In this communication, an attempt was taken to study the influence of machining parameters like g... more In this communication, an attempt was taken to study the influence of machining parameters like gap voltage, capacitance and depth of hole on machining performances for 2D and 3D surface finish of blind micro holes and electrode wear length in micro electrical discharge drilling (MEDD) process. The experimentation was carried out employing full factorial design (3 3 ) with three levels of each machining parameter to study simultaneous effect of factors on machining performance. Mathematical models have been developed for the mentioned machining outputs by multiple linear regression analysis. Response surface methodology was utilized to carry out multiple response optimization and to find the optimum process parameter settings for a desired yield by contour overlapping method using statistical software MINITAB 16 with 95% confidence level and with levels of factors in coded units. The models so developed are excellent for acceptance as the coefficients of multiple determinations (R 2...
Abstract— Virtual cellular manufacturing systems (VCMS) have gained popularity quite recently a... more Abstract— Virtual cellular manufacturing systems (VCMS) have gained popularity quite recently after realizing a fact that it overcomes the difficulty posed by traditional cellular manufacturing systems (CMS) in terms of rearrangements and reconfiguration of the existing machineries and facilities. Worker assignments are crucial for VCMS since many of the benefits associated with it come from deriving an optimal worker assignment and adequate worker flexibility levels. Artificial neural networks (ANNs) are quite popular in mapping input and output variables to find out similar patterns and clusters. In this paper, a simulated ANN model has been proposed, for worker assignments into virtual cells, which is driven by genetic algorithm (GA) for optimizing ANN architectural parameters. Key findings and analysis on findings are presented and discussed.
The International Journal of Advanced Manufacturing Technology, 2020
Micro milling is a suitable micro cutting process to create micro features. This paper presents a... more Micro milling is a suitable micro cutting process to create micro features. This paper presents an analytical model of the specific cutting energy in micro cutting and analyses the specific cutting energy in micro milling of amorphous bulk metallic glass. The analytical results are compared with the experimental results, where the experimental work comprises of micro milling amorphous bulk metallic glass at different cutting speeds and a wide range of feed rates. The analytical model considers an isotropic and homogeneous work material that macroscopically resembles the bulk metallic glass. In the experimental study, the influence of the cutting parameters on the specific cutting energy and the surface roughness generated in micro end milling is analysed. Experimental results show appreciable dependence of specific cutting energy and surface roughness on the feed rate. Size effect phenomenon is exhibited in both the analytical and experimental values of the specific cutting energy. The micro mechanism behind the size effect in bulk metallic glasses is discussed in the article. Experimental results indicate that for feed per tooth higher than the cutting edge radius, increase in the feed rate results in the deterioration of the surface quality and reduced values of the specific cutting energy. Results of the experimental study show a decrease in the specific cutting energy and surface roughness values with the increase in the cutting speed.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
In the present study, an analysis is presented for the formulation of a model in top burr formati... more In the present study, an analysis is presented for the formulation of a model in top burr formation to estimate the width of the top burrs formed in micro end milling process. In this analysis, the width of the top burrs, considered to be the measure of burr size of top burrs represents the extent of burr formation. The model is applied to quantify the burr formation in Zr-based bulk metallic glass, an amorphous metallic alloy. In this study, micro milling experiments were carried out on the bulk metallic glass work material at different levels of feed rate, axial depth of cut and cutting speed to compare the experimental values of top burr width with the predicted values. Analysis is carried out to characterize top burr formation based on the experimental results of burr sizes in the up-milling and down-milling side edges and the influential effects of the cutting parameters on the burr formation are analyzed.
Precision micro-component fabrication demands suitable manufacturing processes that ensure making... more Precision micro-component fabrication demands suitable manufacturing processes that ensure making of parts with good form and finish. Mechanical micro milling represents a flexible and powerful process that exhibits enhanced capability to create micro features. Bulk metallic glass (BMG) represents a young class of amorphous alloy material with superior mechanical and physical properties and finds appreciable micro scale applications like biomedical devices and implants, micro parts for sport items and various other micro- components. In the present work, an attempt has been made to analyze the influence of the cutting parameters like spindle speed, feed per tooth and axial depth of cut on the machinability of BMG, in mechanical micro-milling process. The micro-milling process performances have been evaluated concerning to cutting forces and surface roughness generated, by making full slots on the workpiece with solid carbide end mill cutters. The paper presents micro-machining resul...
