Usama Umer

Layout design optimization of dynamic environment flexible manufacturing systems

The proper positioning of machine tools in flexible manufacturing system is one of the factors that lead to increase in production efficiency. Choosing the optimum position of machine tools curtails the total part handling cost between machine tools within the flexible manufacturing system. In this article, a two-stage approach is presented to investigate the best locations of the machine tools in flexible manufacturing system. The location of each machine tool is selected from the available specific and fixed locations in such a way that it will result in best throughput of the flexible manufacturing system. In the first stage of the two-stage approach, the throughput of randomly selected locations of the machine tool in flexible manufacturing system is computed by proposing a production simulation system. The production simulation system utilizes genetic algorithms to find the locations of the machine tools in flexible manufacturing system that achieve the maximum throughput of the flexible manufacturing system. In the second stage, the generated locations are fed into artificial neural network to find a relation between a machine tool’s location and the throughput that can be used to predict the throughput for any other set of locations. Artificial neural network will result in mitigating the computational time.

Performance Evaluation of Tandem Bladed Centrifugal Compressor

Abstract A tandem-bladed centrifugal compressor which may have better performance than the conventional designs has not yet been studied for its potential turbocharger application. In addition, no numerical study of the entire stage (including tandem impeller and volute) has been performed to fully exploit the benefits of such design with variation in axial clearance levels, circumferential clocking fractions, blade geometries/angles, number of inducer blades and the thickness of inducer blades. This paper presents a thorough experimental and numerical study on the performance of a moderate pressure ratio, unshrouded, tandem-bladed centrifugal compressor in comparison to a conventional compressor of commercial use in china for turbocharger application. The characteristics of a tandem compressor are investigated and compared for various parameters. Conventional impeller was first modified into tandem-bladed design but with no modifications in backsweep angle, meridional gas passage and camber distributions in order to have a true comparison. The tandem design was further modified and investigated by (1) narrowing down the meridional gas passage, (2) using straight or concave leading edge of exducer, (3) reducing the thickness and (4) the number of inducer blades. CFD and experimental results were found to be in good agreement. The study reveals a shift of surge point towards lower mass flow rate in all cases of tandem designs. A maximum of 25% increase in the range of operation is observed. All in all there is little influence of the different circumferential clocking fractions and axial spacings of the inducer. Computational investigations of a modified tandem compressor with 20% reduction in inducer thickness have shown better performance than the conventional design. Use of fourteen inducer blades with reduced blade thickness can further enhance the performance.

Simulation of Oblique Cutting in High Speed Turning Processes

A Finite Element Model is developed for Oblique cutting process in high speed turning of H-13 tool steel. The material model used for workpiece is elastic-thermoplastic including the strain rate sensitivity effect. In order to predict the tool performance, tool is considered as non-rigid and direct stresses are determined around the tool tip. Lagrangian approach is utilized along with adaptive meshing to minimize element distortion around the tool tip. The model predicts cutting forces in 3-directions at different inclination angles. The results are compared with experimental data and found to be in good agreement. The model is also able to predict stress and temperature contours in the workpiece and the cutting tool which help in predicting workpiece surface integrity and performance of the cutting tool. KeywORdS Finite Element (FE) Model, H-13, High Speed Turning, Oblique Cutting

Assessment of finite element and smoothed particles hydrodynamics methods for modeling serrated chip formation in hardened steel

This study aims to perform comparative analyses in modeling serrated chip morphologies using traditional finite element and smoothed particles hydrodynamics methods. Although finite element models are being employed in predicting machining performance variables for the last two decades, many drawbacks and limitations exist with the current finite element models. The problems like excessive mesh distortions, high numerical cost of adaptive meshing techniques, and need of geometric chip separation criteria hinder its practical implementation in metal cutting industries. In this study, a mesh free method, namely, smoothed particles hydrodynamics, is implemented for modeling serrated chip morphology while machining AISI H13 hardened tool steel. The smoothed particles hydrodynamics models are compared with the traditional finite element models, and it has been found that the smoothed particles hydrodynamics models have good capabilities in handling large distortions and do not need any geometric or mesh-based chip separation criterion.

