The principle of the injection blow molding machine (injection preform - blow molding machine) is to combine the injection molding process with the blow molding process, and realize the automated production of hollow plastic products through the two-step method of "injection molding preform first, then blow molding". The following is a detailed analysis from the aspects of process flow, core principles, equipment operation mechanism, etc.: 
 . Overall process principle: the logic of two-step molding The core principle of the injection blow molding machine can be summarized as "precision preform making + blowing and shaping". Its essence is to transform plastic raw materials into hollow products with specific shapes and functions through two mold molding. The specific process is as follows:
Raw material melting and injection molding ◦ Plastic particles (such as PE, PP, PET, etc.) are fed into the extruder through the hopper and heated and melted into a flowing state. The molten plastic is injected into the injection mold through the injection molding system and formed into a hollow bottle preform with a bottle mouth thread and a blowing channel (similar to the shape of a "test tube", with a closed bottom and an open bottle mouth).
Key: The injection mold determines the dimensional accuracy of the bottle preform (such as the bottle mouth thread and the wall thickness of the bottle preform), laying the foundation for subsequent blow molding. Blow molding and cooling demolding, the hot preforms of injection molding are transferred to the blow mold through a robotic arm or a turntable. Compressed air (usually 0.5-2MPa) is introduced into the preform, and the preform expands under the action of air pressure, fits the inner wall of the blow mold, and forms the final product shape (such as bottles, cans, barrels). After the product is cooled and shaped, the mold is opened, and the mold is demolded through the ejection device to complete the production. 
 . Core working principle: from equipment structure to process realization, injection molding system principle Structure: It consists of a barrel, a screw, an injection nozzle, and an injection mold. Principle: The screw rotates to push the raw material forward, and at the same time, the raw material is melted through the electric heating ring to form a uniform melt. The screw retreats to accumulate material. After reaching the set amount, the screw advances forward (or through a hydraulic device), and the melt is injected into the cavity of the injection mold at high pressure (80-150MPa), and cooled and solidified into a preform. Key parameters: injection temperature (affects melt fluidity), injection pressure (affects preform density and size), cooling time (affects preform strength). Principle of blow molding system • Structure: includes blow molding mold, blowing device (trachea, solenoid valve), and pressure control system. Principle: The blow molding mold is divided into two halves, which form a complete cavity of the product (such as the outline of the bottle body) after closing. After the preform is fed into the mold, the blowing needle is inserted into the blowing channel of the bottle mouth, and compressed air is introduced. The thermoplastic plastic of the preform undergoes "plastic deformation" under air pressure, extending and fitting the inner wall of the mold. ◦ Circulating water is introduced into the cooling water channel in the mold to quickly reduce the temperature of the product and make it fixed (cooling time accounts for 60%-70% of the production cycle). Key parameters: blowing pressure (affects the uniformity of the product wall thickness), blowing speed (to prevent the preform from cooling too quickly and being unable to be blown), and mold temperature (affects surface finish). The principle of multi-station rotary table transmission, the injection blow molding machine often adopts a three-station rotary table design, the three stations are: Injection station: complete preform injection molding; Blow molding station: the preform is transferred here for blow molding; Demolding station: the product is demolded after cooling. The turntable is driven by a motor or hydraulic system and rotates at a set angle (120°) to achieve continuous flow of preforms between stations, forming a "preform injection - blow molding - demolding" cycle production, and the efficiency can reach 2-3 times that of traditional single-station equipment. 
 . Key technical points in the process principle, preform temperature control, the injection blow molding process adopts "hot preform blow molding", and the preform needs to maintain a certain temperature after injection molding (such as PE about 110-130℃). If the temperature is too low, it is easy to crack during blow molding; if the temperature is too high, the product is easy to deform. Some equipment is equipped with a preform heating device (such as an infrared heating coil) to ensure uniform temperature during blow molding. Mold precision and matching ◦ The injection mold and the blow mold must be precisely matched: The bottle mouth thread of the injection mold must match the bottle mouth positioning groove of the blow mold to avoid air leakage during blow molding; The cavity size of the blow mold must take into account the shrinkage rate of the plastic after cooling (such as the shrinkage rate of PE is about 1.5%-3%) to ensure the accuracy of the product size. Coordinated control of pressure and speed ◦ Injection stage: high pressure and fast filling to ensure the density of the preform; Blow molding stage: low pressure pre-blowing first (to make the preform initially stretch), then high pressure inflation (fitting the mold) to avoid local wall thickness being too thin.