Search

We report the applicability of the ultrafast pulse laser inscription technique to achieve high ablation depth on uncoated silicon wafer despite its higher surface reflectivity. The proposed methodology of this research work can be an alternative approach for the usual industrial practice of coating silicon surface with highly reflective materials for increasing the absorption phenomenon. To unveil the potential of the proposed methodology, a comparative study was carried out by fabricating microchannels of higher depth on uncoated and coated silicon wafer by varying repetition rate from 10 kHz to 500 kHz at a constant pulse energy of 18 μJ. The formation of ablation depth, ablation width and amorphous layer thickness was taken as the standard for evaluating the effectiveness of the proposed methodology. The experimental results revealed the formation of a higher ablation depth of 6.6 μm and an amorphous layer thickness of 0.039 μm for uncoated silicon material. Whereas, in the case of coated silicon material the ablation depth was found to be 3.199 μm with an amorphous layer thickness of 0.101 μm. This justified the applicability of the ultrafast pulse laser inscription technique for achieving quality microchannels having higher depth on silicon material without any surface coating. The underlying mechanism for the improved performance is due to the low temporal separation (μs) property of ultrafast lasers which results in negligible heat diffusion into the bulk material, thereby minimizing the collateral thermal damages. This was further proved based on an analytical model by evaluating the surface temperature at various repetition rates. The experimental and analytical results from the present work will be highly beneficial for the electronic industry, where the laser micro structuring of MEMS components made of silicon material is highly challenging due to its reflective property.

Die-sinking electrical discharge machining produces components with low repeatability as the process is inherently stochastic. Effects of its inputs and process parameters on the components’ dimensions are difficult to predict. This paper investigates the influence of input parameters like gap voltage, current, and pulse characteristics like percentage of “open”, “normal”, “arc” and “short” pulses on the dimensional features of the machined components. It discusses the methodology for extraction and estimation of amount of area machined, undercut and dimension by image processing. Support vector machine regression is applied to predict the dimension features based on the input and condition parameters.

The stochastic nature in the electrical discharge machining (EDM) is inherent to the process. The process instabilities like short-circuiting and arcing instances damage the workpiece and reduce machining efficiency. Pseudo-empirical or empirical relationships are presently in use for in-process control of parameters like discharge efficiency, energy consumption, and surface roughness. In this paper, a field-programmable gate array (FPGA)–based control strategy for discharge stabilisation is proposed, and a non-linear model for energy consumption is formulated to predict the in-process energy consumption. The model captures the dynamic behaviour of the EDM process. A novel method of pulse discrimination based on the pulse train gradient is used to determine the pulse duration, classify the pulses and finally calculate the discharge energy for building the model. A lumped control parameter named as gap condition number or “Gc number” is proposed to quantify the amount of debris and contaminants like soot and suspended particles in the electrode gap. Numerical simulations at various gap conditions and analysis for stability and sensitivity at different operating scenarios are studied. The simulation shows that the model converges to a single root for Gc number up to 1.93, undergoes periodic oscillations between two roots for the values between 1.93 and 2.42 and exhibits chaos for greater Gc numbers. Stability analysis of the model finds that the values of the non-dimensionalised discharge energy for which the energy oscillations during the discharge avoids arcing or short-circuiting are 60% of the maximum discharge energy. The present model has an increased monostability of 20% in comparison to a similar model and has a correlation of 63.48% with the experimental data. The proposed control strategy can be implemented to achieve stability control over the process, eventually improving the quality of machining.

In the work, the design and development of a novel Wire-EDM setup with double-wire guide discs is presented. It facilitates sparks to be generated between the workpiece and wire at two locations separated by the helical pitch distance. This sparking causes two helical grooves to be generated simultaneously on the surface of the workpiece when it is given suitable rotational speed and table feed. In this work, machining is carried out on rods of 1.5 mm diameter. Helical groves with helix angles ranging from 35 to 500 were generated and characterized. This method of machining the double helical grooves with a single pass reduces the machining time and eliminates the complexities involved in machining one groove at a time. It was observed that the proposed method is suitable for machining double helical grooves with helix angles in the range of 40 - 50°. The parts produced by the mentioned method can be used as EDM tools for generation of high aspect ratio holes in turbine blades and injection nozzles.

