Plastic injection molding is a widely used manufacturing process for producing plastic parts. Here’s a one-minute understanding of the eight essential steps involved in the process:
- Mold Design: The first step is to create a mold design that outlines the shape and specifications of the desired plastic part. The mold design includes details such as the part geometry, cooling channels, and ejection mechanisms.
- Material Selection: The appropriate plastic material is chosen based on the part’s requirements, such as strength, flexibility, and temperature resistance. Common plastic materials used in injection molding include ABS, PP, PE, and PC.
- Material Melting: Plastic pellets or granules are fed into the injection molding machine’s hopper and melted in the heated barrel. The molten plastic is then ready for injection.
- Injection: The molten plastic is injected under high pressure into the mold cavity through a nozzle and runner system. It fills the mold’s cavities, taking the shape of the desired part.
- Cooling: After injection, the mold remains closed, and the plastic cools and solidifies within the mold cavity. The cooling process determines the part’s final structure and minimizes defects.
- Ejection: Once the plastic has sufficiently cooled and solidified, the mold opens, and ejector pins or plates push the finished part out of the mold cavity.
- Trimming: The part may have excess material or flash along its edges due to the molding process. Trimming removes these excesses and ensures the final part meets the desired specifications.
- Quality Inspection: The finished parts undergo thorough inspection to check for defects, dimensions, and other quality parameters. Defective parts are discarded, and only approved parts are prepared for assembly or distribution.
In summary, plastic injection molding involves designing the mold, selecting the appropriate material, melting and injecting the plastic, cooling and solidifying the part, ejecting and trimming it, and finally inspecting the quality to ensure the production of high-quality plastic parts efficiently and accurately.
Injection molding, also known as injection molding, is an injection molding method. The advantages of the injection molding method are fast production speed, high efficiency, automatic operation, a wide variety of patterns, shapes from simple to complex, and sizes from large to small. Moreover, the product size is accurate, the product is easy to be updated, and it can form parts with complex shapes. Injection molding is applicable to mass production, products with complex shapes and other molding processing fields.
What are the steps of plastic injection molding?
- Heating and pre plasticizing
Driven by the drive system, the screw conveys and compacts the materials from the hopper forward. Under the shearing and friction of the heater outside the barrel, the screw and the barrel, the materials gradually melt. A certain amount of molten plastic has accumulated at the head of the barrel. Under the pressure of the melt, the screw slowly retreats. The retreating distance depends on the amount required for one injection of the metering device. When the predetermined injection amount is reached, the screw stops rotating and retreating.- Mold closing and locking
The mold locking mechanism pushes the template and the mold moving part installed on the moving template to close and lock with the mold moving part on the moving template, so as to ensure that sufficient clamping force can be provided to lock the mold during molding.- Injection device moves forward
When the mold closing is completed, the entire injection base is pushed forward to make the nozzle of the injection machine fully fit with the main runner of the mold.- Injection and pressure maintaining
After the mold locking and nozzle fully fit the mold, the injection pressure cylinder enters the high-pressure oil to push the screw forward relative to the barrel, injecting the melt accumulated at the head of the barrel into the mold cavity with sufficient pressure. The plastic volume shrinks due to the temperature drop. In order to ensure the compactness, dimensional accuracy and mechanical properties of the plastic parts, it is necessary to maintain a certain pressure on the melt in the mold cavity to supplement materials.- Pressure relief
When the melt at the mold gate freezes, the pressure can be relieved.- Injection device retreats
Generally speaking, after the pressure relief is completed, the screw can rotate and retreat to complete the next feeding and pre plasticizing process. (In general, the action that the injection base withdraws from the main gate of the mold has been canceled for existing injection molding. This action is performed for materials with serious salivation, such as PA).- Mold opening
After the plastic parts in the mold cavity are cooled and shaped, the clamping mechanism opens the mold and pushes out the plastic parts in the mold.
