Preform Injection Molding with Enlarged Geometry and Inflation
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Solution Overview
Problem
Conventional preform production methods face challenges in efficiently producing preforms with special geometries, such as undercuts or widened bases, which require aggressive cooling and lengthy cycle times, and struggle to maintain preform integrity during the transition from injection molding to blow molding.
Innovation Solution
A method and device that inject polymer melt into an injection mold with specifically designed cavities, allowing for preforms with enlarged geometries, where transfer pins introduce positive pressure to condition and shape the preforms, enabling quicker cooling and inflation, and transferring them to post-cooling devices with enlarged cavities for further expansion, reducing cycle time and material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If aggressive cooling is applied via core and cavity device to dissipate heat from preforms, then cooling efficiency is improved, but preform geometry precision deteriorates due to thermal distortion
Solution Approach 1:
The cooling system is segmented into multiple independent cooling zones (core cooling channels and cavity cooling channels) that can be controlled separately. This allows different regions of the preform to be cooled at different rates, maintaining geometric precision while achieving efficient heat dissipation.
Solution Approach 2:
Different cooling intensities are applied to different regions of the preform based on local thermal requirements. The core and cavity regions receive customized cooling profiles, allowing critical geometric areas to maintain precision while other areas are aggressively cooled for efficiency.
2Productivity
If preforms are produced with enlarged geometry in comparison with cavity, then productivity is improved by reducing cycle time, but manufacturing precision deteriorates due to difficulty in forming special geometries
Solution Approach 1:
The injection mold cavities are pre-designed with specific geometric features (such as pull rods and ejector mechanisms) that enable the formation of enlarged preform geometries directly during injection molding. This preliminary preparation allows complex shapes to be formed without requiring subsequent machining or forming operations, maintaining precision while improving productivity.
Solution Approach 2:
The mold cavity geometry is designed to dynamically adapt during the injection process, with movable components that allow the cavity shape to change and accommodate enlarged preform geometries. This dynamic approach enables complex shapes to be formed with high precision through controlled deformation during molding.
3Adaptability or versatility
If preforms with special geometries such as undercuts are produced, then adaptability is improved, but device complexity increases due to additional molding features
Solution Approach 1:
The injection mold incorporates nested components where pull rods, ejector mechanisms, and cooling channels are integrated within each other. This nesting allows multiple functions to be achieved within a compact structure, increasing geometric versatility without proportionally increasing overall device complexity.
Solution Approach 2:
The injection mold is designed with multi-functional components that serve multiple purposes. For example, ejector pins also serve as pull rods for undercut features, and cooling channels are integrated into the same structural elements. This multi-functionality increases adaptability while controlling device complexity.
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 reduces crystallization risk, shortens cycle times, and allows for energy savings and lower investment costs in blow molding, while enabling the production of preforms with thinner walls and enhanced surface structures for improved processing efficiency.
Implementation Method 1
injecting a polymer melt into an injection mould
Implementation Method 2
a first cooling process is carried out, in order to achieve a sufficient rigidity for the preforms
Implementation Method 3
the preforms are either inflated in the removal gripper and/or in the post-cooling device using positive pressure with respect to the cavity situated in the injection mould
Data Source
AI summary
Preforms with a neck region and a preform body and having an enlarged geometry in comparison with the cavity of the injection mold are produced by injecting a polymer melt into the mold with a geometry of the cavity in the mold such that the radial extent of an inner space in the preform body thereby produced is not greater than the radial extent of the inner space in the neck region, the preforms are removed from the open mold by a removal gripper, and the preforms in the removal gripper are inflated using positive pressure such that the geometry of the inflated preform body is larger than the cavity in the injection mold.