How To Paint Aluminum enameled wire

  • Painting is the process of coating the enamelled wire paint on the metal conductor to form a uniform paint layer with a certain thickness. This is related to several physical phenomena of liquids and painting methods.


    Viscosity When the liquid is flowing, the molecules collide with each other to make the molecules of one layer move with the molecules of the other layer. Due to the mutual force, the molecules of the latter layer hinder the movement of the molecules of the previous layer, thus showing the movement of the molecules. Hysteresis, which is called viscosity. Different painting methods and different wire specifications have different requirements for the viscosity of the paint. The viscosity is mainly related to the molecular weight of the resin. The molecular weight of the resin is large, and the viscosity of the paint is large. It is used to paint thick lines, because the mechanical properties of the paint film obtained with a large molecular weight are better. Low-viscosity ones are used for coating thin wires. The resin's molecular weight is small and it is easy to coat evenly and the paint film is smoother. There are molecules around the molecules inside the surface tension liquid, and the gravitational force between these molecules can reach a temporary equilibrium. On the one hand, a layer of molecules on the surface of the liquid receives the gravitational force of the liquid molecules, and its force points to the depth of the liquid. On the other hand, the gas molecules are attracted by the gravitational force of the gas molecules, but the gas molecules are smaller and farther apart than the liquid molecules. Therefore, the molecules on the surface of the liquid are attracted by the gravitational force inside the liquid, causing the surface of the liquid to shrink as much as possible to form a bead shape. In the geometric shape of the same volume, the surface area of ​​the sphere is the smallest. If the liquid is not affected by other forces, it will always be spherical under the action of surface tension. According to the surface tension of the paint surface, the uneven surface has different curvatures everywhere, and the positive pressure at each point is unbalanced. Before entering the enameling furnace, the thick paint will flow to the thin part under the action of surface tension. The paint solution is uniform, and this process is called the leveling process. In addition to the leveling effect, the uniformity of the paint film is also affected by the effect of gravity, which is the result of the combined force of the two.


    After the painted wire comes out of the felt, there is a rounding process. After the wire is coated with lacquer and felt, the shape of the lacquer is olive-shaped. At this time, under the action of surface tension, the lacquer overcomes the viscosity of the lacquer and turns into a circle in an instant.


    If the wire size is smaller, the viscosity of the paint is smaller, and the time required for rounding is less; if the wire size is increased, the viscosity of the paint also increases, and the time required for rounding is also longer. In high-viscosity paint, sometimes the surface tension cannot overcome the internal friction of the paint solution, which causes the paint layer to be uneven.


    When the lacquered wire comes out of the felt, there is still a problem of gravity in the rounding process of the lacquer layer. If the rounding action time is short, the olive-shaped sharp corners will disappear quickly, the effect of gravity will affect it for a short time, and the coating liquid layer on the wire will be relatively uniform. If the rounding time is longer, the sharp corners at both ends will exist for a longer time, and the time of gravity action will be longer. At this time, the paint layer at the sharp corners has a tendency to flow downwards, which will increase the thickness of the paint layer in local areas. The tension forces the lacquer to be drawn into balls and become particles. Since the gravity effect is very prominent when the paint layer is thick, it should not be painted too thick for each paint coating. This is one of the reasons why "thin paint and more paint" is used in the coating of enameled wire.


    When the thin thread is applied thickly, it shrinks under the action of surface tension to form wavy or bamboo-shaped wool.


    If there are very fine burrs on the wire, the burrs are not easy to paint under the action of surface tension, but also easy to lose and thin, resulting in pinholes in the enameled wire.


    If the round wire itself is elliptical, the paint layer will be thinner at the two ends of the long axis of the ellipse and thicker at the two ends of the short axis under the action of the additional pressure when painting, forming a significant unevenness, so the enameled wire is used The out-of-roundness of the round copper wire should meet the requirements.


    When bubbles are generated in the paint, the bubbles are the air entrapped in the paint solution during the agitation and feeding process. Due to the small specific gravity of the air, it rises to the external surface by buoyancy, but the surface tension of the paint makes the air unable to It breaks through the surface and stays in the paint. This paint with air bubbles is applied to the surface of the wire and enters the enameling furnace. After heating, the air expands sharply, and it rushes out of the surface when the surface tension of the paint decreases due to heating. The surface of Aluminum Enameled Wire is not smooth.


    Wetting phenomenon Mercury droplets shrink into an oval shape on the glass plate, and the water droplets spread out on the glass plate to form a thin layer with a slightly convex center. The former is a wetting phenomenon, and the latter is a non-wetting phenomenon. The wetting phenomenon is a manifestation of molecular forces. If the gravitational force between the liquid molecules is less than the gravitational force between the liquid and the solid, the liquid will wet the solid, and then the liquid can be evenly coated on the surface of the solid; if the liquid molecules The gravitational force between the liquid and the solid is greater than the gravitational force between the liquid and the solid. The liquid cannot wet the solid, and the liquid will shrink into a ball when it is applied to the solid surface. All liquids can wet some solids but not others. The angle between the tangent of the liquid surface and the tangent of the solid surface is called the contact angle. The contact angle is less than 90° for liquid wetting solids, and greater than or equal to 90° for liquids not wetting solids.


    If the surface of the copper wire is bright and clean, it can be coated with a layer of paint. If the surface is stained with oil, it will affect the contact angle between the two interfaces of the wire and the paint solution, and the paint solution will change from wetting to non-wetting on the wire. If the copper wire is hard, the irregular arrangement of the surface molecular lattice will have little attraction to the paint, which is not conducive to the wetting of the copper wire by the paint solution. Capillary phenomenon The phenomenon that the liquid that wets the tube wall rises in the tube, and the phenomenon that the liquid that does not wet the tube wall falls in the tube is called capillary phenomenon. This is due to the wetting phenomenon and the effect of surface tension. Felt painting is to use capillary phenomenon. When the liquid wets the tube wall, the liquid rises along the tube wall to form a concave surface, which increases the surface area of ​​the liquid, and the surface tension should minimize the shrinkage of the liquid surface. Under this force, the liquid surface tends to be horizontal. The medium liquid rises until the wetting and surface tension pull up and the weight of the rising liquid column in the tube reach equilibrium, the liquid in the tube stops rising. The thinner the capillary, the smaller the specific gravity of the liquid, the smaller the wetted contact angle, the greater the surface tension, the higher the liquid level in the capillary rises, and the more significant the capillary phenomenon.