Browsing by Subject "Cutting tools"
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Item Open Access Comparative analysis of PCD drill designs during drilling of CFRP laminates(Elsevier, 2015) Karpat, Yiğit; Bahtiyar, O.As a result of increased use of CFRPs in the aerospace industry, the machining of CFRPs has been studied extensively. The majority of these studies consider drilling of CFRPs, since it is the most common process in the machining of structural parts used in aircraft. It has been shown that drilling process parameters and drill geometry significantly influence the quality of holes. In this study, a systematic approach has been used to compare the influence of drill geometry on process outputs such as drilling forces, torques and tool wear. Custom-made double point angle polycrystalline diamond (PCD) drills from the same manufacturer were used in the experiments. The advantage of this approach is that it eliminates the drill material and edge preparation effects on the experimental measurements, thus helps reveal the influence of drill geometry on the process outputs. The pros and cons of different drill designs are discussed and an appropriate design is identified for the drilling of thick CFRP laminate considered in this study.Item Open Access Energy based investigation of process parameters while drilling carbon fiber reinforced polymers(Elsevier B.V., 2016) Karpat, Yiğit; Bahtiyar, O.Carbon fiber reinforced polymers (CFRPs) are widely used in the aerospace industry due to their light weight, high strength, and low thermal conductivity. Drilling is a critical process that affects the quality of CFRP parts. This work studies the influence of process parameters on delamination and tool wear. Polycrystalline diamond helical drills are used in the experiments. It has been shown that drilling energy calculations can be used to set appropriate feed and speed parameters and for increasing drilling performance of CFRPs. The results also indicate the importance of thermal modeling of CFRP laminate for better understanding of the drilling process. © 2016 The Authors.Item Open Access Experimental investigations on micro milling of stavax stainless steel(Elsevier, 2014) Oliaei, Samad Nadimi Bavil; Karpat, YiğitMicro 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.Item Open Access Influence of tool wear on machining forces and tool deflections during micro milling(Springer, 2016) Oliaei, S. N. B.; Karpat, Y.Tool wear on the cutting edges of micro end mills is an important issue affecting process outputs such as tool deflections and surface roughness, especially when difficult-to-cut materials such as titanium alloys, stainless steel, etc. are machined at micro scale. An understanding of the interactions between tool wear, machining forces, tool deflections, and surface roughness is important in order to maintain component quality requirements. However, in literature, the number of studies concerning tool wear in micro end mills is limited. The goal of the paper is to better understand tool wear patterns (flank wear, edge rounding) of micro end mills and their relationship to machining parameters. In this study, first, the influence of tool wear on micro milling forces and surface roughness parameters is analyzed and favorable micro milling process parameters are identified. It is shown that, when machining with worn end mills, forces are affected by the tool wear patterns. Then, the influence of increased milling forces due to tool wear on tool deflections and tool breakage is studied using both experimental techniques and finite element analysis. The finite element model-based tool deflection and tool breakage predictions are validated through experiments. The results of this study can be used in process parameter selection in pocket micro milling operations and tool condition monitoring systems.Item Open Access 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.Item Restricted Makine ve kesici takım üretiminde: Netmak Group(Bilkent University, 2020) Türksever, Burak; Kılıç, Eylül; Ustaoğlu, Murat Kaan; Başaran, Semanur; Şahinli, EcemÇalışmanın amacı, 1972 yılında Ankara Mobilyacılar Sitesinde bir makine ve kesici takım üreticisi olan Netmak Group‟un kuruluşunun, sektördeki yerinin, makine ve kesici takım üretiminin, şirketin gelişmesine olanak sağlayan koşulların incelenmesidir. Aynı zamanda Türkiye'de oluşmuş ekonomik dalgalanmaların ve aile şirketi olmanın Netmak üzerindeki etkileri de çalışma kapsamında incelenecektir.