Browsing by Author "Mgwatu, Mussa I."
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Item Analysis of Manufacturing Capability Variables for Small Metalworking Industries(The Tanzania Engineer, IET Journal, 2010) Mgwatu, Mussa I.Item Analysis of Power Efficiency of a Direct Driven Locally Fabricated Permanent Magnet AC Generator for Small-Scale Wind Power Applications in Tanzania(Tanzania Journal of Engineering and Technology, 2013) Msuya, R. A.; Kainkwa, R. R. M.; Mgwatu, Mussa I.Item Applying Data Envelopment Analysis to Measure the Efficiency of Healthcare Industry in Dar es Salaam Region of Tanzania(The Tanzania Engineer, IET Journal, 2012) Mapunda, B.; Mgwatu, Mussa I.Item Empirical Model to Predict Wind Speed for Wind Turbine Power Generation at Makambako(2012) Msuya, R. A.; Kainkwa, R. R. M.; Mgwatu, Mussa I.Item Establishing a Probabilistic Model of Extrapolated Wind Speed Data for Wind Energy Prediction(World Academy of Science, Engineering and Technology Journal, 2012) Mgwatu, Mussa I.; Kainkwa, R. R. M.Wind is among the potential energy resources which can be harnessed to generate wind energy for conversion into electrical power. Due to the variability of wind speed with time and height, it becomes difficult to predict the generated wind energy more optimally. In this paper, an attempt is made to establish a probabilistic model fitting the wind speed data recorded at Makambako site in Tanzania. Wind speeds and direction were respectively measured using anemometer (type AN1) and wind Vane (type WD1) both supplied by Delta-T-Devices at a measurement height of 2 m. Wind speeds were then extrapolated for the height of 10 m using power law equation with an exponent of 0.47. Data were analysed using MINITAB statistical software to show the variability of wind speeds with time and height, and to determine the underlying probability model of the extrapolated wind speed data. The results show that wind speeds at Makambako site vary cyclically over time; and they conform to the Weibull probability distribution. From these results, Weibull probability density function can be used to predict the wind energy.Item Integrated Approach for Optimising Machining Parameters, Tool Wear and Surface Quality in Multi-Pass Turning Operations(Advances in Production Engineering and Management Journal, 2013) Mgwatu, Mussa I.This paper implements a holistic decision approach for determining tool wear and surface quality together with machining parameters such as cutting speed, feed rate, depth of cut, and cutting passes during turning operations. As a consequence, two machining optimisation models are formulated with the objectives of maximising the material removal rate and minimising the production cost so that the decisions regarding machining parameters can be determined as well as the status of tool wear and surface quality between intermediate cutting passes. The feasibility and applicability of the formulated models have been tested through computational analyses, and a comparison made between the two performance objectives. The results show that the integrated decisions of machining parameters, tool wear and surface quality can be made and thus avoid the application of expensive on-line equipment for measuring tool wear and surface quality. Furthermore, the feasible removal of material during turning operations can be achieved through proper selection of depths of cut and number of cutting passes. The proposed optimisation models can also be used to provide tool replacement schedules based on the number of processing parts and cutting passes.Item Integrated Decision Model for Interrelated Sub-Problems of Part Design or Selection, Machine Loading and Machining Optimization(American Society of Mechanical Engineers, 2009) Mgwatu, Mussa I.; Opiyo, E. Z.; Victor, M. A. MIn the work presented in this paper, we made an attempt to integrate the decisions for interrelated sub-problems of part design or selection, machine loading and machining optimization in a random flexible manufacturing system (FMS). The main purpose was to come up with an optimization model for achieving more generic and consistent decisions for the FMS and which can be practically implemented on the shop floor to help designers and other engineers in several ways, including, for instance, to optimize the designs of parts for specific FMS. In order to attain the generic decisions, an integer nonlinear programming (INLP) problem was formulated and solved to maximize the FMS throughput. Based on the results, the part design or selection, machine loading and machining optimization decisions can be simultaneously made. To get more insights of the results and also to check the validity of the model, a two-factor full factorial design was implemented for the sensitivity analysis, analysis of variance (ANOVA) and residual analysis. The computational analyses show that the tooling budget and available processing time were both statistically significant to throughput and confirmed that the model is valid with the data normally distributed.Item Integration of Cutting Parameter Selection and Tool Adjustment Decisions for Multipass Turning(Springer (International Journal of Advanced Manufacturing Technology), 2001) Liang, M.; Mgwatu, Mussa I.; Zuo, M.This paper presents an integrated approach to simultaneous optimisation of machining parameters, including machining speed, feedrate and depth of cut, number of passes, tool adjustment interval, and the amount of adjustment. Associated models have been developed for both small parts, where each tool can be used to machine several parts, and large parts, where several tools may be required for a single workpiece. Examples are given to demonstrate the application of the proposed models. The impact of machining parameters and tool cost on tool adjustment and the effect of rapid reverse on the final solution are also discussed.Item Integration of Part Selection, Machine Loading and Machining Optimisation Decisions for Balanced Workload in Flexible Manufacturing System(International Journal of Industrial Engineering Computations, 2011) Mgwatu, Mussa I.This paper demonstrates the importance of incorporating and solving the machining optimisation problem jointly with part selection and machine loading problems in order to avoid unbalanced workload in the FMS. Unbalanced workload renders to ineffective FMS such that some machines on the manufacturing shop floor become more occupied than others. Since CNC machine tools employed in the FMS are rather expensive, it is mostly important to balance the workload so that all machines can be effectively utilised. Therefore, in this study, two mathematical models are presented and solved in efforts to balance the workload and improve the performance of the FMS. A two-stage sequential approach is adopted whereby the first stage deals with the maximum throughput objective while the second stage deals with the minimum production cost objective. The results show that when part selection, machine loading and machining optimisation