To ensure the uniformity and adhesion of the coating, the electronic door lock electrostatic coating line needs to systematically control multiple links such as equipment debugging, coating performance, workpiece pretreatment, process parameter control, spraying operation specifications, environmental management and quality inspection. The coordination of each link is the key to ensure the coating effect.
The precise debugging of the electronic door lock electrostatic coating line is the foundation. The core equipment of the electrostatic coating line, such as electrostatic spray guns, paint supply systems, conveying devices, etc., need to be adjusted according to the material, shape and size of the electronic door lock. The electrode position, atomization pressure and electrostatic voltage of the electrostatic spray gun will directly affect the charging effect and adsorption capacity of the paint particles. If the electrode is too close to the workpiece or the voltage is too high, it may cause the coating to be too thick or discharge breakdown; if the distance is too far or the voltage is insufficient, the paint particles will be unevenly dispersed, affecting the uniformity. The flow control of the paint supply system is also very important. A stable paint output can avoid inconsistent coating thickness due to intermittent paint supply or flow fluctuations. The running speed of the conveyor must match the spraying rhythm. Too fast or too slow may lead to uneven coating thickness. Therefore, the optimal running speed needs to be determined through debugging so that the workpiece receives uniform coating coverage in the spraying area.
The performance parameters of the coating are key influencing factors. The coating's viscosity, solid content and conductivity and other indicators must meet the requirements of electrostatic coating. Too high viscosity will lead to poor atomization of the coating, coarse particles, and difficulty in evenly adhering to the surface of the workpiece; too low viscosity may cause excessive atomization of the coating during the spraying process, resulting in dry spraying and affecting adhesion. Too low solid content will lead to thin coating and insufficient covering power, requiring multiple spraying to achieve the effect, increasing the risk of unevenness; too high solid content may cause the coating to accumulate and produce sagging. The conductivity of the coating is also closely related to the electrostatic effect. If the conductivity is too low, the coating particles are difficult to be fully charged, affecting its adsorption ability to the workpiece surface. Therefore, it is necessary to adjust the conductive properties of the coating by adding conductive additives, etc., to ensure that a stable charged particle flow can be formed in the electrostatic field and evenly adsorbed on the workpiece surface.
The quality of the pretreatment of the workpiece directly determines the adhesion of the coating. Electronic door locks are mostly made of metal (such as zinc alloy, stainless steel) or engineering plastics. There may be pollutants such as grease, oxide film, and dust on the surface. If not thoroughly removed, it will hinder the direct contact between the coating and the substrate, resulting in decreased adhesion. The pretreatment process usually includes steps such as degreasing, rust removal, phosphating (for metal parts) or flame treatment (for plastic parts). Degreasing can be done by solvent cleaning or alkaline degreasing agent to ensure that the lubricating oil and fingerprints remaining during the processing are completely removed; rust removal removes the oxide scale on the metal surface by sandblasting or chemical pickling, so that the surface of the substrate forms a microscopic rough structure and increases the mechanical bite ability of the coating; phosphating can generate a layer of phosphate conversion film on the metal surface, further improving the bonding between the coating and the substrate; for plastic parts, flame treatment or corona treatment can increase the surface energy and improve the wettability and adhesion of the coating. The pretreated workpiece needs to be painted in time to avoid secondary pollution or re-oxidation of the surface.
Accurate control of process parameters is an important guarantee for coating uniformity. During the electrostatic coating process, parameters such as electrostatic voltage, spraying distance, spray gun movement speed and paint flow rate need to match each other. The level of electrostatic voltage determines the charging strength of the paint particles. Within a certain range, the higher the voltage, the stronger the charging effect and the more uniform the coating adsorption. However, too high a voltage may cause spark discharge, damage the workpiece or cause safety hazards. The spraying distance is usually controlled between 15-30 cm. If the distance is too close, it is easy to cause the coating to be too thick or locally accumulated. If the distance is too far, the coating will become thinner and uneven due to the scattering of paint particles. The movement speed of the spray gun needs to be kept stable. If it is too fast, the coating will be too thin, and if it is too slow, it may cause sagging. Generally, it needs to be adjusted according to the drying speed of the paint and the complexity of the workpiece to ensure that a uniform coating thickness is formed within a unit time. In addition, for the complex structure of the electronic door lock (such as handles, lock holes, etc.), it may be necessary to adjust the angle and position of the spray gun, or use multiple guns to spray in coordination to ensure that every corner can be evenly covered.
The standardization of the spraying operation has a direct impact on the quality of the coating. Operators need to undergo professional training, be familiar with the performance and process requirements of the equipment, and master the correct gun holding posture and movement trajectory. When holding the gun, the spray gun should be kept perpendicular to the surface of the workpiece to avoid uneven coating thickness due to excessive inclination angle; the movement trajectory should be parallel and reciprocating, and there should be appropriate overlap between adjacent spray strokes (usually 30%-50%) to eliminate spray joints and ensure continuous and uniform coating. During the spraying process, it is also necessary to pay attention to the atomization state of the paint and the immediate effect of the coating. If problems such as poor atomization, sagging or leakage are found, the equipment parameters should be adjusted or the paint should be replaced in time to avoid quality defects in batch products. For electronic door locks with irregular shapes or deep concave parts, manual re-spraying or adjustment of the automatic spray gun program may be required to ensure the coating quality of these special parts.
Stable management of the coating environment cannot be ignored. The temperature, humidity and cleanliness of the paint shop will affect the drying process of the paint and the coating quality. Too low temperature will cause the paint to dry slowly, which may cause sagging or coating contamination; too high temperature will cause the paint to dry too quickly during the spraying process, resulting in dry spraying. When the humidity is high, the moisture in the air may mix into the coating or condense on the surface of the workpiece, affecting the adhesion of the coating and the appearance quality of the coating. Therefore, the ambient temperature needs to be controlled at 15-25℃ and the relative humidity needs to be controlled at 50%-70% through air conditioning and dehumidification equipment. In terms of cleanliness, if dust, particles and other pollutants in the air adhere to the surface of the wet coating, they will form bulges or particle defects, affecting the flatness and adhesion of the coating. Therefore, the workshop needs to be sealed and an air filtration system needs to be installed. The floor and equipment need to be cleaned regularly to reduce the source of dust.
Quality inspection and feedback mechanism are the key to continuous improvement. After the coating is completed, the coating quality needs to be evaluated by visual inspection, film thickness inspection, adhesion test (such as cross-cutting method, circle-cutting method) and other means. Visual inspection mainly observes whether the coating surface is uniform and smooth, and whether there are defects such as sagging, orange peel, and particles; the film thickness detection uses a magnetic thickness gauge or an eddy current thickness gauge to ensure that the coating thickness meets the design requirements; the adhesion test uses the cross-cutting method to observe whether the coating peels off and judge its bonding strength with the substrate. If the coating uniformity or adhesion is found to be substandard, the production process must be traced back in time to analyze whether the problem is caused by equipment parameters, coating performance, pretreatment quality or environmental factors, and the process must be adjusted in a targeted manner to form a closed-loop management and continuously optimize the coating effect.
In short, ensuring the coating uniformity and adhesion of the electronic door lock electrostatic coating line is a systematic project involving equipment, materials, processes, operations and environment. It is necessary to start from the details, strictly control the quality of each link, and ensure the stability of the coating process through continuous testing and improvement. Only by achieving precise coordination of various elements can a uniform, firm and beautiful coating be formed on the surface of the electronic door lock, which not only improves the appearance and texture of the product, but also enhances its corrosion resistance and service life, and meets the market demand for high-quality smart locks.
