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High-feed axial ultrasonic vibration turning (HFUVT) is studied to explore its effects on the machining characteristics of Ti6Al4V alloy. A feed rate that is greater than the ultrasonic vibration amplitude was employed to turn this titanium alloy. The kinematics and tool flank extrusion models were established for the cutting process. Then, systematic simulation and experimental investigations were carried out to compare and analyze the cutting characteristics including the chip geometry, subsurface plastic deformation and cutting force in conventional turning (CT) and HFUVT. The results indicated that the cutting efficiency of HFUVT increased by more than 3.4 times compared with that of CT. The HFUVT produced more severely deformed Sawtooth chips, smaller shear band spacing, higher chip splitting frequency, deeper subsurface plastic deformation layer and lower cutting force. The insightful findings contribute to a comprehensive understanding of the HFUVT process and offer valuable guidance for the improving of cutting efficiency in machining difficult-to-cut materials. [ABSTRACT FROM AUTHOR]

The results of the computer simulation of the cutting process of gears by the power skiving method are presented. Following the kinematics of the process, a method for generating 3D geometric models of undeformed sheared layers were developed, and their parameters were analyzed. The influence of tool geometry and technological parameters on cutting conditions is investigated. The simulation results and calculation of the tangential force and torque on the tool axis and their influence on the error due to angular elastic deformation of the tool are given.

Orthogonal turn-milling as a multi-axis machining operation introduces several advantages compared to conventional turning operations in terms of productivity and accuracy of complex parts. On the other hand, the multi-axis nature of the process adds several complexities in terms of cutter-workpiece engagement (CWE) and process kinematics which eventually affect process mechanics, dynamics, and surface integrity. This study presents generalized and accurate models of CWE, process kinematics, and mechanics to predict the cutting forces in orthogonal turn-milling. To fulfill the gaps in the literature, all the effective parameters such as eccentricity, minor cutting edge geometry, and feed motion are included to address all the possible configurations and conditions in orthogonal turn-milling. The uncut chip geometry is evaluated analytically using process geometry and kinematics. The cutting forces and torque in orthogonal turn-milling are calculated accordingly for standard and serrated end mills. It is shown that this general model is adoptable to the milling tools with complex geometry. The effect of different parameters on cutting forces is examined and verified experimentally. [ABSTRACT FROM AUTHOR]

The present study aimed to implement a sustainable machining method to improve energy efficiency in helical milling (HM) of AISI 1020. Therefore, ultrasonic vibration is integrated with conventional helical milling to reduce cutting forces. A model was developed for power consumption in terms of cutting forces in x, y and z directions, tangential and axial feed speeds. Series of plain and ultrasonic vibration helical milling (UVHM) experiments are conducted using 10 and 8 mm diameter mill cutters at different working conditions and experimental results for cutting forces are collected. Formation of chip and its geometry are investigated using the cutting trajectories of the bottom cutting edges of the cutter. Cutting forces and power consumption are estimated related to chip geometry in plain and UVHM processes and compared. In UVHM, the axial force is reduced by around 47% as the ultrasonic vibration is applied in the axial direction and the power consumption is reduced by 34%. The results showed that ultrasonic vibration has a significant effect on chip morphology, cutting force and power consumption, indicating that ultrasonic vibration assisted machining has a wide application in manufacturing. The process parameters are optimised as 2000 rpm of cutter rotational speed, 156 rpm of cutter orbital speed and 0.3 mm of axial depth of cut using 8 mm diameter cutter and the chip thickness, chip depth and power consumption are found to be 0.3969 mm, 0.2665 mm and 835.6 W respectively at optimal working condition. [ABSTRACT FROM AUTHOR]