Surface texturing principle has already been reported to be successful in enhancing the tribological characteristics of various mechanical components including bearings, mechanical seal, piston rings, cylinder liner, etc. The current research work investigates the application of surface texturing principle on drill tools while machining titanium alloy. One of the major challenges pertaining to drilling of Ti-6Al-4V is the accumulation of heat at the machining zone due to the poor thermal conductivity property of the material. This factor deteriorates its applicability in various fields including aerospace, automobile, spacecraft, bio medical, etc. Accumulation of heat over the cutting regime will lead to rapid tool wear affecting the tool life and machined surface quality, which will eventually increase the total production cost. In drilling as the machining phenomenon occurs inside the hole, dissipation of accumulated heat is a real challenge. Moreover, the reachability of cutting fluids will get obstructed by the upward motion of chips along the helical groove. The above-mentioned challenge can be addressed by creating micro scale textures on drill tool surfaces, thereby controlling the heat generation by minimizing the sliding friction. Hence in the present work, micro scale textures in the form of circular dimples were created on the drill tool, and the same was coated for increasing the wear strength. Drilling experiments were performed under dry, wet and MQL conditions for evaluating the effectiveness of micro textured tools in cutting force reduction. From the experimental results, a net thrust force reduction of 13.83% in dry, 22.85% in wet and 21.65% in MQL condition were achieved while machining Ti-6Al-4V using coated flute and margin textured tool. Reduction in chip clogging phenomenon and lubrication enhancement provided by the coated micro scale textures are observed to be the underlying mechanism responsible for the lower cutting forces under all machining conditions.

Cooling holes in turbine blades made of high-temperature materials such Titanium alloys are produced by laser processing. A priori knowledge on laser interaction with material will be useful in the selection of laser parameters in practice. In the present work, two-temperature model consisting of a set of coupled Partial Differential Equations in spatial and time domain is used to study ultra-short pulse laser-matter interaction. The model is solved using finite element simulation available in COMSOL Multi-physics software. The present approach is validated taking gold as bench mark material as results for 1D and 2D cases are already reported in literature. The simulation approach is then extended to titanium alloy (Ti6Al4V), the material under investigation in our present work. The simulation results are obtained for 2.00 mm thick Ti6Al4V using 2D axi-symmetric two-temperature model. In order to compare the results, single-shot laser ablation experiments are carried out at laser fluency ranging from 0.84 to 8.4 Jcm−2. A method has been proposed in this work for assessing the crater depth and diameter uniquely from the images of the ablated specimens obtained using laser scanning confocal microscope. The simulation and experimental results are presented and discussed.

The real challenge pertaining to high aspect ratio drilling is the rapid increase in chip evacuation force due to the chip clogging phenomenon occurring at higher drilling depths. The clogged chips will further impede the reachability of cutting fluid at the machining zone leading to the tool temperature buildup. This will eventually result in the catastrophic failure of the tool. Hence, in the present work, an attempt has been made to minimize the chip evacuation force by functionalizing the drill tool surfaces based on the laser microtexturing principle. Microscale textures in the form of circular dimples were created on the flute and margin side of the drill tool with an objective to control the sliding friction, thereby minimizing the chip clogging effect. The effectiveness of the functionalized drill tools were assessed mainly based on the variation in thrust force and torque. Drilling experiments showed a net reduction of 17.18% in thrust force and 26.98% in torque while machining Ti–6Al–4V using the flute and margin textured tool, which justified the effectiveness of micro scale textures in minimizing the chip evacuation forces. The experimental analysis was further extended in terms of burr height evaluation, where FMT tools were found to be highly effective in burr height reduction (1.29 mm), showing a net reduction of 54.26% when compared with the non-textured tool. The outcomes from this research work will be highly beneficial for the manufacturing industries including aerospace, automobile, and spacecraft as high aspect ratio drilling of titanium alloys are still categorized to be the most challenging machining process owing to its lower thermal conductive property.

Coordinate Measuring Machines(CMM) are widely used in form inspection of free-form surfaces. Generally, the form error at each measured point is estimated using the widely known and accurate point-inversion method. This method has relatively high time complexity and cannot be preferred for fast inspection. Hence in this work, an alternative two-stage methodology based on the concept of the Voronoi diagram is proposed. In the first stage, the poles data is extracted from the Voronoi diagram of the discretized surface. In the second stage, the form-error-estimate algorithm executing in O(mlogn) time estimates the errors using the poles data and the discretized surface. Numerical and experimental implementations are executed using NURBS surfaces. The proposed method’s accuracy is on par with the point-inversion method and is 94.97% faster than the latter. Hence this method can be used for fast and accurate CMM and CNC based(in-situ) free-form surface inspection.

The present work investigates the effectiveness of micro textures in reducing the sliding friction at the contact surfaces and its application on drill tools for the sustainable machining of Ti-6Al-4V. Preliminary experimental results from the pin on disc tests substantiated the tribology enhancing phenomenon of micro textured surfaces, with a better performance in case of micro dimpled surfaces recording a friction coefficient of 0.42. Hence for the first time, an attempt has been made to create micro textures on both the flute and margin side of the drill tools with an objective to minimize the cutting forces by reducing the sliding friction at the tool-chip and tool-work piece interfaces. Micro textures in the form of dimples were created on the flute and margin side of drill tool using laser micromachining technique. Drilling experiments were performed on Ti-6Al-4V work material by drilling a through hole of 10 mm depth using non-textured, flute textured and margin textured tools. From the cutting forces recorded during machining, it was observed that even at the higher cutting speed of 60 m/min and feed 0.07 mm/rev, the margin textured tool performed better than all other tool types recording a net reduction of 10.68% in thrust force and 12.33% in torque compared to non-textured tools. The investigations on the chip morphology further revealed less clogging of chips in case of flute textured tool which is a clear indication of a reduction in the chip evacuation force. The experimental results from this research work proved micro texturing of drill tool to be a viable technique for minimizing the energy loss due to reduction in frictional forces at the cutting regime while machining Ti-6Al-4V.

