Hole-defects in soluble core assisted aluminum droplet printing: Metallurgical mechanisms and elimination methods

Abstract Using droplet-based 3D printing to directly fabricate microwave devices with smooth inner surfaces remains an elusive goal, because of the naturally scalloped shapes of solidified droplets and the staircase effect in 3D printing. In order to address this issue, a novel manufacturing process involving deposition of molten metal droplets on soluble cores is proposed. However, complete elimination of hole-defects formed during this manufacturing process is very challenging. This paper presents the study on the transport phenomena among four neighboring droplets using both numerical modeling and experimental methods. The formation mechanisms of hole-defects and their elimination are also discussed. The results show that the hole-defects on the inner surfaces are caused by the incomplete fusion and filling of residual liquid metal between neighboring droplets. Furthermore, these defects can be effectively eliminated by selecting the proper temperatures of droplets and substrates. Finally, a modified parameter mapping of solidified morphologies about the inner surfaces is established to help with printing temperature selection.

[1]  Chao Sun,et al.  Toward 3D Printing of Pure Metals by Laser‐Induced Forward Transfer , 2015, Advanced materials.

[2]  Hejun Li,et al.  Influence of Interfacial Bonding between Metal Droplets on Tensile Properties of 7075 Aluminum Billets by Additive Manufacturing Technique , 2016 .

[3]  Weng-Sing Hwang,et al.  Investigation of molten metal droplet deposition and solidification for 3D printing techniques , 2016 .

[4]  Lehua Qi,et al.  3D numerical simulation of successive deposition of uniform molten Al droplets on a moving substrate and experimental validation , 2012 .

[5]  Jun Luo,et al.  Direct fabrication of unsupported inclined aluminum pillars based on uniform micro droplets deposition , 2017 .

[6]  Ibrahim T. Ozbolat,et al.  A comprehensive review on droplet-based bioprinting: Past, present and future. , 2016, Biomaterials.

[7]  R. Rumpf,et al.  Effects of extreme surface roughness on 3D printed horn antenna , 2013 .

[8]  Javad Mostaghimi,et al.  A three-dimensional model of droplet impact and solidification , 2002 .

[9]  J. Brackbill,et al.  A continuum method for modeling surface tension , 1992 .

[10]  Ehsan Toyserkani,et al.  A hybrid additive manufacturing method for the fabrication of silicone bio-structures: 3D printing optimization and surface characterization , 2018 .

[11]  Chul B. Park,et al.  Building three‐dimensional objects by deposition of molten metal droplets , 2008 .

[12]  Wilhelm A. Groen,et al.  Toward inkjet printing of small molecule organic light emitting diodes , 2013 .

[13]  Hejun Li,et al.  Remelting and bonding of deposited aluminum alloy droplets under different droplet and substrate temperatures in metal droplet deposition manufacture , 2013 .

[14]  R. Hague,et al.  3-dimensional inkjet printing of macro structures from silver nanoparticles , 2018 .

[15]  Sanjeev Chandra,et al.  Impact, recoil and splashing of molten metal droplets , 2000 .

[16]  Lehua Qi,et al.  Effect of the surface morphology of solidified droplet on remelting between neighboring aluminum droplets , 2018, International Journal of Machine Tools and Manufacture.

[17]  Michael Rethmeier,et al.  Numerical simulation of full-penetration laser beam welding of thick aluminium plates with inductive support , 2012 .

[18]  Lee Yong Tsui,et al.  A study of the staircase effect induced by material shrinkage in rapid prototyping , 2005 .

[19]  Jun Yang,et al.  A laser printing based approach for printed electronics , 2016 .

[20]  Chul B. Park,et al.  Experiments on Remelting and Solidification of Molten Metal Droplets Deposited in Vertical Columns , 2007 .

[21]  Jiming Zhou,et al.  A novel selection method of scanning step for fabricating metal components based on micro-droplet deposition manufacture , 2012 .

[22]  W. Xiong,et al.  Formation of uniform metal traces using alternate droplet printing , 2017 .

[23]  Yifu Shen,et al.  Balling phenomena in direct laser sintering of stainless steel powder: Metallurgical mechanisms and control methods , 2009 .

[24]  Jun Xiong,et al.  Finite element analysis and experimental validation of thermal behavior for thin-walled parts in GMAW-based additive manufacturing with various substrate preheating temperatures , 2017 .

[25]  J. Ghazanfarian,et al.  Experimental and numerical study of thermal conductivity of plasma-sprayed thermal barrier coatings with random distributions of pores , 2018, Applied Thermal Engineering.

[26]  Wenbin Cao,et al.  Freeform fabrication of aluminum parts by direct deposition of molten aluminum , 2006 .

[27]  Denis Cormier,et al.  Inkjet Printed Polyethylene Glycol as a Fugitive Ink for the Fabrication of Flexible Microfluidic Systems. , 2018, Materials & design.

[28]  Jun Du,et al.  Numerical analysis of fused-coating metal additive manufacturing , 2017 .

[29]  Zhengying Wei,et al.  Numerical analysis of pileup process in metal microdroplet deposition manufacture , 2015 .

[30]  Jonathan Stringer,et al.  Formation and stability of lines produced by inkjet printing. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[31]  S. Schiaffino,et al.  Molten droplet deposition and solidification at low Weber numbers , 1997 .

[32]  Jun Luo,et al.  Quantitative characterization and influence of parameters on surface topography in metal micro-droplet deposition manufacture , 2015 .

[33]  Yao Yingxue,et al.  Rapid prototyping based on uniform droplet spraying , 2004 .

[34]  Yuanhai Xiao,et al.  Manufacturing of micro thin-walled metal parts by micro-droplet deposition , 2012 .

[35]  Lehua Qi,et al.  Impact-driven ejection of micro metal droplets on-demand , 2016 .

[36]  Weiwei Deng,et al.  Pinhole formation from liquid metal microdroplets impact on solid surfaces , 2016 .

[37]  Matthew W. Williams,et al.  A balanced-force algorithm for continuous and sharp interfacial surface tension models within a volume tracking framework , 2006, J. Comput. Phys..

[38]  Pierre Fauchais,et al.  Experimental and Theoretical Study of the Impact of Alumina Droplets on Cold and Hot Substrates , 2003 .

[39]  Mehdi Raessi,et al.  Producing molten metal droplets smaller than the nozzle diameter using a pneumatic drop-on-demand generator , 2013 .

[40]  Jun Luo,et al.  Simulation on deposition and solidification processes of 7075 Al alloy droplets in 3D printing technology , 2014 .