The main purpose of the study was to define the machining conditions that ensure the best quality of the machined surface, low chip temperature in the cutting zone and favourable geometric features of chips when using monolithic two-teeth cutters made of HSS Co steel by PRECITOOL. As the subject of the research, samples with a predetermined geometry, made of AZ91D alloy, were selected. The rough milling process was performed on a DMU 65 MonoBlock vertical milling centre. The machinability of AZ91D magnesium alloy was analysed by determining machinability indices such as: 3D roughness parameters, chip temperature, chip shape and geometry. An increase in the feed per tooth fz and depth of cut ap parameters in most cases resulted in an increase in the values of the 3D surface roughness parameters. Increasing the analysed machining parameters did not significantly increase the instantaneous chip temperature. Chip ignition was not observed for the current cutting conditions. The conducted research proved that for the adopted conditions of machining, the chip temperature did not exceed the auto-ignition temperature. Modelling of cause-and-effect relationships between the variable technological parameters of machining fz and ap and the temperature in the cutting zone T, the spatial geometric structure of the 3D surface "Sa" and kurtosis "Sku" was performed with the use of artificial neural network modelling. During the simulation, MLP and RBF networks, various functions of neuron activation and various learning algorithms were used. The analysis of the obtained modelling results and the selection of the most appropriate network were performed on the basis of the quality of the learning and validation, as well as learning and validation error indices. It was shown that in the case of the analysed 3D roughness parameters (Sa and Sku), a better result was obtained for the MLP network, and in the case of maximum temperature, for the RBF network. [ABSTRACT FROM AUTHOR]

A novel approach for modeling and simulation of cutting force and power consumption in relation to chip geometry has been proposed in end milling‌ of AISI D2 steel. It is carried out in two stages: experimental work and finite element method based numerical simulation. In the first stage, experiments are conducted on the AISI D2 steel at two levels of spindle rotational speed, axial depth of cuts and four levels of feed per tooth using 10 mm and 8 mm diameter mill cutters. Cutting forces and amplitude of cutter vibration are measured in X and Y directions. Mechanistic models in terms of chip geometry and cutting force coefficients are developed to predict cutting forces and power consumption relative to chip geometry at 30°, 60° and 90° of cutter rotation. In the second stage, numerical simulation is carried out to predict cutting forces and power consumption relative to chip geometry at 30°, 60° and 90° of cutter rotation and compared with estimated values of cutting forces and power consumption. The maximum error between the two approaches for the cutting forces in X and Y directions and power consumption is estimated as 10.80%, 8.33% and 7.70% respectively. At spindle rotational speed of 2000 rpm, 0.3 mm of axial depth of cut and 50 µm of feed per tooth, the cutting forces and cutting power consumption are found minimum. [ABSTRACT FROM AUTHOR]

Chip geometry can play a crucial role in understanding the rock cutting efficiency in mechanical excavation. In this study, the shape and size distribution of chips produced in laboratory scale rock cutting tests and their relationship with cutting geometry and rock cuttability were analyzed. For this purpose, a series of small-scale linear rock cutting tests (SSLRCT) were carried out with a simple chisel tool in unrelieved mode at cutting depth of 1, 2, 3, and 4 mm to determine the cuttability of four rock types (sandstone, marl, salt, and coal) and two synthetic (dental plaster and concrete) specimens. The size distribution of all cuttings collected from the grooves in different samples was determined by sieve analysis. The results were used to create a comprehensive particle size analysis, including a Rosin–Rammler plot (d′), coarseness index (CI), median (d50) and Krumbein mean particle size (dMPS). Also, the chips remained on the 4-mesh sieve and greater were chosen for chip shape analysis. The results obtained from chip analysis indicated that 85.6% of selected chips were fragmented in very platy and very bladed shape. Also, the analysis results showed that an inverse exponential correlation exists between specific energy and particle size indicators including CI, dMPS, d50, and d′ as anticipated based on rock fragmentation and grinding theories. Furthermore, a strong inverse correlation was found between specific energy and representative chip volume. The findings highlight the relationship of rock cutting efficiency with chip shape and size. [ABSTRACT FROM AUTHOR]

