Injection Screw Valve Closing Speed Control
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Solution Overview
Problem
Conventional injection molding techniques face challenges in preventing backflow of low-viscosity resin, leading to metering dispersion due to the reliance on reverse screw rotation for valve closure, which is inefficient and increases leak quantity as viscosity decreases.
Innovation Solution
The method involves setting a higher valve closing operation speed than the initial injection filling speed and controlling the screw forward movement speed to ensure the ring valve is closed before injection filling, using a valve closing operation time of 10 to 50 milliseconds to minimize resin compression and leak.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reverse rotation of the screw is used to close the ring valve, then the valve closing is achieved, but the metered resin flows back to the feed part side causing leak and affecting product weight
Solution Approach 1:
The invention performs preliminary valve closing action by moving the ring valve to the closed position before starting the injection filling process. The screw is moved forward at a first speed to close the ring valve, ensuring it is sealed before resin injection begins, thereby preventing backflow and leak of metered resin to the feed part side.
Solution Approach 2:
The invention dynamically controls the screw movement speed in two stages: first moving the screw forward at a first speed to close the ring valve, then moving it forward at a second speed (different from the initial injection filling speed) to complete the injection filling process. This dynamic speed adjustment ensures proper valve closing timing and prevents resin backflow.
2Reliability
If the ring valve is closed by resin pressure from screw compression, then the valve closes, but the moving stroke is longer for low-viscosity resin causing simultaneous closure issue
Solution Approach 1:
The invention replaces the passive resin-pressure-based valve closing mechanism with an active mechanically-controlled valve closing system. The screw movement speed is actively controlled to move the ring valve to the closed position at a specific timing, independent of resin pressure generation, thereby achieving reliable valve closing even for low-viscosity resin.
Solution Approach 2:
The invention changes the screw movement speed parameter during the valve closing phase. By moving the screw forward at a first speed (different from the normal injection filling speed) specifically for valve closing, the system achieves precise control over the valve closing timing and position, ensuring effective sealing before injection filling begins.
3Productivity
If the screw moves forward at normal injection filling speed from the beginning, then injection filling is efficient, but the ring valve cannot be closed simultaneously causing resin backflow
Solution Approach 1:
The invention segments the screw movement process into two distinct phases: (1) a valve closing phase where the screw moves forward at a first speed to close the ring valve, and (2) an injection filling phase where the screw moves forward at a second speed to complete the injection. This segmentation ensures the valve is closed before injection begins, preventing resin backflow and maintaining metering precision while preserving injection filling efficiency.
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 effectively reduces metering dispersion and ensures accurate molding weight by preventing backflow and leak during injection filling, especially with low-viscosity resins, while maintaining the efficiency of the injection molding process.
Implementation Method 1
the ring valve moves with the injection screw to a position where the metered resin is sufficiently compressed by the top end surface of the screw to generate the resin pressure contributive to the valve closing
Implementation Method 2
a molten resin plasticized on a feed part side is carried through a flowing gap between the rear end surface of the valve ring and a sheet ring on the circumference of a screw shaft toward the screw tip via the inside of the valve ring by rotation of the screw
Implementation Method 3
the ring valve is closed by the resin pressure generated by compression of the metered resin at the time of stopping the rotation and moving the injection screw forward to inject and fill the metered molten resin
Data Source
AI summary
Leak of a metered resin by backflow in injection filling is prevented not depending on reverse rotation of a screw but by closing a ring valve by controlling a screw forward movement speed in injection filling. An injection filling speed and a valve closing operation speed are set to the screw forward movement speed. The valve closing operation speed is different from an initial speed of the injection filling speed, and the operation time thereof is set to the time necessary for moving the injection screw by a distance capable of performing the valve closing after the end of metering. The valve closing is performed with the set operation speed and the set operation time.