The reasons for defects in color coated aluminum coils during the roll coating process can be analyzed from the quality of raw materials, equipment operation, coating process, coating environment and technician operation.
Paint quality
Paint quality is the factor that most affects the coating quality during the coating process of color-coated aluminum coils. The color difference between batches of paint, insufficient paint fineness leading to low coating rate or poor matching of paint and solvent, stratification, etc. will directly affect the coating effect
Aluminum coil quality
When selecting raw materials, the quality should be strictly controlled. Problems such as unevenness of colored aluminum coils, uneven film thickness, and poor edge deflection also directly affect product quality and overall use.
Equipment operation
The colored aluminum coil coating line requires that the coating equipment is intact and operates smoothly, without horizontal and vertical jitter, and the coating roller is required to be finely ground. The lateral jump of all rollers of the coating machine must be controlled within the allowable range, otherwise it will seriously affect the surface quality of the coating.
Process control
The coating process is closely related to the quality of the coating, and the relative linear speed ratio of the coating roller, paint lifting roller, metering roller and substrate is required to be controlled within a certain range. When coating, a certain viscosity range should be set for the coating according to different systems and the film thickness of the coating product to ensure smooth coating and promote the improvement of product quality. The curing process of the coating is controlled as required and shall not be changed arbitrarily, otherwise it will seriously affect the coating quality.
Coating environment
When coating color-coated aluminum coils, the interior of the coating room is required to be clean, dust-proof, insect-proof and have certain ventilation performance to ensure that the surface quality of the coating is not polluted. At the same time, the process conditions need to be changed in time according to the temperature changes.
Technician operation
The operator's technical proficiency and the standardization of operation are the key to obtaining high-quality coating effects. The production department should continuously strengthen the training of operators and let the operators master the principles and key points of coating technology, strengthen responsibility, and strictly operate according to the operating procedures to ensure high-quality prepainted aluminum coils.
How to avoid roller coating defects?
To prevent defects in color coated aluminum coils, we need to understand the common defects in the coating process and their causes and analyze and prevent them one by one. Common defects in the coating process of aluminum coils include roller marks, poor paint adhesion, stains on the coating, etc.
Preventing Roller Marks
a. Before coating, aluminum coils need to be sanded to improve the flatness of the aluminum coils. Generally, the curvature of a 1m long aluminum coil must be controlled within ±2mm, and the thickness error must be controlled within ±0.05mm.
b. When the room temperature is too low or the viscosity is too high, the paint can be preheated to reduce the viscosity of the paint.
c. When coating, technicians need to appropriately adjust the paint amount and roller speed, the distance between the metering roller and the coating roller, and the distance between the coating roller and the object to be coated according to the actual situation, and regularly check whether the coating roller and the conveyor belt speed are basically synchronized.
Preventing pooradhesion
a. Aluminum coils should be pre-treated before coating, and the moisture content should be controlled within 12%. The coating products and process design should be reasonably selected.
b. The recommended single coating amount for roller coating is: 20-25g/㎡ for transparent primer, 5-8g/㎡ for transparent topcoat, 15-25g/㎡ for color primer, and 8-14g/㎡ for color topcoat.
c. During the processing, oil and water pollution on the substrate surface or between coatings is strictly prohibited, and the oil-water separator needs to be drained in time.
d. Sanding should be carefully ensured to ensure sand leakage and the next process should be carried out within 4 hours after sanding.
Preventing surface stains
a. Workshop technicians need to regularly clean and maintain relevant equipment pipelines.
b. Before coating color coated aluminum coils, check whether the roller coating equipment is contaminated by impurities or foreign matter. During the coating process, the paint bucket and oil return tank should be shielded and protected.
b. After the color coated aluminum coils are coated, the roller coating machine, oil return tank and conveyor belt should be cleaned and dried with the special solvent (mass production does not require daily cleaning.)To ensure the energy and service life of the UV curing machine lamp, it is recommended to wipe and clean the lamp and reflector with a cotton ball dipped in special alcohol every week.
c. Regularly manage the coating environment and pay attention to workshop ventilation.
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