The additive manufacturing technique of laser direct metal deposition (DMD) has had an impact in rapid prototyping, tooling and small-volume manufacturing applications. Components are built from metallic materials that are deposited by the continuous injection of powder into a moving melt pool, created by a defocused laser beam. The size of the melt pool, the temperature distributions around it and the powder flux are critical in determining process characteristics such as deposition rate. In this paper, the effects that changes in the distance between the laser deposition head and the melt pool have on these factors as a part is built using a coaxial powder feeding system are considered via a two-part analytical model. A heat flow model considers three-dimensional temperature distributions due to a moving Gaussian heat source in a finite volume and a simple mass-flow model considers changes in powder concentration with distance from the deposition head. The model demonstrates the effect of adjusting the melt pool standoff in different ways on melt pool and powder flow characteristics as a DMD structure is built, and hence allows the effect on build rate to be predicted. Its validity is verified by comparison with a series of 316L stainless steel walls, built using different standoff adjustment methods. The model is found to be able to explain the dimensional characteristics found.
MazumderJ.KarA.Nonequilibrium processing with lasers. World Laser Almanac, 1988, 1, 17–24.
2.
PustovalovV. K.BobuchenkoD. S.Thermal processes in gas-powder laser cladding of metal materials. Int. J. Heat and Mass Transfer, 1993, 36(9), 2449–2456.
3.
HoadleyA. F. A.RappazM.A thermal model of laser cladding by powder injection. Metall. Trans. B (Process Metallurgy), 1992, 23B, 631–642.
4.
VasinontaA.BeuthJ.GriffithM.Process maps for laser depositio of thin-walled structures. In Proceedings of the 10th Solid Freeform Fabrication Symposium, Austin, Texas, 1999, pp. 383–391.
5.
VasinontaA.BeuthJ.GriffithM.Process maps for controlling residual stress and melt pool size in laser-based SFF processes. In Proceedings of the 11th Solid Freeform Fabrication Symposium, Austin, Texas, 2000, pp. 200–208.
6.
VasinontaA.BeuthJ. L.OngR.Melt pool size control in thin-walled and bulky parts via process maps. In Proceedings of the 12th Solid Freeform Fabrication Symposium, Austin, Texas, 2001, pp. 432–440.
7.
VasinontaA.BeuthJ. L.GriffithM. L.A process map for consistent build conditions in solid freeform fabrication of thin-walled structures. Trans. ASME, J. Mfg Sci. Engng, 2001, 123, 615–622.
8.
PicassoM.HoadleyA. F. A.Finite element simulation of laser surface treatments including convection in the melt pool. Int. J. Num. Meth. Heat and Fluid Flow, 1994, 4(1), 61–83.
9.
HuD.MeiH.KovacevicR.Improving solid freeform fabrication by laser-based additive manufacturing. Proc. Instn Mech. Engrs, Part B: J. Engineering Manufacture, 2002, 216(B9), 1253–1264.
10.
MeriaudeauF.TruchetetF. B.Image processing applied to the laser cladding process. Proc. Soc. Photo-opt. Instrum. Engrs (SPIE), 1996, 2789, 93–103.
11.
YangL. X.PengX. F.WangB. X.Numerical modeling and experimental investigation on the characteristics of molten pool during laser processing. Int. J. Heat and Mass Transfer, 2001, 44(23), 4465–4473.
12.
ChanC. L.MazumderJ.ChenM. M.Three-dimensional model for convection in laser weld pool. In Proceedings of International Congress on Applications of Lasers and Electro-optics (ICALEO'84), Boston, Massachusetts, 1984, Vols 43–48, pp. 17–27.
13.
HoadleyA. F. A.RappazM.ZimmermannM.Heat-flow simulation of laser remelting with experimental validation. Metall. Trans. B: Process Metallurgy, 1991, 22(1), 101–109.
14.
HofmeisterW.GriffithM.EnszM.SmugereskyJ.Solidification in direct metal deposition by LENS processing. J. Metals (JOM), 2001, 53(9), 30–34.
15.
GeddaH.PowellJ.WahlstromG.LiW.-B.EngstromH.MagnussonC.Energy redistribution during CO2 laser cladding. J. Laser Applic., 2002, 14(2), 78–82.
16.
NoeckerF. F.IIDuPontJ. N.Functionally graded copper-steel using LENS™ process. In Proceedings of the Minerals, Metals and Materials Society (TMS) Fall Meeting, 2002, pp. 139–147.
17.
American Society of Mechanical Engineers (ASME)ASM Speciality Handbook—Stainless Steels, 1994, p. 10 (ASM International, Metals Park, Ohio).
