Coinjection Nozzle Tip with Segmented Melt Passages
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Solution Overview
Problem
Conventional coinjection hot runner injection molding systems face inaccuracies in reciprocating movement and difficulties in keeping melt streams separated, leading to complexity in manufacture, assembly, and operation, as well as challenges in aligning valve sleeve and pin members with the mold gate.
Innovation Solution
A coinjection molding apparatus with a nozzle design that includes separate melt passages for skin and core materials, where the skin material melt stream is directed through a central passage and an annular outer layer passage, with tunnel channels crossing the core material melt stream, allowing for precise control and separation of the melt streams within the nozzle tip and at the mold gate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If valve pin member and valve sleeve member are axially reciprocated to control melt stream flow, then simultaneous or sequential injection of multiple melt streams is achieved, but inaccuracies in reciprocating movement and difficulties in keeping melt streams separated occur
Solution Approach 1:
The nozzle is divided into multiple independent melt channels (first melt channel, second melt channel, third melt channel) that are spatially separated. Each channel has its own gate (first gate, second gate, third gate) allowing independent control of each melt stream without requiring complex reciprocating valve mechanisms. This segmentation eliminates cross-contamination between melt streams while maintaining simultaneous or sequential injection capability.
Solution Approach 2:
A valve member is introduced as an intermediary component that selectively blocks specific melt channels. The valve member can be positioned to block the second melt channel while allowing first and third channels to flow, or block the first and third channels while allowing the second channel to flow. This intermediary mechanism provides precise control over which melt streams are injected without requiring complex reciprocating movements of multiple valve components.
2Ease of operation
If valve pin member and valve sleeve member are used for melt stream control, then injection flow control is achieved, but complexity in manufacture, assembly, and operation increases
Solution Approach 1:
The injection system is segmented into multiple independent melt channels, each with its own gate and flow control capability. This allows simple on/off control for each channel without requiring complex valve mechanisms. The nozzle body itself is designed with integrated flow control features rather than adding separate valve assemblies.
Solution Approach 2:
The valve member serves multiple functions: it can block the second melt channel, block the first and third channels, or be positioned to allow all channels to flow. This single multi-functional component replaces what would otherwise require multiple separate valve mechanisms, simplifying both the structure and operation while maintaining flexible injection control.
3Productivity
If conventional nozzle design is used, then injection molding is performed, but difficulties in aligning valve sleeve and pin member with mold gate occur
Solution Approach 1:
The nozzle is designed with multiple separately positioned melt channels and gates instead of a single centralized valve mechanism. Each melt channel (first, second, third) has its own gate positioned at specific locations on the nozzle tip. This segmentation allows each gate to be independently aligned with the mold during assembly, eliminating the cumulative alignment errors that occur with complex valve mechanisms.
Solution Approach 2:
The complex valve alignment requirement is extracted and replaced by a simpler valve member that blocks predefined channels. The gates are positioned at fixed locations on the nozzle tip, requiring only simple alignment with the mold rather than precise alignment of multiple valve components. This extraction of the alignment problem from the valve mechanism simplifies the overall assembly process.
Data Source
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AI summary
A coinjection molding apparatus is disclosed that provides a skin material melt stream and a core material melt stream to a nozzle. A nozzle tip of the nozzle defines a central skin material melt passage for receiving the skin material melt stream, an annular core material melt passage for receiving the core material melt stream and an annular outer layer melt passage, which receives a portion of the skin material melt stream from the central skin material melt passage. The skin material melt stream from the central skin material melt passage forms an inner layer of a molded article, the core material melt stream from the core material melt passage forms a core layer of the molded article, and the skin material melt stream from the outer layer melt passage forms an outer layer of the molded article, wherein the three melt streams combine prior to entering a mold cavity.