problems are jointly solved, more practical decisions can be made and a wide range of balanced workload in the FMS can be realised with minimum production cost objective. The results also show that the available machine time and tooling budget have enormous effects on throughput and production cost.Item Interactive Decisions of Part Selection, Machine Loading, Machining Optimisation and Part Scheduling Sub-Problems for Flexible Manufacturing Systems(International Transaction Journal of Engineering, Management, and Applied Sciences and Technologies, 2011) Mgwatu, Mussa I.More often, the decisions of part selection, machine loading, machining optimisation and part scheduling sub-problems are made at different decision-making levels. As a result, part selection, machine loading and machining optimisation decisions at higher-production planning level may fail to interact with part scheduling decisions at lower-scheduling level. This paper presents a two-stage sequential methodology aimed at integrating the decisions of part selection, machine loading, machining optimisation and part scheduling sub-problems for flexible manufacturing systems (FMSs) and avoiding disparities of decisions which can be difficult to implement on the FMS shop floor. In this case, two mathematical models were presented and solved. Results from the models show that more interactive decisions and well-balanced workload of the FMS can be achieved when part selection, machine loading, machining optimisation and part scheduling sub-problems are solved jointly.Item Investigating the Impact of Un-optimised Cutting Tool Selection on Tool Path Generation for CNC Milling Operations(2013) Faraji, Adam; Mwinuka, Tito E.; Mgwatu, Mussa I.Item Machining Optimisation and Operation Allocation for NC Lathe Machines in a Job Shop Manufacturing System(Journal of Engineering and Technology, 2013) Mgwatu, Mussa I.Numerical control (NC) machines in a job shop may not be cost and time effective if the assignment of cutting operations and optimisation of machining parameters are overlooked. In order to justify better utilisation and higher productivity of invested NC machine tools, it is necessary to determine the optimum machining parameters and realize effective assignment of cutting operations on machines. This paper presents two mathematical models for optimising machining parameters and effectively allocating turning operations on NC lathe machines in a job shop manufacturing system. The models are developed as non-linear programming problems and solved using a commercial LINGO software package. The results show that the decisions of machining optimisation and operation allocation on NC lathe machines can be simultaneously made while minimising both production cost and cycle time. In addition, the results indicate that production cost and cycle time can be minimised while significantly reducing or totally eliminating idle times among machines.Item Optimisation of Machining Parameters with Consideration of Tool Adjustment in Turning Operations(University of Ottawa, 1996) Mgwatu, Mussa I.This thesis presents six optimization models which are developed and solved in two stages in order to integrate tolerancing and machining parameters decisions. One model is developed in the first stage. The first-stage model is related to a design problem and provides better part tolerance to be used in the second stage to incorporate tool adjustment decisions into the optimization of machining parameters. Five models are developed in the second stage and are divided into single-machine and multi-machine turning operation problems. For single-machine turning operations, three models are formulated. The first is a single-product multi-pass model considering pass selection for determining optimum cutting speed, feed rate, depth of cut, dimension deviation and number of passes. The second is a single-product multi-pass model considering inventory and setup costs to find optimum cutting speed, feed rate, depth of cut, dimension deviation and batch size. The third is a multi-product multi-pass model considering inventory and setup costs for selection of optimum cutting speed, feed rate, depth of cut, dimension deviations and production cycle time. For multi-machine turning operations, two models are formulated. One is a multi-feature multi-pass model with the objective of minimizing total cost for determining optimum workload assignment, cutting speed, feed rate, depth of cut, and feature dimension deviations of machine-pass-feature combinations. The second is a multi-feature multi-pass model with the objective of minimizing cycle time which, once solved, will give optimum workload assignment, cutting speed, feed rate, depth of cut, and feature dimension deviations of machine-pass-feature combinations. A solution method and illustrative examples are given to test the feasibility of the developed optimization models.Item Optimisation of Machining parameters, Tool Wear and Surface Quality in Multipass Turning(2012) Mgwatu, Mussa I.Item Planning of Flexible Manufacturing Systems Based on Integrated Part Selection, Machine Loading and Machining Optimisation Decisions(University of Dar es Salaam, 2009) Mgwatu, Mussa I.Item Technological Capacity of Metal Manufacturing Industries in Tanzania(2008) Nyichomba, B. B.; Mgwatu, Mussa I.Item Tool Selection for Rough and Finish CNC Milling Operations Based On Tool-Path Generation and Machining Optimisation(2015-03) Mwinuka, Tito E.; Mgwatu, Mussa I.Most of CAD/CAM systems lack fully‐automated process planning capabilities and depend on semi‐automatic capabilities that necessitate the traditional selection of tools and cutting parameters. This paper attempts to determine proper combinations of cutting tools through the generation of tool paths and optimisation of machining parameters using an example of the CNC milling process. Several machining simulations with different combinations of tool sizes were performed using MasterCAM software. Based on these simulations, substantial variations in tool paths were observed for different tool combina‐ tions and as such the optimum tool combination could only be obtained arbi‐ trarily. The tool paths derived from machining simulations were used to opti‐ mise machining parameters, that is, cutting speed, feed rate and depth of cut with the objective of minimising production time. In this case, an optimisation model was developed as a nonlinear programming problem and solved using extended LINGO nonlinear software. The results show that the subjectivity when selecting cutting tools can be avoided when appropriate tools are chosen alongside with the generation of a tool path within a CAD/CAM system using optimised machining parameters. As a consequence, CNC machine tools could be effectively utilised and the productivity significantly improved at shorter production time and cost.Item A Two-Step Approach to Maximizing Throughput and Minimizing Processing Time in Flexible Manufacturing Systems(American Society for Engineering Education, 2009) Mgwatu, Mussa I.