Coinjection Hot Runner Nozzle Tunnel Channels
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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 hot runner injection molding nozzle that includes separate passages for two melt streams, where one melt stream is directed through tunnel channels to form an outer layer, and the other forms a core or barrier layer, allowing for precise control and separation of flows within the nozzle tip or gate area before entering the mold cavity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a 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 injection system is divided into separate channels: a first material melt passage for the first melt stream, a second material melt passage for the second melt stream, and an outer layer melt passage. Tunnel channels cross the second material melt stream to direct the first melt stream to the outer layer passage, physically segmenting the flow paths to prevent mixing while enabling controlled injection sequences.
Solution Approach 2:
Different regions of the nozzle are assigned different functions: the first material melt passage delivers material for inner layer formation, the second material melt passage delivers material for core or barrier layer formation, and the outer layer melt passage (accessible via tunnel channels) delivers material for outer layer formation. This local differentiation ensures precise control over where each melt stream is injected and how it is separated.
2Extent of automation
If a valve pin member and valve sleeve member are axially reciprocated to control melt stream flow, then simultaneous or sequential injection is achieved, but complexity in manufacture, assembly, and operation increases
Solution Approach 1:
The complex reciprocating valve mechanism with multiple sleeve members is extracted and replaced with a simpler system using tunnel channels that cross the second material melt stream. This allows the first material melt stream to be directed to the outer layer melt passage without requiring complex valve assemblies, reducing manufacturing and assembly complexity while maintaining control capability.
Solution Approach 2:
The functions of multiple valve members are merged into an integrated nozzle structure where tunnel channels provide both the crossing path for the first melt stream and the delivery path to the outer layer passage. This consolidation reduces the number of separate components and simplifies the overall system architecture.
3Ease of operation
If valve sleeve and pin members are used to control melt stream flow, then injection control is achieved, but alignment with the mold gate becomes difficult
Solution Approach 1:
The nozzle is segmented into distinct passages (first material melt passage, second material melt passage, outer layer melt passage) with dedicated tunnel channels for interconnection. This segmentation allows each passage to be independently optimized and aligned with the mold gate, improving positioning precision compared to a unified valve-controlled system.
4Extent of automation
If conventional valve mechanisms are used for coinjection, then multi-stream injection is achieved, but gate wear increases
Solution Approach 1:
The valve members that directly contact and reciprocate near the gate are extracted from the system. Instead, tunnel channels provide a fixed, wear-resistant path for the first melt stream to reach the outer layer passage, eliminating the sliding friction and wear associated with reciprocating valve members at the gate location.
Data Source
AI summary
A coinjection molding apparatus is disclosed that provides first and second material melt streams to a nozzle. The nozzle defines a first material melt passage for receiving the first material melt stream, a second material melt passage for receiving the second material melt stream and an outer layer melt passage, which receives a portion of the first material melt stream from the first material melt passage. The first material melt stream from the first material melt passage forms an inner layer of a molded article, the second material melt stream from the second material melt passage forms a core layer of the molded article, and the first 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.