Injection blow molding machine (injection preform - blow molding machine) is a special equipment for plastic container molding. Its principle combines the two processes of injection molding and blow molding. It is mainly used to produce high-precision, high-transparency plastic bottles, containers and other products. The following is a detailed analysis from the core principles, process stages, equipment composition and other aspects:

The core principle of injection blow molding machine The molding principle of injection blow molding machine can be summarized as: first make a plastic blank (preform) by injection molding, then put the preform into the blow molding mold while it is hot and blow it to finally get a hollow container. Its core is to use the plasticity of plastic in the molten state to achieve precise molding through the combined process of "injection + blow molding".

Process stages and principles of injection blow molding machines The injection blow molding process is mainly divided into three stages. The principles and actions of each stage are as follows: Injection molding parison stage • Principle: The plastic raw materials (such as PET, PP, PE, etc.) are heated and melted in the barrel, and the melt is injected into the parison mold under high pressure through the injection screw. After cooling and solidification, a hollow tubular parison (similar to the shape of a test tube, one end is closed and the other end has a bottle mouth prototype) is formed. • Key actions: The raw materials are heated and melted into a flowing state; The injection system injects the melt into the parison mold, and the mold accurately controls the size of the parison and the shape of the bottle mouth thread; The parison is quickly cooled and shaped in the mold, retaining a certain amount of residual heat (or later heating) for subsequent blow molding. Parison transfer stage • Principle: The molded parison is transferred from the injection mold to the blow mold through a robotic arm or a turntable to ensure the accurate position of the parison and avoid deformation. • Key actions: The mechanical device clamps the neck of the parison (the bottle mouth) and moves smoothly; The blow mold closes and wraps the parison, leaving only the blowing hole connected to the inside of the parison. Blow molding stage • Principle: Compressed air is introduced into the parison, and the hot parison is inflated by air pressure to make it fit the inner wall of the blow mold, and the final container shape is formed after cooling. • Key actions: Compressed air is injected into the parison through the blow needle or the mold pore, and the pressure is usually 0.5-2MPa; The parison expands under the action of air pressure, fills the mold cavity, and forms the contours of the bottle body and bottle bottom; The cooling system in the mold (such as water channels) quickly cools down to solidify the plastic; The mold is opened, the molded container is taken out, and the cycle is completed.

Main structure and function of injection blow molding machine The structural design of the injection blow molding machine serves the above principle and mainly includes the following parts: Injection system • Function: melt plastic and inject the parison. • Composition: hopper, heating barrel, injection screw/plunger, nozzle, parison mold (including mold cavity and bottle mouth insert). Blow molding system • Function: provide air pressure and mold the container. • Composition: Blow mold (including cavity, cooling water channel), blow needle/air hole, compressed air supply device. Mold movement and positioning system • Function: realize the transfer of parison between injection mold and blow mold. • Composition: robotic arm, turntable (such as three-station turntable: injection station, blow molding station, removal station), precise positioning mechanism. Cooling system • Function: control the cooling speed of parison and container to ensure molding quality. • Composition: water channel, cooling tower, water pump, respectively cool the injection mold and blow molding mold. Control system • Function: coordinate the action of each component and control process parameters such as temperature, pressure, time, etc. • Composition: PLC (programmable logic controller), touch screen, sensor (temperature, pressure sensor, etc.).

Process advantages of injection blow molding machine • High precision: the size of the injection molded parison is accurate, the wall thickness of the container after blow molding is uniform, and the bottle mouth thread is clear, which is suitable for high-requirement packaging such as medicine and food. • High efficiency: Injection blow molding, reducing intermediate links (such as traditional blow molding requires preforms to be made first), short production cycle, suitable for mass production. • Less waste: The parison is directly molded, no need to trim the flash, and high material utilization. • Good transparency: Especially suitable for materials such as PET, the finished product has high transparency, suitable for beverage bottles, cosmetic bottles, etc.

Application scenarios Injection blow molding machines are widely used to produce the following products:
• Food packaging: mineral water bottles, beverage bottles, condiment bottles; • Medical packaging: medicine bottles, infusion bottles (high cleanliness required); • Daily necessities: cosmetic bottles, shampoo/shower gel bottles; • Industrial supplies: chemical reagent bottles, hollow parts, etc.

Comparison with other molding processes • Compared with extrusion blow molding: the parison of injection blow molding is made by injection, with more precise dimensions and better wall thickness uniformity, suitable for small-capacity, high-precision containers; extrusion blow molding is suitable for large-capacity, low-cost products (such as trash cans). • Compared with stretch blow molding: Injection blow molding can be directly molded, while stretch blow molding requires an additional stretching step (such as biaxial stretching of PET bottles) to improve strength and barrier properties.