Rheometer System for Polymer Filament Rheological Properties
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Solution Overview
Problem
Current methods for characterizing the rheological properties of polymers in Fused Filament Fabrication (FFF) are inadequate, leading to imperfect prints and substandard material properties due to reliance on traditional approaches that are costly and inaccurate, especially for non-Newtonian fluids.
Innovation Solution
A low-cost, accurate rheometer system and method that measures filament feeding rate and force to compute polymer melt volumetric flow and pressure drop, using inverse analysis for nonlinear curve fitting to determine rheological parameters, independent of apparent viscosity calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional laboratory rheometers are used to measure polymer rheological properties, then measurement precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent extracts the essential measurement function from complex laboratory rheometers by identifying that only specific parameters (pressure drop and flow rate) are needed to determine rheological properties. The system uses a simplified extruder setup with pressure sensors and flow rate measurement capabilities, eliminating the need for complex rheometer instrumentation while maintaining measurement accuracy through targeted parameter collection and inverse analysis.
Solution Approach 2:
The patent replaces mechanical rheometer systems with a computational approach using inverse analysis and nonlinear curve fitting. Instead of relying on complex mechanical measurement devices, the system uses digital signal processing, mathematical models, and computer algorithms to extract rheological parameters from simpler pressure and flow rate measurements, thereby reducing device complexity while maintaining precision.
2Measurement precision
If traditional rheological measurement methods are used, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent employs inexpensive pressure sensors, standard extruder components, and readily available computational tools to replace expensive laboratory rheometers. The system uses off-the-shelf electronic components, open-source software algorithms, and standard manufacturing equipment to achieve accurate rheological measurements, dramatically reducing the cost barrier while maintaining measurement precision through clever measurement design and data analysis.
Solution Approach 2:
The patent makes the extruder system multi-functional by using it not only for polymer extrusion but also for rheological characterization. The same pressure sensors and flow rate measurement capabilities used for process monitoring are leveraged to determine rheological properties, eliminating the need for separate dedicated measurement equipment and reducing overall system cost while maintaining accuracy.
3Ease of operation
If apparent viscosity calculations are used to characterize non-Newtonian fluids, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The patent inverts the traditional approach by using inverse analysis to determine rheological parameters from pressure drop and flow rate measurements, rather than directly measuring viscosity and calculating apparent viscosity. This inversion process uses nonlinear curve fitting and mathematical models to extract accurate rheological properties, providing both ease of operation through automated computation and high precision through rigorous data analysis, thereby resolving the contradiction between simplicity and accuracy.
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 high accuracy at a fraction of the cost of laboratory rheometers, enabling precise control of material deposition and improving the quality of FFF components.
Implementation Method 1
a force transducer coupled to the liquefier and configured to provide force data to measure a filament force caused by the filament feeding system on the liquefier nozzle through feeding the filament
Implementation Method 2
a temperature sensor for measuring temperature of the liquefier, the at least partially melted filament, or a combination thereof
Implementation Method 3
a liquefier configured to at least partially melt the filament
Data Source
AI summary
The present disclosure provides a low-cost and accurate rheometer system and method capable of determining melt flow rheological properties of polymers, such as from Fused Filament Fabrication (“FFF”) polymeric materials. The device can include a filament feeding system, liquefier for filament melting, force transducer for measuring filament feeding force, and a temperature control system for controlling polymer melt temperatures. An electronic control system can capture data and manage operations. The system can measure a filament velocity and filament force required to extrude the FFF filament for printing. The filament velocity and force data can be used to compute data sets of melt volumetric flow relative to pressure drop across a FFF nozzle. An inverse analysis process transforms the computed data sets through nonlinear curve fitting to determine rheological parameters, independent of the customary calculation of apparent viscosity from shear stress and strain rate, that can assist in controlling the filament deposition.