Large Nose Radius Research Articles

Ultra-Precision Cutting of Single Crystal Silicon Using Diamond Tool with Large Top Corner Radius

A lot of studies on the ultra-precision cutting of single crystal silicon have been reported and they used the single crystal diamond cutting tools having the sharp cutting edge. However, the diamond cutting tools having small chamfer at the cutting edge are usually used in practical machining shops. In addition, studies on the relationship between the tool wear and the machined surface have been reported little although the relationship is important in practical applications. In this study, ultra-precision cutting of single crystal silicon, using cutting fluids, feed rate, and depth of cut as experimental parameters, were carried out by using the single crystal diamond cutting tools having small chamfer and large nose radius, and effects of the cutting fluids, the feed rate, and the depth of cut on the machining accuracy and tool wear were studied. As a result, the optimum cutting conditions was obtained as follows: the cutting fluid was kerosene, the feed rate was 2.0μm/rev, and the depth of cut was 1.0μm.

Influence of Roller on Tooth Height of Internal Spline Formed by Spin-Forming

Spin-forming of part with internal tooth is a new technology of the near-net forming in gear manufacturing field. And the main purpose of the parts spin-forming is to shape teeth on the internal surface of blank. In order to improve the forming quality of internal tooth, the effect of roller on tooth height of spline was investigated by processing experiments and finite element simulation. The result indicates that, for full-radius roller, a large nose radius has also witnessed a discernible growth in spinning force and tooth height; considering the uniformity of tooth height distribution of spun part and decrease in forming force, the bio-conical roller is more suitable for this forming process

Tollmien-schlichting wave amplitudes on a semi-infinite flat plate and a parabolic body: comparison of a parabolized stability equation method and direct numerical simulations

In this paper, the interaction of free-stream acoustic waves with the leading edge of an aerodynamic body is investigated and two different methods for analysing this interaction are considered. Results are compared for a method which incorporates Orr–Sommerfeld calculations using the parabolized stability equation to those of direct numerical simulations. By comparing the streamwise amplitude of the Tollmien–Schlichting wave, it is found that non-modal components of the boundary layer response to an acoustic wave can persist some distance downstream of the lower branch. The effect of nose curvature on the persisting non-modal eigenmodes is also considered, with a larger nose radius allowing the non-modal eigenmodes to persist farther downstream.

Machinability Investigation on High Speed Hard Turning of ZrO2 with PCD Tools

This paper presents an initial study on the feasibility of machining zirconia ceramics in the hard state. A fully sintered Yttria stabilized tetragonal zirconia poly crystalline ceramic (Y-TZP) was used as work piece material and experiments were performed on a Mori Seiki turn-mill centre. PCD tools with small rake angle (0˚) and large nose radius (0.8 mm) were chosen for the experiments. The study on the influence of process parameters, such as depth of cut, feed and cutting speed (>300 m/min), on the surface quality and tool wear was approached by means of a mixed full factorial experimental design. Machined samples and process chips were also analysed by scanning electron microscope (SEM) to achieve a deep understanding of the occurring material removal mechanisms (MRM) and achievable surface quality; also the PCD inserts were inspected after usage. The findings show that surface roughness (Ra) values below 0.6μm are easily achievable; the material removal mechanism is mainly based on a combined ductile-brittle material removal. Adhesion of work piece material to the tool is regarded as the most significant tool wear mechanism.

Cutting Forces when High-Speed Milling of SiC<sub>P</sub>/Al Composites

High speed milling tests were performed on the SiCp/2009Al composites to investigate the cutting forces by using PCD tools in the speed range of 600-1200m/min. The results showed that the peak value of the cutting force Fy (in the tool radial direction) was in the range of 700-1450N under the present cutting condition. The maximum amplitude of cutting force vibration in the tool radial direction can reach 700N. Cutting forces increased with increasing feed rate or radial depth of cut and decreased with increasing cutting speed. Negative rake angle and relatively large tool nose radius were recommended as far as cutting forces was concerned. Materials with higher volume fraction or smaller reinforcement particle size had the bigger cutting forces. T6 heat treatment can increase the cutting forces significantly but the using of coolant can decrease the cutting forces evidently.

単結晶ダイヤモンド工具によるAl合金の超精密切削加工における工具摩耗の監視（第１報）

Geometrical quality like surface roughness and accuracy of form has been very important in ultra-precision machining. However, because of improvement of quality of finished surface with progress of ultra-precision machining technology, quality of subsurface material like affected layer also becomes important lately. In ultra-precision cutting tool wear is serious problem since tool wear fairly affects surface integrity of machined part. However it is difficult to directly detect tool wear on machine since the tool wear affecting surface integrity is extremely small. Therefore the purpose of this study is to find out effective parameters obtained during cutting to detect single crystal diamond tool wear in ultra-precision cutting of aluminum alloy. Wear of cutting edge with large nose radius was observed by a scanning electromicroscope. Cutting forces and AE signals during cutting were also measured to calculate values of the parameters from them. As a result of cutting tests and considerations, it was concluded that area of flank wear land can be related with static and dynamic components of cutting forces and area of rake wear land can be related with RMS values of AE signals.

