Stepped Liquefier Assembly Meniscus Control
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Solution Overview
Problem
Extrusion-based additive manufacturing systems face challenges in controlling the flow rate of molten filament material, leading to inconsistencies in 3D model quality due to meniscus dry down effects, latent heating, and filament diameter variations, which affect part resolution and build times.
Innovation Solution
A stepped liquefier assembly with a downstream portion having a larger inner cross-sectional area and an upstream portion with a smaller area, featuring a hollow liner and an extrusion tip, restricts the movement of the melt meniscus to maintain a consistent flow rate, reducing meniscus dry down and compensating for filament diameter changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a traditional liquefier assembly with uniform cross-sectional area is used, then the structure is simple, but the meniscus position becomes unstable due to thermal expansion and latent heating, leading to inconsistent extrusion rates
Solution Approach 1:
The liquefier tube is divided into multiple zones with different cross-sectional areas along its length. The tube includes a first portion with a larger inner cross-sectional area and a second portion with a smaller inner cross-sectional area, creating distinct functional regions that control meniscus behavior and extrusion characteristics separately.
Solution Approach 2:
Different portions of the liquefier tube are given different cross-sectional areas to perform different functions. The larger cross-sectional area portion handles thermal expansion and meniscus stability, while the smaller cross-sectional area portion controls extrusion rate and flow characteristics, optimizing each region for its specific purpose.
2Force
If the inner cross-sectional area of the liquefier tube is reduced to increase extrusion pressure, then extrusion force improves, but the meniscus becomes more susceptible to dry down effects and position instability
Solution Approach 1:
The liquefier tube is segmented into zones with different cross-sectional areas. The first portion maintains a larger area to stabilize the meniscus and prevent dry down, while the second portion has a smaller area to generate sufficient extrusion pressure, distributing the functional requirements across different sections.
Solution Approach 2:
Instead of uniformly reducing the cross-sectional area along the entire length, the invention varies the cross-sectional area along the longitudinal dimension, creating a gradient structure that simultaneously achieves meniscus stability and adequate extrusion pressure through spatial distribution.
3Use of energy by moving object
If the liquefier tube length is increased to improve melting efficiency, then material processing improves, but the response time and build time increase
Solution Approach 1:
The liquefier tube uses varying cross-sectional areas along its length to optimize different functions in different regions. The larger cross-sectional area portions provide adequate melting volume and thermal processing, while the overall compact design with strategic area variations reduces the effective thermal mass and response time compared to a uniformly long tube.
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
The solution improves control over extrusion rates and response times, resulting in better part quality and reduced build times by maintaining a stable meniscus height and preventing upward flow due to thermal expansion, thus enhancing the accuracy and efficiency of 3D model construction.
Implementation Method 1
preventing upward flow due to thermal expansion
Implementation Method 2
The hollow liner is disposed at least partially within the liquefier tube such that an outlet end of the hollow liner is disposed within the liquefier tube
Implementation Method 3
The modeling material is extruded through an extrusion tip carried by an extrusion head, and is deposited as a sequence of roads on a substrate in an x-y plane
Implementation Method 4
an upstream portion disposed adjacent to the downstream portion, the upstream portion being configured to receive a consumable material
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
A liquefier assembly (62, 162, 262, 362, 462, 562, 662) for use in an extrusion-based additive manufacturing system (10), the liquefier assembly (62, 162, 262, 362, 462, 562, 662) comprising a downstream portion (62b, 162b, 262b, 362b, 462b, 562b, 662b) having a first average inner cross-sectional area, and an upstream portion (62a, 162a, 262a, 362a, 462a, 562a, 662a) having a second average inner cross-sectional area that is less than the first inner cross-sectional area, the upstream portion (62a, 162a, 262a, 362a, 462a, 562a, 662a) defining a shoulder (88, 188, 288, 388, 488, 588, 688) configured to restrict movement of a melt meniscus (94, 194, 294, 394, 494, 594, 694) of a consumable material (90, 190, 290, 390, 490, 590, 690).