Browsing by Author "Oliaei, Samad Nadimi Bavil"

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Open Access
Design and fabrication of micro end mills for the machining of difficult-to-cut materials
(2016-08) Oliaei, Samad Nadimi Bavil
Micromilling is a cost-e ective method of fabricating miniaturized components with complex, three-dimensional features made from di cult-to-cut materials. Microcutting tools are exposed to harsh conditions during machining of such materials, which leads to short tool life and thus a ects the economics of the process. The aim of this thesis is to develop a systematic approach to the design and fabrication of high-precision micro-cutting tools. Machining characteristics of three di erent di cult-to-cut materials–stainless steel, titanium alloy, and silicon–have been investigated using experimental techniques. The results reveal the importance of interaction between tool micro geometry and work material mechanical properties. This observation leads to the development of tailored micro-end mills which are designed and fabricated based on the requirements of the specific machining task. This study also examines in detail built-up edge, an important but usually overlooked issue in micromachining of ductile materials, which a ects the process forces, tool wear, and tool deflections. The protective e ect of built-up edge has been exploited by creating micro-dimples on the tool surface using electrical discharge machining. Its positive influence on tool performance has been demonstrated. As for the micromachining of silicon, the flow of cut material around the cutting edge is paramount in tool design. A novel tool design for machining of silicon has been proposed and its e ectiveness has been validated through experiments. It has been shown that the selection of proper process parameters together with tailored tool design may increase the productivity of micromachining and improve surface quality and dimensional accuracy of micro-scale parts.
Open Access
Experimental investigations on micro milling of stavax stainless steel
(Elsevier, 2014) Oliaei, Samad Nadimi Bavil; Karpat, Yiğit
Micro mechanical milling of Stavax (modified AISI 420) stainless steel which is commonly used in the plastic injection molding industry due to its high corrosion resistance, machinability and wear resistance is studied in this paper. The goal of this study is to investigate the influence of process input parameters such as cutting speed, depth of cut, feed per tooth, radial immersion percentage, and plunging method on process outputs during circular pocketing operation. Tool wear, machining forces and surface roughness measurements are considered to identify the relationships between process inputs and outputs. It is observed that plunging method has a significant influence on tool wear which in turn affects micro milling forces and surface quality. The positive impact of micro milling with a pre-drilled hole is demonstrated. The relationship between radial immersion and feed per tooth is shown to be important in terms of tool wear and surface roughness.
Open Access
Fabrication of PCD mechanical planarization tools by using μ-wire electrical discharge machining
(Elsevier, 2016) Oliaei, Samad Nadimi Bavil; Karpat, Yiğit
Fabrication of micro components made from difficult-to-cut materials require the use of micro cutting tools which can withstand the harsh conditions during machining. Polycrystalline diamond micro tools, produced using micro wire electro discharge machining, have been used to machine silicon. In this study, fabrication of PCD planarization tools having micro-pyramid lattice structure is considered. A tungsten wire with 30 μm diameter was used, which makes it possible to obtain very precise micro-features by employing extremely low discharge energies. The performance of the tools is investigated through micro scale grinding of silicon and appropriate machining parameters which resulted in ductile regime machining of silicon are determined.