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2017
In this research study, empirical mathematical models for cutting forces and surface roughness ha... more In this research study, empirical mathematical models for cutting forces and surface roughness have been developed to investigate the effect of axial depth of cut, feed, radial depth of cut and cutting speed in high-speed ball-end milling of Al2014-T6. Ball-end milling experiments have been planned using central composite design based on response surface methodology. The mathematical models have been established and tested for adequacy. A full quadratic model has been adopted for modelling. It has been found that axial depth of cut is the most dominant cutting parameter for the tangential and axial cutting forces, accounting for 49.38 and 47.12% contributions, respectively. Radial depth of cut is the most dominant parameter for radial force and contributes 69.94% for it. Results also revealed that force components decrease with increase in cutting speed. There is very small variation in cutting force components in the cutting speed range of 75-150 m/min at lower values of axial and radial depth of cut. Surface roughness is effected by cutting speed largely followed by feed. Multi-objective optimization has been performed using composite desirability to optimize the cutting parameters for minimum surface roughness and cutting forces simultaneously. Confirmation tests have been conducted using optimal set of cutting parameters. The results of confirmation tests are very close to the predicted results.
International Journal of Machining and Machinability of Materials, 2017
The influences of machining parameters has a like gap voltage, capacitance and spindle speed on m... more The influences of machining parameters has a like gap voltage, capacitance and spindle speed on machining performances for surface finish R a and S a of high aspect ratio through micro holes drilled in zirconium-based bulk metallic glass Vitreloy 1 or Vit 1 with cylindrical tungsten tool electrodes in micro electrical discharge drilling were studied. The experimentation was carried out adopting Taguchi's L 27 (3 13) orthogonal array. The simultaneous effects of machining parameters on machining performance were studied by applying response surface methodology. Adopting analysis of variance technique, it was observed that the machining parameters selected have great significant effects on responses. Second order regression models were developed for responses and found excellent for acceptance. Predicted optimal designed value for responses was computed using Taguchi's algorithm. Validity of the models was checked statistically and found acceptable. The proposed model could be considered as valuable tools for process planning for cost effective machining of Vit 1. Tool electrode material tungsten was deposited on the hole surface as observed from energy dispersive X-ray spectroscopy study.
Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2016
Surface roughness is one of the most important requirements of the finished products in machining... more Surface roughness is one of the most important requirements of the finished products in machining process. The determination of optimal cutting parameters is very important to minimize the surface roughness of a product. This article describes the development process of a surface roughness model in high-speed ball-end milling using response surface methodology based on design of experiment. Composite desirability function and teaching-learning-based optimization algorithm have been used for determining optimal cutting process parameters. The experiments have been planned and conducted using rotatable central composite design under dry condition. Mathematical model for surface roughness has been developed in terms of cutting speed, feed per tooth, axial depth of cut and radial depth of cut as the cutting process parameters. Analysis of variance has been performed for analysing the effect of cutting parameters on surface roughness. A second-order full quadratic model is used for mathe...
Efficiency of any machining process depends on the effectiveness of final outcomes. Surface integ... more Efficiency of any machining process depends on the effectiveness of final outcomes. Surface integrity plays an important role in functional performance of a part or component. Traditionally, surface roughness is considered to be the principal parameter to assess the surface integrity of a machined surface. In this paper, the influences of machining parameters like gap voltage, capacitance and depth of hole on the surface finish parameters like Ra and Sa of micro holes have been studied in micro electrical discharge drilling. The high aspect ratio blind micro holes were drilled on titanium alloy (Ti-6Al-4V) with cylindrical tungsten tool electrodes. The experimentation was carried out adopting a full factorial design (33). The simultaneous effects of machining parameters on responses were analysed using response surface methodology. Multiple linear regression models were developed for responses to obtain the correlation between machining parameters and machining outputs. Multi-object...
