Ten Issues to Pay Attention to in the Production of Two-Color Aluminum Profiles

(1) Choose a film with moderate width and thickness; due to the complex cross-sectional shapes of aluminum profiles, the surface varies significantly between wide and narrow areas, which can easily cause the edges to lift, reducing the film's coverage ability and affecting the spray painting quality. If the film is too narrow, it cannot cover properly and obviously cannot be sprayed. On the other hand, when selecting the film thickness, it only needs to be elastic enough to provide coverage; it is not necessary to choose a very thick film, as thicker films will increase the production cost of aluminum profiles and are generally unnecessary.

(2) Spray painting promptly after applying the film. After applying the film to the profile, spraying should be done promptly, and the shorter the wait, the better. If the waiting time is too long, the adhesive on the film will dry and lose its stickiness. If exposed to wind, the film may peel off, making spray painting difficult. Therefore, to ensure both film adhesion and spray painting 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 film is crucial. If the film's viscosity is too low, it won't stick well. The film may easily fall off, causing significant difficulties during painting. If the film's viscosity is too high, it means there is too much adhesive on the film. When the film is removed, the adhesive may stick to the profile, affecting the surface quality. Additionally, when choosing a film, it is best to select one whose adhesive composition is the same as or close to the paint composition, which can reduce the impact on the paint's appearance.

(4) Determine colors, dividing surfaces, and dividing lines. Before painting aluminum profiles, it is essential to clarify which color should be applied to each surface based on the profile's function and customer requirements, determine which surface is the dividing surface, and identify the dividing line and its position. Generally, the inside is a light color, and the outside is a dark color. After clarifying the dividing surfaces, dividing lines, and color requirements, the film can be applied. It is crucial to ensure that the film is not applied in the wrong position.

(5) Film quality: Applying film is a key process in the processing of two-color aluminum profiles. The quality of the film directly affects the surface quality of the aluminum profiles, and mainly includes the following aspects: First, when applying the film, try not to create excessive tension in the film, meaning the film should not deform. Otherwise, the applied film is prone to shrinkage, causing the ends of the aluminum profiles to have uncoated areas. On the other hand, when the film at the ends of the aluminum profile is disconnected, it should be cut with a blade rather than pulled apart, because a pulled film will still shrink. Second, the film width should match the coating width. Generally, the film width should be slightly larger than the width of the aluminum profile surface. If the film is too wide, extending too far beyond the edge of the profile, it can be lifted by compressed air during spraying. If the film is too narrow and cannot fully cover the surface, it is obviously not acceptable. Fourth, when the surface boundary is at the edge of a groove, the excess film must be pressed into the groove, otherwise, airflow during spraying can lift the film, affecting the spray coating quality. Fifth, when applying the film, it should be applied smoothly to prevent wrinkles or curling. Sixth, for profiles with complex cross-sectional shapes, if applying the film in one step is difficult, it can be done in two or more steps to ensure full coverage. Seventh, for special profiles with thin walls or large cantilevers, the film should not be pressed too tightly; care must be taken to prevent deformation of the aluminum profile. Eighth, after the first spray coating, the aluminum profiles should not be left standing for too long, otherwise dust can settle on the surface, making it difficult to apply the film and thus affecting film quality.

(6) Strictly implement the film application process. When applying film to aluminum profiles, it must be done after the first coating. Directly applying the film after chromating the profile is not allowed because the film has adhesive on it. If the film is applied directly onto the chromated layer, the adhesive will stick to the chromated layer, or when removing the film, it may peel off the chromated layer, which will greatly reduce the adhesion of the paint film and ultimately affect the quality of the sprayed coating on the aluminum profile, potentially causing the paint film to fall off, with serious consequences.

(7) Film removal timing. After applying the film and spraying the aluminum profile, the film needs to be removed, but it should not be removed immediately after spraying. The timing of film removal must be controlled. Generally, after spraying, the paint film should level and solidify, a process that should take no less than 10 minutes, before the film can be removed. Otherwise, if the paint film hasn’t set, removing the film can leave adhesive residues on the aluminum profile, affecting the paint quality. Additionally, the removal process should be done quickly to prevent compromising the quality of film removal.

(8) Avoid multiple reworks. In the production of double-color aluminum profiles, reworks are sometimes unavoidable due to various factors. However, each rework requires an additional curing process. For the paint film, multiple coatings increase the thickness, and repeated curing can reduce adhesion, making the paint film prone to peeling. Therefore, in the production of double-color aluminum profiles, multiple reworks should be avoided as much as possible.

(9) Reasonable control of film thickness: The production of two-color aluminum profiles requires more than one coating. If we operate as if it is a single coating, it will result in some areas having a thicker finish and others thinner, leading to severe unevenness in film thickness. Therefore, proper control is required during spraying. During the first spray, focus on key areas of one surface, while the other surface can be left uncoated or lightly coated. The second spray should target the necessary areas as much as possible, leaving other areas uncoated or lightly coated. At the same time, the thickness of the second spray should be reasonably controlled based on the first spray and the chosen paint color, while ensuring the second spray properly covers the first spray.

(10) Spraying sequence: For two-color aluminum profile processing, two colors need to be applied. These two colors inevitably include a dark color and a light color, so the spraying order must be considered. It depends on the specific situation which color is applied first. If the light color is sprayed first and the dark color later, the light color will undergo two curing processes (two baking cycles), which can easily cause discoloration of the light color. If the dark color is sprayed first and the light color later, the coverage of the light color over the dark color will be somewhat limited. To cover the dark color, the paint layer thickness must be increased, but if the thickness becomes too great, it can easily lead to peeling. Therefore, in actual production, the process of spraying light color first and then dark color is more feasible.