Valve Pin Flow Control for Injection Molding Defects
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Solution Overview
Problem
Injection molding systems face challenges in controlling the flow rate of fluid material during the injection cycle, leading to visible defects in the molded product due to uneven flow velocities through multiple gates, which results in lines or defects in the final product.
Innovation Solution
A method and apparatus that utilize a valve pin with a drive path and an actuator system, allowing the valve pin to move between obstructive, restrictive, and free-flow positions, controlled by a valve system adjustable between start, intermediate, and high drive rate positions, with position sensing and control mechanisms to manage the flow rate precisely, ensuring consistent material distribution across the mold cavity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a valve pin is used to control flow rate during injection molding, then the flow rate can be controlled to prevent defects, but the system complexity increases due to the need for precise position control mechanisms
Solution Approach 1:
The patent replaces complex mechanical position control mechanisms with a sensor-based detection system that automatically senses valve pin position and provides feedback to the controller. This substitution reduces mechanical complexity while maintaining precise flow rate control through electronic sensing and control.
Solution Approach 2:
The patent implements a feedback control system where a sensor detects the valve pin position and sends signals to the controller, which then adjusts the valve pin position accordingly. This closed-loop feedback mechanism enables precise flow rate control without requiring overly complex mechanical control systems.
2Productivity
If the valve pin moves at high speed to increase productivity, then the injection cycle time is reduced, but flow uniformity deteriorates causing visible defects in the molded product
Solution Approach 1:
The patent employs dynamic control of the valve pin movement, allowing it to move at varying speeds during different phases of the injection cycle. The valve pin can move quickly when flow uniformity is less critical and slow down when precise flow control is needed, optimizing both productivity and flow uniformity through speed variation.
Solution Approach 2:
The patent uses periodic adjustment of the valve pin position during the injection cycle, moving it to different positions at specific intervals to maintain optimal flow rates. This periodic control action ensures flow uniformity is maintained throughout the injection process while keeping the overall cycle time short.
3Productivity
If multiple gates are used to fill the mold cavity, then the productivity increases, but flow distribution becomes uneven causing lines or defects in the final product
Solution Approach 1:
The patent applies local quality control by independently controlling the flow rate to each gate through individual valve pins. Each gate receives optimized flow control tailored to its specific requirements, ensuring uniform flow distribution across all gates while maintaining high productivity through parallel filling of the mold cavity.
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 solution effectively reduces or eliminates visible defects by controlling the flow rate of injection fluid material, ensuring uniform material distribution and reducing the appearance of lines or defects in the molded product by managing the valve pin's position and travel speed, thereby enhancing the quality of the injection molding process.
Implementation Method 1
a valve system that is controllably adjustable between a start position, one or more intermediate drive rate positions and a high drive rate position... a first valve interconnected to the source that is selectively adjustable to adjust rate of flow of the drive fluid from the source
Implementation Method 2
A sensor senses a condition of the fluid material or of the apparatus such as pin position and sends a signal indicative of the sensed condition to a program contained in a controller
Data Source
Figure 1
Figure 1A~1C
Figure 1D~1E
AI summary
An apparatus for controlling the rate of flow of fluid mold material from an injection molding machine to a mold cavity, the apparatus comprising: a manifold having a delivery channel that delivers fluid material to a first gate; an actuator interconnected to a valve pin having a tip end drivable along a drive path that extends between a first position, a second position upstream of the first position and a third position upstream of the second position, the actuator and the valve pin being translationally driven at a controllable rate of travel by a valve system that is controllably adjustable between a start position, one or more intermediate drive rate positions and a high drive rate position, the valve system comprising a source of valve drive fluid that pumps the drive fluid at a maximum drive rate, a first valve interconnected to the source that is selectively adjustable to adjust rate of flow of the drive fluid from the source to a selected less than maximum drive rate and a second valve controllably movable between a first position and a second position; a controller instructing the valve system to drive the actuator and the valve pin continuously upstream from the start position to the second position to the third position; the controller including instructions that instruct the second valve to move from the second position to the first position on receipt by the controller of a signal that is indicative of the valve pin having reached the second position or an elapse of a predetermined amount of time.