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2016
List of symbols a p Axial depth of cut (mm) a e Radial depth of cut(mm) f z Feed per tooth (mm/to... more List of symbols a p Axial depth of cut (mm) a e Radial depth of cut(mm) f z Feed per tooth (mm/tooth) N Rotational speed (rpm) R Cutter radius (mm) R z Local radius of cutter (mm) R zi Local radius of ith cutting edge element on cutter (mm) R(δ i) Local radius of cutter considering local lag angle (mm) β Radial immersion angle (radian) κ Axial immersion angle (°) β ij Radial immersion angle of i th element of j th cutting edge (radian) δ i Local lag angle (°) δ i (z) Local lag angle at axial position z (°) δo Maximum lag angle (°) θ Cutter rotation angle (radian) φ p Pitch angle (radian) ψ Helix angle (°) ψ i Local helix angle (°) F x,y,z Average force in x-, y-and z-directions (N)
In high-speed ball end milling, cutting forces influence machinability, dimensional accuracy, too... more In high-speed ball end milling, cutting forces influence machinability, dimensional accuracy, tool failure, tool deflection, machine tool chatter, vibration, etc. Thus, an accurate prediction of cutting forces before actual machining is essential for a good insight into the process to produce good quality machined parts. In this article, an attempt has been made to determine specific cutting force coefficients in ball end milling based on a linear mechanistic model at a higher range of rotational speeds. The force coefficients have been determined based on average cutting force. Cutting force in one revolution of the cutter was recorded to avoid the cutter run-out condition (radial). Milling experiments have been conducted on aluminum alloy of grade Al2014-T6 at different spindle speeds and feeds. Thus, the dependence of specific cutting force coefficients on cutting speeds has been studied and analyzed. It is found that specific cutting force coefficients change with change in rotational speed while keeping other cutting parameters unchanged. Hence, simulated cutting forces at higher range of rotational speed might have considerable errors if specific cutting force coefficients evaluated at lower rotational speed are used. The specific cutting force coefficients obtained analytically have been validated through experiments.
Machine tool chatter is a serious problem which deteriorates surface quality of machined parts an... more Machine tool chatter is a serious problem which deteriorates surface quality of machined parts and increases tool wear, noise, and even causes tool failure. In the present paper, machine tool chatter has been studied and a stability lobe diagram (SLD) has been developed for a two degrees of freedom system to identify stable and unstable zones using zeroth order approximation method. A dynamic cutting force model has been modeled in tangential and radial directions using regenerative uncut chip thickness. Uncut chip thickness has been modeled using trochoidal path traced by the cutting edge of the tool. Dynamic cutting force coefficients have been determined based on the average force method. Several experiments have been performed at different feed rates and axial depths of cut to determine the dynamic cutting force coefficients and have been used for predicting SLD. Several other experiments have been performed to validate the feasibility and effectiveness of the developed SLD. It is found that the proposed method is quite efficient in predicting the SLD. The cutting forces in stable and unstable cutting zone are in well agreement with the experimental cutting forces.
A WEDM process may be called as a Micro WEDM (MWEDM) process when it is used for manufacturing mi... more A WEDM process may be called as a Micro WEDM (MWEDM) process when it is used for manufacturing micro parts. The rest underlying theory is same as traditional WEDM. A micro part is machined with good dimensional accuracy and surface finish when the kerf (slot) width becomes considerably smaller compared to that obtainable in conventional WEDM. Truly speaking, the cutting tool in WEDM/MWEDM is not the wire, but it is the pulse (electrical discharge). A minimum kerf is ensured in Micro WEDM, when (i) pulse sizes are made extremely small, (ii) extremely thin wire is used (ϕ = 20–100 μm), and (iii) process inaccuracies along with the discharge gap are minimized. It is required for Micro WEDM to maintain the pulse energy in the order of 10−5–10−7 J. Process inaccuracies are minimised by minimising the amplitude of wire vibration and wire lag. Hence, for an MWEDM machine, the following subsystems are modified as compared to a conventional WEDM setup: (a) the machine tool configuration is designed mainly to eliminate stray capacitance or leakage of charges from the gap, (b) the pulse generator produces discharges with pulse energy preferably in the order of 10−6–10−7 J, (c) a pulse discrimination system is installed to avoid arc or other abnormal discharges, (d) a closed-loop controlled proper wire transportation system is needed, (e) the wire diameter should be 20–80 μm and preferably of tungsten, (f) a suitable oil dielectric is used and lastly, (g) a precise closed-loop controlled servo mechanism is used for gap and work-table feed control to operate at steps at submicron level.
