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Item Improvement of production process variations of bolster spring of a train bogie manufacturing industry: a six-sigma approach.(Taylor and Francis Group, 2022-11-29) Daniyan, Ilesanmi; Adeodu, Adefemi; Mpofu, Khumbulani; Maladzh, Rendani; Kanakana-Katumba, Grace MukondeleliThe need for improved productivity without sacrificing quality, which is in line the prime target of many manufacturing industries. The aim of this study is to investigate the causes of production variation: a case study of the rail manufacturing industry, South Africa. In this study, the six-sigma Define, Measure, Analyse, Improve and Control (DMAIC) phases were applied to enhance the process capability (long term) in the production of bolster compression springs in the main line of bogie secondary suspension system. In every phase of DMAIC method, a combination of both qualitative and quantitative techniques was utilized. First, process capability index Cpk of the current process was computed which was found less than 1. The results obtained indicated that the process capability index values were found to be 1 after the improvement phase. Hence, significant improvement was achieved in the area of reduction in process variation and product quality after taking corrective actions. From outcomes of the study, it can be concluded that process performance of a train manufacturing plant can be improved significantly by implementing six-sigma DMAIC methodology. The novelty of this study lies in the fact that the implementation of the six-sigma DMAIC phases to enhance the process capability (long term) and minimise variations in the production of bolster compression springs has not be sufficiently highlighted by the existing literatureItem Design concept evaluation technique via functional link matrix and fuzzy VIKOR based on left and right scores.(Taylor and Francis, 2021-08-19) Olabanji, Olayinka; Mpofu, KhumbulaniThis article presents a new technique for determining the weights of design features by searching for functional links between their sub-features. The method further applies fuzzy VIKOR based on left and right scores to determine the optimal design concept from a decision matrix obtained from three experts view. The application of this technique to the design of a Reconfigurable Assembly Fixture (RAF) shows that it is a viable method for determining the weights of design features and identifying the optimal design concept from a set of alternative designs. In order to support the viability of this technique, the results obtained from its application to the design of a RAF was compared with the results of other Multi- Criteria Decision-Making (MCDM) methods when applied to the design of the RAF. The comparison shows that the technique is feasible and can be employed to determine the weights of design features in order to identify optimal design at the conceptual phase.Item Re-balancing problem for assembly lines: New mathematical model and exact solution method.(Emerald Group Publishing Limited, 2014-11-03) Makssoud, Fatme; Battaïa, Olga; Dolgui, Alexandre; Mpofu, Khumbulani; Olabanji, OlayinkaPurpose The purpose of this study is to develop a new mathematical model and an exact solution method for an assembly line rebalancing problem. When an existing assembly line has to be adapted to a new production context, the line balancing, resources allocation and component management solutions have to be revised. The objective is to minimize the number of modifications to be done in the initial line in order to reduce the time and investment needed to meet new production requirements. The proposed model is evaluated via a computational experiment. The obtained results the efficacy of the proposed method. Design/methodology/approach This paper develops a new mathematical model and an exact solution method for an assembly line rebalancing problem with the objective to minimize the number of modifications to be done in the initial line to reduce the time and investments needed to meet new production requirements. Findings The computational experiments show the efficacy of the proposed method. Originality/value These reconfiguration costs were analysed for different part-feeding policies that can be adopted in an assembly line.Item Appraisal of conceptual designs: Coalescing fuzzy analytic hierarchy process (F-AHP) and fuzzy grey relational analysis (F-GRA).(Elsevier B.V., 2020-12-08) Olabanji, Olayinka Mohammed; Mpofu, KhumbulaniThe importance of concept selection in the engineering design process cannot be overemphasized. It is a major activity that can assist manufacturers to identify optimal conceptual design before prototyping can commence. This article presents the identification of optimal conceptual design by hybridizing two Multi-Criteria Decision-Making (MCDM) models which are; Fuzzy Analytic Hierarchy Process (F-AHP) and Fuzzy Grey Relational Analysis(F-GRA). The selection of F-AHP and F-GRA is based on the ability of the F-AHP to determine weights of design features and sub-features without prejudice and the ability of the F-GRA to create comparability elements for the design concepts considering their distances from an ideal design. An extensive analysis on the formulation of mathematical model for the two MCDM models is presented which is followed by the application of the hybridized model to the appraisal of conceptual designs of pipe bending machine. The hybridized model provided satisfactory results by its ability to identify one of the designs as an optimal design considering the values obtained from the fuzzified grey relational grades. The performance of the model was validated by a sensitivity analysis using two defuzzification methods and various values of the distinguishing or resolving coefficient. The variation of the resolving coefficient shows that the application of the hybridized model to design concept selection is viable in terms of stability and uniformity over a wide range of resolving coefficient.Item Improvement of production process variations of bolster spring of a train bogie manufacturing industry: a six-sigma approach.