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Development and Simulation of Metallic Mesostructures Manufacturing Process by Integrated Vat Polymerization and Electroforming

Fahimi Hanzaei, Amir | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57871 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Akbari, Javad
  7. Abstract:
  8. Nowadays, metallic microsystems such as miniature and meso-scale gears, microgrippers, and comb structures constitute a significant portion of key components in various microelectromechanical systems (MEMS). Due to their extremely lightweight nature, small size, high dimensional accuracy, superior performance, and extended lifetime, the manufacturing process of these microsystems has always been a subject of discussion and research. The goal is to enhance the strength and precision of the products while reducing production costs.LIGA and wire-cut electrical discharge machining (WEDM) are two well-known methods for fabricating microstructurs. Despite their advantages, such as high dimensional accuracy and smooth surface finish, these methods have limitations, including complex and expensive equipments, inflexibility in design and production, and high manufacturing costs.As an alternative approach, electroforming has been proposed, in which the target metal is sequentially deposited into a mold cavity fabricated using additive manufacturing. The proposed process offers several advantages, including high dimensional accuracy, absence of residual stresses, ultra-high purity of the final product, the ability to create sharp edges, and lower production costs compared to competing methods. In this proposed fabrication approach, efforts are made to overcome the limitations of LIGA and WEDM while leveraging their strengths, such as superior surface finish, high aspect ratio, and proper mechanical strength.In the present study, aimed at further developing the proposed innovative process for manufacturing microsystems with higher dimensional precision and filling quality, the first step involved investigating the effects of key process parameters;such as dimensions and number of anodes, electrodes spacing, current density, and mold height on uniformity of deposited surface through Box-Behnken-designed simulation experiments. The results indicated that mold thickness and current density were the most significant parameters, with their high levels 5.5 mm and 5 A/dm², respectively leading to the optimization of the response variable, i.e., profile thickness non-uniformity. The minimum calculated response value was 3.895%.In the next phase, using the optimized parameter levels, the feasibility of achieving sharp corners in the microstructures and the influence of mold design parameters (corner radius and length) on the dimensional accuracy of fabricated samples were experimentally investigated. The sharpest designed corner, with a vertex angle of 30 degrees and a corner radius of 200 microns, was successfully electroformed.Finally, to assess the capability of the process in fabricating functional components, a prototype heat sink made of copper was successfully electroformed
  9. Keywords:
  10. Microstructure ; Microelectromechanical Systems (MEMS) ; Three Dimentional Printing ; Electroforming ; Numerical Simulation ; Finite Element Method ; Additive Manufacturing

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