Abstract An attempt was made to examine the relationship between various TBM operational factors, its performance, and muck geometry during the excavation of a short geologically uniform section of Golab II water transfer tunnel. A database based on nine field testing data derived from machine operating and performance parameters along with muck shape and size was formed. Subsequently, it was used for analyzing the correlation among variables. The analysis results point out that there is a strong inverse correlation between specific energy (SE), an indicator parameter of rock cutting efficiency, and three muck size indicators including: coarseness index (CI), mean particle size, and absolute grain size (last one is the correlation with R 2 = 0.93). Typically, for the small sized muck with the mean grain size ranging from 3 to 9 mm examined in shale formation in this study, the in situ SE varies between 3.4 and 8.1 kWh/m3. Also, the TBM penetration rate (PRev) follows reasonable trends with respect to other field performance parameters such as boreability index (BI), instantaneous cutting rate (ICR), and machine operational factors including the cutterhead thrust force and torque, in agreement with findings of several similar both laboratory and field scale studies. For example, for the PRev ranging from 5.5 to 10 mm/rev, the BI decreases in power function from 34.8 to 16.8 kN/cutter/mm/rev, and the ICR increases logarithmic from 50 to 85 m3/h. These results highlight the potential development of a real-time monitoring based system can be come on the scene for controlling TBM operation. However, the range of the input data available is very limited, therefore a deep analysis along with an extended database is required for enhancing outcomes of this study. [ABSTRACT FROM AUTHOR]

Knowing that the chip geometry helps predict machining forces, energy and consequently the machined surface quality, in the past, various models for the prediction of the undeformed and deformed chip geometries in ball-end milling have been evolved. It is observed that most of the models use volume constancy (VC) between the undeformed and deformed chip geometries towards evaluation of deformed chip thickness. This work presents a new approach to the deformed chip geometry evaluation, which involved considering strains in the deformed chips (SDC). In the strains developed in the deformed chip (SDC) approach, bending, compression/shear and thermal strains have been modelled using a simplified tapered cantilever shape of the undeformed chip. The cutting edge-work interactions on horizontal as well as work surfaces inclined at different angles have been considered during the model development. As the workpiece inclination increases from 0° (horizontal) to 60 ° , the deformed chip thickness increases by 63% due to a higher effective feed per tooth. However, the instantaneous shear angle found constant at 50 ° throughout the cut for a typical machining parametric combination. A comparison of SDC and VC approach shows that the magnitudes of deformed chip thickness, shear angle and the resultant cutting forces obtained using SDC models match more closely (within 90%) with the experimental data. It is envisaged that such models when incorporated in the cutting force models, would help predict cutting forces more accurately. [ABSTRACT FROM AUTHOR]

Producing miniaturized components from a wide variety of engineering materials is one of the most important fields of interest in manufacturing industry. Micro end milling is considered to be one of the efficient methods to produce complex 3D micro components. In micro machining, undeformed chip thickness is comparable to the tool edge radius, which introduces a critical undeformed chip thickness. Below the regime of critical undeformed chip thickness material is not removed but plowed. Ti-6Al-4V is one of the most popular titanium alloy because of its superior properties such as resistance to heavy loads, corrosion resistance, lightness, and bio-compatibility. This paper investigates micro end milling characteristics of the Ti-6Al-4V titanium alloy through a series of cutting experiments. Here the size effect in micro end milling was observed by studying the effect of the cutting edge radius on process performance. In order to understand the effect of the cutting edge radius on machining performance, range of feed per tooth was selected in such a way that it includes both within and outside the size effect region. This paper explores how cutting edge radius affects the cutting force, coefficient of friction, surface roughness, and chip formation during the micro end milling process. A size effect region was obtained from the variation of cutting force with feed per tooth. It was found that feed per tooth in the vicinity of 1-μm range is critical feed per tooth value, which is approximately one third of the cutting edge radius. Below this value, the cutting edge radius effect is predominant which would result in more ploughing mechanism. This was evident from the deviation of cutting force from the linear trend, increase in coefficient of friction, and surface roughness value at lower feed per tooth. In addition, a cutting force model was proposed considering the cutting edge radius effect and has been validated with experimental results. [ABSTRACT FROM AUTHOR]

