Electrostatic 3D Printer with Addressable UV Crosslinking
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Solution Overview
Problem
In three-dimensional (3-D) printing using electrostatic processes, the mechanical integrity of thin printed materials is compromised, and the transfer process can impose stripping shear forces, making it difficult to separate build and support materials with similar melt rheological properties, which limits the selection of materials and affects the mechanical properties of the printed parts.
Innovation Solution
The method combines electrostatic printing with addressable LED curing, using a single uniform UV radiation curable toner material for both build and support portions, where only the build portions are exposed to UV light to be crosslinked, allowing for selective separation of the support material after printing, and utilizing LEDs for efficient and cost-effective curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If electrostatic printing process is used to transfer materials, then printing speed and efficiency are improved, but mechanical integrity of thin printed materials is compromised due to stripping shear forces
Solution Approach 1:
The process segments the transfer operation into two distinct stages: first transferring both build and support materials to an intermediate transfer surface, then selectively transferring only the build material to the final substrate. This segmentation allows the support material to remain on the intermediate surface during the first transfer, avoiding the stripping shear forces that would damage thin printed materials, while still enabling high-speed electrostatic printing.
Solution Approach 2:
An intermediate transfer surface is introduced as a mediator between the printing system and the final substrate. This intermediate surface temporarily holds both build and support materials after the first electrostatic transfer, allowing selective processing without directly transferring the fragile thin layers to the final substrate in one step, thereby protecting mechanical integrity while maintaining printing efficiency.
2Adaptability or versatility
If build and support materials have similar melt rheological properties, then material selection flexibility is improved, but separation difficulty increases due to similar properties
Solution Approach 1:
The patent applies local quality by treating build and support materials differently through selective UV irradiation. Both materials are deposited with similar properties for flexibility, but then only the build material is exposed to UV light, creating a local chemical difference (crosslinked vs. uncrosslinked) that enables easy separation despite the materials' initially similar rheological properties.
Solution Approach 2:
The patent changes the chemical parameter of the build material by applying UV irradiation to induce crosslinking, while leaving the support material unchanged. This parameter change (from uncrosslinked to crosslinked state) creates a fundamental difference between the two materials, allowing easy separation through selective dissolution or mechanical means despite their similar base properties.
3Strength
If UV light is applied to crosslink polymers in build material, then mechanical properties are improved, but support material may be inadvertently crosslinked
Solution Approach 1:
The process segments the crosslinking operation from the transfer operation. First, both materials are transferred to the intermediate surface without crosslinking. Then, after the build material is selectively transferred to the final substrate, UV irradiation is applied only to the build material on the substrate. This segmentation ensures that only the build material is crosslinked, preventing inadvertent crosslinking of the support material that remains on the intermediate surface.
Solution Approach 2:
The intermediate transfer surface acts as a mediator that physically separates the build material from the support material during the crosslinking stage. By holding the support material on the intermediate surface while transferring the build material to the final substrate, the intermediate surface prevents UV light from reaching and crosslinking the support material, ensuring selective crosslinking control.
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 enhances the mechanical properties of the printed parts by maintaining the integrity of both build and support materials, improving strength and impact resistance, while allowing for faster and more cost-effective 3-D printing with reduced material complexity and cost.
Implementation Method 1
The LED curing station selectively applies the LED ultraviolet light to the layer to crosslink polymers together in portions of the layer that are to be the build material
Implementation Method 2
After being transfused to the platen or to the top of the existing freestanding stack on the platen, a fusing station applies heat and pressure to fuse the layers on the platen together
Implementation Method 3
The electrostatic (electro-photographic) process is a well-known means of generating two-dimensional digital images, which transfer materials onto an intermediate surface
Data Source
AI summary
A 3-D printer includes a development station positioned to electrostatically transfer layers of material to an intermediate transfer surface, and a transfuse station adjacent the intermediate transfer surface. The transfuse station is positioned to receive the layers as the intermediate transfer surface moves past the transfuse station. Also, a platen is included that moves relative to the intermediate transfer surface. The intermediate transfer surface transfers a layer of the material to the platen each time the platen contacts one of the layers on the intermediate transfer surface at the transfuse station to successively form a freestanding stack of the layers on the platen. A curing station is positioned to apply ultraviolet light to each layer, after each layer is transferred from the transfuse station to the platen. The curing station selectively applies the ultraviolet light to crosslink polymers only in a portion of the material within the layer.