Shunmugam M S

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.

A fillet curve is provided at the root of the spur gear tooth, as stresses are high in this portion, The fillet curve may be a trochoid or an arc of suitable size as specified by designer. The fillet stress is influenced by the fillet geometry as well as the number of teeth, modules, and the pressure angle of the gear. Because the relationship is nonlinear and complex, an artificial neural network and a backpropagation algorithm, are used in the present work to predict the fillet stresses. Training data are obtained from finite element simulations that are greatly reduced using Taguchi's design of experiments. Each simulation takes around 30 min. The 4-5-1 network and a sigmoid activation function are chosen. TRAINLM function is used for training the network with a learning rate parameter of 0.01 and a momentum constant of 0.8. The neural network is able to predict the fillet stresses in 0.03 s with reasonable accuracy for spur gears having 25-125 teeth, a 1-5 mm module, a 0.05-0.45 mm fillet radius, and a 15°-25° pressure angle. Copyright © 2008 Cambridge University Press.

Mass production of holes having good surface finish and geometrical accuracy necessitates the need for precision in assembly. This cannot be satisfied by the conventional twist drills and reaming is carried out as a secondary operation. The reamers are developed for enlarging and finishing of holes accurately and stock removal is less. A survey of medium size industries revealed 40% of machining time is devoted to hole-making and as high as 70% for prismatic component. The nature of surface layer produced has an influence on mechanical properties and service performance of components. The condition of the manufactured surface will be explained in terms of surface integrity. Surface integrity is taken to represent the enhanced condition of a surface produced in machining and other surface generating operations. The nature of surface produced by reaming will be highlighted. The results of surface topography and surface and sub surface metallurgical studies will be elaborated upon and discussed.

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.

Verification of engineering components having freeform profiles on a coordinate measuring machine (CMM) requires accurate measurement of sufficient number of sample points. While the measurement accuracy increases with increased sample size, it is often limited by cost and time considerations. Thus, for a given sample size, the locations of the measurement points are to be determined such that the actual shape may be effectively characterized. Several attempts are reported in the literature. A simple algorithm based on dominant points is proposed in this paper. Simulation studies have been carried out on a freeform profile. Comparison of the results with those obtained from uniform spacing and equi-parameter sampling methods reveals that the proposed method performs effectively.

The present work deals with evaluation of form error from the measured profiles obtained using a form tester, namely roundness/cylindricity measuring instrument. In Part I, details of circularity evaluation are presented. Due to eccentricity in component setting and radius-suppression inherent in the measurement, circularity error has to be evaluated with reference to a limacon. A computational geometry-based algorithm is proposed for establishing minimum circumscribed, maximum inscribed and minimum zone limacons. A new type of control hull for directly constructing equi-angular diagrams and a new procedure for updating are introduced. Validation has been done with bench-mark data set and corresponding results available in the literature. Being geometry-based algorithm, it is simple to follow and each iteration can be visualized and interpreted geometrically. On comparison with simplex search method, the proposed algorithm is found to be computationally efficient in terms of accuracy and time taken. The proposed methods can be easily implemented in computer-aided roundness measuring instruments. Extension of this work for evaluation of cylindricity error has been dealt in Part II. © 2006 Elsevier Ltd. All rights reserved.

Magnetorheological Abrasive Honing (MRAH) is a recently developed process to finish engineering surfaces. The process makes use of a magnetically stiffened abrasive-mixed magnetorheological fluid as the flexible tool and rotation-cum-reciprocation movements between the finishing medium and the work piece surface for providing finishing action. In the present work, a finite element analysis with Mechanical/Emag module of ANSYS is performed to understand the nature of magnetic field developed in the process and verification is done with actual measurements. Considering the simulated magnetic field, a model to predict final roughness value (Ra) is developed. The model, when applied for different work materials and various process parameters, such as magnetic flux density, process duration and work piece rotation, yields results that are in good agreement with experimental results.

To automate planning activities in a computer integrated manufacturing environment, an integrated system of feature recognition and reasoning is essential. An attempt is made in the present work to develop such a system for 3D sheet metal components. Though certain part-modellers use feature-based methodology, they lack the information required for manufacturing and entire feature information is lost when converted to a neutral format such as STEP AP-203. The proposed feature recognition identifies manufacturing features in a generic manner, while feature reasoning gives the information required for manufacturing. Taking 3D model data in STEP AP-203 format as input to the feature recognition system, the central plane of the component is first generated. Further processing of faces is carried out and various features with similar manufacturing attributes are identified using a set of rules based on the topology, geometry and Boolean logic. Different types of manufacturing features such as cut, stretched, drawn and bent features as well as composite features are effectively identified irrespective of their shape. The system proposed here was tested with components taken from industry and examples available in the published literature. The proposed feature recognition system serves as input to the feature reasoning system dealt with in Part II of this work (Kannan, T.R. and Shunmugam, M.S., Processing of 3D Sheet metal components in STEP AP-203 format. Part II: feature reasoning system. Int. J. Prod. Res., 2009 (in press)).

Titanium and titanium alloys (e.g., Ti6Al4V) are increasingly used in aerospace and automotive industries, and also used as medical implant material in wide variety of applications. Wire-electro discharge machining (WEDM) is an important non-traditional machining process, widely used for machining a variety of difficult-to-machine materials including titanium alloys with intricate shapes. The process is essentially a thermal process and the nature of surface produced is studied in this paper. It is observed that more uniform surface characteristics are obtained with coated wire electrode. Among the parameters such as time between two pulses, pulse duration, injection pressure, wire speed and wire tension that have more influence on the surface characteristics, the time between two pulses is the most sensitive parameter. © 2004 Elsevier B.V. All rights reserved.

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.