New microproducts need the utilization of a diversity of materials and have complicated three-dimensional (3D) microstructures with high aspect ratios. To date, many micromanufacturing processes have been developed but specific class of such processes are applicable for fabrication of functional and true 3D microcomponents/assemblies. The aptitude to process a broad range of materials and the ability to fabricate functional and geometrically complicated 3D microstructures provides the additive manufacturing (AM) processes some profits over traditional methods, such as lithography-based or micromachining approaches investigated widely in the past. In this paper, 3D micro-AM processes have been classified into three main groups, including scalable micro-AM systems, 3D direct writing, and hybrid processes, and the key processes have been reviewed comprehensively. Principle and recent progress of each 3D micro-AM process has been described, and the advantages and disadvantages of each process have been presented.

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A review on 3D micro-additive manufacturing technologies

Additive manufacturing (AM) of metallic structures by laser based layered manufacturing processes involve thermal damages. In this work, the feasibility of mask-less electrochemical deposition as a nonthermal metallic AM process has been studied. Layer by layer localized electrochemical deposition using a microtool tip has been performed to manufacture nickel microstructures. Three-dimensional free hanging structures with about 600 μm height and 600 μm overhang are manufactured to establish the process capability. An inhouse built CNC system was integrated in this study with an electrochemical cell to achieve 30 layers thick microparts in about 5 h by AM directly from STL files generated from corresponding CAD models. The layer thickness achieved in this process was about 10 μm and the minimum feature size depends on the tool width. Simulation studies of electrochemical deposition performed to understand the pulse wave characteristics and their effects on the localization of the deposits.

Mask-Less Electrochemical Additive Manufacturing: A Feasibility Study

Micro-droplet deposition manufacture is a novel direct metal rapid prototyping for building the miniaturized parts. In this paper, the relationship between the droplet diameter and the operating parameters is investigated to obtain the optimal condition for the accurate droplet generation. The droplet generator is designed to adjust the parameters such as the infinitesimal disturbance and the jet velocity. Experiments with the different materials have been conducted to study the feasibility of the accurate droplet generation for the manufacturing. Spherical and uniform water micro-droplets within 2.4% variation are generated using an orifice diameter of 150 μm, and tin–lead alloy droplets are produced with an orifice diameter of 100 μm in the argon environment. The results show that the generator can produce accurate micro-droplets which meet the requirements of fabricating the miniaturized parts.

Chia-Chin Chen

Papers

The new expression of the effectiveness of powder classification

Effect of oxidation on the breakup and monosized droplet generation of the molten metal jet