucial for ensuring consistent and stable coating quality. In actual production, operators must strictly adhere to all operating procedures, not only mastering the methods for adjusting process parameters but also paying close attention to the execution and monitoring of every small step. By scientifically calibrating the spray gun position, precisely controlling the fluidizing air pressure, rationally recycling powder, ensuring a sealed and clean spray booth, regularly cleaning and maintaining the air pipes, standardizing the management of spare powder bins, and accurately and efficiently replenishing powder, common defects such as uneven coating, particles, pinholes, and missed spraying can be effectively avoided, thus improving the quality of profile surface coating. Meanwhile, for spraying dead zones caused by the profile structure, scientific judgment and reasonable handling are necessary to avoid quality problems and material waste caused by blind operation. Only by organically combining process parameter control with detailed operational management can high-quality, high-efficiency, and economical spray booth production be achieved, laying a solid foundation for subsequent baking, curing, and finished product quality. Enterprises should also strengthen the professional training of operators to improve their understanding of process principles and operating procedures, ensuring that all requirements are implemented effectively and continuously improving the stability and reliability of spray production.
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