Glow discharge polymer (GDP) ablators with complex microstructures are critical in confined inertial fusion applications. Micro-milling with controllable chip formation is of great interest. This work studies the effect of cutting tool inclination on the chip geometry and surface integrity in micro-milling of GDP. A novel model framework was proposed for undeformed and deformed chip geometries including chip length, width, and thickness by considering the tool inclination angle, effective cutting radius and tool orientation. Milling of micro-grooves was conducted on GDP films using a single-edge diamond tool (SDT). The mechanism of chip formation and surface generation were analyzed. The instantaneous cutting speed and material removal rate were calculated based on the proposed models. Moreover, the effect of tool inclination angles on the surface quality and machining profile accuracy was explored. The chip morphology and surface texture of the micro-groove were also analyzed. The results show that the proposed model could accurately predict the chip geometries with an average goodness of fit of 99.68%. Case Ⅰ with a positive inclination of 20° along the feed direction was found the best for micro-milling of GDP polymer using a SDT with an excellent surface roughness of 11.35 nm and a maximum PV value of 0.072 µm. The study could provide guidance for chip formation and surface finishing modeling during micro-milling. [ABSTRACT FROM AUTHOR]

During the tapping process, chip snarling at high cutting speeds is a major obstacle in the improvement of machining efficiency. A cut tap tool coated with nickel-phosphorus (Ni-P)/abrasive particle composite film reduced the chip curl diameter and prevented chip snarling under high cutting speed conditions (50 m/min). In this study, the local coefficient of friction at the sliding zone of the chip-tool interface was estimated on the basis of the sticking-sliding friction model and using the cutting torque and thrust force measured during the tapping process. In addition, the effects of the local coefficient of friction at the sliding zone on chip curl diameter and secondary shear zone thickness were analyzed to investigate the mechanism of preventing chip snarling when using tapping tools coated with composite film. Tapping tests were conducted using four tapping tools that were steam treated, TiCN film coated, Ni-P/cBN film coated, or Ni-P/SiC film coated. The workpiece material was a rolled structure steel. The cutting speeds were 10, 30, and 50 m/min. The results demonstrated that chip curl diameter decreased with an increase in the local coefficient of friction at the sliding zone. The local coefficients of friction for tapping tools coated with composite films (1.51-1.91) were higher than those for tapping tools with conventional surface treatments (1.35-1.58). The secondary shear zone thickness also increased with an increase in the local coefficient of friction at the sliding zone. These results indicated that the tapping tool coated with Ni-P/abrasive particle composite film provided a high local coefficient of friction at the sliding zone, which increased the secondary shear zone thickness and reduced the chip curl diameter.

The manufacturing of titanium airframe parts involves significant machining and low buy-to-fly ratios. Production costs could be greatly reduced by the combination of an additive manufacturing (AM) process followed by a finishing machining operation. Among the different AM alternatives, wire arc additive manufacturing (WAAM) offers deposition rates of kg/h and could be the key for the production of parts of several meters economically. In this study, the influence of the manufacturing process of Ti6Al4V alloy on both its material properties and machinability is investigated. First, the mechanical properties of a workpiece obtained by WAAM were compared to those in a conventional laminated plate. Then, drilling tests were carried out in both materials. The results showed that WAAM leads to a higher hardness than laminated Ti6Al4V and satisfies the requirements of the standard in terms of mechanical properties. As a consequence, higher cutting forces, shorter chips, and lower burr height were observed for the workpieces produced by AM. Furthermore, a metallographic analysis of the chip cross-sectional area also showed that a serrated chip formation is also present during drilling of Ti6Al4V produced by WAAM. The gathered information can be used to improve the competitiveness of the manufacturing of aircraft structures in terms of production time and cost.

