Systems and methods for designing and fabricating support structures for overhang geometries of parts in additive manufacturing
Inventors
Chou, Yuag-Shan • Cooper, Kenneth
Assignees
Alabma, University of, Trustees of • National Aeronautics and Space Administration NASA • University of Alabama at Birmingham UAB
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Publication Number
US-10010936-B2
Publication Date
2018-07-03
Expiration Date
2035-11-13
Abstract
Systems and methods are provided for designing and fabricating contact-free support structures for overhang geometries of parts fabricated using electron beam additive manufacturing. One or more layers of un-melted metallic powder are disposed in an elongate gap between an upper horizontal surface of the support structure and a lower surface of the overhang geometry. The powder conducts heat from the overhang geometry to the support structure. The support structure acts as a heat sink to enhance heat transfer and reduce the temperature and severe thermal gradients due to poor thermal conductivity of metallic powders underneath the overhang. Because the support structure is minimally or not connected to the part, the support structure can be removed with minimal or no post-processing step.
Core Innovation
Systems and methods are provided for designing and fabricating contact-free support structures for overhang geometries of parts fabricated using electron beam additive manufacturing (EBAM). The invention involves disposing one or more layers of un-melted metallic powder within an elongate gap between an upper horizontal surface of the support structure and a lower surface of the overhang geometry. The powder conducts heat from the overhang to the support structure, which acts as a heat sink to enhance heat transfer, reduce part temperature, and alleviate severe thermal gradients caused by the poor thermal conductivity of metallic powders underneath the overhang.
Conventional support structures in EBAM are bonded to the part’s overhang geometry, requiring mechanical removal post-fabrication. This post-processing is laborious, time-consuming, and degrades surface quality. The disclosed contact-free support structures minimize or eliminate direct connection to the part, facilitating support removal with minimal or no additional processing.
Claims Coverage
The patent includes one independent claim that defines the article of manufacture comprising a primary part with at least one overhang portion and a secondary support structure fabricated simultaneously with the part.
Contact-free support structure with elongate gap
An article comprising a primary part with an overhang portion having a lower surface, and a secondary support structure that includes a parallel support portion substantially parallel to the lower surface, and at least one substantially vertical support portion extending between the parallel support portion and the lower surface of the overhang. An elongate gap is defined between the upper surface of the parallel support portion and the lower surface of the overhang, with un-melted metallic powder disposed within the gap.
Minimal contact area between support and overhang
The at least one vertical support portion has a first surface area in contact with the lower surface of the overhang, and the ratio of this first contact surface area to the total lower surface area of the overhang is less than or equal to about 0.02.
Vertical support portion perimeter ratio
The vertical support portion has a first outer perimeter length around the contact surface area, and the lower surface of the overhang has a second outer perimeter length, wherein the ratio of the first to the second is less than or equal to about 0.13.
Secondary part includes lower vertical support portions
The support structure further includes lower vertical support portions extending from the parallel support portion to the build plate, configured to conduct heat from the parallel support portion to the build plate.
Support structure orientation and features
The parallel support portion and elongate gap are either substantially parallel to the build plate or disposed at an angle greater than 0°. Lower vertical support portions may comprise legs or side walls spaced apart and extending between the parallel support portion and the build plate.
Heat conduction without fusion
The un-melted powder in the gap is configured to conduct heat from the overhang to the secondary support part without causing fusion between the part and support structure during the single fabrication process.
Fabrication process
The entire structure, including the part and the support structure, is fabricated in one process using electron beam additive manufacturing where un-melted powder layers are disposed layer-by-layer within the gap to prevent fusion while allowing heat conduction.
The independent claim covers an article with a primary part having overhang geometry supported by a contact-free or minimally contacting support structure fabricated simultaneously using EBAM. The support structure features an elongate gap filled with un-melted powder that conducts heat but prevents fusion, with low contact surface area ratios and vertical support features aiding heat conduction to the build plate.
Stated Advantages
Eliminates overhang-associated defects such as warping and curling.
Requires minimal or no post-processing removal of support structures, reducing labor and time.
Improves process performance and simplifies support structure design.
Enhances part quality by reducing thermal gradients and thermal stresses during fabrication.
Documented Applications
Use in electron beam additive manufacturing (EBAM) of metallic parts with overhanging geometries.
Fabrication of parts with cantilevered overhangs or undercut portions to prevent defects during powder-based additive processes.
Design and manufacture of contact-free support structures to act as heat sinks and improve heat dissipation under overhang portions.
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