Preform Temperature Adjustment for Uniform Resin Container Blow Molding
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Solution Overview
Problem
Conventional blow molding apparatuses struggle to uniformly adjust the temperature of preforms made from thermoplastic resins like PET, leading to issues such as thickness unevenness and whitening, especially when the cooling time after injection molding is shortened.
Innovation Solution
A manufacturing apparatus and method that includes an injection molding part and a temperature adjustment part, where the preform is cooled in the temperature adjustment part to lower its outer surface temperature by 10°C to 50°C relative to its initial temperature, using a temperature adjustment core mold and cavity mold or air circulation to compress-deform and uniformly cool the preform before blow molding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the cooling time after injection molding is shortened, then the molding cycle time is reduced and productivity is improved, but the temperature unevenness in the preform cannot be sufficiently removed and thickness distribution becomes non-uniform
Solution Approach 1:
The temperature adjustment process is divided into multiple stages: a first temperature adjustment stage using a heating block to heat the preform, and a second temperature adjustment stage using a heating rod to locally heat the bottom portion. This segmentation allows each stage to address specific temperature distribution issues, achieving uniform temperature and thickness distribution even with shortened cooling time.
Solution Approach 2:
The heating rod is positioned to locally heat only the bottom portion of the preform, creating a non-uniform temperature distribution that compensates for the shortened cooling time. This local heating approach allows the bottom portion to reach optimal temperature for blow molding while the rest of the preform maintains appropriate temperature, ensuring uniform thickness distribution.
2Productivity
If the cooling time is shortened, then productivity is improved, but temperature unevenness remains and causes whitening and thickness unevenness in the container
Solution Approach 1:
The preform is subjected to a first temperature adjustment using a heating block before the blow molding process. This preliminary heating action ensures that the preform reaches a uniform temperature state, preventing whitening and thickness unevenness that would otherwise occur due to residual temperature gradients from the shortened cooling process.
Solution Approach 2:
The temperature of the preform is actively changed and controlled through the heating block and heating rod. By adjusting the temperature parameters to specific ranges, the system prevents crystallization and whitening while ensuring uniform thickness distribution, even when the overall cooling time is reduced.
3Manufacturing precision
If a temperature adjustment part is added between injection molding and blow molding, then the preform temperature can be adjusted to suitable levels, but the device complexity increases
Solution Approach 1:
The temperature adjustment part is merged with the blow molding part, sharing the same mold structure. The heating block and heating rod are integrated into the blow molding apparatus, allowing temperature adjustment functionality to be combined with the existing blow molding structure, thereby reducing overall device complexity.
Solution Approach 2:
The heating block and heating rod serve multiple functions: they adjust the preform temperature before blow molding, compensate for shortened cooling time, and ensure uniform temperature distribution. This multi-functionality reduces the need for separate dedicated temperature adjustment equipment, simplifying the overall apparatus 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 allows for the production of high-quality resin containers with uniform thickness and transparency by effectively addressing temperature unevenness and shortening the molding cycle time.
Implementation Method 1
the temperature adjustment part uses a heating pot mold (heating block) and a heating rod, and adjusts the temperature of the preform by heating the preform in a non-contact manner
Implementation Method 2
cooling a preform in an injection molding part and further cooling the preform in a temperature adjustment part
Data Source
AI summary
A manufacturing apparatus for manufacturing a resin container, the manufacturing apparatus includes an injection molding part, a temperature adjustment part, a blow molding part, a take-out part, and a rotation plate. The temperature adjustment part includes a first temperature adjustment mold into which the preform is inserted, the first temperature adjustment mold being configured to cool the preform from an outer surface of the preform, a second temperature adjustment mold into which the preform is inserted, the second temperature adjustment mold being configured to cool the preform from an inner surface of the preform, and wherein, in the temperature adjustment part, the preform is cooled so that at least the outer surface temperature of the preform is lowered within a temperature range from 10° C. to 50° C. as compared to the outer surface temperature of the preform when the preform is carried into the temperature adjustment part.