Painting Injection Molding Parts

Injection molding is a widely used manufacturing process that involves injecting molten material into a mold to create various parts and products. While injection molding provides excellent precision and efficiency, the final parts often require additional finishing touches to enhance their appearance and functionality. One of the most common methods employed for this purpose is painting. Painting injection molding parts offers numerous advantages. Firstly, it allows manufacturers to achieve a desired aesthetic appeal by adding color and texture to the parts. This is particularly important in industries such as automotive, consumer electronics, and home appliances where visual appeal plays a crucial role in customer satisfaction. Moreover, painting can also provide functional benefits. For instance, it can protect the parts from environmental factors such as UV radiation or corrosion. Additionally, certain types of paints can improve the part's resistance to wear and tear or enhance its electrical conductivity. To ensure successful painting of injection molding parts, several factors need consideration. The choice of paint should be compatible with the material used for injection molding to ensure proper adhesion and durability. Surface preparation techniques like cleaning or sanding may be necessary to remove any contaminants or imperfections that could affect paint adhesion.
 
In conclusion, painting injection molding parts is an essential step in achieving both aesthetic appeal and functional performance. It allows manufacturers to customize their products while protecting external elements. Proper selection of paint type and surface preparation techniques are crucial for ensuring successful outcomes in this process.
 
It is common for injection molded parts to be scorched during fuel injection. Of course, the painting department has a set of solutions, such as adjusting the painting formula and controlling the painting speed. However, if the plastic parts need to be sprayed with silver oil, scorching will occur very often and is difficult to solve by the painting department alone, which requires the cooperation of the injection molding department.
 
The silver painting is relatively thin, which can significantly magnify the surface defects of the injection molded product. Therefore, after the injection molded parts are sprayed with silver oil, slight defects on the surface, such as spots and lines will be displayed. What is more serious is that if there are air marks or welding marks on the surface of the plastic parts, even if they are very small, they will be exposed. Even if it is slight, there will be scorch marks that are difficult to solve in the injection department after injection. At this time, the injection molding department must solve these problems of the injection molded parts to ensure that the injection department can produce normally.
 
These air marks and welding marks that cause scorching usually appear around the pouring gates of injection molded parts and at locations with concave and convex corners in the plastic parts, or locations with bosses, because these locations are more likely to generate gas lines and welding lines during injection molding. The fundamental cause of gas marks and welding lines is the trapped air caused by the failure of the gas in the cavity to be discharged smoothly. At this time, the injection speed must be slowed down. When the filling is about to reach the position where gas lines and welding lines will occur, immediately switch to a slower injection speed to avoid gas lines. After filling the position where the problem occurs, you can switch to a faster injection speed. Fill at a high speed to prevent insufficient filling of injection molded parts.
 
There are more problems when producing parts made of styrene-butadiene copolymer. You can’t even see gas marks and injection marks with your eyes. They may exist, but burning will occur after spraying silver oil. The solution is still the same, which is to reduce the injection speed. Sometimes, scorching at the pouring gate is particularly difficult to solve. Adding a buffer bag and blocking plug to the flow channel will improve it. At the same time, when solving this type of problem, the mold temperature should be kept high in the middle. Generally, cold water from a chiller should not be used to cool the mold, except when the mold temperature is very high. In addition, special attention should be paid to the fact that the molded plastic parts cannot be stored in a humid place, otherwise, the injection molded parts will be burned in a large area after being sprayed with moisture; the injection molded parts must be baked before being sprayed. A similar phenomenon also occurs when spraying plastic parts made of HIPS (impact-resistant polystyrene). The HIPS material itself is very easy to burn after spraying. If there are gas marks, jet marks and trapped gas marks on the injection molded parts, When there is a problem, no matter what kind of paint is sprayed, the burning is difficult to solve. Therefore, the gas marks and injection marks should be removed first to ensure the normal production of a painting.