The solution to the bad "yin and yang" appearance of the product

The external yin and yang surface of injection molding products refers to the appearance of the product on the surface of the product, which is partially shiny or black, with obvious gloss inconsistency, which is called the yin and yang surface phenomenon in the same industry. Such products are often shipped directly from injection molding materials without post-processing processes such as spraying and PVD. Dark products are especially obvious, and light-colored products have less impact.

Areas prone to yin and yang:
1. Near the periphery of the parting line;

2. Near the gate, the area near the gate is bright, and the area away from the gate is black;

3. Areas with uneven product thickness and large flow velocity variations

4. The corners of the two sides of the product structure;

5. Areas with rib features on the back of the product;

6. Flow end, near the junction line;

7. The area where trapped air is concentrated during the injection molding process, and the area where the product has stagnation phenomenon;

8. The product water cooling gap is too large.

Causes and solutions of Yin and Yang faces:
1. The yin and yang surfaces near the parting line

The parting surface is the main channel for exhaust in the injection molding process. The gas will heat up rapidly during the rapid extrusion and cannot be discharged quickly and effectively, resulting in high temperature of the plastic material, which is the main reason for the brightness around the parting surface, (sometimes It is not ruled out that the problem of grain surface strain needs to be identified.) To solve the yin and yang surfaces around the parting surface, it is necessary to exhaust adequately. Ensure that the exhaust is smooth and communicated with the atmosphere.

2. Near the gate, the area close to the gate is bright, and the area away from the gate is black
Under high speed, high pressure and high mold temperature, the appearance of the product will be bright as a whole. Otherwise, it will be black. This is common sense in injection molding. It is very obvious for large-area products. I believe everyone should know this.

3. Areas where the meat thickness of the product is uneven and the flow speed changes greatly
The uneven meat thickness of the product is the biggest factor causing the yin and yang noodles. The main reason is that the material flows slowly in the area where the product is thick, and the surface of the product is easy to become black, while the area with thin meat is the opposite.

4. The corners of the two sides of the product structure
The corner of the product is also a high incidence area of yin and yang surfaces, mainly because the material flow at the corner is resisted, and the flow speed and pressure change rapidly. One of the reasons is the uneven thickness change at the corner, and the thickness at the corner should also be The thickness of the side wall is uniform, reducing the influence.