The main principles of enameled winding wire painting

Painting is the process of applying enameled winding wire paint on metal conductors to form a uniform paint layer with a certain thickness. This is mainly related to the liquid painting method, and there are several physical phenomena.

1. Viscosity. When a liquid flows, molecules collide with each other, causing one layer of molecules to move with another layer of molecules. Due to the mutual force, the molecules of the latter layer hinder the movement of the molecules of the previous layer, thus showing the hysteresis of the activity, which is called viscosity.
Different painting methods and different winding wire specifications have different viscosity requirements for paint. The viscosity is mainly related to the molecular weight of the resin. The larger the molecular weight of the resin, the higher the viscosity of the paint, which is used for coating thick lines. Because of the large molecular weight, the paint film obtained has better mechanical properties. The one with low viscosity is used for coating thin lines. The resin has small molecular weight and is easy to apply evenly, and the paint film is smooth.

2. Surface tension. There are molecules surrounding the molecules inside the liquid. The gravitational force between these molecules can reach a temporary balance and form a layer of molecules on the surface of the liquid. On the one hand, it is subject to the gravitational force of liquid molecules, and its force points to the depth of the liquid. On the other hand, it is attracted by the gas molecules, but the gas molecules are fewer and farther away than the liquid molecules. Therefore, the molecules on the surface layer of the liquid are strongly gravitated by the interior of the liquid, causing the surface of the liquid to shrink as much as possible to form a bead shape. geometry in the same volume
The spherical shape has the smallest surface area among shapes. If the liquid is not acted upon by other forces, it will always be spherical under the action of surface tension.
After the painted wire comes out of the felt, there is a process of rounding. Because after the wire is coated with paint and passed through the felt, the shape of the paint liquid becomes olive-shaped. At this time, the paint liquid overcomes the viscosity of the paint liquid itself under the action of surface tension and transforms into a round shape in an instant.
If the wire specifications are smaller, the viscosity of the paint will be smaller and the rounding time required will be less. If the wire specifications increase, the viscosity of the paint will also increase, and the rounding time required will also be longer. In high-viscosity paints, sometimes the surface tension cannot overcome the internal friction of the paint liquid, resulting in uneven paint layers.

3. Moisture phenomenon. The 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 humid phenomenon, and the latter is a non-humid phenomenon. The wetting phenomenon is a manifestation of molecular forces. If the attraction between liquid molecules is less than the attraction between liquid and solid, the liquid will wet the solid, and then the liquid can be evenly coated on the surface of the solid. If the attraction between liquid molecules is greater than the attraction between liquid and solid, the liquid will not be wet.
Solids and liquids will shrink into balls when applied to a solid surface. All liquids moisturize some solids but not others. The angle between the tangent line of the liquid surface and the tangent line of the solid surface is called the contact angle. If the release angle is less than 90°, the liquid will moisten the solid, and if it is greater than or equal to 90°, the liquid will not moisten the solid.
Once the surface of the 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 liquid, and the paint liquid will change from wet to non-wet to the wire. If the wire is hard and the surface molecular lattice is irregularly arranged, the attraction to the paint will be small, which is not conducive to the wetting of the wire by the paint liquid.