Preform Mold Stack Stripper Assembly Ejection
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Solution Overview
Problem
Existing molding systems face challenges in efficiently forming and removing the neck region of preforms, particularly in blow-molding processes, due to the complexity of forming threads and anti-pilferage structures, which are not easily achieved using traditional split mold inserts.
Innovation Solution
A stripper assembly is introduced, comprising a stripper plate, neck rings, and a stripper ring that cooperate to define the neck region, allowing for coordinated movement along the ejection path, enabling the preform to be removed from the mold stack by actuating the neck rings and stripper ring in unison, both parallel and perpendicular to the mold stack axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional split mold inserts are used to form the neck region, then the molding cavity can be simplified, but the ability to form threads and anti-pilferage structures is insufficient
Solution Approach 1:
The neck region forming capability is segmented into multiple independent components: a cavity lock insert with thread-forming cavity, a core lock insert with anti-pilferage structure, and complementary male/female portions. These segmented inserts can be independently designed, manufactured, and positioned to achieve complex neck region features that cannot be formed by traditional single-piece inserts
Solution Approach 2:
The cavity lock insert and core lock insert are nested within the molding cavity structure, with the cavity lock insert positioned in the cavity plate and the core lock insert positioned in the core plate. These nested inserts work together to form the complete neck region, allowing complex geometries to be achieved within the constrained space of the molding cavity
2Ease of operation
If split mold inserts are used for the neck region, then the neck region can be formed, but the ejection process becomes complex requiring multiple actuators
Solution Approach 1:
The ejection functions of the cavity lock insert and core lock insert are merged into a single coordinated action. Both inserts are designed to be actuated by the same stripper plate mechanism, which moves in a single direction to simultaneously eject both the cavity and core portions of the preform. This eliminates the need for separate actuators for each insert, simplifying the ejection process while maintaining the ability to form complex neck regions
3Productivity
If conventional ejection methods are used, then the mold structure can be simple, but demolding defects occur and cycle time increases
Solution Approach 1:
The stripper plate is designed to actuate the ejection process before the mold plates fully separate. By initiating the ejection action of both cavity and core inserts simultaneously during the mold opening sequence, the preform is released from undercut features before complete mold separation occurs. This preliminary ejection action prevents demolding defects such as distortion or damage that would occur if ejection were delayed until after full mold opening
Solution Approach 2:
The ejection system incorporates dynamic movement through the stripper plate mechanism that can adjust its actuation timing and force. The stripper plate moves dynamically during the mold opening sequence, providing controlled ejection force to both cavity and core inserts simultaneously. This dynamic ejection process adapts to the specific requirements of the preform geometry, ensuring reliable demolding without defects while optimizing cycle time
Data Source
AI summary
According to embodiments of the present invention, there is provided a stripper assembly and a mold stack incorporating same. More specifically, there is provided the stripper assembly (212) for use in a mold stack (202) for forming a preform (210) suitable for blow-molding into a final-shaped container. The stripper assembly (212) comprises a stripper plate (214) connectable, in use, to a stripper plate actuator; neck rings (220) configured to cooperate to define a portion a neck region (226) of the preform (210); a stripper ring (230) configured to define at least a portion of a top sealing surface of the neck region (226) of the preform (210); the stripper plate (214) being configured to actuate the neck rings (220) and the stripper ring (230), in unison, along substantially the whole length of a complete ejection path, which is substantially parallel to a longitudinal axis of the mold stack (202); and wherein the neck rings (220) are configured for movement in a direction substantially perpendicular to the longitudinal axis of the mold stack, over at a portion of the complete ejection path, whereby at a completion of the complete ejection path, the stripper ring (230) and the neck rings (220) render the preform (210) removable from the mold stack (202).