Sequential Injection Molding Valve Control for Pressure Homogeneity
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Solution Overview
Problem
Current sequential injection molding technologies face challenges in controlling injection pressure, leading to surface defects such as pressure lines and non-homogeneous pressure distributions in the mold cavity, which affect the quality of molded articles, especially in high-aesthetic applications.
Innovation Solution
The method involves controlling the injector valves by partially closing them during the filling step and further opening them during the packing step, optimizing the pressure in the mold cavity to minimize or eliminate surface defects and ensure uniform pressure distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the injector valve is opened completely during the filling step, then the filling speed is improved, but surface defects such as pressure lines appear on the molded piece
Solution Approach 1:
The patent applies partial action by opening the injector valve only to the extent necessary for optimal filling, rather than completely opening it. The valve is positioned at a specific opening degree that balances filling speed with pressure control, preventing surface defects while maintaining efficient filling. This is achieved through the control unit that regulates the actuator to achieve the desired valve opening position.
Solution Approach 2:
The patent changes the parameter of valve opening degree from a binary state (fully open/closed) to a continuous variable that can be precisely controlled. By adjusting the opening degree parameter and the timing of valve operation, the system optimizes both filling speed and pressure distribution, eliminating surface defects while maintaining high filling efficiency.
2Manufacturing precision
If the injector valve is kept in complete opening position during the packing step, then the pressure control accuracy deteriorates, but the filling completeness is improved
Solution Approach 1:
The patent applies dynamics by making the valve opening degree variable throughout the injection process. During the filling step, the valve is opened to a greater extent to ensure complete filling. During the packing step, the valve opening degree is dynamically adjusted to a more restricted position, enabling precise pressure control for optimal packing and preventing excessive pressure that would cause surface defects.
Solution Approach 2:
The patent uses periodic action by dividing the injection process into distinct phases (filling and packing) with different valve opening configurations. The control unit manages the transition between these phases, applying appropriate valve opening degrees for each phase to achieve both complete filling and precise pressure control during packing.
3Productivity
If multiple injectors are opened at different speeds in cascade fashion, then the filling efficiency is improved, but the pressure distribution in the mold cavity becomes non-homogeneous
Solution Approach 1:
The patent applies local quality by allowing each injector to have independent control of its opening degree and timing. The control unit can adjust each injector's valve position individually based on its location in the mold cavity, ensuring that pressure is distributed homogeneously throughout the cavity while maintaining efficient filling. This localized control enables optimization of each injector's contribution to the overall filling process.
Data Source
AI summary
A molding method for the production of articles molded by injecting plastic material into a mold cavity by a plurality of injectors electrically sequentially actuated under an electronic control according to a cycle providing for a step for filling the mold cavity, followed by a step for packing the plastic material in the mold cavity. Each injector, regardless of both its position with respect to the mold cavity and its opening speed, is controlled in at least one of the following control modes: i) partially closing the injector from a maximum open condition to a less opened condition in the filling step, ii) setting the injector in a partially open condition and then opening the injector to a more opened condition, in the packing step.