Monitoring for Ultra-Precision Turning of Single Crystal Silicon using Diamond Tool with Large Nose Radius and Small Chamfer at Cutting Edge

Monitoring for Ultra-Precision Turning of Single Crystal Silicon using Diamond Tool with Large Nose Radius and Small Chamfer at Cutting Edge

超精密切削加工されたAl合金の仕上げ面性状に及ぼす工具摩耗の影響（第１報）

Geometrical quality like surface roughness and accuracy of form has been very important in ultra-precision machining. However, because of improvement of quality of finished surface with progress of ultra-precision machining technology, quality of subsurface material like affected layer also becomes important lately. Workpieces are actually machined with a worn diamond tool in machining shops whereas ultra-precision cutting with a single crystal diamond tool is well known as a machining method owing high quality finished surface to a sharp cutting edge of the tool. The purpose of this study is to find out the relation between the tool wear and the work hardened layer and residual stress of a surface machined with a worn tool in ultra-precision cutting process. Wear of cutting edge with large nose radius was observed by a scanning electromicroscope at intervals of a fixed cutting distance. The surface hardness, depth of hardened layer, and residual stress of the machined surface were also measured at the intervals. As a result of experiments and considerations, it was concluded that depth of hardened layer, Vickers hardness, and residual stress increased with increase in tool flank wear and they could be generalized by undeformed chip thickness and width of flank wear at part of cutting edge generating finished surface.

Prediction of chip flow direction during machining with self-propelled rotary tools

This paper presents a model for chip flow prediction during tube-end machining process using self-propelled rotary tools. The analysis performed is based on the transformation of the relative kinematic relationships in rotary cutting to that of the conventional cutting with large nose radius. Both relative and absolute chip flow angles are investigated. Tests were performed to measure the absolute chip flow angle, insert self propelled motion, and the deformed chip thickness during machining with self-propelled rotary tool under different cutting conditions. The predicted values of the absolute chip flow angle were in good agreement with that measured experimentally.

Modeling of Cutting Forces Under Hard Turning Conditions Considering Tool Wear Effect

Quantitative understanding of cutting forces under hard turning conditions is important for thermal modeling, tool life estimation, chatter prediction, and tool condition monitoring purposes. Although significant research has been documented on the modeling of forces in the turning operation in general, turning of hardened materials involves several distinctive process conditions, including negative tool rake angle, large tool nose radius, and rapid tool wear. These process conditions warrant specific treatment in the analysis of cutting forces. This paper first addresses these issues by formulating an oblique chip formation force model through the extension of a two-dimensional (2D) mechanistic force model while considering the effect of tool geometry complexities. The coefficients of the mechanistic force model are estimated by applying a genetic algorithm in overcoming the lack of explicit normal equations. Then the forces occurring due to flank wear are modeled by extending a 2D worn tool force modeling approach into a three-dimensional analysis to accommodate the effect of low feed rate, small depth of cut, and relatively large tool nose radius in hard turning. The total cutting forces are the linear summation of forces due to chip formation and forces due to flank wear. The model-predicted forces match well with experimental results in the turning of hardened 52100 bearing steel under practical cutting conditions (low feed rate, small depth of cut, and gentle cutting speed) using cubic boron nitride (CBN) tools under the progressive tool flank wear conditions.

Tool nose radius effects on finish hard turning

Tool nose radius effects on finish turning of hardened AISI 52100 steels have been investigated. Surface finish, tool wear, cutting forces, and, particularly, white layer (phase transformation structures) were evaluated at different machining conditions. Results show that large tool nose radii only give finer surface finish, but comparable tool wear compared to small nose radius tools. Specific cutting energy slightly increases with tool nose radius. For new tools, white layers only occur at aggressive feeds (=0.3 mm/rev) and small nose radius results in deeper white layers. For worn tools, white layers appear even at mild feeds (0.05 mm/rev), but in contrast, large nose radius leaves deeper white layers. Smaller tool nose radius gives larger uncut chip thickness, and thus, greater shear plane heat source that may induce deeper white layers for new tool conditions. For worn tools, where the wear-land sliding is the major heat source, temperature analysis at machined surfaces reveals that the larger the tool nose radius, the deeper the temperature penetration due to a shorter transition-material zone from the cutting edge to the final machined surface.