Wire electrical discharge turning (WEDT) process was developed to generate cylindrical form on any electrically conductive material applied in aerospace and automotive industry. The mechani...

In manufacturing industries, high-speed machining of aluminum alloys is highly recommended for achieving better productivity in terms of cutting force reduction and improved surface finish. Even though an overwhelming number of process parameters affect the high-speed machining operations, tool material is considered to be the most predominant factor in determining the machining performance. Hence, in the present work, experimental and simulation analyses are carried out for understanding the effect of different tool materials in high-speed machining of aluminum alloy. Formation of dead metal zone is taken as the fundamental criterion for analyzing the discrepancy in cutting forces, and the same is discussed in detail in the present paper.

Design and development of microscale features are found to be an evolving field of interest in various manufacturing industries including aerospace, automobile, spacecraft, and biomedical. Even though there are various advancements in ultraprecision machining techniques, accomplishment of microscale features with higher geometrical quality is still found to be the critical area of research, which needs to be explored as it affects the performance of the micro-components. Hence, in the present work a detailed investigation on the lasing parameter with respect to the surface integrity of microfeature has been carried out, and it is discussed in detail. Microfeatures in the form of channels and circular profile were machined on Ti6Al4V using ultra-short pulsed laser trepanning technique at various scan speeds. All the laser processed surfaces were analyzed using an optical microscope and 3D profilometer to evaluate the formation of heat-affected zone. Experimental results show a significant reduction in the width of heat-affected zone with the increase in scan speed from 2 to 2000 mm/s. Further analysis on the profile of the microfeature depicted the occurrence of higher order distortions at scan speed of 2 mm/s, which can be attributed to the occurrence of re-solidification layer and debris entrapment. A benchmark can be set from the current observations for the future investigations in selecting the optimal scan speed for achieving high-quality microfeatures on Ti6Al4V.

High-aspect-ratio high-quality microholes are required in turbine blades to improve cooling performance. These cooling holes are drilled by pulsed laser and hence dimensional as well as geometrical tolerances like circularity and cylindricity are important. The measurement of geometrical features of the microholes is a very challenging task without destroying the components. In the present work, the microholes are produced on Ti6Al4V alloy by ultra-short pulse laser. The geometrical features of microholes are then captured using a non-destructive technique, namely computed tomography. CT-scanned 3D data is directly used for geometrical analysis using open-source software, GOM Inspect. Since algorithms used in the GOM Inspect are proprietary in nature, the extracted coordinate data are also analyzed using the computational methods developed by the authors based on least squares technique. The dimension, circularity, and cylindricity of microholes are compared with the results obtained from GOM Inspect software and a close match is found.

In recent years, material ablation at solid-solid interface by laser micromachining technique is emerging as a novel method for synthesising nanoparticles. It generates chemically pure fine crystalline particles compared to traditional methods. Moreover, it enables higher confinement of plume, thereby favouring nanoparticle growth compared to liquid-solid interface and gas-solid interface. This paper demonstrates the novel method of synthesising crystalline nanoparticles of titanium dioxide (TiO2), zinc oxide (ZnO), and graphite by laser ablation at solid-solid interface. The interface was maintained by preparing transparent ice on the target placed in a glass vessel. The size of synthesised nanoparticles is in the range of 1.5 nm to 5 nm for TiO2, 100 nm to 500 nm for graphite, and 2-10 μm for ZnO (agglomerated). From the observations, it can be inferred that the process employed gives an improved rate of synthesising crystalline nanoparticles.

Energy conservation is one of the most important aspects of electrical discharge machining process in which the material removal is by means of spark erosion. Metal removal in wire electrical discharge turning is a complex erosion mechanism which involves melting, vaporization and rapid cooling of molten material. In this work, the significance of discharge energy on the performance of wire electrical discharge turning process, namely, material removal rate, surface finish, thickness of recast layer and surface crack, is analyzed. New model to estimate material removal rate and surface finish in wire electrical discharge turning process have been proposed. Erosion energy and kinetic energy imparted by electrons and average physio-thermal properties of work material are utilized for the modeling. Proposed models are validated by conducting experiments on AISI 4340 steel material. The results obtained from the model are well in agreement with the experimental values. The influence of discharge energy on surface crack and recast layer thickness is analyzed using scanning electron microscope micrographs and energy-dispersive x-ray spectroscopy analysis. Surface crack is observed at higher discharge energy. The thickness of recast layer increases with the increase in discharge energy. Three-dimensional surface topography reveals the turbulent nature of machining process resulted from transient erosion phenomena of wire electrical discharge turning process. Higher material removal rates of the order of about 0.06 g/min with consistent average roughness in the range of 4.5–5.5 µm at the expense of 1.6–2.6 J of discharge energy are achieved in this work. The proposed models can be utilized for machining of difficult to machine material by effective utilization of energy that leads to energy conservation in wire electrical discharge turning process.

