3D Printing Semi-Crystalline Polymer Crystallization Control
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Solution Overview
Problem
Existing additive manufacturing techniques face challenges in printing dimensionally stable 3D parts using semi-crystalline polymers due to difficulties in controlling crystallization kinetics, leading to issues like curling and sagging, as maintaining a suitable temperature window for annealing these materials is challenging, especially in extrusion-based systems.
Innovation Solution
The method involves using a part material comprising semi-crystalline polymers blended with amorphous polymers that are miscible with them, controlling the crystallization kinetics by maintaining the build environment at specific temperatures between the glass transition temperature and cold crystallization temperature, and optionally reheating the printed parts to enhance crystallinity, thereby reducing residual stresses and improving mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If semi-crystalline polymers are used as part material in additive manufacturing, then mechanical properties of the printed parts are improved, but controlling crystallization kinetics becomes difficult leading to dimensional instability
Solution Approach 1:
The patent applies parameter changes by precisely controlling the build environment temperature within a specific window (between glass transition temperature Tg and cold crystallization temperature Tc) to manage the crystallization kinetics of semi-crystalline polymers. This temperature control prevents unwanted crystallization during printing while maintaining mechanical properties, thereby resolving the contradiction between strength and dimensional stability
Solution Approach 2:
The patent uses composite materials by blending semi-crystalline polymers with amorphous polymers or other secondary materials that retard crystallization. This composite approach allows the material to maintain the mechanical benefits of semi-crystalline structures while suppressing excessive crystallization that causes dimensional instability, thus resolving the technical contradiction
2Strength
If the build environment temperature is maintained for annealing, then residual stresses are reduced and mechanical properties are improved, but the temperature window for annealing is limited
Solution Approach 1:
The patent extends the effective annealing temperature window by maintaining the build environment at temperatures between Tg and Tc, which is a broader and more practical range than conventional annealing. This parameter optimization allows sufficient time for stress relaxation and crystal structure development without causing excessive crystallization, thereby improving mechanical properties while working within practical temperature constraints
Solution Approach 2:
The patent performs preliminary annealing during the printing process itself by maintaining the build environment at the appropriate temperature range. This preliminary action allows residual stresses to be reduced and crystal structures to develop during fabrication, eliminating the need for separate post-processing annealing steps and working effectively within the available temperature window
3Manufacturing precision
If crystallization is retarded using secondary materials, then dimensional stability is improved, but the part material composition becomes more complex
Solution Approach 1:
The patent uses composite materials by formulating part materials that blend semi-crystalline polymers with amorphous polymers or other secondary materials in specific ratios. This composite approach systematically manages crystallization kinetics through material composition rather than process complexity, achieving dimensional stability while maintaining relatively simple processing requirements
Solution Approach 2:
The patent applies local quality by having different materials perform different functions within the blend: semi-crystalline polymers provide mechanical strength while amorphous polymers or secondary materials locally retard crystallization. This functional differentiation within the composite material achieves dimensional stability without requiring complex overall material composition or processing
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 allows for the production of 3D parts with mechanical properties similar to semi-crystalline polymers while minimizing distortions, achieving dimensional stability and relieving residual stresses, and can be applied in various additive manufacturing techniques including extrusion-based, electrophotography-based, and selective laser sintering systems.
Implementation Method 1
melting the part material in the additive manufacturing system
Implementation Method 2
maintaining the build environment at an annealing temperature that is between a glass transition temperature of the part material and a cold crystallization temperature of the part material
Implementation Method 3
controlling crystallization kinetics by maintaining the build environment at specific temperatures between the glass transition temperature and cold crystallization temperature
Data Source
AI summary
A method for printing a three-dimensional part with an additive manufacturing system, which includes providing a part material that compositionally has one or more semi-crystalline polymers and one or more secondary materials that are configured to retard crystallization of the one or more semi-crystalline polymers, where the one or more secondary materials are substantially miscible with the one or more semi-crystalline polymers. The method also includes melting the part material in the additive manufacturing system, forming at least a portion of a layer of the three-dimensional part from the melted part material in a build environment, and maintaining the build environment at an annealing temperature that is between a glass transition temperature of the part material and a cold crystallization temperature of the part material.