The effect of tool nose radius in ultrasonic vibration cutting of hard metal

A tool edge with a small nose radius can alleviate the regenerative chatter. In general, it is important for conventional cutting to use the smallest possible tool nose radius. However, a sharp tool shape has an adverse effect on tool strength and the instability of machining process still occurs. Previous researches have shown that vibration cutting has a higher cutting stability as compared with conventional cutting. In the present paper, the influence of tool nose radius on cutting characteristics including chatter vibration, cutting force and surface roughness is investigated by theory. It is found from the theoretical investigation that a steady vibration created by motion between the tool and the workpiece is still obtained even using a large nose radius in vibration cutting. This article presents a vibration cutting method using a large nose radius in order to solve chatter vibration and tool strength problem in hard-cutting. With a suitable nose radius size, experimental results show that a stable and a precise surface finish is achieved.

Force modelling in shallow cuts with large negative rake angle and large nose radius tools?application to hard turning

In finish turning, the applied feedrate and depth of cut are generally very small. In some particular cases, such as the finishing of hardened steels, the feedrate and depth of cut are much smaller than tool nose radius. If a tool with a large tool nose radius and large negative rake angle is used in finish turning, the ploughing effect is pronounced and needs to be carefully addressed. Unfortunately, the ploughing effect has not yet been systematically considered in force modelling in shallow cuts with large negative rake angle and large nose radius tools in 3-D oblique cutting. In this study, in order to model the forces in such shallow cuts, first the chip formation forces are predicted by transforming the 3-D cutting geometry into an equivalent 2-D cutting geometry, then the ploughing effect mechanistic model is proposed to calculate the total 2-D cutting forces. Finally, the 3-D cutting forces are estimated by a geometric transformation. The proposed approach is verified in the turning of hardened 52100 steel, in which cutting conditions are typified as shallow cuts with negative rake angle and large nose radius tools. The workpiece material property of hardened 52100 steel is represented by the Johnson-Cook equation, which is determined from machining tests. The comparison between the experimental results and the model predictions is presented.

The Mechanism of Chip Formation with Hard Turning Steel

Steels having a hardness of H RC 60 or greater are presently being finished by turning instead of grinding. This is usually done using a polycrystalline cubic boron nitride insert having a rather large nose radius on a very rigid machine at a relatively high cutting speed. In order to understand this process it is important that the sequence of events occurring in the formation of the unique type of chip involved be correctly identified. Experimental evidence to this end is presented and discussed in fundamental terms.

An experimental design for surface roughness and built‐up edge formation in lathe dry turning

Investigates the effects of the most influential cutting parameters (cutting speed, feed rate, depth of cut, tool nose radius, tool length and work piece length) on surface roughness quality and on the formation of built‐up edge in a lathe dry turning process of mild carbon steel samples. A full factorial design (384 experiments), taking into account the three‐level interactions between the independent variables has been conducted. The results show that the following three‐level interactions: feed rate × cutting speed × depth of cut, feed rate × cutting speed × tool nose radius and tool nose radius × depth of cut × tool length have significant effects on surface roughness in this type of machining operation. Shows that the analysis of main effects alone and even two‐level interactions could lead to a false interpretation of the results. The analysis of variance revealed that the best surface roughness is achieved with a low feed rate, a large tool nose radius and a high cutting speed. The results also show that the depth of cut has no significant effect on surface roughness when operating at cutting speeds higher than 160m/min. Furthermore, it is shown that built‐up edge formation deteriorates surface roughness when machining mild carbon steel at specific feed rate, tool nose radius and cutting speed levels. Proposes a new model for evaluating the limiting cutting speed to avoid the built‐up edge formation. Finally, shows through experimentation that an increase in depth of cut would lead to improved surface roughness when tool vibration is increased.

