Samson Mhlanga

Scheduling linearly deteriorating jobs on parallel machines: A simulated annealing approach

Scheduling deteriorating jobs on parallel machines is an NP-hard problem, for which heuristics would be the first solution option. Two variants of linearly deteriorating jobs are considered. The first is that with simple linear deterioration, i.e. where there is a deterioration rate only, which is meaningful only if the jobs are assumed to be available at a positive time t0. In the second variant, there is a basic processing time and a deterioration rate and all jobs are available at time t = 0. In both cases, we seek to minimize the makespan. Starting from simple heuristics, both steepest descent search and simulated annealing are designed and implemented to arrive at optimal or near-optimal solutions. Computational results for randomly generated problem instances with different job/machine combinations are presented.

A decision support tool for rural electrification grid design

This paper investigates the optimization of the electricity grid network in rural community of Chegutu district, in Zimbabwe. The Kruskals algorithm is used to minimize the total distance of the network connections, thus optimise resources for carrying out projects. Rural Electrification Agency has been failing to meet their targets for extension of the electricity grid network because of shortage of resources and input capital, thus this research adopts the idea of network optimization as a way of saving resources so that they can be used for other projects. The optimisation process shows that a total of 74km of 11kV power line could be saved from the network.

Design of comminution circuits for improved productivity using a multi-objective evolutionary algorithm (MOEA)

The performance of a processing plant has a large impact on the profitability of a mining operation, yet plant design optimisation decisions are based on past experience and intuition rather than on scientific analysis. Genetic algorithms as a tool for circuit analysis in plant design and optimisation was considered. The multi-objective evolutionary algorithm initialises the plant design and optimisation based on experimental results, which are used to formulate and determine the objective function values. A simulation was conducted to assess the performance of candidate solutions. The two optima are then traded-off using cost objective, which is sought to be minimized. Once an optimum was selected, the circuit mass balance and equipment design was performed, bringing the theory of network design and genetic algorithms into unison. Results of the study provide financial benefits, optimal parameter settings for the comminution equipment and ultimately better plant performance.

Development of a computer-aided production management course in industrial engineering curriculum

This paper describes the successful development and demonstration of an integrated computer-aided production management course which is very user-friendly and which facilitates integration of decisions. An icon-menu system that associates icons with the various decision models which were all implemented under the same environment allows students to easily integrate individual decision situations. Decisions were edited and their effect on other decisions confirmed that the hierarchical individual decisions situations in production management need to be integrated. The software developed runs on a personal computer coupled to a projection panel and overhead projector. This arrangement makes it an effective teaching facility for production management.

POM: a highly visual production and operations management environment

Reports the development and successful implementation of a computer‐integrated production and operations management system (POM), encompassing schedule activities such as aggregate production plan, master production schedule and material requirements plan, and capacity activities such as financial plan, resource requirements plan, rough‐cut capacity plan and capacity requirements plan, at the planning level. POM’s icon‐menu driven system which associates icons with decision model spreadsheets makes it very user‐friendly, and facilitates the integration of decisions encountered by industrial/ manufacturing engineers and operations managers.

Implementation of an Energy Usage Optimization System on a Pharmaceutical Company

Companies in this era are under severe competition due to globalization and in order to sustain a competitive edge they need to adopt appropriate manufacturing systems that address optimum utilisation of machinery and energy. This will result in reduction of production costs and make the companies competitive. The paper shows attempts to improve Energy Usage at a Pharmaceutical industry using monitoring and targeting techniques. An audit in a company was done so as to get the energy consumption trends and to find opportunities for energy savings. An ABC analysis of energy cost savings for machinery in the plant was made. A monitoring and targeting system was then developed to increase awareness of energy consumed.

A fuzzy controller based demand - side management system design for optimization of induction furnaces.

From Conference Proceeding (714) Power and Energy Systems - 2011,The paper is a design of an automated Demand-side management system that will optimize electricity usage in a manufacturing plant using induction furnaces, through a multi-furnace controller. The multi-furnace controller controls two furnaces which alternate in between being a melting and a holding furnace. The control system selectively delivers preselected percentages of available power to furnaces. The power supply delivers power to both furnaces. A capacitor station in parallel connection to the power supply and the furnaces is tuned to form a tank circuit therewith and acts as the power factor correction device. Switches control the selected power delivered to the furnaces respectively and control the delivery of a first portion of the power for holding molten product in the hold furnace as the master control. Simulation model was design using fuzzy logic controller.The results show that using the multi-furnace controller results in a 30% decrease in the operating costs of the furnaces as demonstrated by the model plots.

Manufacturing strategy - a potential competitive tool for J&S Botswana (Pty) Ltd [case study]

It is quite common a practice for organizations in developing countries with manufacturing functions, particularly small to medium enterprises, to operate without a defined strategy for competitiveness. This has seen many potential businesses failing to survive the competition in the dynamic business environment. In order to thrive in any chosen market, an organization needs to have a well-defined manufacturing strategy that is periodically audited. An effective manufacturing strategy must clarify and define the links between overall competitive strategy and the development of the company’s resources. Strategy formulation provides direction, purpose and coherence; ensures that manufacturing’s interests are taken into account at corporate level; clarifies and emphasizes priorities and potential conflicts; and helps integrate functions. An understanding of the consumer’s needs is critical and a clear awareness of order winning and order qualifying criteria is essential. Thus a manufacturing strategy sets the destination (and course), and implementation of the same defines how to get there. This work therefore outlines a customized methodology for formulating a manufacturing strategy through a strategic audit of a local case study company. The results of the audit carried out indicate that the company is operating without a defined strategy for competitiveness and is performing very badly with respect to the desired levels of competitive performance objectives. Suggestions are made for the effective implementation of a performance improvement programme within the context of the company’s current limitations. Keywords: Competitive strategy, Competitive performance objectives, Manufacturing strategy