International Journal of Machining and Machinability of Materials, 2016
Specific cutting force coefficients play an important role in study of cutting forces in ball end... more Specific cutting force coefficients play an important role in study of cutting forces in ball end milling. Due to the complicated geometry of ball end milling cutter the effective diameter of the tool (with active cutting edges) varies along the axis of the tool during machining which leads to the discrepancies in the prediction of cutting forces. In this paper, an improved method of identification of specific cutting force coefficient is proposed for ball end milling cutter. The cutter is discretized into finite number of axial discs along the axis of the cutter. A semi-mechanistic force model is adopted to relate the cutting forces in each disc and specific cutting force coefficients are calculated by inverse method and a fourth order polynomial fitting has been obtained. Several experiments were carried out at different feed and depth of cut to calibrate the proposed identification method and the same is used for predicting the cutting forces. The shearing force coefficients have larger value at lower depth of cut and they decrease with increase in depth of cut. Edge force coefficients do not vary with the depth of cut significantly.
Journal of The Institution of Engineers (India): Series C, 2016
Friction stir welding (FSW) has been the most attracting solid state welding process as it provid... more Friction stir welding (FSW) has been the most attracting solid state welding process as it provides better mechanical and metallurgical properties of the weld. Non-weldable alluminium alloys like 5XXX, 7XXX series can be welded by this process without any difficulty. The butt welding is done using two thin plates (200mm × 100mm × 6mm) of similar metals, i.e, alluminium alloys of grade AA1100. The tool material was made of stainless steel (SS-310 tool steel). In the present study, the traverse speed of the tool was kept constant while four different types of tool geometry, two different rotational speed of the tool alongwith two different plunging forces were used. Thus, a set of eight experiments were conducted and mechanical properties like micro-hardness and tensile strength of the welded specimens have been studied for different process parameters settings. Also, a mathematical model is developed to estimate the generated heat in the welding zone. It was noticed that friction is the major contributor for the heat generation. It was observed that the tool rotational speed and traverse speed have varying effects on tensile strength and hardness of FSWed joints. An attempt is also made to validate the theoretical model of the heat generation in the FSW process.
Micro features machined through micro electrical discharge machining (micro EDM) are adversely af... more Micro features machined through micro electrical discharge machining (micro EDM) are adversely affected by tool wear. Tool electrode and machined parts are deformed due to stochastic behaviour of discharge processes. Deposition of tool electrode material on workpiece deteriorates the surface quality of the micro part. Study of the surface quality of blind micro hole is very difficult in non-destructive method due to its miniature size. In this communication, attempts have been made to study the surface quality of high aspect ratio blind micro holes by opening the holes in destructive method. High aspect ratio blind micro holes were drilled in wear resistant high grade steel (block gauge material), zirconium based bulk metallic glass (BMG) Vit 1, titanium super alloy Ti-6Al-4V, oxygen free high thermal conductivity (OFHC) copper, Monel 400 and hard anodized aluminium alloy 6082 T6 in micro EDM by cylindrical tungsten (W) electrode and opened the holes axially through wire EDM (WEDM) to study the surface texture of the opened holes using 3D optical profilometry technique. Elemental analysis of materials of tips of tool electrode and surfaces of the opened micro holes were studied by using energy dispersive X-ray spectroscopy (EDS) technique in scanning electron microscope (SEM). Deformations of tool electrode and tool profile on the workpiece were also studied.
