The Manufacturing Process of 28mm PET Preforms: A Step-by-Step Guide

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The beverage packaging industry has witnessed remarkable advancements, particularly with the use of 28mm PET preforms. These preforms serve as the foundational elements for producing bottles that store various beverages, from water to soft drinks.

Step 1: Material Selection

The journey of creating 28mm PET preforms begins with the selection of materials. Polyethylene terephthalate (PET) is chosen for its clarity, strength, and barrier properties. These characteristics ensure that the finished preforms are not only visually appealing but also effective in preserving the quality of the beverages. The raw PET material is usually supplied in the form of pellets.

Step 2: Drying the PET Pellets

Before processing, the PET pellets must be dried to remove any moisture. Moisture can adversely affect the quality of the final product, bring about defects such as poor clarity or weakened structural integrity. Typically, the drying process involves using a hopper dryer, which maintains specific temperature and time conditions to achieve the desired moisture content, usually below 0.02%.

Step 3: Extrusion

Once the PET pellets are adequately dried, they are fed into an extruder. During this phase, the pellets are melted and formed into a continuous parison, which is a hollow tube of molten PET. The extrusion process involves heating the material to approximately 250°C to achieve the desired viscosity. The 28mm diameter is established during this stage, as the parison is formed to precise specifications.

Step 4: Injection Molding

The next crucial step in the manufacturing of 28mm PET preforms is injection molding. The molten PET is injected into preform molds that define the shape and dimensions of the preforms. Each mold cavity is designed to create a preform with a 28mm neck finish, which is compatible with various closures. The injection molding process takes only a few seconds, allowing for high production rates.

Step 4.1: Cooling

After the injection process, the newly formed preforms must cool rapidly to solidify. The cooling phase is essential to ensure that the preforms maintain their shape and structural integrity. Cooling is typically achieved through water circulation in the mold, which efficiently dissipates heat.

Step 5: Ejection

Once cooled, the molds are opened, and the 28mm PET preforms are ejected. This stage is automated in modern manufacturing setups, enhancing efficiency and reducing labor costs. Ejected preforms are carefully collected and inspected for quality to ensure that they meet industry standards.

Step 6: Quality Control

Quality control is a vital part of the manufacturing process for 28mm PET preforms. Several tests are conducted to assess the preforms' clarity, dimensions, and strength. Common assessments include:

Visual Inspection: Checking for defects such as bubbles, scratches, or discoloration.

Dimensional Checks: Measuring the neck finish and overall dimensions to ensure compliance with specifications.

Mechanical Tests: Evaluating the tensile strength and impact resistance of the preforms.

This rigorous quality control process ensures that only the higher-quality preforms proceed to the next stage.

Step 7: Packaging and Storage

Once quality checks are completed, the 28mm PET preforms are packaged for distribution. They are usually placed in large cardboard boxes or pallets, ensuring protection during transportation. Proper storage conditions are also essential, as PET preforms should be kept away from direct sunlight and temperatures to maintain their integrity.