Blow Molding Apparatus for PET Container Shrinkage Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for blow molding plastic containers, such as PET, face challenges in maintaining material integrity and efficiency due to variations in crystallinity and shrinkage during the molding process, which affect the quality and consistency of the final product.
Innovation Solution
A molding apparatus that uses a primary mold to blow mold a preform into a primary form, followed by controlled shrinkage using positive pressure and reheating, before forming a secondary form that can be further molded into the final container shape, utilizing a secondary mold with internal surfaces and channels for even fluid distribution to manage shrinkage and crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the primary form is shrunk outside the primary mold using conventional methods, then shrinkage control is achieved, but production time increases and productivity decreases
Solution Approach 1:
The patent combines the shrinkage operation with the primary mold by integrating a shrinkage chamber directly into the mold structure. This allows the primary form to be shrunk within the same mold cavity without removal, eliminating transfer time and enabling continuous production while maintaining precise shrinkage control through the integrated chamber.
Solution Approach 2:
The shrinkage chamber is prepared and positioned within the primary mold before the blow molding process completes. By having the shrinkage infrastructure ready in advance within the mold structure, the transition from blowing to shrinking occurs seamlessly without removing the primary form, reducing cycle time while ensuring controlled shrinkage.
2Adaptability or versatility
If multiple separate molds are used for primary and secondary forms, then flexibility in design is improved, but device complexity and production time increase
Solution Approach 1:
The primary mold is designed with multi-functionality by incorporating both the blow molding cavity and the shrinkage chamber as integrated components. This single mold structure performs multiple operations (blowing and shrinking) that would traditionally require separate molds, reducing overall device complexity while maintaining design flexibility through programmable control of each operation sequence.
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 enhances the efficiency and consistency of container production by controlling shrinkage and crystallinity, allowing for precise formation of the final container shape while optimizing the design of molds and reducing reheat time, thereby improving the material integrity and quality of blow-molded PET containers.
Implementation Method 1
applying positive pressure within the primary mold to thereby shrink the primary form
Implementation Method 2
the primary form is reheated after being blow molded in the primary mold to facilitate and control the amount of shrink back
Data Source
Figure 1
Figure 2
AI summary
A method of forming a container includes blow molding a primary form of the container inside a primary mold. The primary form has an exterior surface. The method also includes applying a fluid to the exterior surface of the primary form to shrink the primary form and to form a shrunken form of the container. Furthermore, the method includes blow molding a secondary form of the container from the shrunken form inside a secondary mold.