18.
NetoDiniz O. O.VilarR.Physical-computational model to describe the interaction between a laser beam and a powder jet in laser surface processing. J. Laser Applic., 2002, 14(1), 46–51.
19.
PinkertonA. J.LiL.Rapid prototyping using direct laser deposition—the effect of powder atomization type and flowrate. Proc. Instn Mech. Engrs, Part B: J. Engineering Manufacture, 2003, 217(B6), 741–752.
20.
LinJ.SteenW. M.Powder flow and catchment during coaxial laser cladding. Proc. Soc. Photo-opt. Instrum. Engrs (SPIE), 1997, 3097, 517–528.
21.
PicassoM.MarsdenC. F.WagniereJ.-D.FrenkA.RappazM.Simple but realistic model for laser cladding. Metallurgical Trans. B (Process Metallurgy), 1994, 25(2), 281–291.
22.
LinJ.Numerical simulation of the focused powder streams in coaxial laser cladding. J. Mater. Processing Technol., 2000, 105(1), 17–23.
23.
PinkertonA. J.LiL.A verified model of the axial powder stream concentration from a coaxial laser cladding nozzle. In Proceedings of International Congress on Applications of Lasers and Electro-optics (ICALEO'02), Scottsdale, Arizona, 2002, U19SA CD.
24.
PinkertonA. J.LiL.Modelling powder concentration distribution from a coaxial deposition nozzle for laser-based rapid tooling. Trans. ASME, J. Mfg Sci. Engng, 2004, 126(1), 34–42.
25.
LiW.-B.EngstromH.PowellJ.TanZ.MagnussonC.Redistribution of the beam powder in laser cladding by powder injection. Lasers in Engng, 1996, 5(3), 175–183.
26.
BeuthJ.KlingbeilN.The role of process variables in laser-based direct metal solid freeform fabrication. J. Metals (JOM), 2001, 53(9), 36–39.
27.
BornefeldH.Temperature measurement in fusion welding (in German). Technische Zentralblatt fur Praktische Metallberbeitung, 1933, 43, 14–18.
28.
ThompsonM. E.SzekelyJ.Transient behavior of weldpools with a deformed free surface. Int. J. Heat and Mass Transfer, 1989, 32(6), 1007–1019.
29.
LeiY. P.MurakawaH.ShiY. W.LiX. Y.Numerical analysis of the competitive influence of Marangoni flow and evaporation on heat surface temperature and molten pool shape in laser surface remelting. Comput. Mater. Sci., 2001, 21(3), 276–290.
30.
JaegerJ. C.Moving sources of heat and the temperature at sliding contacts. Proc. R. Soc. NSW, 1942, 76, 203–224.
31.
CarslowH. S.JaegerJ. C.Conduction of Heat in Solids, 2nd edition, 1959 (Oxford University Press, Oxford).
32.
TianT.KennedyF. E.Jr.Maximum and average flash temperatures in sliding contacts. Trans. ASME, J. Tribology, 1994, 116(1), 167–174.
33.
ClineH. E.AnthonyT. R.Heat treating and melting material with a scanning laser or electron beam. J. Appl. Physics, 1977, 48(9), 3895–3900.
34.
RosenthalD.The theory of moving sources of heat and its application to metal treatments. Trans. ASME, 1946, 68(11), 849–866.
35.
McLeanM. A.ShannonG. J.SteenW. M.Mouldless casting by laser. Proc. Soc. Photo-opt. Instrum. Engrs (SPIE), 1997, 3102, 131–141.
36.
DausingerF.ShenJ.Energy coupling efficiency in laser surface treatment. Iron and Steel Inst. Japan (ISIJ) Int., 1993, 33(9), 925–933.
37.
SteenW. M.WeerasingheV. M.MonsonP.Some aspects of the formation of laser clad tracks. Proc. SPIE, 1986, 650, 226–234.
38.
EagerT. W.TsaiN. S.Tempeature fields produced by travelling distributed heat sources. Weld. J., 1983, 62(12), 346s–355s.
39.
DoumanidisC.KwakY.-M.Geometry modeling and control by infrared and laser sensing in thermal manufacturing with material deposition. Trans. ASME, J. Mfg Sci. Engng, 2001, 123, 45–52.
40.
MeriaudeauF.TruchetetF.GreveyD.VannesA. B.Laser cladding process and image processing. Lasers in Engng, 1997, 6, 161–187.
41.
BambergerM.GelerM.Energy coupling between CO2-laser irradiation and metallic substrates. Lasers in Engng, 1997, 6(3), 213–234.