The broaching process is used to generate high quality surfaces in very short times. In order to improve the understanding of the evolution of surface quality in broaching, a sensitivity study of the influence on the surface roughness of several broaching parameters dealing with the tool design, the cutting conditions or the workpiece material was performed. Forces and chip formation have also been analyzed so as to highlight the surface roughness generation. This paper shows how the process parameters (such as cutting speed or lubrication), tool design (rise per tooth, tooth angles, substrate material), and workpiece material affects the surface roughness. [ABSTRACT FROM AUTHOR]

This study investigates the influence of cutting parameters on longitudinal turning of high Silicon cast aluminium alloy AlSi9Cu3 using PCD tools with and without chip breaker geometry. In order to build the 3D numerical model, the experimental and predicted cutting forces were used for inverse calibration of the Johnson–Cook material model which was implemented in DEFORM TM finite element software. A sensitivity analysis has been performed in order to obtain an acceptable prediction of the machining parameters such as chip geometry and cutting forces as well as to understand the influence of friction and mesh size effects in the predicted results. Results have shown a satisfactory correlation between experimental turning data and numerical estimates based on assumptions that have been taken for the material behaviour. [ABSTRACT FROM AUTHOR]

This article aims at predicting machining performances for oblique turning in relation to tool-nose radius. A new geometric analysis for the uncut chip area is proposed as function of depth of cut, feed rate, tool-nose radius, and edge direction angle. Cutting edge is discretized into increments and average uncut chip thickness, elementary direction angle and elementary depth of cut are determined for each one. A new thermomechanical model is developed for each increment which is supposed to be an oblique machining with single cutting edge. The predicted cutting force components are in good agreement with experimental data over a wide range of cutting conditions. In particular, the effect of tool-nose radius and cutting parameters on chip geometry, cutting temperature, and cutting force components are studied. It is underlined that tool-nose radius promotes the increase in radial force, however, its influence on the other parameters is negligible. [ABSTRACT FROM AUTHOR]

Understanding the chip formation is one of most important issues in controlling the grinding wheel performance or the work surface finish in grinding process. This article discusses the effects of the ultrasonic vibration and peripheral speed of grinding wheel on the chip size and geometry in ultrasonic assisted grinding (UAG) of Inconel 718 with an electroplated cBN grinding wheel. Firstly, scanning electron microscopic (SEM) observations were performed on the chips formed at different vibration amplitudes and wheel peripheral speeds. The obtained 3D SEM images were used to determine the length and cross-section area of chips. Then, the geometries of chips were observed with SEM. The obtained results demonstrated that (1) chip size and geometry were distinctly affected by the ultrasonic vibration of grinding wheel but hardly by the wheel peripheral speed, e.g., the cross-section area of chips became smaller by 64.3 % and the length decreased by 36.3 %, respectively, once the ultrasonic vibration with an amplitude of A = 9.4 μm has been imposed to the grinding wheel; (2) the UAG is potentially avoiding the formation of shear chips and prefers the flow chips, especially at larger amplitude; (3) little changes were found on the chip geometry as the wheel peripheral speed increased in UAG; (4) the change in the chip size and geometry caused by the ultrasonic vibration was supposed to be owing to the ultrasonic lubrication and the vibration in the rake angle of grain cutting edge. [ABSTRACT FROM AUTHOR]

During tapping processes, the chip snarling problem must be resolved to improve manufacturing efficiency. In this study, we used an electroless plating method to develop a tapping tool coated with Ni−P/abrasive-particle composite film to solve the chip snarling problem. The tapping test was conducted at 10 m/min (conventional cutting velocity) and 50 m/min with a machining center. The cutting torque and thrust force were measured using a dynamometer. The results of the tapping test indicate that the developed tapping tool coated with the composite film prevented chip snarling at 10 m/min and 50 m/min. The dimensionless diameter for the developed tapping tool, which is the diameter of the chip curl divided by the width of the helical flute, was less than 1.0 for both cutting conditions, whereas that for steam-treatment and TiCN film is greater than 1.0. Furthermore, we estimated the coefficient of friction between the rake face of the cutting edge of the tapping tool and the chip from the thrust force and cutting torque. The estimated coefficient of friction for the tapping tool coated with the composite film (>1.23) was greater than that for the other methods (<1.23). These results indicate that a high coefficient of friction (>1.23) is necessary to prevent chip snarling, and due to the high coefficient of friction, the developed tapping tool can prevent chip snarling even at a speed of 50 m/min. [ABSTRACT FROM AUTHOR]

