Core-Shell Extrudate for FDM Stress Relief
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Solution Overview
Problem
Fused Deposition Modeling (FDM) printed objects often suffer from residual stresses due to differential cooling, leading to warping and deformations, which existing techniques fail to adequately address.
Innovation Solution
The method involves 3D printing using a core-shell extrudate with a core material having low glass transition and melting temperatures and a shell material with higher glass transition and melting temperatures, allowing for the reduction of residual stresses and tuning of physical properties at specific positions within the printed object.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single-material FDM printing is used, then manufacturing simplicity is maintained, but residual stresses cause warping and deformations
Solution Approach 1:
The patent employs composite materials consisting of two different thermoplastic materials with distinct glass transition temperatures. The first material has Tg1 of at most 0°C and the second has Tg2 of at least 60°C. This composite approach allows the materials to compensate for each other's thermal contraction during cooling, thereby reducing residual stresses and improving shape conservation without requiring complex printing process modifications.
Solution Approach 2:
The invention changes the thermal parameters of the printing materials by selecting materials with specific glass transition temperatures. By using a first thermoplastic material with Tg1 ≤ 0°C and a second with Tg2 ≥ 60°C, the patent creates a material system where the differential thermal contraction occurs at different temperature stages, reducing overall residual stress accumulation and warping during the printing process.
2Reliability
If multi-material core-shell extrudate is used, then residual stresses are reduced, but manufacturing complexity increases
Solution Approach 1:
The patent uses composite materials in the form of core-shell extrudates where the core consists of a first thermoplastic material and the shell consists of a second thermoplastic material, or vice versa. The specific glass transition temperature difference (Tg1 ≤ 0°C vs Tg2 ≥ 60°C) between the two materials enables stress reduction while the core-shell structure simplifies the manufacturing process by allowing both materials to be extruded simultaneously through a single nozzle system.
Solution Approach 2:
The core-shell extrude structure allows different materials to be placed in specific locations within the printed object. The first thermoplastic material with lower Tg can be positioned in regions requiring flexibility, while the second material with higher Tg provides structural stability in other regions, achieving local optimization of mechanical properties and stress distribution.
3Adaptability or versatility
If uniform material properties are used, then material selection is simple, but anisotropic properties cannot be achieved
Solution Approach 1:
The patent employs composite materials with two distinct thermoplastic components having different glass transition temperatures (Tg1 ≤ 0°C and Tg2 ≥ 60°C). This composite structure enables the printed object to exhibit anisotropic properties, where different regions or orientations can display different mechanical behaviors. The versatility is enhanced as the ratio and distribution of the two materials can be adjusted to achieve desired property profiles for specific applications.
Solution Approach 2:
By using a core-shell extrude system with two different thermoplastic materials, the patent enables local quality variation within the printed object. The first material with Tg1 ≤ 0°C can provide flexibility and stress relief in specific zones, while the second material with Tg2 ≥ 60°C can provide rigidity and dimensional stability in other zones, allowing tailored mechanical properties for different functional requirements within the same object.
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 results in more reliable and flexible 3D printed objects with reduced stress levels, enabling the creation of parts with anisotropic properties and improved shape conservation.
Implementation Method 1
the first thermoplastic material is an elastomeric material having a Young's modulus in the range of 2 to 200 MPa, (ia) a first low glass transition temperature T LG1 of at maximum 0 °C
Implementation Method 2
the first thermoplastic material is an elastomeric material
Implementation Method 3
the first thermoplastic material is an elastomeric material having (ia) a first low glass transition temperature T LG1 of at maximum 0 °C, and (ib) a first high glass transition temperature T HG1 or a first high melting temperature T HM1 of at minimum at 60 °C
Implementation Method 4
the shell material comprises a second thermoplastic material different from the first thermoplastic material, or the core material comprises the second thermoplastic material and the shell material comprises the first thermoplastic material
Data Source
Figure 1A~1B
Figure 1C~2A
Figure 2B~2C
AI summary
The invention provides a method comprising 3D printing a 3D item (1) by means of fused deposition modelling, the method comprising a 3D printing stage comprising layer-wise depositing an extrudate (321) comprising 3D printable material (201) to provide the 3D item (1) comprising 3D printed material (202), wherein during at least part of the 3D printing stage the extrudate (321) comprises a core-shell extrudate (1321) comprising a core (2321) comprising a core material (2011), and a shell (2322) comprising a shell material (2012), wherein the core material (2011) comprises a first thermoplastic material (111) and the shell material (2012) comprises a second thermoplastic material (112) different from the first thermoplastic material (111), or vice versa, wherein the first thermoplastic material (111) is an elastomeric material having a Young's modulus in the range of 2 to 200 MPa, a first low glass transition temperature TLG1 of at maximum 0 °C, and a first high glass transition temperature THG1 or a first high melting temperature THM1 of at minimum at 60 °C, and wherein the second thermoplastic material (112) has a Young's modulus in the range of 1 to 10 GPa, and one or more of a second glass transition temperature TG2 and a second melting temperature TM2 of at minimum 60 °C.