Principles of injection molding and characteristics of ordinary processing and molding

Injection molding is the high-speed injection of plastic melt into a closed mold cavity under high pressure, followed by cooling and shaping to obtain plastic products that are completely consistent with the shape of the mold cavity.
Injection processing and molding must meet two necessary conditions for molding: plastic must be injected into the cavity of the Injection mold construction in a molten state, and the injected plastic melt must have sufficient pressure and flow speed to fully fill the cavity of the mold. Therefore, injection processing and molding must have the basic functions of plastic plasticization, melt injection and pressure maintaining molding.
Plastic plasticization: during the plasticization process of injection molding, solid plastics continuously move forward along the direction of the screw groove through the conveying function of the rotating screw. After heating, compaction, shearing and mixing of screw threads, they are heated and transformed into a viscous plastic melt with uniform density, viscosity, composition and Stable distribution.
Injection molding process: The plasticized plastic melt is stored in the material storage area of the machine barrel. During injection molding, the screw moves axially. Under the injection pressure of the screw, the plastic melt has flowed through the nozzle installed in the front section of the machine barrel, the mold pouring system, etc. at a certain rate and injected into the mold cavity of the mold.
Cooling and shaping process: the plastic melt injected into the mold cavity of the Injection mold construction overcomes various flow resistance and fills the mold cavity. The plastic melt filled with the mold cavity is subjected to the huge pressure from the mold cavity. This pressure has the tendency to drive the plastic melt back to the barrel. The cooling effect of the mold cavity causes the plastic melt to cool and shrink.
At this point, the injection molding screw continues to provide pressure to keep the plastic melt filling the mold cavity without backflow, and appropriately replenishes the plastic melt into the mold cavity to fill the shrinkage space in the mold cavity until the plastic melt gradually cools and solidifies into the product.
Details determine success or failure, which has become a standard pursued by every industry. Nowadays, the precision of products is becoming increasingly high, and the quality requirements are becoming increasingly strict. This requires strict control and supervision of every aspect of the product during the production process, especially in the injection molding product industry.
Injection molded parts processing products have penetrated into every industry, and the continuous improvement of plastic properties has made many parts that previously had to be made of metal completely replaceable with plastic accessories.
However, due to the inherent good fluidity of plastic and the difficulty in controlling its size, the manufacturing process of injection molded parts is more difficult than other industries. Especially in the details, if not paid attention to, injection molding is prone to pores, color differences, flash edges, and other phenomena. In severe cases, the product is directly scrapped. These common problems in the injection molding process directly test whether injection molding engineers have control over the details of injection molded products.
The characteristics of ordinary injection molding are:
The dimensional accuracy requirements for injection molded parts are not high, usually based on the standard of being able to assemble. The appearance requirements for injection molded parts are relatively high, and if necessary, secondary processing (such as oil injection) may be used to improve the appearance defects.
Ordinary injection molding does not require the use of particularly precise injection molding machines or specific materials. Commonly used thermoplastic plastics can be used for production, so ordinary injection molding processes are widely used in the modern plastic industry.
Injection molding: If the wall thickness of the injection molded part is uneven, it can cause deformation or shrinkage of the product. To solve this problem, it is recommended that the customer modify the product. Of course, if the product cannot be modified, the transition can only be done by chamfering the C or R angle at the transition point between thick and thin. This will reduce the stress problem of the plastic during flow, reduce stress, and the product will not be easily deformed. Of course, the thickness and thin area cannot exceed 60%, Otherwise, it must be thinned or thickened.