Effect of tool vibrations on surface roughness during lathe dry turning process

Choice of optimized cutting parameters is very important to control the required surface quality. In fact, the difference between the real and theoretical surface roughness can be attributed to the influence of physical and dynamic phenomena such as: built-up edge, friction of cut surface against tool point and vibrations. The focus of this study is the collection and analysis of surface roughness and tool vibration data generated by lathe dry turning of mild carbon steel samples at different levels of speed, feed, depth of cut, tool nose radius, tool length and work piece length. A full factorial experimental design (288 experiments ) that allows to consider the three-level interactions between the independant variables has been conducted. Vibration analysis has revealed that the dynamic force, related to the chip-thickness variation acting on the tool, is related to the amplitude of tool vibration at resonance and to the variation of the tool's natural frequency while cutting. The analogy of the effect of cutting parameters between tool dynamic forces and surface roughness is also investigated. The results show that second order interactions between cutting speed and tool nose radius, along with third-order interaction between feed rate, cutting speed and depth of cut are the factors with the greatest influence on surface roughness and tool dynamic forces in this type of operation and parameter levels studied. The analysis of variance revealed that the best surface roughness condition is achieved at a low feed rate (less than 0.35 mnt/rev), a large tool nose radius (1.59 mm) and a high cutting speed (265 m/min and above). The results also show that the depth of cut has not a significant effect on surface roughness, except when operating within the built-up edge range. It is shown that a correlation between surface roughness and tool dynamic force exist only when operating in the built-up edge range. In these cases, built-uṕ edge formation deteriorates surface roughness and increases dynamic forces acting on the tool. The effect of built-up edge formation on surface roughness can be minimized by increasing depth of cut and increasing tool vibration. Key words:design of experiments, lathe dry turning operation, full factorial design, surface roughness, measurements, cutting parameters, tool vibrations.

Some aspects in the surface integrity associated with turning of powder metallurgy compacts

The shape of the tool insert geometry, particularly the size of the tool nose radius, plays a significant role in influencing a variety of surface integrity characteristics such as surface finish, roundness, tool life, edge frittering etc. It has been found in previous work that a large tool nose radius is beneficial in improving the component quality. This paper substantiates these facts and shows that increasing the feed rate generally debilitates the surface integrity but, probably due to some elasticity in the porous compact's surface, this does not cause residual hardening to the machined surface. Abrasion during secondary machining suggests that flank, rather than crater, wear determines the end point during cutting operations. Tool nose geometry plays a significant role in improving surface topography, by reducing the cusp height—when the nose radius is large. The manufacturing envelopes defined by skewness and kurtosis for the machined surfaces suggest that there is a general drift either from a bearing to a locking surface or vice versa. Furthermore, the dispersion of these envelopes reduces with increasing feed rate. These conditions can be attributed to the tool nose geometry, feed rate and depth of cut which modifies the machined surface topography.

砥石の切削に関する研究

The machining of grinding wheel is an important research problem related to wheel finishing process. This subject is also a typical example of ceramic composite material machining. However, there is insufficient information about this type of cutting. In this study, a turning experiment was performed on white alumina grinding wheels by the use of cemented carbide, sintered CBN and sintered diamond single point cutting tools. The cutting speed ranged from 0.003 to 150 m/min, the maximum depth of cut was 1.0 mm, and the feed was 0.6 mm/rev. Thus, the tool wear and cutting force were measured for various cutting conditions, and the optimum operating condition and mechanism of chip formation were obtained. The effects of cutting speed, rake angle, and nose radius were specially investigated. The cutting mechanism was also studied from a specially low speed orthogonal cutting experiment and FFT analysis. It is evident from this study that grinding wheel can be cut easily by using a proper cutting tool, such as K01 and sintered diamond tool, and by selecting relatively low cutting speeds, great negative rake angle and large nose radius. The chip is mainly formed by compressive fracture.

プランジ研削における砥石の接触状態に関する研究 (第4報)

The grinding experiment is carried out at high speed and small cutting depth with a single grit, of which locus is a trochoidal curve, to investigate the surface generation mechanism. The surface generation curves with a single grit or successive grits are experimentally made clear by analyzing normal force, rubbing, grit displacement and workpiece spring back. Then the effects of shape and supporting stiffness of grit are discussed upon the surface generation curve. The residual stock due to contact stiffness, which is the difference between surface generation curve and geometrical interference curve, is given as the sum of grit displacement and workpiece spring back. The grit displacement is decided by normal force and supporting stiffness, and the workpiece spring back by the real depth of cut. The residual stock due to contact stiffness increases with lower supporting stiffness and with larger nose radius and vertical angle of grit.

Asymptotic solution for the viscous radiating shock layer.

The viscous flow of a transparent radiating gas in a stagnation region is studied by means of matched asymptotic expansions. The boundary-layer equations are taken as the appropriate model of the shock layer. An exact solution is obtained for a special case; by considering asymptotic expansions of this solution in terms of Reynolds number, the interaction of the viscous and in viscid regions is clarified. With this solution as a model, the asymptotic solution for the general case is constructed by the method of matched inner and outer expansions. Owing to the coupling between velocity and enthalpy profiles, the inner expansion is characterized by powers and logarithms of Reynolds number, rather than the usual square root dependence. To first order, the boundary layer is shown to be exactly equivalent to that on a body having larger nose radius and lower flight speed in a nonradiating gas. The asymptotic results are compared with solutions obtained by direct integration using an electronic computer.