Browsing by Author "Matope, Stephen"

Now showing 1 - 14 of 14
  • Thumbnail Image
    Item
    Application of lean principles in the South African construction industry
    (Southern African Institute for Industrial Engineering, 2019-11) Maradzano, Isabellah; Dondofema, Richmore Aron; Matope, Stephen
    ENGLISH ABSTRACT: South Africa is a developing country that invests billions of rands annually in the construction industry. This industry consumes resources and, inevitably, waste is generated during the process. Although numerous approaches have been developed to improve quality, efficiency, and effectiveness in this industry, lean principles offer the ability to minimise and/or eliminate non-value adding work, thus increasing value for the client. This paper highlights the lean construction tools currently used worldwide, and the benefits of adopting lean construction. The study surveyed publications on the application of lean principles in the construction industry, and identified tools yet to be implemented in the South African construction industry with specific reference to electrical and mechanical engineering services. The study used a systematic review methodology to identify different lean construction concepts, and developed a lean implementation framework. The framework was then evaluated using a local case focusing on electrical and mechanical engineering services in the construction industry. The improved framework after evaluation consists of eight steps.
  • Thumbnail Image
    Item
    Application of Van-der-Waals forces in micro-material handling
    (Stellenbosch : Stellenbosch University, 2012-12) Matope, Stephen; Van der Merwe, A. F.; Stellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering.
    This doctoral dissertation focuses on the application of Van-der-Waals’ forces in micromaterial handling. A micro-material handling system consists of four main elements, which include: the micro-gripper, the micro-workpart, the picking up position and the placement position. The scientific theoretical frameworks of Van-der-Waals’ forces, presented by Van der Waals, Hamaker, London, Lifshitz, Israelachvilli, Parsegian, Rumpf and Rabinovich, are employed in exploring the extent to which these forces could be applied in a micromanufacturing situation. Engineering theoretical frameworks presented by Fearing, Bohringer, Sitti, Feddema, Arai and Fukuda, are employed in order to provide an in-depth synthesis of the application of Van-der-Waals’ forces in micro-material handling. An empirical or pragmatic methodology was adopted in the research. The Electron Beam Evaporation (e-beam) method was used in generating interactive surfaces of uniform surface roughness values. E-beam depositions of copper, aluminum and silver on silicon substrates were developed. The deposition rates were in the range of 0.6 – 1.2 Angstrom/s, at an average vacuum pressure of 2 x 10-6 mbar. The topographies were analysed and characterised using an Atomic Force Microscope and the corresponding rms surface roughness values were obtained. The Rumpf-Rabinovich equation, which gives the relationship of the exerted Van-der-Waals’ forces and the rms surface roughness values, is used to numerically model the results. In the final synthesis it is observed that the e-beam depositions of copper are generally suited for the pick-up position. Aluminum is suited for the micro-gripper and silver is suited for the placement position in an optimised micro-material handling system. Another Atomic Force Microscope was used in order to validate the numerically modelled results of the exerted Van- der-Waals’ forces. The aim was to measure the magnitude of Vander- Waals’ forces exerted by the e-beam depositions and to evaluate their applicability in micro-material handling operations. The measurements proved that Van-der-Waals’ forces exerted by the samples could be used for micro-material handling purposes on condition that they exceeded the weight of the micro-part being handled. Three fundamental parameters, ie: material type, geometrical configuration and surface topography were used to develop strategies of manipulation of micro-materials by Van-der- Waals’ forces. The first strategy was based on the material type variation of the interactive surfaces in a micro-material handling operation. This strategy hinged on the fact that materials have different Hamaker coefficients, which resulted in them experiencing a specific Van-der- Waals’ forces’ intensity during handling. The second strategy utilised variation in the geometrical configuration of the interacting surfaces. The guiding principle in this case was that, the larger the contact area was, the greater the exerted Van-der-Waals’ forces would be In the analytical modelling of Van-der-Waals’ forces with reference to geometrical configuration, a flat surface was found to exert more force than other configurations. The application of the design, for purposes of manufacturing and assembling (DFMA) criteria, also proved that flat interactive surfaces have high design efficiency. The third strategy was based on surface roughness. The rougher the topography of a given surface was, the lesser the Van-der-Waals’ forces exerted were. It was synthesised that in order for a pick-transfer-place cycle to be realised, the root-mean-square (rms) interactive surface roughness values of the micro-part (including the picking position, the micro-gripper, and the placement position) should decrease successively. Hybrid strategies were also identified in this research in order to deal with some complex cases. The hybrids combined at least two of the aforementioned strategies.
