Unlocking the Power of the PET Preform Injection Molding Machine: Deep Integration of Principles and Technologies

1. Understand the working principle of the injection molding machine.

In the daily production process of plastic products, PET preform injection molding machines are indispensable. From the beverages we drink every day to everyday chemicals, condiments, medicines, etc., everything is involved in the PET preform packaging industry. The production of these packaging preforms requires extremely high-precision injection molding technology. It is very important for companies to have a thorough understanding of their working principles in order to improve production efficiency.

Raw Material Pretreatment and Drying

PET resin is hygroscopic, and high-temperature humidity will cause hydrolysis and degradation of the material, affecting the mechanical properties of the preform. Therefore, the raw materials must be processed through a drying system (usually a dehumidifying dryer) at 160–180°C for 4–6 hours to reduce the moisture content to less than 50 ppm. The dried PET pellets enter the hopper of the injection molding machine through a vacuum conveying system to ensure the purity of the raw materials.

Plasticization and Injection Molding

During this step, the barrel is surrounded by multiple heating zones, each equipped with an independent heating device and a temperature sensor. The computer control system precisely sets the temperature of each heating zone according to the characteristics of the PET raw materials and the requirements of the production process. The screw rotates in the heating barrel, heating the PET particles to 270–285°C through frictional heat and external electrical heating, melting them into a viscous fluid state. The plasticized PET raw material is in a molten state with good fluidity, ready for subsequent injection. Once the PET raw material is plasticized, it enters the injection stage. The injection system is primarily composed of an injection barrel, a screw, and other components. Under the powerful thrust of the injection barrel, the screw advances rapidly, injecting the plasticized PET melt into the front end of the barrel and into the mold cavity at extremely high speed and pressure.

Cooling and Demolding

After the melt is injected into the mold, the mold cooling system (cooling water at 10–15°C) rapidly reduces the temperature of the preform to 80–100°C, allowing it to solidify and take shape. The cooling time directly affects production efficiency, which is typically 5–15 seconds and should be optimized according to the preform's wall thickness. The ejection mechanism then pushes the preform out of the mold, and a robot or automated device transfers it to a conveyor belt for further inspection or packaging. During the cooling process, the cooling medium circulates in the cooling channel inside the mold, removing heat from the PET preform in the mold cavity, allowing the preform to cool and form quickly.

2. Core Technology of the PET Preform Injection Molding Machine

The core technology determines the quality of an injection molding machine and determines its efficiency and working quality.

 

Screw Design: As a key component in the injection molding system, screw design is crucial. Depending on the characteristics of the PET raw materials, the screw generally adopts a special structural design to improve plasticizing efficiency and mixing uniformity. For example, parameters such as screw thread groove depth, pitch, and compression ratio must be optimized according to the fluidity and melting characteristics of the PET raw material.

Clamping Force Control: The clamping force must be accurately calculated and adjusted according to the mold size, number of cavities, and injection molding process parameters. If the clamping force is insufficient, the high-pressure PET melt can create a gap between the mold's parting surfaces during the injection process, resulting in plastic overflow and the formation of burrs, which affects product quality. If the clamping force is too high, it will not only increase the equipment's energy consumption but can also cause excessive pressure on the mold and shorten its lifespan. Modern PET preform injection molding machines are typically equipped with advanced clamping force control systems, which can automatically adjust the clamping force according to actual production conditions, ensuring efficient equipment operation and long-term stable use of the mold while ensuring product quality.

Data-Driven Intelligent Control:The introduction of Industrial Internet technology enables injection molding machines to achieve remote monitoring and predictive maintenance through MES (Manufacturing Execution System). For example, AI algorithms analyze historical production data and automatically recommend optimal process parameters; Vibration sensors monitor screw wear and provide early warning of failures. These technologies increase overall equipment effectiveness (OEE) to over 85%.

3. Future Development Trends

With tightening environmental regulations and the demand for smart manufacturing, PET preform injection molding machines are evolving in the following directions:

Low carbonization: Developing bio-based PET raw material adaptation technology and promoting all-electric injection molding machines to reduce the carbon footprint.

Miniaturization: Developing miniaturized equipment to meet the needs of customization and small-batch production.

Intelligence: Deepening the application of digital twin technology to achieve virtual debugging and real-time process optimization.