Hot Runner Nozzle with Differential Gate Diameters
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Solution Overview
Problem
In multi-layer injection molding using a hot runner nozzle, the intermediate layer often protrudes into the sprue portion, leading to separation issues when the sprue is cut, due to the complex configuration and small gate size, which disrupts resin flow and adhesion between layers.
Innovation Solution
A hot runner nozzle design with a smaller nozzle gate diameter and a larger shut pin hole diameter, featuring a projection on the shut pin to push molten resin into the mold cavity and a mechanism for controlled opening and closing of resin discharge ports, ensuring stable resin flow and preventing intermediate layer exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the nozzle gate diameter is reduced to prevent intermediate layer protrusion, then the intermediate layer exposure is prevented, but the resin flow stability deteriorates and temperature distribution worsens
Solution Approach 1:
The invention segments the flow control function by introducing a shut pin mechanism that independently controls resin flow from multiple discharge ports. The shut pin divides the single gate into multiple controlled discharge ports, allowing precise control of intermediate layer resin flow while maintaining overall flow stability through the larger outer diameter structure.
Solution Approach 2:
The invention applies local quality by creating different diameter zones within the gate structure. The outer diameter remains large for stable flow and temperature distribution, while the inner discharge port diameter is controlled for precise intermediate layer positioning. This local differentiation allows simultaneous optimization of both flow stability and positioning precision.
2Ease of operation
If the shut pin hole diameter is increased to improve shut pin movement, then the resin flow control precision deteriorates, but the flow disturbances are reduced
Solution Approach 1:
The invention segments the shut pin hole into two functional zones: a larger outer diameter portion that facilitates smooth shut pin movement and reduces flow disturbances, and a smaller inner discharge port portion that maintains resin flow control precision. This segmentation allows the shut pin to move easily while still controlling resin flow accurately.
3Device complexity
If a single gate structure is used to simplify the nozzle configuration, then the device complexity is reduced, but the intermediate layer concentration in mold cavity increases
Solution Approach 1:
The invention segments the single gate into multiple discharge ports arranged around the shut pin. This segmentation allows different resins to be discharged through different ports in a controlled sequence, preventing intermediate layer concentration in the mold cavity while maintaining a relatively simple overall nozzle structure.
Solution Approach 2:
The invention applies preliminary action by using the shut pin to control the opening and closing sequence of different discharge ports before resin injection. This preliminary control ensures that surface layer resin is discharged first, followed by the intermediate layer, preventing concentration issues before the molding process begins.
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
Prevents intermediate layer exposure during sprue cutting, maintains stable resin flow, and allows for a larger shut pin hole diameter while keeping the nozzle gate small, reducing flow disturbances and enhancing temperature distribution.
Implementation Method 1
a projection is provided at a tip of the shut pin so as to push out the molten resin in the nozzle gate toward the mold cavity when the shut pin moves forward to close all of the resin discharge ports
Implementation Method 2
the nozzle gate has a diameter smaller than a diameter of the shut pin hole... allowing for a larger shut pin hole diameter while keeping the nozzle gate small, reducing flow disturbances and enhancing temperature distribution
Data Source
AI summary
At a filling termination stage when performing multi-layer molding by means of a hot runner nozzle, an intermediate layer in a multi-layer molded article is prevented from being formed in a shape causing the intermediate layer to enter into a sprue in a portion of a mold cavity in a mold corresponding to the sprue. The multi-layer molded article with no intermediate layer being exposed in a sprue cut portion can be therefore obtained. In this manner, a diameter of a discharge port opening and closing mechanism part for opening and closing the resin discharge ports in the shut pin is made different from a diameter of a nozzle gate opening and closing mechanism part configured of the projection for pushing out the molten resin in the nozzle gate.