  • Thumbnail Image
    Item
    A decision support system framework for machine selection
    (South African Institute for Industrial Engineering, 2014) Nyanga, Lungile; Van der Merwe, Andre Francois; Matope, Stephen; Dewa, Mncedisi Trinity
    ENGLISH ABSTRACT: Selecting the right machinery to machine a part is a multi criteria decision making problem which is crucial in production planning. The process becomes more complex and tedious when one has to choose from a variety of machines available in an online registry. This paper investigates this decision making process with the objective to increase machineutilisation for small, medium and micro enterprises. A real time information based decision support system is necessary to assist the decision maker. A decision support system framework for machine selection for a manufacturing agent is proposed based on the Analytical Hierarchy Process (AHP). A human expect uploads parameters for a part that has to be machines. Based on these parameters, suitable machines are sought for from an online machine registry and ranked according to their capability to produce the desired part.
  • Thumbnail Image
    Item
    A decision-making framework for implementing digitalisation in the South African tooling industry
    (Southern African Institute for Industrial Engineering, 2018-12-10) Dewa, Mncedisi Trinity; Van Der Merwe, Andre Francois; Matope, Stephen
    ENGLISH ABSTRACT: In this paper, a decision-making framework for implementing the concept of digitalisation within the South African tool, die, and mould-making (TDM) industry context is developed and employed. The purpose of this framework is to answer the following question: “Which digital technologies currently available on the market can be employed to improve the efficiency of shop-floor operations in the South African TDM industry?” An exhaustive literature study of existing digital technologies is conducted. Thereafter, TDM processes requiring digitalisation are identified through knowledge engineering. Based on the system requirements analysis, digital technologies relevant to the South African TDM context are then proposed.
  • Thumbnail Image
    Item
    Digitalisation of shop-floor operations in the south African tool, DIE, and mould-making industry
    (Southern African Institute for Industrial Engineering, 2018-08-31) Dewa, Mncedisi Trinity; Van Der Merwe, Andre Francois; Matope, Stephen
    ENGLISH ABSTRACT: Digitalisation has been advocated as a possible strategy to improve the competitiveness of tool, die, and mould-making (TDM) companies in the 21st century. The recent rise of digital technologies, such as Internet of Things devices, now makes digitalisation an achievable reality. This paper focuses on the digitalisation of shop-floor operations in the South African TDM industry through the development of a novel mobile data collection (MDC) tool known as a shop-floor management system (SMS). The developed SMS was deployed to, and validated in, a selected tooling company for various products. The developed system improved the shop-floor’s real-time data collection.
  • Thumbnail Image
    Item
    Effect of process parameters on residual stresses, distortions, and porosity in selective laser melting of maraging steel 300
    (MDPI, 2019) Mugwagwa, Lameck; Yadroitsev, Igor; Matope, Stephen
    ENGLISH ABSTRACT: Selective laser melting (SLM) is one of the most well-known additive manufacturing methods available for the fabrication of functional parts from metal powders. Although SLM is now an established metal additive manufacturing technique, its widespread application in industry is still hindered by inherent phenomena, one of which is high residual stresses. Some of the effects of residual stresses–such as warping and thermal stress-related cracking–cannot be corrected by post processing. Therefore, establishing input process parameter combinations that result in the least residual stress magnitudes and related distortions and/or cracking is critical. This paper presents the influence of laser power, scanning speed, and layer thickness on residual stresses, distortions and achievable density for maraging steel 300 steel parts in order to establish the most optimum input parameter combinations. An analysis of the interdependence between process outcomes shows that high residual stress magnitudes lead to high dimensional distortions in the finished parts, whilst porous parts suffer relatively lower residual stresses and associated distortions.