In this communication, an attempt was taken to study the influence of machining parameters like g... more In this communication, an attempt was taken to study the influence of machining parameters like gap voltage, capacitance and depth of hole on machining performances for 2D and 3D surface finish of blind micro holes and electrode wear length in micro electrical discharge drilling (MEDD) process. The experimentation was carried out employing full factorial design (3 3 ) with three levels of each machining parameter to study simultaneous effect of factors on machining performance. Mathematical models have been developed for the mentioned machining outputs by multiple linear regression analysis. Response surface methodology was utilized to carry out multiple response optimization and to find the optimum process parameter settings for a desired yield by contour overlapping method using statistical software MINITAB 16 with 95% confidence level and with levels of factors in coded units. The models so developed are excellent for acceptance as the coefficients of multiple determinations (R 2...
Abstract— Virtual cellular manufacturing systems (VCMS) have gained popularity quite recently a... more Abstract— Virtual cellular manufacturing systems (VCMS) have gained popularity quite recently after realizing a fact that it overcomes the difficulty posed by traditional cellular manufacturing systems (CMS) in terms of rearrangements and reconfiguration of the existing machineries and facilities. Worker assignments are crucial for VCMS since many of the benefits associated with it come from deriving an optimal worker assignment and adequate worker flexibility levels. Artificial neural networks (ANNs) are quite popular in mapping input and output variables to find out similar patterns and clusters. In this paper, a simulated ANN model has been proposed, for worker assignments into virtual cells, which is driven by genetic algorithm (GA) for optimizing ANN architectural parameters. Key findings and analysis on findings are presented and discussed.
The International Journal of Advanced Manufacturing Technology, 2020
Micro milling is a suitable micro cutting process to create micro features. This paper presents a... more Micro milling is a suitable micro cutting process to create micro features. This paper presents an analytical model of the specific cutting energy in micro cutting and analyses the specific cutting energy in micro milling of amorphous bulk metallic glass. The analytical results are compared with the experimental results, where the experimental work comprises of micro milling amorphous bulk metallic glass at different cutting speeds and a wide range of feed rates. The analytical model considers an isotropic and homogeneous work material that macroscopically resembles the bulk metallic glass. In the experimental study, the influence of the cutting parameters on the specific cutting energy and the surface roughness generated in micro end milling is analysed. Experimental results show appreciable dependence of specific cutting energy and surface roughness on the feed rate. Size effect phenomenon is exhibited in both the analytical and experimental values of the specific cutting energy. The micro mechanism behind the size effect in bulk metallic glasses is discussed in the article. Experimental results indicate that for feed per tooth higher than the cutting edge radius, increase in the feed rate results in the deterioration of the surface quality and reduced values of the specific cutting energy. Results of the experimental study show a decrease in the specific cutting energy and surface roughness values with the increase in the cutting speed.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
In the present study, an analysis is presented for the formulation of a model in top burr formati... more In the present study, an analysis is presented for the formulation of a model in top burr formation to estimate the width of the top burrs formed in micro end milling process. In this analysis, the width of the top burrs, considered to be the measure of burr size of top burrs represents the extent of burr formation. The model is applied to quantify the burr formation in Zr-based bulk metallic glass, an amorphous metallic alloy. In this study, micro milling experiments were carried out on the bulk metallic glass work material at different levels of feed rate, axial depth of cut and cutting speed to compare the experimental values of top burr width with the predicted values. Analysis is carried out to characterize top burr formation based on the experimental results of burr sizes in the up-milling and down-milling side edges and the influential effects of the cutting parameters on the burr formation are analyzed.
Precision micro-component fabrication demands suitable manufacturing processes that ensure making... more Precision micro-component fabrication demands suitable manufacturing processes that ensure making of parts with good form and finish. Mechanical micro milling represents a flexible and powerful process that exhibits enhanced capability to create micro features. Bulk metallic glass (BMG) represents a young class of amorphous alloy material with superior mechanical and physical properties and finds appreciable micro scale applications like biomedical devices and implants, micro parts for sport items and various other micro- components. In the present work, an attempt has been made to analyze the influence of the cutting parameters like spindle speed, feed per tooth and axial depth of cut on the machinability of BMG, in mechanical micro-milling process. The micro-milling process performances have been evaluated concerning to cutting forces and surface roughness generated, by making full slots on the workpiece with solid carbide end mill cutters. The paper presents micro-machining resul...
