Semi-Crystalline Polymer Powder for Low-Warp Laser Sintering
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Solution Overview
Problem
Commercially available polymers for laser sintering require meticulous temperature control and result in issues like warping, curling, and reduced recyclability due to narrow temperature windows and rapid crystallization, limiting their practical application in additive manufacturing.
Innovation Solution
Development of a semi-crystalline polymer with specific thermal properties, including a glass transition temperature of at least 70°C, onset melting temperature of at least 125°C, and a heat of fusion of at least 21 J/g, achieved through solvent and thermal annealing processes, allowing it to be used in existing laser sintering printers designed for Nylon 12.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the powder bed temperature is maintained near the recrystallization point to prevent warping, then shape stability is improved, but the sintering process becomes difficult to control and production time increases
Solution Approach 1:
The patent modifies the thermal parameters of the polymer material by selecting specific polymers with optimized glass transition temperatures (Tg) and melting temperatures (Tm). The polymer is designed to have a Tg of 80-120°C and Tm of 160-200°C, creating an expanded processing window. This parameter change allows the powder bed to be maintained at lower temperatures while still achieving proper sintering, thus preventing warping without excessive production time.
Solution Approach 2:
The patent applies preliminary thermal treatment to the polymer material before the sintering process. The polymer is pre-heated to a temperature between Tg and Tm to facilitate controlled crystallization and reduce subsequent warping during cooling. This preliminary action prepares the material in advance to maintain shape stability without requiring excessive temperature control during the actual sintering process.
2Reliability
If the powder bed temperature is increased near the melting point to improve sintering, then fusion quality is improved, but unfused powder partially melts making separation difficult and reducing recyclability
Solution Approach 1:
The patent changes the thermal parameters of the polymer to have a broader melting range and optimized Tm between 160-200°C. This parameter modification allows sintering to occur at lower temperatures where unfused powder remains stable and does not partially melt. The fusion quality is maintained through the optimized polymer structure rather than high temperature, preserving material recyclability.
Solution Approach 2:
The patent introduces an intermediary thermal treatment step where the polymer is heated to a temperature below Tm to achieve partial crystallization before sintering. This intermediary state allows the polymer to have improved fusion characteristics during sintering while remaining stable at lower temperatures, preventing unwanted melting of unfused powder and maintaining recyclability.
3Adaptability or versatility
If conventional polymers are used in laser sintering, then existing equipment can be utilized, but meticulous temperature control is required resulting in warping, curling, and reduced recyclability
Solution Approach 1:
The patent fundamentally changes the thermal parameters of the polymer material with Tg of 80-120°C and Tm of 160-200°C, creating a material that is inherently more stable during the sintering process. This parameter change eliminates the need for meticulous temperature control while maintaining compatibility with existing laser sintering equipment, thereby improving dimensional accuracy without sacrificing adaptability.
Solution Approach 2:
The patent develops a composite polymer system that combines specific polyesters or copolyesters with controlled crystallization properties. This composite material integrates multiple functional characteristics: equipment compatibility, warping resistance, and recyclability. The composite nature of the material provides built-in stability that reduces manufacturing precision issues while maintaining versatility across existing equipment platforms.
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 semi-crystalline polymer enables stable printing with reduced warping and curling, improving process control and recyclability, while maintaining compatibility with existing laser sintering equipment.
Implementation Method 1
irradiating selected or desired part locations/shape with laser energy to sinter those portions
Implementation Method 2
heating a portion of the material; irradiating selected or desired part locations/shape with laser energy to sinter those portions
Implementation Method 3
the temperatures required to consolidate the powder after laser exposure would require impractical, long laser irradiation and long print times
Implementation Method 4
the temperature-related and/or temperature-dependent characteristics and parameters of the polymer powder such as glass transition temperature, melt temperature, crystallinity and rate of crystallization
Implementation Method 5
glass transition temperature, measured by scanning at 20°C/min using DSC
Data Source
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AI summary
A build material for additive manufacturing applications is disclosed. The build material includes a build composition in powder form, The build composition includes a semi-crystalline polymer having a glass transition temperature of at least 70° C and an onset melting temperature of at least 125°C, as measured by DSC, and that exhibits an amorphous return. A semi- crystalline polymer useful in additive manufacturing applications and a method for making the semi-crystalline polymer article are also described.