Low-Temperature Powder Additive Manufacturing Using Fusible Polyurethane
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Solution Overview
Problem
Powder-based additive manufacturing processes face challenges in achieving homogeneous material properties due to temperature gradients and irregular morphology of semi-crystalline polymers, leading to brittle components with inadequate mechanical properties.
Innovation Solution
A method involving the use of a meltable polyurethane polymer with a specific melting range and complex viscosity, applied in a controlled temperature chamber to reduce deformations and porosity, allowing for the production of components with improved mechanical properties and reduced tackiness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If laser sintering or high speed sintering is used to process semi-crystalline polymers, then the particles can be selectively melted and bonded to form objects, but the resulting components become brittle with inadequate mechanical properties due to irregular morphology and temperature gradients
Solution Approach 1:
The patent changes the temperature parameter by maintaining isothermal conditions (20°C to 80°C) throughout the chamber, eliminating temperature gradients that cause irregular morphology. It also changes the polymer type from semi-crystalline to amorphous polymers with lower glass transition temperatures, fundamentally altering the material's thermal and mechanical behavior to achieve ductile, reliable components
Solution Approach 2:
The patent utilizes the glass transition phase transition of amorphous polymers instead of melting semi-crystalline polymers. By heating above the glass transition temperature (Tg) and then cooling, the polymer transitions from a rigid glassy state to a rubbery state and back, enabling particle bonding while maintaining homogeneous morphology and avoiding the brittleness associated with crystalline structures
2Productivity
If high energy is applied to melt particles quickly, then productivity increases, but temperature gradients cause irregular morphology and reduced manufacturing precision
Solution Approach 1:
The patent changes the energy application parameters by using lower temperatures (20°C to 80°C) and longer processing times to achieve gradual heating and cooling. This eliminates thermal shocks and temperature gradients, ensuring uniform morphology throughout the component while maintaining productivity through efficient isothermal processing
Solution Approach 2:
The patent applies preliminary heating of the entire chamber to the processing temperature before selective energy application. This pre-heating step ensures uniform temperature distribution throughout the powder bed, preventing localized overheating and morphology irregularities during subsequent selective melting or glass transition processing
3Adaptability or versatility
If conventional polymers are used in powder-based additive manufacturing, then the process can be performed with available materials, but the processed objects lose the characteristic properties of the original materials
Solution Approach 1:
The patent changes the processing parameters to lower temperatures (20°C to 80°C) that match the glass transition temperatures of amorphous polymers. This allows conventional amorphous polymers like polystyrene, polycarbonate, and acrylic to be processed while retaining their characteristic mechanical properties, as the gentler processing avoids the degradation and morphology irregularities caused by high-temperature sintering
Solution Approach 2:
The patent utilizes amorphous polymers as composite powder materials that combine the advantages of conventional polymer properties with additive manufacturing capabilities. By selecting amorphous polymers with appropriate Tg values and processing them under isothermal conditions, the resulting components maintain the ductility, toughness, and other characteristic properties of the original polymers while enabling complex geometry fabrication
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 method enables the production of components with enhanced mechanical properties and reduced deformations, avoiding warping and caking, while maintaining low processing temperatures, thus improving the economic viability and quality of the materials.
Implementation Method 1
applying energy to a selected portion of the layer, corresponding to a cross section of the object, in a chamber so that the particles in the selected portion are bonded
Implementation Method 2
at least a portion of the particles comprising a fusible polymer
Implementation Method 3
the particles in the selected portion are bonded
Data Source
AI summary
A process for manufacturing an article comprises the steps of: applying a layer that consists of particles to a target area; allowing, in a chamber, energy to act on a selected portion of the layer, according to a cross-section of the article, so that the particles in the selected portion are bonded, and repeating the steps of applying and allowing energy to act for a plurality of layers so that the bonded portions of the adjacent layers are bonded to form the article, at least part of the particles comprising a fusible polymer. The fusible polymer has a fusion range (DSC, differential scanning calorimetry; 2nd heating at a heating rate of 5 K/min.) of ≥ 20 °C to ≤ 100 °C. The fusible polymer further has a complex viscosity \η*\ (determined by viscosity measurement in the melt using a plate-plate oscillating viscometer according to ISO 6721-10 at 100 °C and a shear rate of 1/s) of ≥ 10 Pas to ≤ 1000000 Pas. Finally, the temperature inside the chamber is ≤ 50°C. The invention also relates to an article manufactured by the process according to the invention, to an article having a substrate and to an article bonded to the substrate, the article being in the form of an adhesive joint or varnish region, and to the use of a particular polyurethane in powder-based additive manufacturing processes.