Browsing by Subject "Ductile mode machining"

Now showing 1 - 3 of 3

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
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.
Open Access
Polycrystalline diamond end mill cutting edge design to improve ductile-mode machining of silicon
(Elsevier, 2018) Oliaei, S. N. B.; Karpat, Yiğit
Silicon is a commonly used material in optoelectronics and micro fluidics devices. Micro mechanical milling of silicon with polycrystalline diamond (PCD) tools has the potential to produce three-dimensional surfaces with good surface finish and an increased material removal rate. PCD micro end mill geometry is known to influence process outputs yet its effect has not been studied in detail. In this study, a PCD end mill with a hexagonal geometry has been considered, and its micro cutting geometry has been modified to have a parallelogram shape featuring a large negative rake angle on the bottom of the tool. The proposed micro geometry also reduces the contact area between the tool and the work material. The proposed geometry was fabricated using wire electric discharge machining (WEDM). Ductile-to-brittle transition conditions and areal surface roughness have been investigated as a function of tool geometry and feed during micro milling of silicon. A significant improvement in material removal rate and surface roughness has been obtained compared to a commercially available PCD end mill having hexagonal geometry with flat bottom. The results show that PCD micro end mill geometry significantly affects the process outputs.