Basic Principles
Preform forming involves heating and melting plastic pellets, then using a molding machine to form the desired bottle shape. The finished bottle then undergoes cooling, separation, and other processes. There are various preform forming methods, among which blow molding, injection molding, and stretching are the more common ones.
Blow Molding
Blow molding involves injecting heated, molten plastic into a mold and then using air pressure to expand the plastic into a desired shape. Blow molding is commonly used to produce small and medium-sized bottles, such as beverage bottles and cosmetic bottles. The finished product is smooth and has a good seal, but the production cycle is long and the cost is high.
Injection Molding
Injection molding involves injecting heated, molten plastic into a mold using an injection molding machine and removing the finished product after cooling. Injection molding is commonly used to produce large bottles, such as oil and water drums. The finished product is smooth and strong, but the production cycle is long and the cost is high.
Stretch Molding
Stretch molding is a plastic molding process in which heated, molten plastic is stretched and formed on a stretching machine. Stretch molding is commonly used to produce high-transparency, high-strength bottles, such as PET bottles. While stretch-molded products offer a smooth surface and high strength, they also come at a relatively high cost.
Summary
Different preform molding methods have their own advantages and disadvantages, and the choice should be tailored to the specific situation. Blow molding is suitable for producing small and medium-sized bottles, such as beverage and cosmetic bottles; injection molding is suitable for producing large bottles, such as oil and water drums; and stretch molding is suitable for producing high-transparency, high-strength bottles, such as PET bottles. When choosing a preform molding method, consider multiple factors, including cost, production cycle, and product quality, and make a comprehensive decision.