(Taylor and Francis Group, 2022-11-29) Daniyan, Ilesanmi; Adeodu, Adefemi; Mpofu, Khumbulani; Maladzhi, Rendani; Kanakana-Katumba, Grace MukondeleliThe need for improved productivity without sacrificing quality, which is in line the prime target of many manufacturing industries. The aim of this study is to investigate the causes of production variation: a case study of the rail manufacturing industry, South Africa. In this study, the six-sigma Define, Measure, Analyse, Improve and Control (DMAIC) phases were applied to enhance the process capability (long term) in the production of bolster compression springs in the main line of bogie secondary suspension system. In every phase of DMAIC method, a combination of both qualitative and quantitative techniques was utilized. First, process capability index Cpk of the current process was computed which was found less than 1. The results obtained indicated that the process capability index values were found to be 1 after the improvement phase. Hence, significant improvement was achieved in the area of reduction in process variation and product quality after taking corrective actions. From outcomes of the study, it can be concluded that process performance of a train manufacturing plant can be improved significantly by implementing six-sigma DMAIC methodology. The novelty of this study lies in the fact that the implementation of the six-sigma DMAIC phases to enhance the process capability (long term) and minimise variations in the production of bolster compression springs has not be sufficiently highlighted by the existing literature.Item Selective laser melting: Evaluation of the effectiveness and reliability of multi-scale multiphysics simulation environments(Elsevier Ltd., 2024-01-31) Mukalay, Thierry Abedi; Trimble, John Alfred; Mpofu, Khumbulani; Muvunzi, RumbidzaiThis study evaluates the effectiveness and reliability of Multi-scale Multiphysics Selective Laser Melting (SLM) Simulation Environments. A literature review and bibliometric analysis were conducted to identify the most widely used SLM Simulation Environments. The effectiveness of simulation environments was assessed through a SWOT analysis enhanced by an Analytic Network Process (ANP). The reliability of simulation environments was analysed through a design of experiment (DoE). The DoE solely assessed the ability of these environments to accurately predict part distortion. The results showed that the most robust SLM process simulation modelling systems are Ansys Additive Print, Comsol, Simufact Additive, Netfabb, and Simulia.Item Conceptual optimal selection of an e-maintenance autonomous strategy in CNC machining: a case study(IEEE, 2024-07-11) Oyesola, Moses Oluwafemi; Mpofu, Khumbulani; Kanakana-Katumba, GraceThis research aims to provide an effective valuable strategy for an effective maintenance management plan (MMP) with the specific needs and demands of a Computer Numerical Control (CNC) machine within a manufacturing plant setting. Given the critical role of the machine in the overall operational success of a factory, this study examines maintenance approaches that encompass autonomy by shifting from Total Productive Maintenance (TPM) involving corrective actions, and a run-to failure strategy. The primary focus of this research lies in the bands of historical data collection and analysis, highlighting three critical component-level failures of paramount importance for closely monitoring of the performance of the CNC machine. In the quest for an optimal maintenance strategy, the study assesses the viability of three distinct approaches: Preventive Maintenance, Predictive Maintenance, and E-Maintenance (Autonomous). To ensure the sustained health and efficiency of the case machine production line, the research employs Pugh's elimination matrix table as an evaluation tool.Item Development of a conceptual framework for quality management system implementation in small and medium enterprises in South Africa.(IOS Press, 2023-07-27) Magodi, Aluwani Yvonne; Daniyan, Ilesanmi; Mpofu, KhumbulaniSustainability challenge remain a prevalent issue among the SMEs in South Africa. This implies that the survival of SMEs in South Africa after few years of existence is a challenge. In order to promote the sustainability and operational efficiency of SMEs in South Africa, this study aims to develop a conceptual framework for the implementation of Quality Management System (QMS). Relevant literature was reviewed to get an insight into the significance and challenges faced by the SMEs in South Africa. The literature also indicated the feasibility for process improvement, profitability and sustainability if the SMEs adopts the culture of QMS. This led to the development of a conceptual quality management framework for implementation in SMEs. The framework incorporates the basic quality management system requirements with a focus on process efficiency and sustainability. It is simple and could easily be implemented or modified by the SMEs.Item Performance evaluation of a smart welding fixture and jig assembly.