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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.

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.

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...

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.

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.

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.

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.

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.

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.

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.

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.

There is an increasing interest in microdrilling of metallic and other miniaturised components. Drill breakage is the most prevalent problem with microdrill that possesses high length-to-diameter ratio. In this paper, finite element modelling approach is used to determine the buckling load of a microdrill while drilling metallic components. The influence of variation in flute length, diameter, helix angle and lip angle on buckling load during machining of metallic components is studied. Empirical loading equation based on the material hardness, feed and diameter of the microdrill is also used to estimate the loading condition during microdrilling operation. Results are in agreement with the buckling loads predicted by proposed finite element model. In the present work emphasis is made on estimating the critical feed and the speed based on modal analysis while machining various materials. Tool failure can be avoided by maintaining the machining conditions within these critical operating parameters. � 2011 Inderscience Enterprises Ltd.

This paper deals with investigation of the behavior of a linear vibratory feeder, used for conveying small parts. A rotating drum with radial fins is designed and developed for carrying out experimental investigations. A tumbling barrel hopper is used for feeding the components onto the track. Special baffles are used for positioning the parts on the track. A linear vibrator is used for conveying the parts through the feed track. This track can be changed depending on the geometry of the components being conveyed. The parameters affecting the feed rate and conveying velocity are the barrel dimension, amplitude and angle of vibration, coefficient of friction, and the operating frequency. A mathematical model is developed to predict the conveying velocity under the influence of these parameters. It is observed that the actual measured values of feed rate and conveying velocity are in good agreement with those predicted by the proposed model. � 2008 Springer-Verlag London Limited.

The brake drum assembly is an essential component in the automobiles. With increasing demand for heavy-duty automobiles, like trucks and buses, there is an increasing demand for these components. With a typical assembly rate of about 400 units a day using manual assembly tools, there is enormous pressure on the operator, prohibiting the company from enhancing their production rates to meet the market demand with existing resources. Keeping in mind the volatility of the market, it is preferred to resort to low cost automation, a technology that creates some degree of automation around the existing resources, using mostly standard components available in the market with very low investment. The method reported here presents such a low cost automation solution. It has been implemented in the real production line and its effectiveness has been proved in terms of planned objectives of increased productivity and reduced operator fatigue. Copyright � 2009, Inderscience Publishers.

In the present work, apart from operating on the structure of a conventional genetic algorithm (GA), a heuristic which uses techniques like differential mutation probability, elitism and local search is used to produce near optimal solutions for large machine loading problems with less computational intensity. Two variants of the machine loading problem are analysed in the present work: single batch model and the multiple batch models. The sensitivity of the problem with respect to the tool capacity constraint is evaluated to find that moderately restricted problems requiring greater computational resources in comparison to lesser restricted and tightly restricted class of problems. The performance of various dispatching rules was compared to infer that the least slack principle fares better than the other tested dispatching rules. It is observed from the results, that the proposed heuristic is efficient in handling large and complex machine loading problems. � 2015 Inderscience Enterprises Ltd.

The coordinate measuring machines (CMMs) have proven to be reliable, flexible and very much suitable for determining the acceptability of manufactured parts. In this paper, techniques for evaluating circularity and sphericity error from CMM data are presented. The form error can be evaluated directly from CMM data by employing circle/sphere as assessment features and using normal deviations. The CMM data can also be transformed by applying appropriate methods that not only suppress the size but also introduce distortion. The form error is evaluated from the transformed data by employing limacon/limacoid as assessment features and using linear deviations. The methods for handling CMM and transformed data are given in this paper. The proposed methods are validated using the data available in literature. ? 2003 Elsevier Science B.V. All rights reserved.

In micro milling, the inherent instability of the cutting process limits the different combinations of parameters to achieve the required material removal rate and surface roughness. A stability lobe diagram shows the boundary between chatter-free machining operations and unstable processes, in terms of axial depth of cut as a function of spindle speed. These diagrams are used to select chatter-free combinations of machining parameters. Time domain simulation models of milling can be used to predict chatter and construct such stability charts. Hence, a chatter prediction model incorporating feed rate influence along with spindle speed and depth of cut, will be helpful. In the present work, time domain simulations of micro-milling were performed and chatter was predicted for three different feed rate conditions. Subsequently, this was validated with experiments by machining series of slots using 1 mm solid carbide end-mill on brass workpiece. There is good agreement between experimental and simulated results.

In the current era of micro/meso mechanical manufacturing (M4) systems, selection of a micro tool plays an important role in executing micromachining operations effectively. Compared with the conventional ultraprecision machine tool the excitation in miniaturised machine tool (MMT) is mainly due to microcutting force. The dynamic response of a MMT must be much more intensive than the ultraprecision machine tool. Hence, study of its dynamic behaviour assumes significance from the viewpoint of obtaining good surface finish and ensuring longer tool life. Furthermore, owing to its smaller size, micro tool fails very frequently and thus the replacement of tool is almost certain in such machining processes. In view of this fact, the present work focuses on estimation of dynamic response of micro end mill cutter by making use of mode superposition method. Also included in this work is the study of effect of damping on its dynamic performance.

The Coordinate Measuring Machines capable of automated measurement are being widely used in on-line and off-line inspection. The measurement data obtained from these inspection devices have to be further processed and analyzed, to assess the geometric form of the manufactured components. In the present work, algorithms based on Computational Geometric techniques have been developed for minimum zone and function-oriented evaluation of straightness and flatness. The algorithms are validated using the simulated data and the data available in the literature.

Current developments towards assessment of surface finish using the area averaging technique have gained attention in the field of automotive manufacturing. In particular, use of tiny non-contact sensors plays a vital role during in-situ and online monitoring and process control. In this work, an attempt has been made for using non-contact capacitive sensor for characterisation of different theoretical (periodic) profiles. The capacitive response model is developed to predict equivalent theoretical capacitive displacement profile and relate accurately to a measured surface finish of the profile. The proposed model is simulated to predict dimensional parameters of various theoretical profiles. Furthermore, the feasibility to relate the capacitive response to dimensional and non-dimensional parameters of the theoretical profile is studied. The developed model is validated with the different theoretical profiles. Further, the model is validated with experimentally processed theoretical profiles using measurement setup. The results show that the observed and predicted non-dimensional parameters are well agreed with model output and measured output results. Further, it can be applied in non-periodic profile measurement using a sensor. Copyright � 2013 Inderscience Enterprises Ltd.

The unique feature of wire electrical discharge machining (EDM) is using thermal energy to machine electrically conductive parts, this distinctive advantage has been utilised in the manufacture of moulds and dies, automotive, aerospace and surgical components. In this paper, the application of wire EDM for machining axisymmetric form and helical profiles on cylindrical workpieces with different diameters is presented. The required rotary and linear motions of the workpiece are obtained by using a special rotary attachment and a motorised linear stage. The rotary motion of the spindle, linear motion of the motorised linear set-up and the wire EDM table movement were controlled to obtain a desired form of the workpiece. The workpieces after machining were measured and evaluated for dimensional accuracies. The dimensional accuracy of the axisymmetric components machined in the present work is found to be about 3.3%. The accuracy of the helical profiles is found to be high, with a maximum error 0.031 mm in average and a standard deviation of 0.028 mm. The present work can be extended to optimise machining parameters for further improving the quality of the machined parts. Copyright � 2012 Inderscience Enterprises Ltd.