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2017
In this research study, empirical mathematical models for cutting forces and surface roughness ha... more In this research study, empirical mathematical models for cutting forces and surface roughness have been developed to investigate the effect of axial depth of cut, feed, radial depth of cut and cutting speed in high-speed ball-end milling of Al2014-T6. Ball-end milling experiments have been planned using central composite design based on response surface methodology. The mathematical models have been established and tested for adequacy. A full quadratic model has been adopted for modelling. It has been found that axial depth of cut is the most dominant cutting parameter for the tangential and axial cutting forces, accounting for 49.38 and 47.12% contributions, respectively. Radial depth of cut is the most dominant parameter for radial force and contributes 69.94% for it. Results also revealed that force components decrease with increase in cutting speed. There is very small variation in cutting force components in the cutting speed range of 75-150 m/min at lower values of axial and radial depth of cut. Surface roughness is effected by cutting speed largely followed by feed. Multi-objective optimization has been performed using composite desirability to optimize the cutting parameters for minimum surface roughness and cutting forces simultaneously. Confirmation tests have been conducted using optimal set of cutting parameters. The results of confirmation tests are very close to the predicted results.
International Journal of Machining and Machinability of Materials, 2017
The influences of machining parameters has a like gap voltage, capacitance and spindle speed on m... more The influences of machining parameters has a like gap voltage, capacitance and spindle speed on machining performances for surface finish R a and S a of high aspect ratio through micro holes drilled in zirconium-based bulk metallic glass Vitreloy 1 or Vit 1 with cylindrical tungsten tool electrodes in micro electrical discharge drilling were studied. The experimentation was carried out adopting Taguchi's L 27 (3 13) orthogonal array. The simultaneous effects of machining parameters on machining performance were studied by applying response surface methodology. Adopting analysis of variance technique, it was observed that the machining parameters selected have great significant effects on responses. Second order regression models were developed for responses and found excellent for acceptance. Predicted optimal designed value for responses was computed using Taguchi's algorithm. Validity of the models was checked statistically and found acceptable. The proposed model could be considered as valuable tools for process planning for cost effective machining of Vit 1. Tool electrode material tungsten was deposited on the hole surface as observed from energy dispersive X-ray spectroscopy study.
Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2016
Surface roughness is one of the most important requirements of the finished products in machining... more Surface roughness is one of the most important requirements of the finished products in machining process. The determination of optimal cutting parameters is very important to minimize the surface roughness of a product. This article describes the development process of a surface roughness model in high-speed ball-end milling using response surface methodology based on design of experiment. Composite desirability function and teaching-learning-based optimization algorithm have been used for determining optimal cutting process parameters. The experiments have been planned and conducted using rotatable central composite design under dry condition. Mathematical model for surface roughness has been developed in terms of cutting speed, feed per tooth, axial depth of cut and radial depth of cut as the cutting process parameters. Analysis of variance has been performed for analysing the effect of cutting parameters on surface roughness. A second-order full quadratic model is used for mathe...
Efficiency of any machining process depends on the effectiveness of final outcomes. Surface integ... more Efficiency of any machining process depends on the effectiveness of final outcomes. Surface integrity plays an important role in functional performance of a part or component. Traditionally, surface roughness is considered to be the principal parameter to assess the surface integrity of a machined surface. In this paper, the influences of machining parameters like gap voltage, capacitance and depth of hole on the surface finish parameters like Ra and Sa of micro holes have been studied in micro electrical discharge drilling. The high aspect ratio blind micro holes were drilled on titanium alloy (Ti-6Al-4V) with cylindrical tungsten tool electrodes. The experimentation was carried out adopting a full factorial design (33). The simultaneous effects of machining parameters on responses were analysed using response surface methodology. Multiple linear regression models were developed for responses to obtain the correlation between machining parameters and machining outputs. Multi-object...
Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2016
List of symbols a p Axial depth of cut (mm) a e Radial depth of cut(mm) f z Feed per tooth (mm/to... more List of symbols a p Axial depth of cut (mm) a e Radial depth of cut(mm) f z Feed per tooth (mm/tooth) N Rotational speed (rpm) R Cutter radius (mm) R z Local radius of cutter (mm) R zi Local radius of ith cutting edge element on cutter (mm) R(δ i) Local radius of cutter considering local lag angle (mm) β Radial immersion angle (radian) κ Axial immersion angle (°) β ij Radial immersion angle of i th element of j th cutting edge (radian) δ i Local lag angle (°) δ i (z) Local lag angle at axial position z (°) δo Maximum lag angle (°) θ Cutter rotation angle (radian) φ p Pitch angle (radian) ψ Helix angle (°) ψ i Local helix angle (°) F x,y,z Average force in x-, y-and z-directions (N)
In high-speed ball end milling, cutting forces influence machinability, dimensional accuracy, too... more In high-speed ball end milling, cutting forces influence machinability, dimensional accuracy, tool failure, tool deflection, machine tool chatter, vibration, etc. Thus, an accurate prediction of cutting forces before actual machining is essential for a good insight into the process to produce good quality machined parts. In this article, an attempt has been made to determine specific cutting force coefficients in ball end milling based on a linear mechanistic model at a higher range of rotational speeds. The force coefficients have been determined based on average cutting force. Cutting force in one revolution of the cutter was recorded to avoid the cutter run-out condition (radial). Milling experiments have been conducted on aluminum alloy of grade Al2014-T6 at different spindle speeds and feeds. Thus, the dependence of specific cutting force coefficients on cutting speeds has been studied and analyzed. It is found that specific cutting force coefficients change with change in rotational speed while keeping other cutting parameters unchanged. Hence, simulated cutting forces at higher range of rotational speed might have considerable errors if specific cutting force coefficients evaluated at lower rotational speed are used. The specific cutting force coefficients obtained analytically have been validated through experiments.
Machine tool chatter is a serious problem which deteriorates surface quality of machined parts an... more Machine tool chatter is a serious problem which deteriorates surface quality of machined parts and increases tool wear, noise, and even causes tool failure. In the present paper, machine tool chatter has been studied and a stability lobe diagram (SLD) has been developed for a two degrees of freedom system to identify stable and unstable zones using zeroth order approximation method. A dynamic cutting force model has been modeled in tangential and radial directions using regenerative uncut chip thickness. Uncut chip thickness has been modeled using trochoidal path traced by the cutting edge of the tool. Dynamic cutting force coefficients have been determined based on the average force method. Several experiments have been performed at different feed rates and axial depths of cut to determine the dynamic cutting force coefficients and have been used for predicting SLD. Several other experiments have been performed to validate the feasibility and effectiveness of the developed SLD. It is found that the proposed method is quite efficient in predicting the SLD. The cutting forces in stable and unstable cutting zone are in well agreement with the experimental cutting forces.
A WEDM process may be called as a Micro WEDM (MWEDM) process when it is used for manufacturing mi... more A WEDM process may be called as a Micro WEDM (MWEDM) process when it is used for manufacturing micro parts. The rest underlying theory is same as traditional WEDM. A micro part is machined with good dimensional accuracy and surface finish when the kerf (slot) width becomes considerably smaller compared to that obtainable in conventional WEDM. Truly speaking, the cutting tool in WEDM/MWEDM is not the wire, but it is the pulse (electrical discharge). A minimum kerf is ensured in Micro WEDM, when (i) pulse sizes are made extremely small, (ii) extremely thin wire is used (ϕ = 20–100 μm), and (iii) process inaccuracies along with the discharge gap are minimized. It is required for Micro WEDM to maintain the pulse energy in the order of 10−5–10−7 J. Process inaccuracies are minimised by minimising the amplitude of wire vibration and wire lag. Hence, for an MWEDM machine, the following subsystems are modified as compared to a conventional WEDM setup: (a) the machine tool configuration is designed mainly to eliminate stray capacitance or leakage of charges from the gap, (b) the pulse generator produces discharges with pulse energy preferably in the order of 10−6–10−7 J, (c) a pulse discrimination system is installed to avoid arc or other abnormal discharges, (d) a closed-loop controlled proper wire transportation system is needed, (e) the wire diameter should be 20–80 μm and preferably of tungsten, (f) a suitable oil dielectric is used and lastly, (g) a precise closed-loop controlled servo mechanism is used for gap and work-table feed control to operate at steps at submicron level.