The demand for manufacturing axi-symmetric Ti-6Al-4V implants is increasing in biomedical applications and it involves micro turning process. To understand the micro turning process, in this work, a 3D finite element model has been developed for predicting the tool chip interface temperature, cutting, thrust and axial forces. Strain gradient effect has been included in the Johnson–Cook material model to represent the flow stress of the work material. To verify the simulation results, experiments have been conducted at four different feed rates and at three different cutting speeds. Since titanium alloy has low Young’s modulus, spring back effect is predominant for higher edge radius coated carbide tool which leads to the increase in the forces. Whereas, polycrystalline diamond (PCD) tool has smaller edge radius that leads to lesser forces and decrease in tool chip interface temperature due to high thermal conductivity. Tool chip interface temperature increases by increasing the cutting speed, however the increase is less for PCD tool as compared to the coated carbide tool. When uncut chip thickness decreases, there is an increase in specific cutting energy due to material strengthening effects. Surface roughness is higher for coated carbide tool due to ploughing effect when compared with PCD tool. The average prediction error of finite element model for cutting and thrust forces are 11.45 and 14.87 % respectively.

Micro-electrical discharge machining is a stochastic process where the interaction between the materials and the process parameters are difficult to understand. Monitoring of the process becomes necessary to achieve the dimensional accuracy of the micro-featured components. Although thermo-mechanical erosion is the most accepted material-removal mechanism, it fails to explain the material removal with very short pulse duration. Alternative postulate like electrostatic force-induced stress yielding provides a stronger argument, rising ambiguity over the material-removal process in the micro-electrical discharge machining regime. In this work, it was found that the stress waves released from the material during micro-electrical discharge-machining process indicate material removal by mechanical deformation and fracture mechanism. These stress waves were captured using the acoustic emission sensor. The discharge pulses were captured by voltage measurement and classified using voltage gradient and machining time duration into three major categories, open pulse, normal pulse and arc pulse. The acoustic emission signal features were extracted and identified by time–frequency–energy distribution analysis. A feed-forward back-propagation neural network mapping of the pulse instances was performed with the obtained acoustic emission signature. The time–frequency–energy distribution analysis of the acoustic emission and the scanning electron microscope images of the craters provide conclusive evidence that the material is removed by mechanical stress and fracture. The feed-forward back-propagation network model was trained to predict the discharge categories of the pulse instances with AE signal inputs which can be used for monitoring the material-removal mechanism in micro-electrical discharge machining operation.

Silicon material has been extensively used in electronics, optoelectronics, and Microelectromechanical Systems (MEMS). In spite of good mechanical behavior exhibited by the silicon material, their brittleness causes difficulty in machining, which greatly affects the surface integrity of the machined parts. This demands a need for further investigations in this area for improving the material removal rate and surface integrity. Ultrashort-pulsed laser machining techniques have brought new perspectives for efficient machining of semiconductor materials in terms of surface integrity and energy consumption. In the present work, the effect of number of pulses and repetition rate at 1064 and 532 nm wavelengths of a picosecond laser has been investigated for dimensional quality and subsurface defects of holes. Further experiments were conducted using a femtosecond laser to understand the effect of repetition rate, pulse duration, pulse energy, and scanning speed on the quality of kerf surface.

Titanium alloy Ti-6Al-4V is commonly used in biomedical applications due to its superior properties such as biocompatibility, high strength-to-weight ratio and corrosion resistance. To understand the mechanics of the micro-turning process of these alloys, a mechanistic model has been developed for predicting the cutting forces. A modified Johnson–Cook material model with strain gradient plasticity is used to represent the flow stress of work material. The micro-turning experiments were conducted to verify the cutting forces predicted by mechanistic model. A finite element model is also developed with different shear friction factors and calibrated using experimental results to confirm and interpret the results of mechanistic model. It is inferred that strain rate increases by increasing cutting speed, whereas it decreases with increase in the feed rate due to increase in adiabatic shear band spacing. Since Ti-6Al-4V has low thermal conductivity, when cutting speed increases, there is an increase in the to...

