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.

Manufactured features generally deviate in size, form and relations with respect to other features from the features desired by the designer. Designers specify certain limits for these deviations that depend on functional requirements. The specification of different form errors is dealt with by the International Organization for Standardization (ISO). ISO also specifies that an ideal geometric feature must be established from the actual measurements such that the maximum deviation between it and the actual feature concerned is the least possible value. In practice, the least squares (LS) method is sometimes used for establishing the ideal feature, as this method is based on sound mathematical principles. However, the least squares procedure does not yield a minimum value. Therefore some attempts have been made to arrive at a form error based on the minimum deviation (MD) principles. A stray peak or valley on the actual feature introduces considerable variation in the results obtained by the minimum deviation method. This paper suggests a new approach based on the minimum average deviation (MAD). In this method, the ideal feature is established by using a search technique for different geometric features such as straight lines, circles, planes, cylinders and spheres. Using simple numerical examples, the values obtained by this approach are compared with the values obtained by the least squares and minimum deviation methods. © 1987.

Gear shaping cutters are provided with top-relief and rake angles to facilitate effective cutting. Due to this, the profile representing the cutting edge (effective profile) is altered. This paper outlines a method of obtaining the effective profile and its deviations from the theoretical involute form required. This paper also deals with a method that modifies the pressure angle, while maintaining zero deviation at the reference circle, so that the effective profile closer to the theoretical form is obtained after grinding the rake face. The Golden section optimization method is used to get the optimum value of the modified pressure angle. The effect of regrinding on the profile error of the cutting edge is also brought out. The method suggested in this paper will be useful to the designers and manufacturers of gear shaping cutters. © 1988, All rights reserved.

An automated planning system extracts data from design models and processes it efficiently for transfer to manufacturing activity. Researchers have used face adjacency graphs and volume decomposition approaches which make the feature recognition complex and give rise to multiple interpretations. The present work recognizes the features in prismatic parts considering Attributed Adjacency Matrix (AAM) for the faces of delta volume that lie on rawstock faces. Conceptually, intermediate shape of the workpiece is treated as rawstock for the next stage and tool approach direction is used to recognize minimum, yet practically feasible, set of feature interpretations. Edge-features like fillets/undercuts and rounded/chamfer edges are also recognized using a new concept of Attributed Connectivity Matrix (ACM). In the first module, STEP AP-203 format of a model is taken as the geometric data input. Datum information is extracted from Geometric Dimension and Tolerance (GD&T) data. The second module uses features and datum information to arrive at setup planning and operation sequencing on the basis of different criteria and priority rules. Copyright © 2013.

This study investigates the nature of the acoustic emission (AE) generated during the reaming of EN4 steel workpieces. For this purpose, experiments were conducted in a horizontal boring and milling machine to determine the effects of cutting parameters. The results show good correlation between the AE parameters and the severity of the contact conditions during chip formation.

Fabrication of microparts with large aspect-ratio and complex shapes remains a huge challenge for industries and microforming is a potential solution to manufacture such microparts. However, similarity in specimen-deformation and microstructural length scales during microforming results in size effect, leading to unpredictable plastic behavior and increased process scatter. One approach to counter size effect is by engineering suitable microstructure in the material. In the present work, three grades of Al (AA1070, AA5083, AA2014) with unique alloy chemistry and microstructural profile are processed by cryorolling (CR) to 95% thickness reduction. By imparting controlled postprocess annealing on the CR materials, three distinctive microstructures – (i) ultrafine grained (UFG) with average grain size around 1 μm, (ii) fine grained (FG) with average grain size near to 5 μm, and (iii) coarse grained (CG) with approximate average grain size of 20 μm are engineered. The influence of alloy chemistry, grain boundary engineering and crystallographic texture on microformability are studied. For pure Al (AA1070), the UFG and FG microstructures show superior microformability than the CG counterparts. The equiaxed UFG grains present in these microstructures mitigate the size effect abnormalities by increasing the number of grains in the deformation volume and uniformly distributing the complex microforming strain via grain boundary mediated plasticity. Their corresponding texture containing strong Copper mixed with scattered Cube elements promotes in-plane strain condition and high resistance to localized thinning. Also, the material shows near-zero planar anisotropy that leads to a homogenous in-plane strain distribution. Unlike pure Al, the UFG and FG Al alloys suffer from increased strain localization due to presence of solute clouds and nanoprecipitates. They influence strain-aging (Portevin–Le Chatelier effect), strain gradient hardening phenomenon, and shear propensity during failure of the Al alloys. A composite texture consisting of a combination of Brass, Dillamore, S, and β-fiber elements in the Al alloys is found to be detrimental to their microformability. The Dillamore texture is contributed by formation of adiabatic shear bands during deformation of Al alloys.

In gear generation processes, the involute profile of the gear is obtained as an envelope of the successive cuts made by the flank of the generating tool. The irregularities of the profile thus generated limit the quality of the gear. This paper reports the minimum achievable quality based on the maximum theoretical height of the irregularity for the involute spur gears. © 1988, All rights reserved.

Computer aided process planning (CAPP) is an important interface between computer aided design (CAD) and computer aided manufacturing (CAM) in computer integrated manufacturing (CIM). Operation sequencing in process planning is concerned with the selection of machining operations in steps that can produce each form feature of the part by satisfying relevant technological constraints specified in the part drawing. A single sequence of operations may not be the best for all the situations in a changing production environment with multiple objectives such as minimizing number of set-ups, maximizing machine utilization and minimizing number of tool changes. This paper demonstrates the application of genetic algorithms as a global search technique for a quick identification of optimal or near optimal operation sequences in a dynamic planning environment. A novel initialization scheme for representing the genetic code and a new crossover operator are designed to retain the local operation precedence for each form feature. Since sequences can be obtained quickly, this approach can actually be used by the process planner to generate alternative feasible sequences for the prevailing operating environment. © 1999 Taylor & Francis Group, LLC.

Kinematic accuracy of path traced by a chosen point of a given mechanism is affected by manufacturing errors that cause variation in link lengths and joint clearances. Tolerance analysis in mechanisms refers to a process of finding out deviation from nominal path of the given point in the mechanism due to the manufacturing errors. In this paper, a new application of screw theory is proposed to analyze the kinematic accuracy of the mechanisms with variations in link lengths and joint clearances. Potential of the proposed approach is demonstrated by its application to the tolerance analysis of four-bar planar mechanisms. Following the intent of the international standard, the deviation from nominal path is quantified in normal direction which is more meaningful from a practical perspective. Applicability of the proposed approach to a spatial mechanism is demonstrated using a serial manipulator with three-revolute joints and having one joint-error. The unified framework presented in this paper can be applied conveniently for closed as well as open loop serial manipulators. Designers can use the results of such analysis to specify the tolerances to achieve a desired degree of kinematic accuracy. © 2013 Elsevier Ltd.