Concave Support Pin Prevents Core Misalignment in Blow Molding
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Solution Overview
Problem
Conventional blow molding devices with convex-shaped support pins fail to stably support the bottom portion of preforms, leading to core misalignment during the blowing process, which can result in molding defects such as thickness variations, breakage, and creases at the container's bottom.
Innovation Solution
A blow molding device featuring a support pin with a concave head and an inclined surface that flares outward, allowing for upward displacement and downward movement to support the preform's bottom, and optionally includes protrusions on the concave surface to enhance stability and prevent resin flow around the pin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a convex-shaped support pin is used, then the structure is simple, but the preform bottom cannot be stably supported leading to core misalignment
Solution Approach 1:
The support pin head is inverted from a convex shape to a concave shape that receives the preform bottom. This inversion allows the preform bottom to be received and stabilized within the concave head, preventing core misalignment during blow molding while maintaining structural simplicity.
Solution Approach 2:
The support pin head is designed with a concave portion that specifically receives the preform bottom, creating a localized fitting interface. This local quality enhancement at the head provides stable support and prevents misalignment without complicating the entire support pin structure.
2Adaptability or versatility
If the support pin is displaced downward to accommodate preform deformation, then the blow molding process is flexible, but core misalignment may occur
Solution Approach 1:
The concave head design provides a receiving space that accommodates the preform bottom while allowing downward displacement. The inverted concave structure maintains core alignment during displacement by providing a stable receiving interface that moves with the preform deformation.
Solution Approach 2:
The support pin is designed to be displaceable downward in accordance with preform deformation during blow molding. This dynamic capability allows the support pin to adapt to the changing shape of the preform while the concave head maintains stable support and prevents core misalignment throughout the deformation process.
3Device complexity
If resin flows around the support pin, then the molding process is simple, but molding defects such as thickness variation and breakage occur
Solution Approach 1:
The concave head design prevents resin from flowing around the support pin by providing a receiving space that contains the preform bottom. The inverted concave structure creates a barrier that stops resin flow, preventing molding defects such as thickness variation and breakage at the container bottom.
Solution Approach 2:
The concave head creates a localized region that receives and contains the preform bottom, preventing resin from flowing around the support pin in that specific area. This local quality control at the head interface prevents molding defects without requiring complex overall process modifications.
Data Source
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AI summary
To prevent core misalignment when performs are stretched during blow molding, provided is a blow molding device 10a that blow molds a preform 20 into a container in a forming mold. The blow molding device 10 includes a support pin P1 that is disposed in the forming mold. The support pin P1 includes a head 13 that supports a bottom portion 24 of the preform 20, and a shaft 14 that is connected to the head 13 and that is displaceable upward and downward in a direction of an axis O2 of the preform 20. The head 13 is provided, at one end thereof supporting the bottom portion 24 of the preform 20, with a concave portion 13c for receiving at least a part of the bottom portion 24.