Machining of aluminium alloys to high quality surface finish is seen as a challenge in dry turning using HSS and coated cemented carbide tools at conventional cutting speeds. The recent technological advancements have led to cutting edge preparation techniques like edge chamfering to provide higher load resistance and strength enhancement to the cutting edge of the inserts. These technologies have led to variation in cutting mode mechanism at lower feed rates and depth of cuts. This paper makes an attempt to develop a finite element model and experimental investigations of the effect of cutting edge chamfer on the cutting modes at low feed rates (0.005-0.125 mm/rev) in high speed turning of AlMgSi (Al 6061 T6) alloy using polycrystalline diamond (PCD) tools. In the present work, the cutting modes are established based on the machining forces, surface roughness and chip morphology at varying cutting edge chamfer widths. Both the shearing and ploughing modes of cutting are observed during turning at low feed rates using edge chamfered tools. It is inferred from the present work that shearing mode of cutting dominates when surface roughness reduces with the reduction in feed rate and ploughing mode dominates when surface roughness increases with the reduction in feed rate. The minimum feed rate in the shearing dominated region is found to yield the best surface finish for different edge chamfer widths. The effect of tool nose radius at a constant edge chamfer width and chamfer angle on surface finish is analysed during the shearing and ploughing dominated modes of cutting. It is found that surface finish improves with the increase in tool nose radius during shearing mode of cutting and surface finish deteriorates at higher value of nose radius during ploughing mode of cutting. The outer surface of chip obtained by shearing mode at higher edge chamfer width is observed to have a distinct and uniformly spaced lamellar structure with the lamellae oriented perpendicular to the direction of chip flow. Whereas, the outer surface of the chip formed during ploughing mode has non-uniform randomly oriented lamellar structure. The present work suggests the minimum feed rate to be used in finish turning using edge chamfered PCD tools. � 2014 Elsevier B.V. All rights reserved.

Wire electrical discharge turning (WEDT) process is one of the emerging non-traditional machining processes for manufacture of micro- and axi-symmetric components. In WEDT process, material is removed by successive sparks that form craters. The material removal by crater formation is associated with energy supplied in the gap referred as discharge energy. This energy must be controlled for effective machining. In this paper, a model is proposed for predicting the crater diameter based on anode erosion. Finite element method (FEM) is used to simulate the crater for different plasma flushing efficiency. Effect of discharge energy developed in the gap, physio-thermal properties of the material are considered for modeling. The erosion energy required to form a crater is also evaluated using anode erosion model. The proposed models are validated by conducting WEDT experiments on high-tensile steel [AISI 4340]. The crater morphology is investigated by using images obtained from scanning electron microscope (SEM) and energy-dispersive X-ray analysis. The crater diameter predicted by anode erosion and FEM models are compared with diameter obtained from SEM micrograph. The results obtained from the proposed models are well in agreement with the experimental results. The anode erosion model predicts the crater diameter and erosion energy with an average absolute error of 5.65 and 17.86 %, respectively. By estimating the energy required to erode a material and by setting appropriate process settings, the discharge energy can be effectively utilized for material removal.

This paper describes the use of non-contact type chromatic confocal displacement sensor for estimation of surface profile parameters such as Ra, Rq and Rt of different machined surfaces. The confocal displacement sensor can measure surface roughness of the order of 5 nm on conducting and non-conducting material. The surface irregularities of the profile measured over the evaluation length is related to the response of chromatic confocal displacement data. Confocal sensor response is analyzed to determine the displacement variations from the profile data points of the surface. Based on the confocal chromatic image principle, a new technique is used to measure the micro level surface finish. The new method is validated by measuring surface roughness of kwon specimen in the range of 1.6 - 3.2 μm using an experimental setup developed and by stylus method. The estimated profile parameter values are in good agreement with the values obtained by stylus method and hence the confocal displacement based method can be implemented to measure surface roughness parameters.

Micro turning is one of the tool based micromachining process used for manufacturing axi-symmetric miniaturized parts. This paper presents the development of micro turning setup and investigations on cutting forces and surface roughness during micro turning process. Titanium alloy (Ti6Al4 V) and coated carbide tool (TiN/AlTiN) is considered as work piece and tool material respectively. Experiments have been conducted by varying the cutting speed, feed and depth of cut. Piezoelectric dynamometer is used to measure the cutting forces during the process. Cutting forces decreases by increasing the cutting speed due to thermal softening where as at low depth of cut, cutting forces increases with increase of cutting speed due to material strengthening effect. Surface roughness increases when uncut chip thickness is less than the edge radius, due to rubbing and ploughing action. Improved roughness is observed when uncut chip thickness and depth of cut is greater than edge radius.

The hardened steel materials have great demand for the manufacturing of automotive, aircraft and machine tool components due to their better strength, wear resistance and high thermal stability. The hard machining offers many potential benefits compared to grinding, which remains the standard finishing process for critical hardened surfaces. To enhance the implementation of this technology, questions about the ability of this process to produce surfaces that meet the surface finish and integrity requirements must be answered and it must be justified economically. With the development of harder work materials, the tool material technology is advancing at a faster rate so as to enable machining of these materials by higher material removal rate with reliability of performance. This review article presents an overview of the previous research on machining of hard steel materials. It mainly focuses on the influence of extrinsic factors on machinability of hardened steels, such as variation of cutting forces, chip morphology, tool wear and resulting surface integrity in the machined surface.

