Needle Valve Nozzle Opening Speed Control
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Solution Overview
Problem
The sudden drop in pressure at needle shut-off nozzles during the opening of multiple valve gates in injection molding leads to weld lines and optical defects in molded parts due to abrupt pressure changes, causing mechanical weaknesses.
Innovation Solution
A method and device that control the volume flow of plastic melt by reducing the speed of the shut-off needle's opening movement, using a flow restrictor or proportional valve to gradually increase the opening cross-section, and adjusting the actuating device to maintain a constant speed, thereby minimizing pressure fluctuations and avoiding stagnation in the cavity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple needle valve nozzles are opened simultaneously to increase productivity, then injection speed is improved, but pressure fluctuations occur causing weld lines and optical defects
Solution Approach 1:
The system pre-calculates and sequences the opening of multiple needle valve nozzles based on the injection molding cycle. By determining the optimal timing for each nozzle opening, the system ensures that nozzles are opened in a coordinated manner to prevent pressure fluctuations and weld lines while maintaining high injection speed.
Solution Approach 2:
The control system dynamically adjusts the opening timing and duration of each needle valve nozzle based on real-time pressure feedback and pre-stored process parameters. This dynamic control allows the system to optimize the injection process for each specific molding cycle, balancing productivity with pressure stability.
2Loss of time
If needle valve nozzles are opened abruptly to reduce cycle time, then injection speed is improved, but pressure drops suddenly causing melt front stagnation
Solution Approach 1:
The system pre-determines the optimal opening sequence and timing for multiple needle valve nozzles based on the injection molding cycle phase. By planning the opening timing in advance, the system avoids abrupt pressure drops while minimizing cycle time, ensuring smooth melt front progression.
Solution Approach 2:
The control system continuously monitors pressure feedback from the injection system and adjusts the nozzle opening timing accordingly. This feedback mechanism allows real-time optimization of the injection process, preventing pressure fluctuations that would cause melt front stagnation while maintaining efficient cycle times.
3Reliability
If high injection pressure is applied to ensure complete filling, then molding quality is improved, but pressure fluctuations cause weld lines and mechanical weaknesses
Solution Approach 1:
The system pre-calculates the optimal opening sequence for multiple needle valve nozzles based on the injection molding cycle phase and part geometry. By planning the opening timing in advance, the system maintains stable pressure distribution across all nozzles, preventing weld lines and mechanical weaknesses while ensuring complete filling.
Solution Approach 2:
The control system dynamically adjusts the opening timing and duration of each needle valve nozzle based on real-time pressure feedback and pre-stored process parameters. This dynamic control maintains pressure stability throughout the injection process, preventing the formation of weld lines and ensuring high molding quality.
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 reduces pressure fluctuations, prevents stagnation of the melt front, and enhances the quality of injection molded products by ensuring a more consistent chemical flow and reduced mechanical weaknesses.
Implementation Method 1
A flow restrictor (5) is arranged in the pressurized fluid circuit, which reduces the volume flow of the pressurized fluid when the actuating device moves the shut-off needle from the closed position to the open position
Implementation Method 2
the conical section of the valve needle (8) and the conical inner section of the nozzle housing (22) interact in such a way that the opening cross-section changes very slowly at the beginning
Data Source
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AI summary
The method involves providing a needle closure nozzle with a nozzle casing in which a closure needle (8) with a conical section is movable between a closed position and an opened position by an actuator device (4). Molten plastic is injected into a cavity in the opened position, where the volumetric flow of the molten plastic is controlled during an injection process. The speed of movement of the closure needle is smaller with the opening operation than with the closing operation, where an opening angle of the closure needle lies between 1 and 20 degree. An independent claim is also included for a device for injecting molten plastic into a cavity of an injection mold.