External Strain Gauge Sensors for Virtual Cavity Pressure Monitoring
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Solution Overview
Problem
Current injection molding processes face challenges in accurately measuring real-time pressure at the melt flow front within the mold cavity without damaging the parts, as direct sensors leave marks and indirect sensors often require downtime and are expensive, and lack optimal placement.
Innovation Solution
The use of external strain gauge sensors, along with a virtual cavity sensor, to approximate pressure and melt flow front position, allowing for adjustments to the injection molding process by emitting electrical signals that correlate with surface strain changes, enabling the monitoring and control of internal mold cavity pressure and flow front location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct sensors are placed within the mold cavity to measure pressure, then measurement precision is improved, but the part surface quality deteriorates due to marks left by sensors
Solution Approach 1:
The patent uses indirect sensors positioned outside the mold cavity that measure parameters (such as clamp load, injection pressure, or thermal fields) which serve as intermediaries to infer the melt flow front position and cavity pressure without direct contact with the part surface, thereby avoiding marks while obtaining measurement data
Solution Approach 2:
The patent creates a virtual model or copy of the cavity pressure and flow front position by correlating external sensor measurements with the expected pressure distribution patterns during injection molding, allowing indirect determination of internal conditions without physical sensors inside the cavity
2Object-affected harmful factors
If indirect sensors are used to avoid part damage, then part surface quality is preserved, but measurement precision and reliability deteriorate due to suboptimal sensor placement
Solution Approach 1:
The patent employs sensors that serve multiple functions: they monitor not only pressure or position parameters but also provide data for determining melt flow front location, cavity filling status, and process optimization, making the indirect measurement system equally reliable for multiple critical measurements
Solution Approach 2:
The patent implements real-time feedback loops where indirect sensor measurements are continuously compared against target pressure profiles and flow front positions, allowing dynamic adjustment of injection parameters to maintain measurement accuracy and process control without direct cavity sensors
3Ease of manufacture
If indirect sensors are installed on existing molds, then ease of installation is improved, but device complexity increases due to additional sensor systems and signal processing requirements
Solution Approach 1:
The patent utilizes existing mold structure components (such as the clamp unit, injection unit, or mold plates) as intermediary elements to mount sensors, avoiding the need for specialized sensor housings or complex integration structures while still enabling indirect measurement of cavity conditions
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 allows for precise control of the injection molding process, preventing mold damage and ensuring optimal part quality by approximating internal pressures and flow front positions without the need for direct sensors, reducing downtime and costs.
Implementation Method 1
Strain gauge sensors are the type of external sensor primarily discussed... strain gauge sensors to approximate conditions, such as pressure within a mold cavity... In many molds, a direct correlation exists between internal mold cavity pressures and change in strain measured by one or more strain gauges on an external portion of a mold
Implementation Method 2
The strain gauge sensor or sensors, along with a virtual cavity sensor, are used as part of a pressure controlling system to sense a parameter within the mold cavity... emit electrical signals that correlate with surface strain changes
Data Source
AI summary
A injection molding method involves measuring, using at least one external sensor, a change in a parameter of a mold side of a mold cavity, approximating a condition within the mold cavity based on the change in the parameter, such as pressure within the mold cavity or flow front position, and comparing the approximated condition to a trigger point. If the approximated condition equals or exceeds the trigger point, activating a virtual cavity sensor having an optimal pre-defined pressure-time curve, and upon activation, the virtual cavity sensor tracks an approximated condition calculated from the change in parameter measurements measured by the at least one external sensor over time. In an embodiment, results of the approximated parameter tracking can be used in conjunction with an optimal pre-defined pressure-time curve.