The hard turning process with advanced cutting tool materials has several advantages over grinding such as short cycle time, process flexibility, compatible surface roughness, higher material removal rate and less environment problems without the use of cutting fluid. However, the main concerns of hard turning are the cost of expensive tool materials and the effect of the process on machinability characteristics. The poor selection of the process parameters may cause excessive tool wear and increased work surface roughness. Hence, there is a need to study the machinability aspects in high-hardened components. In this work, an attempt has been made to analyze the influence of cutting speed, feed rate, depth of cut and machining time on machinability characteristics such as machining force, surface roughness and tool wear using response surface methodology (RSM) based second order mathematical models during turning of AISI 4340 high strength low alloy steel using coated carbide inserts. The experiments were planned as per full factorial design (FFD). From the parametric analysis, it is revealed that, the combination of low feed rate, low depth of cut and low machining time with high cutting speed is beneficial for minimizing the machining force and surface roughness. On the other hand, the interaction plots suggest that employing lower cutting speed with lower feed rate can reduce tool wear. Chip morphology study indicates the formation of various types of chips operating under several cutting conditions. � 2012 Elsevier Ltd.

Miniaturized machine tools have been established as a promising technology for machining the miniature components in wider range of materials. Spindle of a miniaturized machine tool needs to provide extremely high rotational speed, while maintaining the accuracy. In this work, a capacitive sensor-based measurement technique is followed for assessing radial errors of a miniaturized machine tool spindle. Accuracy of spindle error measurement is affected by inherent error sources such as sensor offset, thermal drift of spindle, centering error, and form error of the target surface installed in the spindle. In the present work, a model-based curve-fitting method is proposed for accurate interpretation and analysis of spindle error measurement data in time domain. Experimental results of the proposed method are presented and compared with the commonly followed discrete Fourier transform-based frequency domain-filtering method. Proposed method provides higher resolution for the estimation of fundamental frequency of spindle error data. Synchronous and asynchronous radial error values are evaluated in accordance with ANSI/ASME B89.3.4M [9] standard at various spindle speeds and number of spindle revolutions. It is found that the spindle speed and number of spindle revolutions does not have much influence on synchronous radial error of the spindle. On the other hand, asynchronous radial error motion exhibits a significant speed-dependant behavior with respect to the number of spindle revolutions. � Springer-Verlag London Limited 2011.

Freeform profiles and surfaces have wider engineering applications. Designers use B-splines, Non-Uniform Rational B-splines, etc. to represent the freeform profiles in CAD, while the manufacturers employ machines with controllers based on approximating functions or splines that can cause deviations in manufactured parts. Deviations also creep in during the manufacturing operations. Therefore the manufactured freeform profiles have to be verified for conformance to design specification. Different points on the profile are probed using a coordinate measuring machine (CMM) and a substitute profile is established from the CMM data for comparison with design profile. The sample points are distributed according to different strategies. In the present work, two new strategies of distributing the points on the basis of curve length and dominant points are proposed considering the geometrical nature of the profiles. Metrological aspects such as probe contact and margins to be provided at the ends have also been included. The results are discussed in terms of form deviation with reference to substitute profile and positional deviation between design and substitute profiles, and compared with results of the strategies suggested in the literature. � 2011 Elsevier Ltd. All rights reserved.

Measurement, Modeling and Evaluation of Surface Parameter Using Capacitive-Sensor-Based Measurement System Surface roughness parameter prediction and evaluation are important factors in determining the satisfactory performance of machined surfaces in many fields. The recent trend towards the measurement and evaluation of surface roughness has led to renewed interest in the use of newly developed non-contact sensors. In the present work, an attempt has been made to measure the surface roughness parameter of different machined surfaces using a high sensitivity capacitive sensor. A capacitive response model is proposed to predict theoretical average capacitive surface roughness and compare it with the capacitive sensor measurement results. The measurements were carried out for 18 specimens using the proposed capacitive-sensor-based non-contact measurement setup. The results show that surface roughness values measured using a sensor well agree with the model output. For ground and milled surfaces, the correlation coefficients obtained are high, while for the surfaces generated by shaping, the correlation coefficient is low. It is observed that the sensor can effectively assess the fine and moderate rough-machined surfaces compared to rough surfaces generated by a shaping process. Furthermore, a linear regression model is proposed to predict the surface roughness from the measured average capacitive roughness. It can be further used in on-machine measurement, on-line monitoring and control of surface roughness in the machine tool environment.

