Preform Base Contour Optimization for Blow Molding
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Solution Overview
Problem
The existing methods for producing preforms for blow molding struggle with achieving a defined base geometry with thinner wall thicknesses, leading to issues like sink marks and uneven heating during the stretch blow molding process, which affects the quality of the final bottles.
Innovation Solution
A method and device that reshape the preform base contour to increase its surface area, allowing for more efficient thermal energy introduction and controlled wall thickness reduction through a modified cooling sleeve and embossing process, preventing direct contact cooling of the preform tip to maintain deformability and optimize mechanical deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the preform wall thickness is reduced in the base cap area to improve blow molding quality, then the heating efficiency and material distribution improve, but the preform becomes prone to deformation and crystallization during cooling
Solution Approach 1:
The patent applies local quality by differentiating the cooling intensity across different regions of the preform. The base cap area receives reduced cooling intensity to maintain deformability and prevent crystallization, while other areas receive standard cooling. This is achieved through a cooling device with selectively adjustable cooling zones that can be independently controlled based on the preform's geometric features and material properties.
Solution Approach 2:
The cooling device incorporates dynamic adaptability by allowing real-time adjustment of cooling intensity based on detected preform characteristics. Sensors monitor the preform's temperature distribution and geometric parameters, and the control system dynamically modifies cooling rates to optimize both the thin-walled base geometry quality and prevent unwanted crystallization or deformation.
2Reliability
If intensive cooling is applied to the preform after demolding to prevent crystallization, then the preform can be removed without damage, but residual heat remains causing reheating and softening that makes the preform unusable
Solution Approach 1:
The patent applies preliminary action by performing selective cooling during the demolding process itself rather than as a separate post-processing step. The cooling device is integrated into the injection molding machine and begins cooling the preform immediately upon ejection, preventing crystallization while removing residual heat within the same production cycle, thus eliminating time loss.
Solution Approach 2:
The cooling process is designed to continue seamlessly from the end of injection through demolding without interruption. The cooling device maintains continuous thermal management, transitioning smoothly from injection cooling to post-demolding cooling, ensuring the preform remains in a controlled thermal state throughout the entire process without requiring separate cooling stages or stopping the production cycle.
3Use of energy by moving object
If the preform base contour is reshaped to increase surface area for better heating, then the infrared heater efficiency improves, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies segmentation by dividing the base cap area into multiple cooling zones with different cooling intensities. This segmented approach allows precise thermal control in the thin-walled regions while maintaining standard cooling elsewhere, achieving the desired base geometry without requiring complex overall mold designs or additional processing steps.
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 results in preforms with significantly thinner wall thicknesses at the tip, which enhances the heating behavior and material distribution during blow molding, reducing crystallization and improving the quality of the bottle base by allowing for precise control over wall thickness and deformation.
Implementation Method 1
the preform, whose outer skin is in direct contact with the intensively cooled mold steel and consequently solidifies there quickly
Implementation Method 2
the infrared heaters of the subsequent blow molding machines can introduce thermal energy more efficiently via this enlarged surface
Data Source
Figure 1~2
Figure 3a
Figure 3b
AI summary
The invention relates to a device and a method for producing a preform (3) having a base geometry optimized for the subsequent stretch blow moulding process. The preform produced in the injection-moulding tool is removed in a cooled removal sleeve (7) and cooled in the shaft by intensive contact cooling, while as far as possible no cooling contact is made with the top of the preform on account of a special contour of the cooling sleeve. On account of the reheating of this top which is possible as a result, the latter can be mechanically deformed into a new geometry which is more advantageous for the blow moulding process and thus the wall thickness of said top can also be influenced. In the subsequent blow moulding process, such a deformed preform has primarily the advantage that the plastics material distributed better in the bottle can result in considerable material savings and higher quality bottle bases.