  • Thumbnail Image
    Item
    An empirical analysis of operational disturbances and their impact on business performance in manufacturing firms : case tooling industry South Africa
    (South African Institute for Industrial Engineering, 2014) Dewa, Mncedisi Trinity; Matope, Stephen; Van der Merwe, Andre Francois; Nyanga, L.
    ENGLISH ABSTRACT: Globalization has managed to break trade barriers and the manufacturing environment has become more competitive. Market share is now determined by quality of goods and services irrespective of location. Today’s business environment for manufacturers requires flexible, responsive and robust systems, which produce a variety of products at competitive prices. To gain a competitive edge, the paradigms of e-manufacturing and distributed manufacturing have been recently advocated by researchers as potential solutions. However, irrespective of these technological advancements, manufacturing firms in the tool and die sector are still struggling to perform efficiently in the face of recurring operational disturbances. The paper identifies the most prevalent operational disturbances which occur in South Africa’s manufacturing firms in the tooling industry and their impact on business performance. A field study was conducted on a number of organizations which form an industrial cluster in the Western Cape manufacturing sector and seven typical disturbances were evaluated together with their root causes. The results gathered portrayed the correlation between identified disturbances and their corresponding consequences. The findings of the study were recommended to be used to develop models and computerized systems to solve the pending pandemic.
  • Thumbnail Image
    Item
    Investigation of the effect of scan vector length on residual stresses in selective laser melting of maraging steel 300
    (Southern African Institute for Industrial Engineering, 2019) Mugwagwa, Lameck; Dimitrov, Dimiter; Matope, Stephen; Yadroitsev, Igor
    ENGLISH ABSTRACT: Selective laser melting scanning strategies influence the quality characteristics of parts, such as form accuracy and residual stresses. Previous research on the effect of laser scanning strategy parameters (such as scan vector length) demonstrates that residual stresses decrease with scan vector length reduction. However, most of these studies overlook the associated porosity and how this can contribute to stress relief. In this work, three scan vector lengths were compared to evaluate their impact on residual stresses, achievable part density, and scanning time. Reducing the scan vector length generally lowers residual stresses magnitudes, but introduces porosity as a result of localised overheating.
  • Thumbnail Image
    Item
    Investigation of the effect of scan vector length on residual stresses in selective laser melting of maraging steel 300
    (Southern African Institute for Industrial Engineering, 2019-12-12) Mugwagwa, Lameck; Dimitrov, Dimiter; Matope, Stephen; Yadroitsev, Igor
    ENGLISH ABSTRACT: Selective laser melting scanning strategies influence the quality characteristics of parts, such as form accuracy and residual stresses. Previous research on the effect of laser scanning strategy parameters (such as scan vector length) demonstrates that residual stresses decrease with scan vector length reduction. However, most of these studies overlook the associated porosity and how this can contribute to stress relief. In this work, three scan vector lengths were compared to evaluate their impact on residual stresses, achievable part density, and scanning time. Reducing the scan vector length generally lowers residual stresses magnitudes, but introduces porosity as a result of localised overheating.
  • Thumbnail Image
    Item
    Lean applications : a survey of publications with respect to South African industry
    (Southern African Institute for Industrial Engineering, 2017) Dondofema, Richmore Aron; Matope, Stephen; Akdogan, Guven
    ENGLISH ABSTRACT: South African industry faces immense global competition from developed countries such as Germany probably because of the adoption of lean manufacturing techniques by the latter. This study is a survey on publications concerning implementation and adoption of lean manufacturing in South Africa. To assess South Africa with regards to research publications on lean manufacturing, a benchmark exercise was conducted with Germany for the period 2014 to 2015. The study concludes by highlighting the gaps identified during this survey and recommendations.
