Layered Manufacturing of Thin-Walled PartsIs Layered Manufacturing really Rapid Prototyping?Raster Scan TechnologiesVector Scan TechnologiesBuilding Solid Parts with QuickSliceQuickSlice Fast BuildFast Build LimitationsCan Approach Be More Aggressive?Idea #1: 3D Offset PipelineIdea #2: Approximate 3D Offset2D Contour Offset2½D Polyhedron OffsetRegularized Boolean Operations1-Layer Thick 2½D OffsetSlide 15Slide 16n-Layer Thick 2½D OffsetSlide 18Slide 19Results: the Bolt PartConclusionThanks to our Sponsors2D Contour Offset ImplementationVoronoi Diagram of a ContourVoronoi MountainOffset SlicingDragon Curve ExampleLayered Manufacturing of Thin-Walled PartsSara McMains, Jordan Smith, Jianlin Wang, Carlo SéquinUC BerkeleyIs Layered Manufacturing really Rapid Prototyping?•How can we speed up these manufacturing technologies?3.5”, 20hrs 3.0”, 25 hrs2.5”, 15hrsRaster Scan Technologies•Example: 3D Printing•Speed of roller limits the process•Build time = z-height•Speed up: pack build volume in xy with many partsVector Scan Technologies•Example: FDM (Fused Deposition Modeling)•Build time = volume scanned (material used)•Our Goal: create a sturdy part that is visually equivalent but uses less material, so that it builds fasterBuilding Solid Parts with QuickSlice•Software interface to Stratasys 1650 FDM Machine•Input: STL boundary representation•Slices model into z-layer contours (SSL)•Builds support structure•Builds roads (nozzle fill path) (SML)FDMRoadsSML3D B-RepSTLSupportSlicerQuickSliceSSLQuickSlice Fast Build•Builds a semi-hollow version of the solid •n solid offset rings•Center filled with a loose crosshatch patternFDMRoadsSML3D B-RepSTLSupportSlicerQuickSliceSSLFastFast Build Limitations•Structurally conservative•Only applied to slice layers whose center area is completely covered by slices above and below it•Gradually sloping surfaces prevent its application•Worst case examplezCan Approach Be More Aggressive?•Our Goal: –Create an automated process –Input: the boundary representation of a desired solid geometry –Output: a sturdy, physical part that is visually equivalent while using less material–Benefits: faster build times and material conservation•Our Assets: –QuickSlice software as a black box–Specifically the loose fill crosshatched roads optionSML3D B-RepFDMAutomated Process?Idea #1: 3D Offset Pipeline•Solid-fill the volume between the input and the offset surfaces•Crosshatch-fill the volume within the offset surfacePolyhedronOffsetFDMQuickSliceSML3D B-RepSTLUnfortunately, the 3D offset is difficult to implement robustly!Assume we have true 3D offset surface at the desired distance inwardzIdea #2: Approximate 3D Offset•Key ideas:–Offsetting is much simpler in 2D than in 3D–The manufacturing process eventually represents the part as a stack in z of layers of 2D contours•Start: slice polyhedron into desired set of 2D contours•End: input SSL to QuickSlice to build support and roadsSMLSlices3D B-RepSlicerFDMRoadsSupportSlicerQuickSliceSSL2D Contour Offset•Data: layers of 2D contours•Offset the 2D contours inward by a specified distance = n layer thicknesses•Near vertical walls, this is the correct 3D offset•Approximation degrades as the walls approach horizontalSlices3D B-RepOffsetsSlicerContourOffsetSMLSSLFDMRSSQuickSlice2½D Polyhedron Offset•Data: layers of 2D contours and offsets•Adjust the loose fill areas in regions where the vertical coverage above or below is less than n layers thick–Perform 2D boolean (CSG) combinations of the contours and offsets of the ith layer with the n layers above and below it–We use OpenGL for the 2D booleansSMLSSLSlices3D B-RepOffsets2½DCSGSlicerFDMContourOffsetRSSQuickSliceRegularized Boolean Operations•Unregularized: op { , , - }•Regularized: op* { *, *, -* }•A op* B = Closure( Interior( A o p B ) )•If A & B are 2D areas and C = A op* B then C is a non-degenerate 2D area or B A * BA A B 11 iiiiSSSSB1-Layer Thick 2½D Offset iSA Offset 11OffsetOffsetiiiSSSCCBAShell z 11 iiiiSSSSB1-Layer Thick 2½D Offset iSA Offset 11OffsetOffsetiiiSSSCCBAShell z 11 iiiiSSSSB1-Layer Thick 2½D Offset iSA Offset 11OffsetOffsetiiiSSSCCBAShell zn-Layer Thick 2½D Offset UUnkkikinkkikiiSSSSSB1111' UUnkkinkkiiSSSC11OffsetOffset''' CBAShell iSA Offsetzn-Layer Thick 2½D Offset UUnkkikinkkikiiSSSSSB1111' UUnkkinkkiiSSSC11OffsetOffset''' CBAShell iSA Offsetzn-Layer Thick 2½D Offset UUnkkikinkkikiiSSSSSB1111' UUnkkinkkiiSSSC11OffsetOffset''' CBAShell iSA OffsetzResults: the Bolt Part•QuickSlice Fast Build–Time: 504 min (8:24)–Filament used: 22.1 m•2½D Offset Method–Time: 232 min (3:52)–Filament used: 7.6 mQuickSlice took 2.71 times as long and used 2.9 times as much filamentConclusion•We have implemented a robust 2D contour offsetting program.•We have conservatively approximated the 3D polyhedron offset using 2D contour slices, 2D offsets, and 2½D boolean operations.•We have demonstrated a novel approach to speeding up FDM manufacturing. –Our approach decomposes the desired geometry into a thin sturdy outer shell with a loosely filled center volume.–Our approach saves time and material as compared to the built-in QuickSlice solution.Thanks to our Sponsors•NSF–CyberCut–CADRE:•MOSIS++: A Distributed Manufacturing Resource (EIA-9905140)•Ford Motor Co.2D Contour Offset Implementation•Difficulties arise from global interactions•Robust approach based on Voronoi diagram–Generalization of the approach described by
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