How to choose the right PET preform injection molding machine？

Choosing the right PET preform injection molding machine is crucial for producing high-quality PET preforms. PET preforms are commonly used in packaging for the food, beverage, pharmaceutical, and cosmetic industries; therefore, the choice of injection molding machine directly impacts production efficiency, cost control, and product quality.

1. Selection of PET Preform Injection Molding Machine

(1). Types of Injection Molding Machines

PET preform injection molding machines are generally divided into two types:

Standard Injection Molding Machines: Suitable for injection molding of conventional plastic products, suitable for producing some simple PET preforms.

PET-Specific Injection Molding Machines: Specially designed for producing PET preforms, with more precise control, suitable for PET preform production requiring high quality and high efficiency.

It is recommended to choose PET-specific injection molding machines because they typically have optimized designs for PET materials, such as higher injection pressure, better temperature control systems, and more precise heating systems, which are crucial for producing high-quality PET preforms.

(2). Clamping Force of the Injection Molding Machine

Clamping force is the ability of an injection molding machine to hold the mold in place and withstand the pressure during the injection process. When producing PET preforms, a high clamping force is typically required to ensure the accuracy of the preform's shape and dimensions.

Standard requirements: The clamping force for PET preforms is generally determined by the preform's weight and the mold size. For preforms of typical capacity (e.g., 500ml, 1L bottles), the clamping force is usually between 80 and 250 tons.

Relationship between preform weight and capacity: The greater the weight of the preform, the higher the required clamping force. If producing large-capacity (e.g., 2L or more) PET bottles, the clamping force may need to be even greater.

(3). Screw and plasticizing system of the injection molding machine

The high viscosity and high crystallinity of PET require the injection molding machine to have an efficient plasticizing system.
Screw design: Selecting a specially designed screw suitable for PET plasticizing provides uniform and efficient plastic melting. The screws of PET injection molding machines are typically longer and more compactly designed than those of ordinary injection molding machines to ensure good plasticizing of the PET material. Heating and Cooling System: PET has a high melting temperature, typically between 250℃ and 280℃. Therefore, selecting an injection molding machine with a precise temperature control system is crucial. The system's heating and cooling should be able to quickly and uniformly control the temperature, preventing the molten material from overheating or cooling on the screw, which would affect the plasticizing effect.

(4) Injection System Control Precision

PET preform production requires high-precision injection control, especially for preform wall thickness uniformity and dimensional control.

High-Precision Injection Control: PET injection molding machines typically require higher injection precision to ensure preform quality. The control system should be able to accurately control injection speed, injection pressure, and injection time to ensure consistency for each preform.

Dual-Runner Injection System: This system can improve injection efficiency while maintaining injection accuracy, contributing to improved production stability and consistency.

(5) Mold and Injection Molding Machine Matching

PET preform production requires not only a high-performance injection molding machine but also a high-quality matching mold. The matching relationship between the injection molding machine and the mold is crucial to preform quality and production efficiency.

Mold Design: Mold design must ensure the precision of the preform's shape, wall thickness, and neck. Choosing an experienced mold manufacturer with technical support ensures long-term stable mold use.

Mold Temperature Control System: PET preform molds typically require a highly precise temperature control system to guarantee mold stability and production efficiency. Poor temperature control can lead to uneven preform wall thickness or difficulty in demolding.

2. How to Extend the Service Life of a PET Preform Injection Molding Machine

(1) Regular Maintenance and Cleaning

Regularly clean the injection molding machine: Regularly clean all parts of the injection molding machine, including the screw, nozzle, injection system, heating elements, etc., to remove accumulated plastic residues and dirt, preventing blockages or corrosion. In particular, PET material has high adhesion and easily accumulates residues on the inner wall of the injection molding machine and on the screw, affecting its performance.
Clean the cooling system: Regularly check whether the pipes and cooling holes of the cooling system are blocked, ensuring smooth cooling water flow and avoiding insufficient cooling that could lead to overheating or wear of parts.

(2) Lubrication and Maintenance of Moving Parts

Regular lubrication: Moving parts of the injection molding machine (such as the clamping system, slider, transmission gears, etc.) need to be lubricated regularly with lubricating oil or grease to reduce friction and wear. Choose a suitable lubricant and adjust the lubrication cycle according to the frequency of use and environmental conditions. Check the hydraulic system: The hydraulic system is crucial to the performance of the injection molding machine. Regularly check the quality and level of the hydraulic oil to ensure there are no leaks and the hydraulic oil is in good condition. When changing the hydraulic oil, choose an oil that meets the equipment requirements.

(3) Reasonable control of temperature and pressure

Temperature control: PET material has a high melting temperature. Prolonged excessively high temperatures may cause premature damage to heating elements or molds. Ensure the injection molding machine's heating system has accurate temperature control to avoid excessively high operating temperatures or overheating. Regularly check the temperature control system and adjust it as needed.

Appropriate injection pressure: Injection pressure that is too high or too low may affect the lifespan of the equipment. Ensure the machine's injection pressure matches production requirements to avoid exceeding the equipment's operating range.

(4) Avoid overload operation

Operate at rated load: Each injection molding machine has its designed maximum load. Avoid prolonged overload operation. Overload operation will cause excessive wear and damage to machine parts (such as screws, motors, hydraulic systems, etc.), thus shortening the equipment's lifespan.

Avoid frequent start-stop: Frequent machine start-stop increases wear on mechanical parts. Minimize unnecessary start-stops. Maintain stable operation of the equipment under normal production load.

(5) Regular Inspection and Troubleshooting

Regularly inspect all systems of the injection molding machine: Regularly conduct a comprehensive inspection of the electrical, hydraulic, and pneumatic systems of the injection molding machine. Address any potential problems promptly to prevent minor issues from escalating into major problems.

Promptly handle faults: If any abnormalities are found in the injection molding machine (such as increased noise, abnormal vibration, decreased production efficiency, etc.), stop the machine immediately for inspection, find the cause, and repair it. Delayed maintenance may lead to serious damage to the equipment and increase repair costs.

(6) Timely Replacement of Aging Parts

Regularly inspect and replace aging parts: Some parts of the injection molding machine (such as seals, nozzles, screws, etc.) will age or wear over long-term use and need to be replaced promptly. Regularly inspect these parts and replace them according to their wear condition to avoid affecting the normal operation of the equipment.