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Requirements for spraying in secondary injection molding of injection molded parts

by:Vowin Rapid Prototyping     2023-02-13
1. Classification of commonly used plastic coating spraying

The requirements of spraying in the secondary injection molding of injection molded parts can be divided into infrared drying spraying and ultraviolet curing spraying according to the drying method. According to the coating composition, it is divided into acrylic coatings; polyurethane two-component coatings; nitro coatings; vinyl resin coatings. ABS and HIPS generally use acrylic resin coatings and polyurethane two-component coatings. If conditions permit and the customer requires, some parts are sprayed with UV coatings after spraying the color paint.

2. Environmental requirements for spraying

The requirements for spraying in the secondary injection molding of injection molded parts. In order to ensure the quality of injection molded products and environmental protection, Shanghai Mulan injection molding processing factory has relatively high requirements for spraying on the environment. Generally, there must be special spraying equipment and environment. Build a clean room, especially in the case of spraying two-component or UV coatings. Due to the high gloss of two-component and UV coatings, as long as there is a little impurity or particle, it will be magnified after being reflected by the high-gloss paint film, making the defects more conspicuous.
The spraying environment is classified as follows according to the dust particle diameter less than 0.5μm.

Level 1: less than 35 pieces/m3; level 2: less than 353 pieces/m3; level 10,000: less than 353,000 pieces/m3; UV coatings and two-component coatings generally use 10,000-level clean rooms.

3. Design requirements of spraying on parts

Shanghai Mulan injection molding processing factory has the following requirements for the structural design and material selection of parts.

(1) The rib position design of injection molding products should be reasonable to prevent too deep and too many surface sink marks, especially after spraying high-gloss paint, these defects will be more obvious.

(2) The location, size, and type design of the nozzle should be reasonable, so that the internal stress of the injection molded product is small, especially the amine material at the nozzle should be dense, otherwise obvious defects will occur after spraying.

(3) The selection of villages should consider materials that are easy to adhere to paint and have good solvent resistance. For example, AS and S grades have better stability, but different grades of resin agents have newly developed materials and must be stored after testing. The adhesive properties of PP and PE are poor, and surface treatment is required before they can be used. spraying. For parts with grids, holes, and grooves on the surface, it is difficult to spray the bottom or side of the grid, hole, and phase.

4. Appearance effects that can be achieved by spraying The effects of spraying are as follows.

(1) Ordinary color effect.

(2) Metal effect.

(3) Color changing effect.

(4) Imitation electroplating effect.

(5) Imitation leather grain effect.

(6) Rubber effect.


V. Quality Control Items of Spray Coating Film The quality control items of coating film are as follows.

(1) Adhesion.

(2) Anti-aging properties.

(3) Hardness.

(4) Scratch resistance.

(5) Scrub resistance.

(6) Solvent resistance.

(7) Other surface quality requirements such as gloss, etc.
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