Core-shell filament for smooth FDM 3D printing
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Solution Overview
Problem
Fused Deposition Modeling (FDM) 3D printing techniques often result in rough surface finishes, which are not suitable for applications requiring smooth surfaces, as post-treatment methods like mechanical polishing or heat treatment can weaken the product and alter its shape or functionality.
Innovation Solution
The method involves using a core-shell filament with a core and shell material where the shell has a lower glass transition temperature (Tg) and melting temperature (Tm) than the core, allowing the outer surface to be heated above its Tg/Tm without melting the core, thereby smoothing the surface while maintaining the structural integrity of the core material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If FDM 3D printing is used to produce items, then manufacturing speed and complexity handling are improved, but surface finish quality deteriorates (rough ribbed surface)
Solution Approach 1:
The filament is segmented into core and shell portions with different material properties. The core provides structural integrity while the shell provides smooth surface finish. This segmentation allows the filament to serve multiple functions simultaneously, resolving the contradiction between manufacturing speed and surface finish quality.
Solution Approach 2:
Different portions of the filament are given different qualities: the core has high melting point for structural support, while the shell has low melting point for surface smoothing. This local differentiation of material properties enables the filament to address both productivity and surface finish requirements in different locations.
2Manufacturing precision
If post-surface treatment methods (mechanical polishing, solvent treatment) are applied, then surface smoothness is improved, but product strength and shape stability deteriorate
Solution Approach 1:
The smooth surface is built into the filament structure before printing occurs. The shell material is designed to melt and smooth the surface during or after printing, eliminating the need for subsequent mechanical polishing or solvent treatment that would compromise product strength.
Solution Approach 2:
The mechanical post-treatment processes (polishing, solvent treatment) are replaced by a thermal process using the shell material's phase change. The shell melts and flows to smooth the surface, substituting mechanical action with thermal action that does not compromise product integrity.
3Manufacturing precision
If heat treatment is applied to the entire 3D printed product, then surface smoothness is improved, but product shape and functionality deteriorate due to weakening
Solution Approach 1:
The heat treatment effect is localized to only the shell portion of the filament through selective heating. The shell material has lower melting point and is heated to melt and smooth the surface, while the core material remains below its melting point and maintains structural integrity and shape stability.
Solution Approach 2:
The melting point parameter is differentiated between core and shell materials. By selecting materials with sufficiently different melting points, the heating process can be tuned to affect only the shell material, enabling surface smoothing without compromising the structural properties of the core material.
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 effectively reduces surface roughness from micrometer to nanometer dimensions, enabling the production of strong 3D printed items with a smooth surface finish without compromising the core material's integrity, and can be achieved through various heating methods including hot gas, IR radiation, or a heating chamber.
Implementation Method 1
the shell having a lower glass transition temperature (Tg) and melting temperature (Tm) than the core, allowing the outer surface to be heated above its Tg/Tm without melting the core
Implementation Method 2
heating the 3D printed material to a temperature equal to or higher than one or more of the shell glass temperature (Tg2) and the shell melting temperature (Tm2), and lower than one or more of the core glass temperature (Tg1) and the core melting temperature (Tm1)
Implementation Method 3
can be achieved through various heating methods including hot gas, IR radiation, or a heating chamber
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 3A~3C
AI summary
The invention provides a method for manufacturing a 3D item (1) by means of 3D printing. The method comprises the step of depositing, during a printing stage, 3D printable material (201) to provide 3D printed material (202), wherein the 3D printable material (201) comprises a core-shell filament (320) comprising (i) a core (321) comprising a core material (1321) having one or more of a core glass temperature Tg1 and a core melting temperature Tm1 and (ii) a shell (322) comprising a shell material (1322) having one or more of a shell glass temperature Tg2 and a shell melting temperature Tm2, wherein one or more of the shell glass temperature Tg2 and the shell melting temperature Tm2 is lower than one or more of the core glass temperature Tg1 and the core melting temperature Tm1. The method further comprises the step of heating, during a finishing stage, the 3D printed material (202) to a temperature equal to or higher than one or more of the shell glass temperature Tg2 and the shell melting temperature Tm2, and equal to or lower than one or more of the core glass temperature Tg1 and the core melting temperature Tm1.