Two-Layered Preform Core Stabilization in Injection Overmolding
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Solution Overview
Problem
In injection overmolding processes for manufacturing two-layered preforms, cores tend to deform elastically due to temperature and fluidity differences in plastic materials, leading to unacceptable variations in layer thicknesses, which can result in irregularities during the blow molding of bottles or containers.
Innovation Solution
A mold design that includes supporting members to stabilize the core during the injection of the first layer, ensuring uniform thickness and preventing deformation, while the second layer is formed to cover the openings created by these supporting members, allowing for precise control of layer thickness and adhesion between the layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the core is left unsupported during injection of the first layer, then the injection process is simpler, but the core deforms elastically causing unacceptable variations in layer thicknesses
Solution Approach 1:
The supporting members are pre-installed in the mold cavity before the injection process begins. These members are positioned to contact the core at critical locations, providing preliminary support that prevents elastic deformation during the injection of the first layer. The support structure is prepared in advance, so when injection occurs, the core is already stabilized and cannot deform under the pressure of the molten material.
Solution Approach 2:
The supporting members act as intermediary elements between the mold cavity and the core. Rather than the mold cavity directly constraining the core (which would require complex positioning mechanisms), the supporting members serve as intermediate structures that contact the core and provide the necessary support. These members are simpler in design and can be easily integrated into the mold while effectively preventing core deformation.
2Reliability
If the neck is formed with the first layer material, then the manufacturing process is simpler, but the barrier effect against light and aesthetic properties are reduced
Solution Approach 1:
The patent applies different materials to different regions of the preform based on local requirements. The first layer material (providing barrier properties) is used for the tubular body, while the second layer material (providing aesthetic properties) is used specifically for the neck region. This local differentiation ensures that each part of the preform has the optimal material properties for its specific function, with the neck gaining improved aesthetic appearance while the body maintains its barrier effectiveness.
Solution Approach 2:
The preform is constructed as a composite structure with two distinct layers made from different materials. The first layer provides the barrier function against light penetration, while the second layer provides aesthetic properties and is specifically used for the neck formation. This composite approach allows the neck to be formed from the second layer material alone, combining aesthetic advantages with the functional requirements of the overall structure.
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 approach ensures uniform layer thicknesses and improved adhesion between the layers, reducing the risk of exfoliation and resulting in high-quality two-layered preforms suitable for blow molding, with the neck formed entirely from the overmolding material for enhanced barrier and aesthetic properties.
Implementation Method 1
an inner layer made of a material capable of providing a barrier effect against light by absorption
Implementation Method 2
an outer layer made of a material capable of providing a barrier effect against light by reflection
Data Source
Figure 1~1A
Figure 2~2A
Figure 3~3A
AI summary
The two-layered preform comprises a tubular body having a mouth providing a neck (61) at a first end thereof and a closed bottom at an opposite second end. At least part of said tubular body is formed by a first layer (P1) made of a primary molding material and a second layer (P2) made of an overmolding material. The first layer (P1) is an inner layer made of a primary molding material providing a barrier effect against light by absorption, and the second layer (P2) is an outer layer made of an overmolding material providing a barrier effect against light by reflection. The neck (61) is formed with the overmolding material of the second layer (P2) not coated by the primary molding material of the first layer (P2).