Capillary Shear Viscosity Profiling for Temperature-Dependent Melt Flow
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Solution Overview
Problem
Current injection molding processes inaccurately simulate the flow behavior of molding materials due to temperature changes, leading to inefficiencies as they fail to account for temperature-dependent shear viscosity.
Innovation Solution
A method is developed to measure the true shear viscosity profile of molding materials using a Cross William-Landel-Ferry (Cross-WLF) model, which determines the setpoint temperature, obtains initial and subsequent shear viscosity profiles, and adjusts these profiles based on temperature differences within predetermined thresholds, ensuring accurate flow behavior simulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If constant melt temperature assumption is used in simulation, then simulation complexity is reduced, but simulation accuracy deteriorates due to temperature changes in molding material
Solution Approach 1:
The patent applies parameter changes by transitioning from a constant temperature assumption to a variable temperature model. The Cross-WLF model is used to describe viscosity as a function of temperature and shear rate, allowing the simulation to account for temperature changes during injection molding. This resolves the contradiction by accepting increased model complexity to achieve accurate temperature-dependent viscosity prediction.
Solution Approach 2:
The patent implements feedback through an iterative measurement and simulation process. Experimental viscosity data at different temperatures and shear rates are used to validate and refine the Cross-WLF model parameters. The simulation results are compared with experimental data, and the model is adjusted until convergence is achieved, ensuring both accuracy and reliability.
2Device complexity
If generalized Newtonian fluids model is used, then mathematical modeling is simplified, but flow behavior prediction accuracy deteriorates for materials with viscoelasticity
Solution Approach 1:
The patent changes the fundamental parameters of the fluid model by adopting the Cross-WLF viscosity model, which accounts for both temperature and shear rate dependencies. This non-Newtonian model captures the viscoelastic behavior of molding materials more accurately than the generalized Newtonian model, resolving the contradiction by accepting increased mathematical complexity for improved predictive accuracy.
3Measurement precision
If iterative fitting process is performed to obtain true shear viscosity profile, then measurement accuracy is improved, but measurement time and computational cost increase
Solution Approach 1:
The patent applies preliminary action by conducting experiments at multiple predetermined temperatures and shear rates before performing the iterative fitting. The Cross-WLF model parameters are pre-determined from these experiments, which accelerates the subsequent iterative process. This preparation reduces the computational burden and time required for the final viscosity profile determination.
Solution Approach 2:
The patent replaces complex mechanical measurement systems with a computational approach using the Cross-WLF model. Instead of direct mechanical viscosity measurement under varying temperature conditions, the system uses pressure and flow rate measurements combined with iterative computational fitting to derive the true shear viscosity profile, reducing measurement complexity and time.
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 provides a more accurate simulation of molding material flow behavior, enhancing the efficiency and accuracy of the injection molding process by accounting for temperature variations.
Implementation Method 1
fitting an initial temperature profile with respect to the shear rate according to the initial shear viscosity based on a Cross William-Landel-Ferry (Cross-WLF) model; fitting a first shear viscosity profile and a first temperature profile with respect to the shear rate according to the initial temperature profile based on the Cross-WLF model
Data Source
AI summary
The present disclosure provides a method of measuring a true shear viscosity profile of a molding material in a capillary and a molding system performing the same. The method includes the operations of: determining a setpoint temperature of the molding material before injecting into the capillary; obtaining an initial shear viscosity profile at the setpoint temperature with respect to a shear rate of the molding material; fitting an initial temperature profile with respect to the shear rate according to the initial shear viscosity based on Cross William-Landel-Ferry model; fitting a first shear viscosity profile and a first temperature profile with respect to the shear rate according to the initial temperature profile based on the Cross-WLF model; and setting the first shear viscosity profile as the true shear viscosity profile when a difference between the first temperature profile and the initial temperature profile is not greater than a threshold.