(Roman Science Publications, 2023-09-01) Sibanda, Palesa S.; Daniyan, Ilesanmi A.; Mpofu, Khumbulani; Sekano, Elvis P.; Seloane, Walter T.The increasing global competitiveness, dynamic customers’ and markets requirements as well as the bottom-line of profitability necessitate the use of smart welding fixture and jigs as work holding and locating devices during component parts manufacturing. This study presents the performance evaluation of a smart welding fixture and jig for welding operation. The smart welding fixture and jig assembly consists of a compressor, proximity sensors, thermostat, cooling system, clamping elements, fixture body support, cables as well as a control panel for pre-programming the conditions for the welding operation. The performance evaluation was carried out by comparing the pressure and the time taken for clamping and unclamping activities. The pressure selected for the evaluation ranges between 241 316.6 Pa - 792 897.4 Pa while measurement was taken in terms of the time it took the edges-gripping clamps to return to their initial states. The results obtained also show that at as the pressure increase, there was a decrease in the time taken for the clamping and unclamping activities up to 379 211.8 Pa. Further increase in the pressure beyond 379 211.8 Pa first resulted in an increase in the time taken up to 792 897.4 Pa. When the pressure was increased beyond 792 897.4 Pa, it was observed that the time taken for the clamping and unclamping activities begin to increase and later reduces. The machine demonstrated the potential for saving 32.26% of the total time during the manual operation when the machine is operated in an automatic mode. This study provides empirical findings that can assist manufacturing industries particularly those who employ welding as a means of product fabrication in achieving welding operations in a timely and cost-effective manner with less human intervention.Item System dynamics modelling and simulation of computer control systems for steel ingot furnaces.(South African Journal of Industrial Engineering, 2023-12-14) Somo, Gabriel; Daniyan, Ilesanmi Afolabe; Swanepoel, Jan; Mpofu, KhumbulaniThe problem that necessitated this study was that some furnaces that were responsible for the further processing of steel pipes at Company X were not connected to a programmable logic control (PLC)–Internet of Things (IoT) system. This slowed down the product flow. To address this problem, PLC-IoT systems were integrated so that the production system could be more effective. This study therefore models and simulates the integrated PLC-IoT control system, using the system dynamics modelling approach to investigate the performance of the automated gas furnaces. The PLC-IoT consists of an internal module that is used to process the data stream. After the implementation of the proposed control system, primary data was acquired by continuously evaluating the performance of the system. The research methodology used involved quantitative analysis and a simulation model using the Anylogic software. The result of the delivery and inventory of ingots from an automated system showed an upward trend with delivery and an inventory of an ingot at about 90 minutes; while a system that was not automated with PLC-IoT showed a downward trend of ingots. This shows that the introduction of the PLC-IoT for control makes the system more effective. The findings of this work could assist the manufacturers in achieving manufacturing or production efficiency, significant time savings, and better monitoring of the manufacturing process.Item Optimising a processing window for the production of aluminium silicon-12 samples via selective laser melting.(Elsevier B.V., 2023-12-07) Nzengue, Alliance Gracia Bibili; Mpofu, Khumbulani; Mathe, Ntombizodwa Ruth; Muvunzi, RumbidzaiSelective laser melting (SLM) SLM has gained interest in processing lightweight metals like aluminium alloys. The SLM processing remains challenging in finding the appropriate process parameters for the desired mechanical properties. Previous studies have used energy density formulas and heat treatment to improve the mechanical properties of materials in different ways. However, the holistic approach to studying the physical and mechanical properties has less been reported. Therefore, this article presents the optimisation of the processing window of the AlSi12 aluminium alloy produced by the SLM process. The design of the experiment (DoE) was carried out using the Response Surface Methodology (RSM) implemented in the Design Expert 2018 environment. It involved two process factors in the following range of scan speed (500–2500 mm/s) and laser power (50–300 W). The combination of a scan speed of 500 mm/s and a laser power of 300 W resulted in a relative density of 97.4 %, an ultimate tensile strength (UTS) of 418 MPa and a hardness of 132.6 HV. The microstructure and fracture analysis provided evidence of reduced defects with the combination of parameters mentioned above. Thus, this study contributes to adding a new set of data to existing work for more comprehensive parameter calibration. This study helps industries that produce aluminium alloys from SLM processes obtain the optimal range of process parameters that produce parts with the desired mechanical properties.