(1) Choose a film of moderate width and thickness; since aluminum profiles have complex cross-sectional shapes, with big differences between wide and narrow parts, edges can easily lift up, reducing the film's coverage and affecting the coating quality. If the film is too narrow, it obviously won't cover properly and can't be used for spraying. On the other hand, when choosing the film thickness, as long as it can cover and is flexible, it doesn't need to be too thick, because thicker film increases production costs for aluminum profiles and isn't really necessary.
(2) Spray paint promptly after applying the film. Once the profile is wrapped with film, it should be sprayed as soon as possible-the shorter the wait, the better. If it sits too long, the glue on the film dries and loses stickiness, and especially if the wind blows, the film may come off, making spraying difficult. So, to ensure film and coating quality, the waiting time after applying the film should generally not exceed 16 hours.
(3) Choose films with moderate viscosity. In the production of two-color aluminum profiles, selecting the right protective film is crucial. If the film's viscosity is too low, it won't stick well and can easily peel off, making spraying quite difficult. On the other hand, if the film's viscosity is too high, it means there's too much adhesive on it. When you peel it off, the glue can stick to the profile and affect its surface quality. Also, when picking a film, try to choose one with an adhesive that's the same as or similar to the paint composition, which can help reduce the impact on the paint's color.
4) Determine the colors, dividing surfaces, and boundary lines. Before spraying, aluminum profile processing must clarify the color to be sprayed on each surface, which surface serves as the dividing surface, and which line is the boundary line, based on the function of the profile and customer requirements. Generally, the inside is a lighter color, and the outside is a darker color. Only after clarifying the dividing surfaces, boundary lines, and color requirements can the film be applied. Be careful not to place the film in the wrong position.
(5) Film application quality: Applying the film is a key process in two-tone aluminum profile processing, and the quality of the film directly affects the surface quality of the aluminum profile. The main points include: First, try not to create excessive tension on the film when applying it, meaning the film should not deform; otherwise, the applied film will shrink, causing the ends of the aluminum profile to have no film. Additionally, when breaking the film at the ends of the profile, it should be cut with a blade rather than pulled apart, as pulling can also cause shrinkage. Second, the film width should match the surface width; generally, the film should be slightly wider than the profile surface. If the film is too wide and extends beyond the edge, it can be blown by compressed air during spraying. If the film is too narrow and doesn't fully cover the surface, that's not acceptable. Fourth, when the dividing line is at the groove edge, make sure the film's excess edges are pressed into the groove; otherwise, airflow during spraying can lift the film and affect spray quality. Fifth, the film must be applied flat to prevent wrinkles or curling. Sixth, for profiles with complex cross-sections, if applying the film in one step is difficult, it can be done in two or more steps to ensure full coverage. Seventh, for profiles with thin walls or large cantilevered sections, the film should not be pressed too tightly, and care must be taken not to deform the profile. Eighth, after the first spraying, the profile should not be left standing for too long, as dust can settle on the surface, making film application difficult and affecting quality.
(6) Strictly follow the film application process. Aluminum profiles must have the film applied only after the first coat of paint. They cannot be directly filmed after chromating because the film has adhesive. If you apply it directly on the chromated layer, the adhesive will stick to it, or when peeling off the film, it could peel off the chromated layer. This greatly reduces the paint's adhesion and ultimately affects the spraying quality of the aluminum profiles, potentially causing the paint to peel off with serious consequences.
(7) Film removal timing. After aluminum profiles are filmed and painted, the film needs to be removed, but it shouldn't be pulled off immediately after painting. The timing must be controlled. Generally, after painting, the coating needs at least 10 minutes to level and basically solidify before removing the film. Otherwise, if the paint hasn't set, pieces of the film might stick to the aluminum during removal, affecting paint quality. Also, the film should be removed quickly to ensure the removal quality.
(8) Avoid multiple reworks. During the production process of two-color aluminum profiles, rework is inevitable due to various factors. However, each rework requires an additional curing. For the paint film, multiple coatings increase its thickness, and repeated curing reduces adhesion, making the paint more likely to peel off. Therefore, in the production of two-color aluminum profiles, it's best to avoid multiple reworks whenever possible.
(9) Reasonable control of film thickness: When producing two-color aluminum profiles, the coating process requires at least two sprays. If we operate as if it's a single spray, some areas of the topcoat will end up thicker while others thinner, causing serious unevenness in film thickness. So, during spraying, we need to control it properly. The first spray should focus mainly on the key surfaces, while the other surfaces can be left uncoated or lightly coated. The second spray should again focus on the needed surfaces, with minimal or no spraying on the others. Also, based on the outcome of the first spray and the color chosen, we should reasonably control the thickness of the second spray, but we must ensure it covers the first layer well.
(10) Spraying order: For two-color aluminum profile processing, two colors are applied, one darker and one lighter. The spraying must follow a certain order. Before spraying, we need to decide which color goes first. If the lighter color is sprayed first and the darker later, the lighter one will undergo two baking cycles, which can easily cause color changes. If the darker color is sprayed first and the lighter later, the lighter may not cover the dark coat fully, requiring a thicker film, but excessive thickness can lead to peeling. So in actual production, spraying light first and dark later is generally more feasible.