Chip breakage is a major machinability criterion of metal cutting operations. Favorable broken chips enable their efficient removal and prevent mechanical damages to the machined surface. Ductile failure on the chip free surface initiates chip breakage. The ductility of most materials depends on the stress triaxiality. Its relationship to the manufacturing parameters has to be understood in order to develop predictive methodologies of tool/process design. The problem can be approached by assessing the relationship between triaxiality and chip geometry, which is an integral representation of all tool/process parameters and material properties. This work presents a novel Finite-Element (FE) modeling approach of the relationship between the 3D chip geometry and the distribution of the stress triaxiality in the chip breakage location. For the derivation of the proposed approach it is shown that the stress state in the chip breakage location mainly develops during the chip bending phase. The approach enables for the first time to study the separate impacts of chip helical radius, helical angle, helical pitch and the shape of the deformed chip cross section on the triaxiality distribution. A sensitivity analysis of all input parameters is conducted and it is shown that all parameters but the helical pitch have characteristic impacts on the triaxiality distribution. The computational effort of the proposed modeling approach is significantly lower of than of available FE-models of metal cutting processes. The validation includes longitudinal turning experiments on steel AISI 1045 and 3D FE-process simulation modeling. [ABSTRACT FROM AUTHOR]

Chip breakage is a major machinability criterion. Stable processes in automated manufacturing systems depend on favorable chip forms, which are efficiently manageable and not hazardous to the machine operators. It is well known that chip breakage initiates with ductile material failure on the chip-free-surface. The ductile failure strain is mainly in-fluenced by the stress-state, the temperature and the strain rate. Little theoretic knowledge exists concerning the relationships between these state variables and the tool/process parameters, which is required for developing predictive methodologies for efficient tool/process design. The task can be approached by relating the state variables to the chip geometry: Both are interdependent results of the complex interactions between the tool/process parameters and the material properties. However, while the influence of the tool/process parameters on the chip geometry is experimentally obtainable by High-Speed-Cameras, state variables like the temperature on the chip-free-surface are hardly measurable. Accordingly, understanding the relationship between chip geometry and state variables on the chip-free-surface creates the foundation for understanding the relationship between tool/process parameters and chip breakability. This work presents an analytical model of the relationship between chip geometry and temperature distribution on the chip-free-surface. The temperature is derived as a function of the 3D-chip geometry parameters, the tool/process parameters and the thermo-mechanical workmaterial properties. It is shown how each of these parameters influences the temperature fields. The derivation assumes a strain dependent fraction of the plastic energy transforming into thermal energy. The model is programmed and confirmed by longitudinal turning experiments and a validated FEM-model of longitudinal turning of steel AISI 1045. [ABSTRACT FROM AUTHOR]

Most often contoured surfaces inclined at several inclinations are generated using ballend milling of aerospace and automobile components. It is understood that the chip morphology and the corresponding cutting mechanisms change with a change in the tool-workpiece interactions on inclined surfaces. Analytical predictive models to accurately evaluate the undeformed and deformed geometries of chip in ball-end milling are not available. Therefore, this work presents development of analytical models to predict the cutting tool-workpiece interaction as the workpiece inclination changes, in terms of undeformed and deformed chip cross sections. The models further evaluate instantaneous shear angle along any cross section of the tool-work interaction on a ball-end cutter in a milling operation. The models illustrate evaluation of a chip segment and mechanism of its formation in ball-end milling on an inclined work surface. It is observed that the chip dimensions, except deformed chip thickness, increase with an increase in the workpiece inclination angle. Also, a higher workpiece inclination results into an easy flow of the deformed chip over the cutting tool flank, which leads to a higher shear angle during the cut. The predictive chip geometry models corroborate 90% to the experimental results obtained at various workpiece inclinations. [ABSTRACT FROM AUTHOR]

