Seite - 146 - in 3D Printing of Metals

Metals 2016,6, 313 manufacturing.Moreover,astatistical investigationonthesurfacefinishof fabricatedspecimenswas alsoperformed. 2. ExperimentalProcedure In order to increase the productivity and reduce cost, a novel metal micro-coating technology—micro-coatingmetal additivemanufacturing (MCMAM)—was proposed. A special micro-coatingnozzlewasdesigned.Moltenmetal is transportedfromthechannelof the fused-coating nozzle to the region between the horizontal moving substrate and the thermal capillary flow. When themelt contacts the substrate or pre-solidified layers, cooling and solidification begin at the interfaceof themeltandsubstrate. Thesolidifiedstructurewillkeepmovingat thesamespeed and in the samedirectionas the substrate. The rapidlymovingandadvancing solidification front under cooling conditionswill produce strong shear stress in themelt near the solidification front. Moreover, the interfacial shear stressmay be able to shed the newly formeddendrites. The new formingprocesscansignificantlyenhancemetal formingefficiency.Asaresult, it isespeciallysuitable for the fabricationof largestructures inaerospace, theautomobile industry,andnationaldefense. 2.1. ExperimentalSystem Aschematic illustrationof theprincipleof theMCMAMprocessandexperimentalplatformis presented inFigure1a. TheequipmentofMCMAMincludesapressurecontrol system,anargongas protectionsystem,andamachinecontrolsystemonthebasisofamovableplatform.Inthisexperiment, theMCMAMwasusedto formspecimensbycontrolling themotionof the3Dplatforminaccordance withdata information. The3DplatformsystemhasaPMAC(programmablemulti-axiscontroller). Underthecombinedactionofgaspressure,hydrostaticpressure,andsurfacetension, themoltenmetal flowsthroughthechannel in the fused-coatinghead,asshowninFigure1b,c. Figure1. (a)Moltenmetalmicro-coatingequipmentschematicdiagram. (b)Nozzlepracticalitypicture. (c)Moltenmetalmicro-coatingequipmentpracticalitypicture. 146