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What is a PET Injection Molding Machine?

A PET injection molding machine functions similarly to other injection molding machines designed for materials like PE or PP, focusing on producing preforms rather than final products. During the injection process, the mold contains both external and internal shapes, and the space between them is filled with plastic to create the desired object. In the case of PET bottles, producing the internal shape presents a challenge since it cannot be easily removed. Thus, preforms are injected, characterized by a threaded top and a hollow, finger-like structure.

PET injection molding machines are ideal for creating preforms used in a variety of products, including mineral water bottles, carbonated drinks, fruit juice containers, edible oil packaging, medicine jars, emulsions, and cosmetic bottles.

Features of PET Injection Molding Machines

  • Versatile Preform Production: Capable of manufacturing different types of PET preforms, such as those for water bottles, hot-fill containers, oil bottles, wide-mouth jars, and large preforms.
  • Comprehensive Auxiliary Equipment: These machines include complete systems for dehumidification, drying, pumping, refrigeration, molds, hot runners, and various automated peripherals.
  • Specialized Injection Design: Tailored specifically to facilitate the molding of PET materials.
  • Precision Control: The injection and clamping mechanisms utilize linear potentiometers for accurate control and high precision.
  • Enhanced Stability Features: Equipped with functions like screw cold storage start limit, wire break detection, and insulation to enhance the stability of the molding process.
  • Consistent Preform Dimensions: Ensures high dimensional stability and low defect rates.

Key Points for Selecting a PET Injection Molding Machine

When choosing a PET injection molding machine, several factors should be taken into account based on the characteristics of PET plastic:

1. Screw Design: The ideal screw length-to-diameter ratio (L/D) for PET is typically above 1:24, as a longer ratio improves the plasticization capabilities.

2. Mold Space: Verify that the maximum column spacing, mold thickness, and mold dimensions align with the requirements of your molds. Ensure that the mold can fit; its width and height should be smaller than the maximum column spacing, and the thickness should fall within the acceptable range.

3. Product Removal Space: Ensure sufficient stroke during the opening and closing movements of the mold for easy product removal. The opening stroke should be at least double the height of the finished product, with adequate ejection stroke and force to eject the item.

4. Clamping Force: The necessary clamping force is determined by the product and the material. Sufficient clamping force must be provided to prevent mold separation during high-pressure injection. The required clamping force can be calculated using the formula:

   Clamping Force = Projected Area of the Product (cm²) × Number of Cavities × Mold Internal Pressure (kg/cm²)

   The machine’s clamping force should exceed this calculated value, ideally by a factor of 1.17 for added safety.

5. Shot Capacity: Assess the required shot capacity based on the finished product’s weight and the number of cavities in the mold. The shot capacity should exceed 1.35 times the weight of the finished product to ensure stable operation, with the product weight within 75% of the shot capacity.

6. Quality of Injection: The performance of PET plastics is influenced by factors such as the screw’s compression ratio and injection pressure. A well-designed screw compression ratio is critical for achieving optimal molding results.

7. Enhanced Energy Storage Motor: Given the high viscosity and temperature requirements of PET, these machines often require a larger screw torque. It’s common to utilize an energy storage motor that exceeds the specifications of standard machines by two levels or more.

8. Upgraded Power System: Along with the energy storage motor, enhancing the power system ensures stable operation and reduces cycle time.

Additionally, consider the design of mold water channels to enhance cooling efficiency. PET molds typically feature specialized water distribution blocks designed for this purpose.

all Electric Plastic Injection Molding Machine

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