Page - 87 - in 3D Printing of Metals

metals Article ALightweightStructureRedesignMethodBasedon SelectiveLaserMelting LiTang,ChunbingWu*,ZhixiongZhang, JianzhongShangandChaoYan CollegeofMechatronicsandAutomation,NationalUniversityofDefenseTechnology,Changsha410073,China; tangli@nudt.edu.cn(L.T.); zzxnudt2010@sina.com(Z.Z.); jz_shang_nudt@163.com(J.S.); mech_yan@foxmail.com(C.Y.) * Correspondence:wuchunbing14@nudt.edu.cn;Tel.:+86-155-7086-4869 AcademicEditor:ManojGupta Received: 10September2016;Accepted: 1November2016;Published: 16November2016 Abstract:Thepurposeof thispaper is topresentanewdesignmethodof lightweightparts fabricated byselective lasermelting(SLM)basedonthe“Skin-Frame”andtoexploretheinfluenceof fabrication defectsonSLMpartswithdifferent sizes. Somestandard latticepartsweredesignedaccordingto the ChineseGB/T1452-2005standardandmanufacturedbySLM.Thenthesesampleswere tested inan MTSInsight30compressiontestingmachine tostudythe trendsof theyieldprocesswithdifferent structuresizes.AsetofstandardcylindersampleswerealsodesignedaccordingtotheChineseGB/T 228-2010standard. Thesesamples,whichweremadeof iron-nickelalloy(IN718),werealsoprocessed bySLM,and then tested in theuniversalmaterial testingmachine INSTRON1346 toobtain their tensile strength. Furthermore,a lightweight redesignedmethodwasresearched. Thensomecommon partssuchasastopperandconnectingplatewereredesignedusingthismethod. Theseredesigned partswere fabricatedandsomeapplication testshavealreadybeenperformed. Thecompression testingresults showthatwhen theminimumstructure size is larger than1.5mm, themechanical characteristicswillhardlybeaffectedbyprocessdefects. Thecylinderpartswere fracturedbythe universalmaterial testingmachine at about 1069.6MPa. These redesignedpartsworkedwell in applicationtests,withboth theweightandfabricationtimeof theseparts reducedmore than20%. Keywords: 3Dprinting; selective lasermelting (SLM);part redesign; SLMstructureperformance; framestructurereconstruction 1. Introduction There is an increasing demand for lightweight parts in the aerospace, automotive, medical industries andotherfieldswithgoodmechanical characteristics andshortermanufacturing times. However, there are often redundantmaterials in conventional parts because of the conventional manufacturingprocesses’ inherent restrictions,whichmake itdifficult togeta lightweightcomponent. Selective lasermelting(SLM)isanadditivemanufacturing(AM)processwhichcandirectlymake complexthree-dimensionalmetalpartsaccordingtoComputerAidedDesign(CAD)databyselectively melting successive layersofmetalpowders [1]. It is analternative to conventionalmanufacturing processes[2,3]. Thetool-less fabricationandgeometric freedomofferedbySLMshowgreatpotential to makeadvancedlightweightstructuresandproductswhicharehighlydesiredbyengineeringsectors. Itpermitsnewdesignmethods for lightweightstructures thatwerenotpossiblebeforebecauseof the limitationsofconventionalmanufacturingprocesses. Currently, there are some approaches for lightweight parts design with the use of SLM. Amongallof themethods, thedesignofcellular structuresandstructure topologicaloptimizationare verycommon. Metals 2016,6, 280 87 www.mdpi.com/journal/metals