Influence of the injection molding process on the quality of injection molded products?

Answer 1

In the molding process of transforming plastic particles into plastic products, plastic is often subjected to high temperatures and pressure and flows under a high shear rate.

Different molding conditions and processes will have different effects on the quality of products, and injection molding has four components: plastic raw materials, injection molding machine, injection mold, and plastic injection molding process.

If the plastic raw materials are correctly selected, the technical process parameters of the injection molding machine and mold structure are in line with the requirements of injection molding conditions, so the quality of processed products is directly related to the injection molding process.

The quality of the product has the internal material quality and appearance quality, the internal material quality is mainly mechanical strength, and the size of the internal stress directly affects the mechanical strength of the product, the main reason for the internal stress is the crystallinity of the product and the orientation of the molecules in plastic molding, etc.

The appearance quality of the products is the surface quality of the products, but the warpage and deformation caused by the internal stress will also affect the appearance quality problems.

The appearance quality of products includes product shortage, product dent, fusion mark, flying edge, bubble, silver wire, black spot, deformation, crack, delamination and discoloration, etc., all related to injection molding temperature, pressure, flow time, and position.

Molding temperature

Barrel temperature, plasticizing temperature, nozzle temperature, mold temperature, and plastic drying temperature, etc.

Barrel temperature: it is the melt temperature of the plastic. If the barrel temperature is set too high, the viscosity of plastic will be low after melting, and the injection speed will be fast under the same injection pressure and flow rate, and the molded products will be easy to fly, silver, discolored, and brittle.

If the barrel temperature is too low, the plastic will be poorly plasticized, the viscosity will be high, the injection speed will be slow under the same injection pressure and flow rate, and the molded products will be easily deficient, with obvious melt marks, unstable size and cold lumps in the products.

Nozzle temperature: high nozzle temperature setting, nozzle salivation, resulting in products with cold material wire. Low nozzle temperature causes clogging in the mold casting system. Injection pressure has to be increased to inject plastic, but there are cold material lumps in the instantly molded products.

Mold temperature: high mold temperature, injection pressure, and flow rate can be set lower, but under the same pressure and flow rate, the products are easy to fly, warp and deform, and the products are difficult to stick to the mold and eject. Mold temperature is low, in the same injection pressure and flow rate, the products are not enough, bubbles, fusion marks, etc.

Plastic drying temperature: various plastics have different drying temperatures. ABS plastic is generally set a drying temperature of 80 ~ 90 ℃, otherwise, it is not easy to dry and evaporate the water and residual solvent, the product is easy to have silver and bubbles, and the strength of the product will also be reduced.