This paper aims at giving an insight into the wire electro discharge turning (WEDT) process, by analyzing the effect of machining parameters on material removal rate (MRR), surface roughness and roundness error, using the pulse train data acquired at the spark gap. To achieve this objective a simple and cost effective spindle is developed for the WEDT process. Pulse train data are acquired with a data acquisition system developed in the present work. A pulse discrimination algorithm has been developed for classifying the discharge pulses into open circuit, normal, arc and short circuit pulses. With the help of algorithm the number of arc regions, average ignition delay time, the width of the normal and arc regions in the data acquired can also be obtained. It has been observed that the rotation of the workpiece has significant influence on the type of the discharges occurring at the spark gap. Preliminary experiments conducted to compare the WEDM and WEDT processes disclosed that MRR is less in WEDT and the number of arcs and arc regions are more in WEDT. It has been observed that the surface roughness and roundness error of the WEDT components are influenced by the occurrence of arc regions, width of arc and normal discharge regions and average ignition delay time. � 2010 Elsevier Ltd. All rights reserved.

Current developments in the miniaturization field focused on fabricating smaller and precise geometric features. As the scale of features and machined parts decreases, the resolution of techniques and specifications, used to measure and quantify these parts, increases. In the present work, an attempt has been made for using a high-resolution noncontact capacitive sensor for characterization of mesoscale dimensional features. The dimensional features such as the width and depth of the channel and diameter of the hole/circular feature are measured, and the size of the feature varies from few micrometers to few millimeters. A miniaturized experimental setup has been developed using capacitive sensor and high-precision XYZ linear stage to carry out the measurement. A strategy is proposed to characterize the dimensional features, and it is formulated based on output voltage gain of the sensor while scanning the channel feature. The algorithm is proposed to estimate the position of the edge coordinates and evaluation of the width of the channel and circular feature based on the output voltage gain of the sensor. Two specimens with a channel and circular feature manufactured by using a miniaturized mesoscale machine tool are examined. The evaluated width of the channels and the diameter of the circular features are in good agreement with the results obtained from optical methods. The proposed measurement system effectively determines the dimensional characterization of mesoscale features, and measurement is limited to the width of the channel at 250�?m. Furthermore, the technique can be adopted for online and in situ monitoring and inspection of mesoscale features during machining. � 2014, Springer-Verlag London.

Laser vision inspection systems are becoming popular for automated inspection of manufactured components. The performance of such systems can be enhanced by improving accuracy of the hardware and robustness of the software used in the system. This paper presents a new approach for enhancing the capability of a laser vision system by applying hardware compensation and using efficient analysis software. A 3D geometrical model is developed to study and compensate for possible distortions in installation of gantry robot on which the vision system is mounted. Appropriate compensation is applied to the inspection data obtained from the laser vision system based on the parameters in 3D model. The present laser vision system is used for dimensional inspection of car chassis sub frame and lower arm assembly module. An algorithm based on simplex search techniques is used for analyzing the compensated inspection data. The details of 3D model, parameters used for compensation and the measurement data obtained from the system are presented in this paper. The details of search algorithm used for analyzing the measurement data and the results obtained are also presented in the paper. It is observed from the results that, by applying compensation and using appropriate algorithms for analyzing, the error in evaluation of the inspection data can be significantly minimized, thus reducing the risk of rejecting good parts.

Automotive industry is one of the most prospective manufacturing industries in the present world. In order to keep up with the challenges of competitors, the automobile industries are taking necessary steps to satisfy the customers by supplying products of good quality at lower cost. The machine vision inspection systems play an important role in quality control with their accurate dimensional measurement capability. The data obtained from these systems have to be analyzed using appropriate algorithms. In the present work, algorithms based on computational geometric techniques have been developed, to set up the coordinate system for the data obtained from the laser vision system for subframe and lower arm assembly of automobile front chassis module. The concept of a convex hull and a modified Voronoi diagram are utilized for establishing the coordinate system for measurement data. The design coordinate system is determined using the Voronoi diagrams. The measurement and design coordinate systems are mapped using 3D transformations. The results obtained for the sample data are also presented in this paper.

The measurement data of a spherical component can be obtained from inspection devices such as coordinate measuring machines (CMMs). The sphericity error is evaluated from such coordinate data based on the minimum circumscribed sphere, the maximum inscribed sphere and minimum zone spheres. Appropriate methods based on the computational geometry have been developed to establish these assessment spheres. The present methods start with construction of 3-D hulls. The 3-D convex outer hull is established using the computational geometric concept presently available. For establishing a 3-D inner hull, a new heuristic method is suggested in this paper. A new concept of 3-D equidistant (ED) line is introduced in the present method. Based on this concept, the authors have constructed 3-D farthest and nearest equidistant diagrams for establishing the assessment spheres. Algorithms proposed in the present work are implemented and validated with the simulated data and the data available in the literature. ? 2001 Elsevier Science B.V. All rights reserved.