International Journal of Machining and Machinability of Materials, 2016
Specific cutting force coefficients play an important role in study of cutting forces in ball end... more Specific cutting force coefficients play an important role in study of cutting forces in ball end milling. Due to the complicated geometry of ball end milling cutter the effective diameter of the tool (with active cutting edges) varies along the axis of the tool during machining which leads to the discrepancies in the prediction of cutting forces. In this paper, an improved method of identification of specific cutting force coefficient is proposed for ball end milling cutter. The cutter is discretized into finite number of axial discs along the axis of the cutter. A semi-mechanistic force model is adopted to relate the cutting forces in each disc and specific cutting force coefficients are calculated by inverse method and a fourth order polynomial fitting has been obtained. Several experiments were carried out at different feed and depth of cut to calibrate the proposed identification method and the same is used for predicting the cutting forces. The shearing force coefficients have larger value at lower depth of cut and they decrease with increase in depth of cut. Edge force coefficients do not vary with the depth of cut significantly.
Journal of The Institution of Engineers (India): Series C, 2016
Friction stir welding (FSW) has been the most attracting solid state welding process as it provid... more Friction stir welding (FSW) has been the most attracting solid state welding process as it provides better mechanical and metallurgical properties of the weld. Non-weldable alluminium alloys like 5XXX, 7XXX series can be welded by this process without any difficulty. The butt welding is done using two thin plates (200mm × 100mm × 6mm) of similar metals, i.e, alluminium alloys of grade AA1100. The tool material was made of stainless steel (SS-310 tool steel). In the present study, the traverse speed of the tool was kept constant while four different types of tool geometry, two different rotational speed of the tool alongwith two different plunging forces were used. Thus, a set of eight experiments were conducted and mechanical properties like micro-hardness and tensile strength of the welded specimens have been studied for different process parameters settings. Also, a mathematical model is developed to estimate the generated heat in the welding zone. It was noticed that friction is the major contributor for the heat generation. It was observed that the tool rotational speed and traverse speed have varying effects on tensile strength and hardness of FSWed joints. An attempt is also made to validate the theoretical model of the heat generation in the FSW process.
Micro features machined through micro electrical discharge machining (micro EDM) are adversely af... more Micro features machined through micro electrical discharge machining (micro EDM) are adversely affected by tool wear. Tool electrode and machined parts are deformed due to stochastic behaviour of discharge processes. Deposition of tool electrode material on workpiece deteriorates the surface quality of the micro part. Study of the surface quality of blind micro hole is very difficult in non-destructive method due to its miniature size. In this communication, attempts have been made to study the surface quality of high aspect ratio blind micro holes by opening the holes in destructive method. High aspect ratio blind micro holes were drilled in wear resistant high grade steel (block gauge material), zirconium based bulk metallic glass (BMG) Vit 1, titanium super alloy Ti-6Al-4V, oxygen free high thermal conductivity (OFHC) copper, Monel 400 and hard anodized aluminium alloy 6082 T6 in micro EDM by cylindrical tungsten (W) electrode and opened the holes axially through wire EDM (WEDM) to study the surface texture of the opened holes using 3D optical profilometry technique. Elemental analysis of materials of tips of tool electrode and surfaces of the opened micro holes were studied by using energy dispersive X-ray spectroscopy (EDS) technique in scanning electron microscope (SEM). Deformations of tool electrode and tool profile on the workpiece were also studied.
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