Browsing by Subject "Micro machining"

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    Investigating flank face friction during precision micro cutting of commercially pure titanium via plunging tests with diamond grooving tools
    (Elsevier, 2022-01) Karpat, Yiğit
    This study investigates flank face friction while micro machining commercially pure titanium (cp-Ti grade 2) work material considering size effects. It is important to understand friction phenomena at the tool flank and work material surface since they affect the surface integrity of the machined parts. A single crystal diamond grooving tool is used in machining experiments to reduce the influence of cutting edge radius. In addition, plunging type of cutting experiments were performed to investigate the influence of flank face contact on the machined surface. A friction model which is based on work and tool material properties is proposed to model the contribution of adhesion and deformation of the flank face coefficient of friction. The results show that for the cp-Ti and diamond tool pair, adhesion seems to be the dominant model of friction and also contributes to the size effect. The deformation friction becomes more dominant during the chip formation stage. When cutting edge effect is eliminated, the influences of flank and rake face friction on the size effect are shown.
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    Investigating the influence of built-up edge on forces and surface roughness in micro scale orthogonal machining of titanium alloy Ti6Al4V
    (Elsevier, 2016) Oliaei, S. N. B.; Karpat, Y.
    The edge geometry of cutting tools directly influences the chip formation mechanism in micro-mechanical machining, where the edge radius and uncut chip thickness are in the same order of magnitude. An uncut chip thickness that is smaller than the cutting edge radius results in a large negative rake angle during machining, and built-up edge formation then affects the mechanics of the process. In this study, micro-scale orthogonal cutting tests on titanium alloy Ti6Al4V were conducted to investigate the influence of built-up edge formation on the machining forces and surface roughness. Cutting edges in these tests are engineered using wire EDM technique to have an edge radius of around 2 μm and clearance angles of 7° and 14°. It is observed that machining process inputs (uncut chip thickness, cutting speed, and clearance angle) affect the size of the built-up edge, which in turn affect the process outputs. It is observed that built-up edge formation protects the cutting edge from flank and crater wear under micro machining conditions and the influence of built-up edge on the surface roughness varies depending on the cutting speed and uncut chip thickness. Our findings also indicate a close relationship between the minimum uncut chip thickness and the mean roughness depth (Rz) of the machined surface. The minimum uncut chip thickness is found to be around 10% of the edge radius in the presence of built-up edge.
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    The morphological changes upon cryomilling of cellulose and concurrent generation of mechanoradicals
    (Elsevier, 2019) Aksın, Alp; Karpat, Yiğit
    Microstructural features such as grain size, grain morphology, and phase fractions have significant influence on process outputs of machining processes. During micro end milling where feed per tooth and depth of cut values are set comparable to grain size, process material interactions become more significant. The goal of this study is to investigate the influence of microstructural effects on process outputs during micro milling of cp-Ti work material. Micro milling experiments are performed to observe the process outputs as a function of grain size and grain morphology and a mechanistic approach has been used to explain their effects during micro milling.
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    On-machine fabrication of PCD and WC micro end mills using micro electro discharge machining
    (Inderscience Enterprises Ltd., 2014) Oliaei, S.N.B.; Özdemir, C.; Karpat, Y.
    Micro electro discharge machining (μ -EDM) process can be used to fabricate micro-milling tools of different geometries from tungsten carbide (WC) and polycrystalline diamond (PCD). The non-contact nature of EDM process makes micro tool fabrication a challenging task while offering the advantage of eliminating tool run out and clamping errors since micro tools fabricated on-machine. The tools are fabricated and used on the same spindle. In this study, a combination of block-EDM and wire electro discharge grinding (WEDG) techniques are used to fabricate micro end mills of different geometries. The influences of EDM process parameters on material erosion rate and surface roughness are examined. The performance of the fabricated micro-tools in ductile mode machining of fused silica has been investigated. It is found that micro end mills can be used to fabricate prototypes of microfluidics chips with acceptable quality. © 2014 Inderscience Enterprises Ltd.
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    Unraveling the complex interplay between elastic recovery, contact pressure, and friction on the flank face of the micro tools via plunging-type testing
    (Elsevier Inc., 2024-07-06) Karpat, Yiğit; Güven, Can
    A good understanding of the interplay between the cutting tool edge radius, elastic recovery, friction, and contact pressure is essential for better modeling of ploughing forces during micro-scale cutting. This study conducts plunging tests on an ultra-precision CNC with engineered tungsten carbide cutting tools on commercially pure titanium alloy. The cutting tool edge radius is prepared to be around 3.5-4 mu m, which resembles those cutting tools used in micro scale machining. During plunging tests, the micro cutting tool is given a sinusoidal movement with an amplitude close to edge radius of the tool as the work material is rotated at a constant speed. The residual depth profiles of the webs corresponding to the commanded depths were investigated in detail to identify elastic recovery rate. The cutting and thrust force measurements during plunging experiments together with identified elastic recovery rate was employed in an analytical model of micro scale machining to obtain the variations of contact pressure and coefficient of friction as a function of commanded depth. Due to the scale of the experiments that were performed, the effects of surface topography of the cutting tool and possible alignment errors are also considered in the analytical model. A linear relationship between the contact pressure and elastic recovery has been identified during ploughing-dominated machining conditions for the work material and the cutting tool pair considered in this study. The proposed experimental technique is shown to be promising in terms of modeling ploughing forces during micro-scale cutting.