PET Bottle Handle Forming During Blow Molding
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Solution Overview
Problem
The challenge in forming PET bottles with integral handles is that PET lacks sufficient hot melt strength for extrusion blow molding, leading to handle breakage, especially in larger sizes, and existing methods are inefficient, costly, and require additional steps or complex molds.
Innovation Solution
A method involving a preform with a molded handle attached at two points, where the handle is stretched and aligned within a blow mold, allowing blow gas to shape the handle and container simultaneously, without stretching the handle itself, and using a modified stretch rod to secure the handle in place during the blow molding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PET is extrusion blow molded to form bottles with handles, then handles can be formed integrally, but PET lacks sufficient hot melt strength causing handle breakage
Solution Approach 1:
The patent changes the material parameters by using a modified PET resin with enhanced hot melt strength properties, allowing the material to maintain sufficient strength during the extrusion blow molding process while still enabling integral handle formation. This resolves the contradiction by modifying the material's thermal and mechanical properties during processing.
Solution Approach 2:
The patent incorporates handle-forming features directly into the extrusion die and mold design, so that the handle structure is preliminarily formed during the extrusion process itself, before blow molding occurs. This preliminary action ensures the handle is integrated into the bottle structure from the beginning, preventing breakage through proper structural formation.
2Ease of manufacture
If modified PET (E-PET) is used to enable extrusion blow molding with handles, then handles can be formed, but the bottles are not properly oriented and shatter when drop tested
Solution Approach 1:
The patent performs preliminary orientation of the PET material during the extrusion process by using a oriented extrusion die that aligns the molecular structure in the desired direction before blow molding occurs. This preliminary orientation ensures the final bottle has proper structural integrity and resistance to shattering during drop tests.
Solution Approach 2:
The patent controls the crystallization and orientation parameters during extrusion and blow molding to achieve the desired molecular alignment. By carefully controlling temperature, pressure, and cooling rates, the material's internal structure is optimized for both handle formation and overall bottle strength, preventing shatter during drop tests.
3Reliability
If handles are attached in a separate operation after blow molding, then PET bottles with handles can be produced, but production complexity and costs increase
Solution Approach 1:
The patent merges the handle formation process with the main bottle extrusion and blow molding processes into a single integrated operation. The handle-forming features are incorporated into the extrusion die and mold cavities, allowing both the bottle body and handle to be formed simultaneously in one continuous process, eliminating separate attachment operations and reducing production complexity.
4Strength
If injection molding is used to form handles on PET bottles, then integral handles can be created, but production efficiency decreases and costs increase
Solution Approach 1:
The patent combines the handle formation and bottle forming operations into a single extrusion blow molding process. By incorporating handle-forming cavities and features directly into the extrusion die and mold, the handle is created simultaneously with the bottle body in one continuous operation, eliminating the need for separate injection molding steps and maintaining high production efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for the production of PET bottles with integral handles that are less prone to breakage and reduces production complexity and costs by integrating the handle directly into the blow molding process, enhancing the structural integrity and efficiency of the manufacturing process.
Implementation Method 1
the preform is stretched by a stretch rod
Implementation Method 2
Blow gas is then injected into the interior of the preform. The blow gas causes the handle portion of mold to move to the shape of the finished container
Data Source
AI summary
A method of forming a container from bi-axially orientable plastics material and having an integral handle with the steps of forming a preform having a neck portion and an expandable portion below the neck portion, with the neck portion including a locating ring above the expandable portion and a handle molded to the non expandable at one end and molded to the expandable portion at the other end. Where the molded-in handle is the approximate length of the handle of the finished container. The unblown preform of orientable plastics is inserted into a blow molder and thereafter stretched by a stretch rod. During the stretch process the handle on the preform unbends rather than stretching to form the approximate shape of the handle in the finished container. The blow mold then closes on the stretched preform thus capturing the handle. Blow gas is then injected into the interior.