On multistage approach for flexible routing in flexible manufacturing systems

Optimizing flexible routing in flexible manufacturing systems is one of the aspects that increase the efficiency of flexible manufacturing systems especially in dynamic environment systems. This article presents a multistage approach to solve flexible routing problem in flexible manufacturing systems. Multistage approach includes three stages; the first stage is a production simulation system to find the fitness of the flexible manufacturing systems corresponding to different products’ routes’ groups. The second stage proposes an artificial neural network approach to predict the products’ routes’ group in flexible manufacturing systems. The last stage combines genetic algorithms and artificial neural network to optimize proper routes for all product types in flexible manufacturing systems. Multistage approach proposed in this study aims to reduce the computational time required to obtain and optimize the flexible routes in flexible manufacturing systems. The results of this study show that the artificial neural network can be used efficiently to predict the flexible routes in flexible manufacturing systems and it reduces the computational time for routes’ optimization required with production simulation system. This characteristic improves the flexibility of flexible manufacturing systems since it can be adapted frequently against any change in production ratios.

Microchannels Fabrication in Alumina Ceramic Using Direct Nd:YAG Laser Writing

Ceramic microchannels have important applications in different microscale systems like microreactors, microfluidic devices and microchemical systems. However, ceramics are considered difficult to manufacture owing to their wear and heat resistance capabilities. In this study, microchannels are developed in alumina ceramic using direct Nd:YAG laser writing. The laser beam with a characteristic pulse width of 10 µs and a beam spot diameter of 30 µm is used to make 200 µm width microchannels with different depths. The effects of laser beam intensity and pulse overlaps on dimensional accuracy and material removal rate have been investigated using different scanning patterns. It is found that beam intensity has a major influence on dimensional accuracy and material removal rate. Optimum parameter settings are found using grey relational grade analysis. It is concluded that low intensity and low to medium pulse overlap should be used for better dimensional accuracy. This study facilitates further understanding of laser material interaction for different process parameters and presents optimum laser process parameters for the fabrication of microchannel in alumina ceramic.

Assessment of Direct Laser Writing using Nd YAG Lasers for Microfluidic Applications

The rapid growth in the use of Micro/Nano products in variety of industries such as Micro electromechanical systems (MEMS), microelectronics, Biomedical/Bio-MEMS, automotive (motion sensors), telecommunications etc, has demanded new micro manufacturing methods. The challenge with the manufacturing of Microfluidic devices/biochips is that they often make use of broad range of materials within a single chip, making it difficult to manufacture these devices with conventional photolithographic based techniques. Laser processing of materials has proved to be an important tool for the development of these devices because of the accuracy, flexibility and the most important one material independence it offers. This research focus on optimization of laser process parameters for the machining of Microfluidic channels with AISI 1045 steel. Design of experiments (DOE) technique was used in order to study the effect of laser process parameters on rectangular and semicircular cross-section channels.

Computer Aided Design of the Die-Set for Sheet Metal Punching and Blanking Dies

Die-Set is one of the Punching/Blanking die components. It includes lower and upper shoes, guide posts and guide bushes. The High demand of Die-Set in industry resulted in the supply of specified die set from many manufacturing companies. The standard components in the market cover only the small and medium die sizes. In many cases, the designers need to build their own die-sets especially in case of progressive die design and non-tradition die sizes. In this paper, a CAD system for building a Die-Set is discussed. This system is built using Visual Basic (VB) interfacing with AutoCAD. The system covers all Die-Sets sizes (small, medium). The proposed CAD system is prepared to work as a standalone or as a subroutine for a blanking die design CAD system. It saves time in Die-Set design operation from hours to minutes. This module is a part of a series of studies to automate the design of sheet metal working tools.