Common quality issues with automotive injection molded parts: color difference: If the color of the injection molded part differs from the standard color sample when viewed with the naked eye, it is judged as color difference under standard light source (D65); Overflow (flash, cape): Thin (flash) adhesive material appears around the injection molding part along the parting line or on the sealing surface of the mold, which is called overflow; Size mismatch: During the molding process of injection molded parts, the inability to maintain the original predetermined size accuracy is called size mismatch; Depression: The surface of injection molded parts is uneven, smooth, and shallow pits or pits are formed inward; Top white/top height: The surface of the injection molded part has obvious whitening or is higher than the original plane; White dots: There are white dots inside the injection molded part, also known as "fish eyes", which are mostly reflected on transparent products; Insufficient strength (brittle cracking): The strength of injection molded parts is lower than expected, making the plastic parts unable to withstand the predetermined load cutting;

Tiger skin pattern often appears on large area automotive injection molded parts such as bumpers, instrument panels, door panels, and pillars. It is a surface defect with wavy stripes that are approximately perpendicular to the direction of melt flow, forming different gloss engravings on the surface of the injection molded parts, resembling patterns on old tiger skin, commonly known as tiger skin pattern. Tiger skin patterns are prone to occur on injection molded parts with thin wall thickness and large process flow. They have the following characteristics: (1) there are periodic alternating light and dark stripes on the surface of the injection molded parts; (2) The stripes are roughly perpendicular to the flow direction of the melt; (3) The stripes are divided into bright and dark areas, with high glossiness in bright areas and poor glossiness in dark areas; (4) If the exterior surface of the injection molded part is a bright area, the back is a dark area, and the two appear alternately.

The performance of plastics is constantly improving, and plastic parts are gradually entering various industries. Nowadays, the annual demand for injection mold processing in fields such as building materials, automobiles, household appliances, electronics, etc. is still relatively strong. The rapid development of these industries has also brought the development of the plastic industry, especially into a stage of rapid development, which involves the production and processing methods of plastic injection molded parts and automotive plastic components.

To solve the problem of adhesion of coatings on automotive plastic parts, it is necessary to have an understanding of the process flow of automotive plastic parts coating. The process flow of automotive plastic parts can be roughly divided into the following parts: blank polishing, chemical treatment, dust removal, primer spraying, color paint (or metal flash paint), polishing, baking, submission for inspection, qualified products entering the warehouse, and unqualified products repairing or peeling. It is understood that among these numerous process steps, the important step to improve the adhesion of plastic parts coating is pre coating treatment. The purpose of pre-treatment for automotive plastic parts before painting is to improve the adhesion of coatings to plastics through a series of physical and chemical methods, reduce various defects in coatings, and thereby improve the quality of plastic coatings. The pre-treatment methods for plastic parts before painting include conventional treatment, acid treatment, flame treatment, interfacial active agent treatment, hot solvent treatment, ultraviolet treatment, and plasma treatment.

Computer paint mixing and spraying method: A technology that combines computer paint mixing and adopts a new process to repair deep scratches. This is a fast repair technique for automobiles, but the main requirement is that the color can be accurately mixed, the repair area should be minimized as much as possible, and after special solvent treatment, the new and old topcoats can be better integrated and achieve good adhesion. If sandpaper and "coarse wax" are used to polish the mirror finish of car paint, it is very difficult to achieve the desired mirror effect. So in the mirror surface treatment of car paint, car paint care materials must be used. At present, the main materials commonly used are atomic ash and polishing agents, and the materials with better mirror effect are polishing agents.