  • Thumbnail Image
    Item
    Production scheduling heuristics for frequent load-shedding scenarios : a knowledge engineering approach
    (Southern African Institute for Industrial Engineering, 2020-11-11) Dewa, Mncedisi T.; Van Der Merwe, Andre F.; Matope, Stephen
    ENGLISH ABSTRACT: Most industrial machinery and equipment used by the South African manufacturing sector is powered by either a direct current or an alternating current electricity supply. With the recent frequent power cuts caused by load shedding, operations managers have a difficult time trying to satisfy demand. Power cuts are a supplier-related operational disturbance that leads to production halts, increased downtime, and a significant compromise in delivery due date conformance. The paper presents heuristic rules of thumb that can be applied during the process planning and scheduling of orders during cases of frequent load shedding to maintain high levels of system reliability and productivity. Different load shedding scenarios are characterised, and an appropriate strategy for production planning and scheduling is outlined for each scenario. A knowledge engineering approach is employed in the study, with expert opinions derived from surveys and the literature employed to generate the strategies. These strategies are validated through a simulation study conducted in a small manufacturing firm.
  • Thumbnail Image
    Item
    South African iron and steel industrial evolution : an industrial engineering perspective
    (Southern African Institute for Industrial Engineering, 2017) Dondofema, Richmore Aron; Matope, Stephen; Akdogan, Guven
    ENGLISH ABSTRACT: The paper focuses on the evolution of the South African iron and steel industry from the industrial engineering perspective. The earliest ironmaking in South Africa dates to the fifth century CE; but the major evolution of the industry began in 1882 and, by the year 1934, steel production from native ore was in full swing. The study highlights the major developments in South Africa’s iron and steel industry, and ends by exploring the extent of the application of industrial engineering techniques to published research into the steel industry.
  • Thumbnail Image
    Item
    Towards the implementation of e-manufacturing : design of an automatic tea drying control system
    (Southern African Institute for Industrial Engineering, 2014-11) Mabvuu, Never; Nyanga, Lungile; Van der Merwe, Andre F.; Matope, Stephen; Mhlanga, Samson
    Many of the production costs for producing tea are attributable to the process of drying the tea. E-manufacturing can assist companies to reduce these production costs by making crucial information available to decision-makers so that they can make informed decisions. This paper presents an application of e-manufacturing to the design of an automatic tea drying control system. This control system will ensure that the multiple drying parameters such as temperature, dryer-exit tea moisture content, and fuel consumption are maintained at optimal states during the course of the drying of tea. The additional aim of this system is to balance the cost of production and the quality of the final product. Using the Guggenheim-Anderson-De Boer (GAB) model, the optimum drying temperature was found to be 100-110°C, while maintaining a dryer-exit tea moisture content of 3 to 3.12 per cent, at a drying rate of 3 per cent per minute. A Barix control application to control the system’s activities, using the web user interface (WUI), was also developed.
  • Thumbnail Image
    Item
    Using failure modes and effects analysis as a problem-solving guideline when implementing SPC in a South African chemical manufacturing company
    (Southern African Institute for Industrial Engineering, 2020-05-29) Appollis, Logan-Lee Miche; Van Dyk, Wynand A.; Matope, Stephen
    ENGLISH ABSTRACT: Quality management has ceased to be an operational extra, and has become imperative to doing business in a saturated market environment with demanding clients. It is now a significant component of holistic operational management. The ultimate aim remains customer satisfaction, using the most effective techniques to ensure the most efficient and cost-effective process. Statistical process control (SPC) and statistical quality control have been widely used in quality management to enhance process performance by reducing process variation. However, SPC can only be effective if implemented with a structured problem-solving tool. The diagnostic ability of statistics, coupled with a failure modes and effect analysis (FMEA) as the problem-solving methodology during an out-of-control action plan, creates an environment conducive to improving processes and empowering employees. The failure modes and effect analysis was used to identify and eliminate sources of variation, which led to a reduction in process variation by 63 per cent and a decrease in defects by 160 961 per million opportunities.