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Minimum Quantity Lubrication
Published in David A. Stephenson, John S. Agapiou, Metal Cutting Theory and Practice, 2018
David A. Stephenson, John S. Agapiou
Drills used for MQL have different body and point geometries than standard wet tooling as summarized in Figures 15.17 and 15.18 [3, 7, 20, 46]. MQL drills commonly have higher backtaper than conventional drills to account for increased thermal expansion during cutting [2, 7, 53]. This limits the number of regrinds, which can be performed before the drill loses size. MQL drills also commonly have thinner webs and wider flutes, and in some cases, flutes which increase in size along the axis, to facilitate chip ejection. Enlarging the flutes also reduces bending stiffness and drill stability [45], which is sometimes compensated for using double or triple margin designs [48, 53]. Flute surfaces are commonly ground or polished to a high finish to inhibit buildup and chip accumulation [6, 7, 9]. The margin land width is typically reduced to reduce frictional heating between the margins and hole wall [2, 3, 7, 46]. Point geometry modifications include optimized chisel edge configurations and special grinding of coolant hole gashes and chip exit features [3, 7, 46]. The web is thinned past the middle to produce a small, radiused chisel edge. Coolant holes are fully gashed for open air and oil flow to prevent material buildup in the center [46]. Smooth grinding of the transitions from the flute to the point eliminates constrictions, which may also cause material buildup during cutting.
Analysis of cutting forces at different spindle speeds with straight and helical-flute tools for conventional-speed milling incorporating the effect of tool runout
Published in Mechanics Based Design of Structures and Machines, 2022
In mechanistic model, cutting forces are proportional to undeformed chip area (Altintas 2000). Kline and DeVor (1983) presented a mechanistic model to predict milling forces for the cutting geometry with tool runout. They calibrated the empirical coefficients with the measured average forces and an undeformed chip thickness approach, which are referred to as force coefficients. Based on a similar mechanistic cutting force model considering the cutter edge trajectories with runout effect, Lu et al. (2018) determined the cutting forces for micro flat-end milling. A general approach was established by Wan and Zhang (2006) for cutting force prediction in milling operations, who included the influences of the tool and workpiece and immersion angle variation. Montgomery and Altintas (1991) proposed a theoretical cutting force method which describes the undeformed chip thickness from the trochoidal motion of the tool. Recently, Wojciechowski (2015) investigated cutting forces in ball-end milling of inclined surfaces by including the effect of surface inclination and tool runout. However, in die and mold making operations, where cutting conditions change, a variety of cut tests are necessary to determine the cutting forces. Considering the cutting tool, workpiece and cutting parameters, a systematic investigation of the influences of tool runout on the milling process based upon trochoidal flute trajectories should be performed.
Influence of ultrasonic vibration assistance in manufacturing processes: A Review
Published in Materials and Manufacturing Processes, 2021
Pankaj Sonia, Jinesh Kumar Jain, Kuldeep Kumar Saxena
Baghlani et al. experimentally found the reduction in thrust force in deep hole drilling of Inconel 738LC superalloy with significant reduction in surface roughness.[139] The similar study on Inconel 738LC superalloy by Baghlani et al. reported a significant improvement in tool life with 40% reduction in thrust force and 90% reduction in machining time. The cylindricity and dimensional accuracy greatly improved by UV-assisted.[140] The comparison between simulated and experimental chip morphology has shown in Fig. 12 (chip morphology), which revealed the effect of UV assisted in drilling for the reduction in drilling force.[141] In case of axial oscillation in UV-assisted drilling enhances the feed of cutting edge in the cutting zone and in results, the smoother surface produces. The simulated images shown in Fig. 12 reveal that the temperature at the interface is less due to intermittent contact, and low temperature reduces the built up edge and support the smooth surface formation. In conventional drilling, the chip morphology shows that the formation of continuous chip occupy the entire flute area of drill bit, which increases the friction between chip and flute surface. Whereas UV assistance under the vibro-impact mechanism increases the plastic deformation and break the chip in a small segments.
Machinability enhancements of ultrasonic-assisted deep drilling of aluminum alloys
Published in Machining Science and Technology, 2020
Ngoc-Hung Chu, Van-Du Nguyen, Quoc-Huy Ngo
Aluminum alloys have been widely used in applications where materials with high strength-to-weight ratio are required, such as in the rapid growing automobile and aerospace industries. Generally, aluminum alloys have been considered as one of the easiest machining materials. However, these materials are considered as the most critical materials for dry drilling (Ashrafi et al., 2012; Kouam et al., 2013; Zheng and Liu, 2013). Different from other conventional machining processes such as turning and milling, where chips are free of external forces after leaving the cutting area, the chips in drilling are constrained by the drill flute, causing the change of chip shape and thus the drilling forces and torque (Ke et al., 2006). In addition, emerging trend of dry cutting, an environmental-friendly machining technique, has also given a real challenge in drilling aluminum alloys (Roy et al., 2009). During the dry drilling of aluminum alloys, long and ductile chips, especially in deep holes, tend to bend and coil and thus cause packing of the drill flutes, interfering with chip ejection (Drozda, 1983). High tendency of aluminum to adhere to cutting tools, causing persistent elongated contact with cutting edges and flutes, produces a high risk of tool breakage.