Wire electrical discharge turning (WEDT) is an emerging area, and it can be used to generate cylindrical forms on difficult to machine materials by adding a rotary axes to WEDM. The selection of optimum cutting parameters in WEDT is an important step to achieve high productivity while making sure that there is no wire breakage. In the present work, the WEDT process is modelled using an artificial neural network with feed-forward back-propagation algorithm and using adaptive neuro-fuzzy inference system. The experiments were designed based on Taguchi design of experiments to train the neural network and to test its performance. The process is optimized considering the two output process parameters, material removal rate, and surface roughness, which are important for increasing the productivity and quality of the products. Since the output parameters are conflicting in nature, a multi-objective optimization method based on non-dominated sorting genetic algorithm-II is used to optimize the process. A pareto-optimal front leading to the set of optimal solutions for material removal rate and surface roughness is obtained using the proposed algorithms. The results are verified with experiments, and it is found to improve the performance of WEDT process. Using this set of solutions, required input parameters can be selected to achieve higher material removal rate and good surface finish. � Springer-Verlag London 2012.

The measurement and evaluation of spindle errors is an important task in the assessment of the accuracy of machine tools. The commonly followed capacitive-sensor-based measurement technique requires a comprehensive error separation method for the identification of the unwanted contributions of centering error, the form error of the artifact and thermal drift. This paper presents a method for form error separation that is suitable for the evaluation of the radial error of high-speed spindles. In the present work, a fixed sensitive radial error motion test is conducted using a capacitive sensor and a cylindrical artifact at different spindle speeds. A mathematical model consisting of a second-order polynomial and Fourier series function is used to interpret the data measured in the time domain. The form profile of the artifact is measured separately in a roundness tester using a capacitive sensor. A harmonic analysis method is proposed to identify and separate the dominant harmonic components in the form profile of the artifact. A mathematical description of the proposed method is described and experimental results are presented. Application of the proposed method to the evaluation of the synchronous radial error of a high-spindle is provided for measured data. The proposed method analyzes the data measured in the time domain and is suitable for the identification of the spindle errors at high-speed conditions.

Hard turning with multilayer coated carbide tool has several benefits over grinding process such as, reduction of processing costs, increased productivities and improved material properties. The objective was to establish a correlation between cutting parameters such as cutting speed, feed rate and depth of cut with machining force, power, specific cutting force, tool wear and surface roughness on work piece. In the present study, performance of multilayer hard coatings (TiC/TiCN/Al 2O 3) on cemented carbide substrate using chemical vapor deposition (CVD) for machining of hardened AISI 4340 steel was evaluated. An attempt has been made to analyze the effects of process parameters on machinability aspects using Taguchi technique. Response surface plots are generated for the study of interaction effects of cutting conditions on machinability factors. The correlations were established by multiple linear regression models. The linear regression models were validated using confirmation tests. The analysis of the result revealed that, the optimal combination of low feed rate and low depth of cut with high cutting speed is beneficial for reducing machining force. Higher values of feed rates are necessary to minimize the specific cutting force. The machining power and cutting tool wear increases almost linearly with increase in cutting speed and feed rate. The combination of low feed rate and high cutting speed is necessary for minimizing the surface roughness. Abrasion was the principle wear mechanism observed at all the cutting conditions. � 2012 Published by Elsevier Ltd. All rights reserved.

In the present work an expert system has been developed for designing of dampers. This expert system takes inputs from user and it will calculate all dimensions, area of free mass, maximum heat dissipation, and the ratio of maximum heat dissipation to area of free mass. Then expert system will select most suitable damper and generates a script file and an Auto LISP file. By running the script file a 2D drawing and sectional view of the damper can be generated. The Auto LISP file can be run using AutoCAD to generate a 3D model for the damper. These drawings and the model can be used directly on the shop floor for manufacture of the dampers. This expert system reduces the design time of engineer and works as an assistant in designing of dampers. By saving time for initial designing of damper, the productivity of engineers can be increased. The present expert system can be used online for interaction between the customers and designers.

Practical Measurement Strategies for Verification of Freeform Surfaces Using Coordinate Measuring MachinesFreeform surfaces have wider engineering applications. Designers use B-splines, Non-Uniform Rational B-splines, etc. to represent the freeform surfaces in CAD, while the manufacturers employ machines with controllers based on approximating functions or splines. Different errors also creep in during machining operations. Therefore the manufactured freeform surfaces have to be verified for conformance to design specification. Different points on the surface are probed using a coordinate measuring machine and substitute geometry of surface established from the measured points is compared with the design surface. The sampling points are distributed according to different strategies. In the present work, two new strategies of distributing the points on the basis of uniform surface area and dominant points are proposed, considering the geometrical nature of the surfaces. Metrological aspects such as probe contact and margins to be provided along the sides have also been included. The results are discussed in terms of deviation between measured points and substitute surface as well as between design and substitute surfaces, and compared with those obtained with the methods reported in the literature.