IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

With an increase in complex designs and tighter tolerances, the Coordinate Measuring Machine inspection process has become increasingly more advanced. By inspection planning, design data can be transferred to an inspection system and an entire inspection operation can be carried out with a minimum of time and with reduced uncertainty. The current need is to automate this process completely so that the inspection plan can be generated directly from the design information. Two modules of inspection planning, i.e. selection of part orientation and probe orientation sequencing, have not been dealt with properly. Also, some important factors for the selection of part orientation have been neglected and proper weights have not been given to the probe-orientation sequencing criteria. An attempt was made to overcome these limitations. Both problems have been approached as the ranking of a number of alternatives based on multiple criteria, where each criterion has unequal importance. To get the optimum probe-orientation sequence and stable part orientation, fuzzy logic was applied. Fuzzy sets were obtained and combined using a suitable methodology. To explain and validate the proposed methodology, an example part was taken. As a practical case, an engine block was considered and the results presented.

Department of Mechanical Engineering

GENERAL

International Journal of Production Research

Application of fuzzy logic in the selection of part orientation and probe orientation sequencing for prismatic parts

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.

Journal of Materials Processing Technology

Evaluation of circularity and sphericity from coordinate measurement data

The measurement data for evaluation of sphericity error can be obtained from inspection devices such as form measuring instruments/set-ups. Due to misalignment and size-suppression inherent in these measurements, sphericity data obtained will be distorted. Hence, the sphericity error is evaluated with reference to an assessment feature, referred to as a limacoid. Appropriate methods based on the computational geometry have been developed to establish Minimum Circumscribed, Maximum Inscribed and Minimum Zone Limacoids. The present methods start with the construction of 3-D hulls. A 3-D convex outer hull is established using computational geometric concepts presently available. A heuristic method is followed in this paper to establish a 3-D inner hull. Based on a new concept of 3-D equi-angular line, 3-D farthest or nearest equi-angular diagrams are constructed for establishing the assessment limacoids. Algorithms proposed in the present work are implemented and validated with the simulated data and the data available in the literature. © 2002 Elsevier Science Ltd. All rights reserved.

International Journal of Machine Tools and Manufacture

Evaluation of sphericity error from form data using computational geometric techniques

Flat pattern development of sheet metal components is a prerequisite for sheet metal fabrication and it also facilitates development of process plans. Commercial softwares for flat pattern development are too expensive and they often require a 3-D model of the component. In fact, most of the component drawings exist as orthographic projections in the majority of industries. A system that can automatically generate a flat pattern using the orthographic projections as the input can be very useful. Such a system is proposed in this paper and it first extracts the features automatically from the orthographic projections and then generates the 3-D wireframe model of the central plane of the component. Using a variant of attributed adjacency graph, the data from the 3-D wireframe model are used for automatic flat pattern development incorporating bending allowances. © 2002 Elsevier Science Ltd. All rights reserved.

Automatic flat pattern development of sheet metal components from orthographic projections

Feature Based System (FBS) capture information regarding manufacturing, function, and assembly at the design stage. This approach generates simple and easy to use database, which is necessary to integrate CAD/CAM. Most of the FBS use solid models, as they provide the most concise representation of part geometry. However special hardware and software are required for solid modeling. Also in majority of the industries, the design data currently exists in the form of 2D orthographic drawings as 3D modeling softwares are too expensive. This paper describes a fully automated experimental feature recognition system for process planning, which extracts the feature information from 2D orthographic drawing of sheet metal components for further use to generate process plan without any user interaction.

International Journal of Industrial Engineering : Theory Applications and Practice

Feature recognition from orthographic drawings for sheet metal components

Computer aided process planning (CAPP) is an important interface between computer aided design (CAD) and computer aided manufacturing (CAM) in the computer integrated manufacturing (CIM) environment. A preliminary planning module developed as a part of a whole CAPP system is described in this paper. The preliminary planning deals with sequencing at the form-feature level. Processing of form feature involves certain degree of abstraction, as it is done independent of the shop-floor resources. Firstly, various feasible sequences are generated from the feature precedence relation based on the precedence and geometric tolerance constraints using an intelligent search strategy. In the next step, optimal/near-optimal sequences are generated using a genetic algorithm (GA) which prunes the initial feasible sequences using multiple optimality criteria with respect to feature adjacency, datum/reference features and preference in processing the features. © 2002 Published by Elsevier Science B.V.

Computers in Industry

A method of preliminary planning for rotational components with C-axis features using genetic algorithm

Coordinate measuring machines (CMMs) have been widely accepted and are increasingly used for carrying out inspections. With the increase in complex designs and tighter tolerances, the inspection process involving a CMM has become critical and there is a need to plan it effectively. In the present work, an object oriented planner for the inspection of prismatic parts (OOPIPP) has been developed. It incorporates interactive feature recognition and carries out all the essential steps of inspection planning, that is, selection of the most stable part orientation, arriving at number and distribution of inspection points, feature accessibility analysis, sequencing of probe orientations, removal of duplicate faces, and, finally, sequencing of faces. Various relationships between different entities of the system and distinct feature of OOM have been used to develop the algorithms of different modules. Fuzzy logic for decision making has also been applied and a suitable method of combining fuzzy sets has been used for the selection of part orientation and for sequencing probe orientations.

International Journal of Advanced Manufacturing Technology

An object oriented planner for inspection of prismatic parts - OOPIPP

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.

