3D Printing Semi-Crystalline Polymers Annealing Temperature Control
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Solution Overview
Problem
Additive manufacturing systems 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 conventional temperature windows are narrow and hard to maintain, especially in extrusion-based systems.
Innovation Solution
The method involves using a part material blend of semi-crystalline polymers and amorphous polymers that are miscible, controlling crystallization kinetics by maintaining the build environment at an annealing temperature between the glass transition and cold crystallization temperatures, and optionally reheating the printed parts to induce further crystallization, thereby minimizing residual stresses and achieving desired mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If semi-crystalline polymers are used for printing 3D parts, then mechanical properties are improved, but dimensional stability deteriorates due to uncontrolled crystallization kinetics causing curling and sagging
Solution Approach 1:
The patent changes the temperature parameter by maintaining the build environment at an annealing temperature between the glass transition temperature and cold crystallization temperature of the semi-crystalline polymer. This parameter change controls the crystallization kinetics during printing, allowing the polymer to crystallize slowly and uniformly without causing dimensional instability, while still achieving the desired mechanical properties through controlled crystallinity.
Solution Approach 2:
The patent applies preliminary action by pre-heating the build environment to the annealing temperature before printing begins. This preliminary heating ensures that as each layer is deposited, the semi-crystalline polymer immediately enters a controlled crystallization environment, preventing uncontrolled crystallization that would cause curling and sagging during the printing process itself.
2Productivity
If conventional printing temperatures are used, then printing speed is maintained, but control over crystallization kinetics deteriorates due to narrow temperature windows
Solution Approach 1:
The patent changes the temperature parameter from conventional printing temperatures to a specific annealing temperature range between the glass transition temperature and cold crystallization temperature. This parameter change creates a wider effective temperature window that maintains printing speed while providing reliable control over crystallization kinetics, as the annealing temperature allows sufficient time for controlled crystallization without requiring excessive cooling.
3Loss of time
If rapid cooling is applied after printing, then production time is reduced, but residual stresses increase leading to part distortion
Solution Approach 1:
The patent applies preliminary action by performing the crystallization process during the printing itself through the annealing temperature environment, rather than requiring separate post-processing cooling steps. This preliminary crystallization reduces residual stresses by allowing controlled stress relaxation during deposition, while the gradual crystallization at annealing temperature minimizes thermal shocks that would cause distortion, all within the normal printing timeframe.
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 reducing distortions, achieving dimensional stability and relieving residual stresses, and can be post-processed for enhanced crystallinity and properties.
Implementation Method 1
melting the part material in the additive manufacturing system
Implementation Method 2
solidifies upon a drop in temperature
Implementation Method 3
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 4
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
Data Source
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AI summary
A method for printing a three-dimensional part (30) with an additive manufacturing system (10), 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 (10), forming at least a portion of a layer of the three-dimensional part (30) from the melted part material in a build environment (12), and maintaining the build environment (12) at an annealing temperature that is between a glass transition temperature of the part material and a cold crystallization temperature of the part material.