Abstract: Chip breakage is one of the most important indicators for process stability in metal cutting. It ensures efficient chip removal in automated systems and prevents mechanical damage to the machined workpiece surface. It is well known that chip breakage initially occurs after the plastic strain on the chip surface, which is not contacting the tool (chip free surface), exceeds a critical value. However, the theoretical understanding on how the plastic strain on the chip free surface is affected by the tool/process parameters remains limited. In a first step this problem can be approached by assessing the relationship between the plastic strain on the chip free surface and the chip geometry. Both are direct and interdependent outcomes of the complex interactions between the cutting conditions, tool geometry and thermo-mechanical material properties. However, the impact of the tool/process parameters on the chip geometry is much easier experimentally assessable than the plastic strain, which is hardly measurable at all. Thus, the scientific understanding of the relationship between chip strain and chip geometry lays the foundation for understanding the influence of the tool/process parameters on the strain in the chip free surface and chip breakage. This paper proposes an analytic model of the equivalent plastic strain fields on the free surface of chips in metal cutting. The local strain tensors are derived as a function of the feed, depth of cut, cutting edge angle, tool nose radius, chip up-curl radius, side-curl radius and side flow angle. It is shown how each of these parameters influences the equivalent strain fields. The validation of the model includes longitudinal turning experiments on steel AISI 1045 and validated FEM-machining simulations. [Copyright &y& Elsevier]

Widespread application of ball end milling operation is an outstanding characteristic in the field of manufacturing of die and molds. Tool inclination angles, which could improve the cutting performance of ball end mill, are critical factor in the ball end milling process, and also chip formation is one of the most important phenomena in the machining process. Numerical simulation, geometric analysis, observation by optical microscope and scanning electron microscope, and energy-dispersive spectroscopy analysis were adopted to study the chip formation during ball end milling of H13 die steels involving tool inclination angles in this work. The theoretical uncut chip geometry and tool–work contact zone were analyzed by computer-aided modeling technology. Finite element modeling of chip formation process involving tool inclination angles was performed, and variations of the maximum chip temperature which could provide assistant understanding of practical chip formation were analyzed. This article also investigated the practical chip morphologies, chip color, and the cutting characteristics under different process conditions and tool inclination angles. The optical microscope and scanning electronic microscope were used to capture the micro-photos of the chips under different process parameters, and the chip color and chip morphologies were discussed together with the cutting characteristics with regard to various process parameters. Energy-dispersive spectroscopy analysis of the chip free surface and back surface was also carried out for some special tool inclination angles. Deep understanding of the chip formation in multi-axis milling process was enhanced, and the research work could provide support for the selection of process parameters to some extent. [ABSTRACT FROM PUBLISHER]

Abstract: The ball end milling process, commonly used for generating complex shapes, involves continuous variation in the uncut chip dimensions, thereby introducing increased complexities in the cutting force prediction. Therefore, usually a mechanistic modeling approach is recommended. This paper however, presents an analytical approach, to predict chip dimensions followed by instantaneous shear angle in ball end milling of superalloys. Subsequently, the cutting forces are predicted considering strain, strain rate, and temperature dependence of work material shear strength by applying Johnson–Cook material model. The proposed analytical model evaluates the uncut and the cut chip dimensions including chip length, width and thickness. The instantaneous shear angle evaluated using the models, is a function of cutter rotation, instantaneous cutter radius, helix angle, and so on. The cutting forces prediction in the framework of oblique cutting theory, takes into account the ploughing forces acting on the cutting tool edges. It is observed that the analytical models for predicting chip dimensions and the cutting forces in X- and Y-directions match well with the corresponding experimental values. [Copyright &y& Elsevier]