Computer Methods in Applied Mechanics and Engineering

Evaluation of sphericity error from coordinate measurement data using computational geometric techniques

Data for evaluating circularity error can be obtained from coordinate measuring machines or form measuring instruments. In this article, appropriate methods based on computational geometric techniques have been developed to deal with coordinate measurement data and form data. The computational geometric concepts of convex hulls are used, and a new heuristic algorithm is suggested to arrive at the inner hull. Equi-Distant (Voronoi) and newly proposed Equi-Angular diagrams are employed for establishing the assessment features under different conditions. The algorithms developed in this article are implemented and validated with the simulated data and the data available in the literature.

Precision Engineering

Evaluation of circularity from coordinate and form data using computational geometric techniques

In hole-making operation, the final size may be obtained by drilling with a single drill or pilot-drilling of one or more holes followed by enlargement to the final size. In this paper, a model based on production cost is presented and the optimal conditions are obtained considering technological and machine tool constraints. This approach is quite useful in arriving at the cutting parameters automatically in a computer-assisted process planning system.

Optimal selection of parameters in multi-tool drilling

Geometric form of engineering surfaces is important in majority of applications. Form conformance is verified using appropriate measuring instruments/set-ups and the production process is monitored with the results of measurement. Confusion still exists in the minds of practitioners and researchers with regard to the form measurement and assessment method. In this paper, the important issues of form measurement and assessment of engineering surfaces are discussed taking appropriate examples.

Journal of the Institution of Engineers (India): Mechanical Engineering Division

Important aspects of form measurement and assessment of engineering surfaces

Intelligent control of any manufacturing process requires an appropriate modeling of the process. Wire-cut EDM, being a highly complex process with non-linear behavior, is modeled by fuzzy logic approach in this paper. The knowledge base for the fuzzy model has been developed using the experimental results. Membership functions are defined for each parameter and a total of 10 input and 2 output parameters are considered to build the model. The results of the fuzzy model are compared with experimental values and a statistical analysis is presented.

Proceedings of SPIE - The International Society for Optical Engineering

Fuzzy logic modeling of wire-cut EDM process

In a Computer-Aided Process Planning (CAPP) system, one of the important steps is the selection of machining parameters which yield optimum results. In this paper, a face-milling operation has been considered. The machining parameters such as number of passes, depth of cut in each pass, speed and feed are obtained using a genetic algorithm, to yield minimum total production cost while considering technological constraints such as allowable speed and feed, dimensional accuracy, surface finish, tool wear and machine tool capabilities.

Selection of optimal conditions in multi-pass face-milling using a genetic algorithm

Reaming is carried out as a second operation, after the holes are machined with twist drills. Reaming is a slow operation and in this surface finish and geometrical accuracy deteriorate when the speed and feed are increased beyond certain limit. An attempt is made in this work to modify the standard reamer to improve its performance and the results are presented in this paper.

World University root node

Performance evaluation of a modified reamer

Wire-cut EDM is a highly complex process, which is characterized by non-linear behavior. Due to very large number of input parameters, a Neural Network Approach is followed in this paper to model this process. A large number of experiments have been carried out to train the network. The model is also tested using additional experimental data. It is found that neural network models of wire-cut EDM process provide results with required accuracy. The important input parameters have been identified and reported in this paper.

Modeling of wire-cut EDM by neural network

Detailed analysis of revolute pairs with single axis, single notch and intermediate shape has been carried out with FEM package. Based on this analysis, the design of monolithic linear stages making use of single axis/single notch revolute pairs have been analyzed. Finally, the design of two axes monolithic stages with single axis and single notch revolute pair structures have been reported.

Monolithic Flexural Micropositioners - Linear Stages

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.

CAD Computer Aided Design

Evaluation of straightness and flatness error using computational geometric techniques

This paper discusses mutually orthogonal revolute pairs in tandem (MORPT) angular stage and mutually orthogonal and coincident revolute pair (MOCRP) angular stage for two axes deflection of ≈ 1° (0.01745 rad). Theoretical analysis has been compared with the results of finite element method (FEM) analysis. Based on this analysis,single notch revolute pair has been selected for MORPT angular stage and single axis revolute pair has been selected for MOCRP angular stage for fabrication. The deflection of prototypes was measured with a Twyman and Green Interferometer set-up. The loading is done with piezo-actuator providing a resolution of 10-6 rad for the range of 1° deflection.

Monolithic flexural micropositioners - Angular stages

Condition monitoring of the machining process is very important in today's precision manufacturing, especially in the case of reaming where in-process measurement of surface quality is difficult. In this paper, a new approach is presented for the condition monitoring in reaming using Artificial Neural Network. Acoustic emission, cutting force and vibration sensor data were measured during reaming operation and a multi-layer neural network was trained using these data with the conventional Back Propagation Algorithm for weight updation. Using force, vibration and acoustic emission parameters as input and Ra value of roughness, roundness error and residual stress as output, the network gave much superior results with sensor fusion.

Neural-network approach for predicting hole quality in reaming

During form error evaluation, as the accuracy requirement increases the measurement sample size should also be increased, thereby increasing the measurement time. In this paper, a new parameter is introduced based on the asymptotic distribution of the range of errors. This new parameter gives the probability that the form error (range of errors) is less than a predicted value based on the current sample size and the corresponding errors. Simulation studies are carried out and the results are presented. © 1999 Taylor & Francis Group, LLC.