Abstract: The mechanics of segmented chip formation during orthogonal cutting of titanium alloy Ti–6Al–4V are studied in detail with the aid of high speed imaging of the chip formation zone. Cutting speeds from 4 to 120 m/min and feeds of 0.05, 0.075 and 0.1mm were used. Segmented chip formation was observed throughout and detailed measurements of recorded video sequences examined the deformation within chip segments and within the shear bands separating the chip segments. The chip segment geometry was characterised in terms of the cutting parameters given above and the shear strains both within the chip segments and the shear bands were analysed. A thermal model of the process was developed and average temperatures for the primary shear zone and for the tool rake face were calculated. [Copyright &y& Elsevier]

Abstract: During the cutting process, the temperature field in the chip is measured by using the principle of pyrometry in the visible spectral range. The mechanical device developed to reproduce orthogonal cutting conditions and to reach very high cutting speed (up to 120m/s) is used for a range of velocities from 10 to 70m/s. The presented experimental results concern two materials chosen following the form of chip generated: a low carbon steel (C15) and a low alloyed medium carbon steel (42CrMo4). The performances of the measurement set-up are completed by the possibility of recording real time photographs of the chip formation. These records make the analysis of temperature maps easier and allow specific parameters as the contact length at the tool-chip interface or the shear angle to be determined. The non-uniform heating in the chip is emphasized by the presence of a maximal temperature area. The temperature fields measured for a cutting speed around 20m/s present maximums of 870°C for 42CrMo4 and 630°C for C15 located near the tool–chip interface. The effects of cutting velocity on the maximum temperature value in the chip and the location of this heat zone are presented. This maximum increases with the cutting velocity contrary to its location which presents few variations. The experimental results are compared with an analytical approach. [Copyright &y& Elsevier]

In vitro study on high rotation (up to over 300,000 rpm) deep removal (up to 150 μm) of ceramic prostheses, made of a machinable ceramic, Vita Mark II, was performed in dental surgery using a high‐speed dental handpiece. Dental clinical removal relevance, including tangential and normal grinding forces, specific grinding energy, and surface roughness, was investigated to establish the relationships among the surgery parameters, chip geometry, and fracture mechanism. The results show that both the tangential and normal grinding forces increased with increases in both depth of cut and maximum undeformed chip thickness, but decreased with an increase in grinding speed. Specific grinding energy decreased with increase in the depth of cut and the maximum undeformed chip thickness, but increased with an increase in grinding speed. Surface roughness and morphology appeared to be independent of the increases in depth of cut, grinding speed, and maximum chip thickness. The limitation for deep removal using the dental handpiece was found that the operation at the depth of cut of 150 μm or beyond resulted in a huge normal force exertion of 3 N with a great variation. The microfracture, the lateral fracture, and the ductile microcutting were found to occur simultaneously in dental surgery to remove the ceramic prostheses. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007 [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates micro- and nano-scale (10nm–2μm) machining characteristics of a non-ferrous structural alloy, aluminum 7075-T6 (87 HRB) through a series of cutting experiments. Aluminum 7075-T6 is used in the die and mold making industry for creating prototype molds. The effects of cutting conditions on the machining forces, chip geometry, surface roughness, and derived parameters such as the specific cutting energy, shear angle and mean friction coefficient in orthogonal micro- and nano-scale cutting of Al 7075-T6 are presented and compared with trends observed in conventional macro-scale cutting. Explanations for the observed trends are given. [Copyright &y& Elsevier]

New strategies are used in manufacturing enterprises due to global competition. High-speed cutting offers a very appropriate opportunity to reduce run times since the high cutting speeds and feed rates involved permit the reduction of production times and minimise rework. There are, however, difficulties in judging tool wear [1]. This paper analyses the formation mechanism of tool wear and presents a complete solution to calculate wear using a ball end cutter for high-speed cutting. Chip geometry generated to calculate tool wear is affected by machining conditions such as turning speed, cutting depth and geometries of tool and work piece which in turn determine the key parameters of chip sections such as length of cut and mean chip thickness. An improved algorithm and a knowledge-based decision model developed to calculate effective tool contact are also discussed to help reduce calculation time and improve calculation efficiency. The calculation results include output form and a 3D wear model showing wear data distributed on the tool contour. [ABSTRACT FROM AUTHOR]