Thesis: M.S., Massachusetts Institute of Technology, Department of Mechanical Engineering, 1981 / Includes bibliographical references. / by Clinton Sebastian Stanovsky. / M.S. / M.S. Massachusetts Institute of Technology, Department of Mechanical Engineering

Interest in accounting for environmental impacts of products, processes, and systems during the design phase is increasing. Numerous studies have undertaken investigations for reducing environmental impacts across the product life cycle. Efforts have also been launched to quantify such impacts more accurately. Life cycle energy consumption and carbon footprint are among the most frequently adopted and investigated environmental performance metrics. As efforts continue to incorporate environmental sustainability into product design, struggles persist in concurrent consideration of environmental impacts resulting from the manufacturing processes and supply chain network design. Thus, the objective of this research is to present a framework for reducing product cradle-to-gate energy consumption and carbon footprint through simultaneous consideration of manufacturing processes and supply chain activities. The framework developed in this thesis relies on unit process modeling, and is demonstrated for production of a bicycle pedal. It is shown that simultaneous consideration of manufacturing and supply chain processes can impact decision-making and improve product environmental sustainability at the design stage. The work presented contributes to the state of the science in sustainable design and manufacturing research. In addition, a point of departure is established for the research community to move current efforts forward for concurrent consideration of multiple stages of the product life cycle in pursuit of environmental, economic, and social sustainability. / Graduation date: 2012

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Vacuum assisted resin transfer moulding (VARTM) belongs to the category of resin infusion techniques that use lower than atmospheric pressure to infiltrate a reinforced cavity. This technique has various advantages; however, manufacturing costs can be relatively high due to more difficult shapes fabricated and a lack of knowledge regarding cost driving factors. The objective of this study was to develop a cost model for composite parts. Such a model allows the estimation of manufacturing costs of shapes of different geometries. Therefore, it provides a comparison to alternative manufacturing techniques, such as metal forming or composite spray lay-up and helps to avoid unnecessarily expensive design features. The proposal was made to split complex shaped composite parts into individual basic shapes, which are further investigated here. For the basic shapes, an experimental approach was used where the manufacturing times of each process step are measured and then statistically analysed. Infusion simulation software was used to obtain additional filling times to complete the design of experiments. This method allows the estimation of manufacturing times of composite parts with different geometries. The manufacturing times were validated to that of a complex shaped industrial part, with reasonable results. Finally, a flexible cost model was developed to compare different manufacturing techniques and to estimate the manufacturing costs. / AFRIKAANSE OPSOMMING: Vakuumgesteunde harsinspuitingsgietwerk (VARTM) behoort tot die kategorie harsinspuitingstegnieke wat laer-as-atmosferiese druk gebruik om ʼn versterkte holte binne te dring. Hierdie tegniek hou verskeie voordele in. Tog kan vervaardigingskoste betreklik hoog wees wanneer dit by ingewikkelder vorms en ʼn gebrek aan kennis met betrekking tot kostesnellers kom. Die doelwit van hierdie studie was om ʼn kostemodel vir saamgestelde onderdele te ontwikkel. Die model maak voorsiening vir die raming van die vervaardigingskoste vir verskillende afmetings. Sodoende bied dit ʼn vergelyking met alternatiewe tegnieke, en help voorkom onnodig duur ontwerpkenmerke. Daar is voorgestel dat dele met ingewikkelde vorms in individuele basiese vorms verdeel word, wat dan hier verder ondersoek word. Vir die basiese vorms word ʼn eksperimentele benadering gebruik waar die vervaardigingstye in elke prosesstap gemeet en statisties ontleed word. Voorts word inspuitingsimulasiesagteware gebruik om komplementêre inspuitingstye te bepaal ten einde die eksperimentele ontwerp te voltooi. Hierdie metode maak dit ook moontlik om die vervaardigingstye vir saamgestelde materiaal onderdele van verskillende afmetings te raam. Die vervaardigingstye word dan bevestig aan die hand van dié van ʼn kompleks gevormde industriële onderdeel, met redelike resultate. Uiteindelik word ʼn buigsame kostemodel ontwikkel om verskillende vervaardigingstegnieke te vergelyk en die vervaardigingskoste te raam.

This research focuses on large-scale manufacturing systems having a number of stations with multiple tools and product types with different and deterministic processing steps. The objective is to determine the production quantities of multiple products and the tool requirements of each station that maximizes net profit while satisfying strategic constraints such as cycle times, required throughputs, and investment. The formulation of the problem, named OptiProfit, is a mixed-integer nonlinear programming (MINLP) with the stochastic issues addressed by mean-value analysis (MVA) and queuing network models. Observing that OptiProfit is an NP-complete, nonconvex, and nonmonotonic problem, the research develops a heuristic method, Differential Coefficient Based Search (DCBS). It also performs an upper-bound analysis and a performance comparison with six variations of Greedy Ascent Procedure (GAP) heuristics and Modified Simulated Annealing (MSA) in a number of randomized cases. An example problem based on a semiconductor manufacturing minifab is modeled as an OptiProfit problem and numerically analyzed. The proposed methodology provides a very good quality solution for the high-level design and operation of manufacturing facilities.

<p dir="ltr">The study aims to prove the need for higher quality production of weight plates which fall under US6746380B2 (expired May 10, 2021), assigned to USA Sports Inc. Literature justifies quality control standards. Selected literature validates posed hypotheses, and a product study is completed using weight plate specimens selected for physical quality testing to prove the common (repeated offense) existence of weight plates which fall out of the designated weight tolerance. Findings of physical product testing are collected and set against each other to determine differences in levels of quality control. Through extensive product testing (quantified within the study’s research methodology), novel quality control ideals are identified for product improvement in the study’s recommendations. Next steps are suggested to improve the understanding and utilization of quality control to work toward creating a sustainable and consistently high-quality product. Findings from the study are available to be used amongst companies in the fitness industry who produce weight plates.</p>

A dynamic job shop control system with a combined input/output control mechanism is developed for achieving improved shop performance. The problem is modelled such that at periodic intervals, the best combination of input and output variables for the forthcoming period are identified. The purpose of the control system is to determine the set of jobs to be released into the shop (input variables) and the capacity levels of machines (output variables) for a planning period such that a composite cost function is minimized. The problem is mathematically formulated as a 0-1 linear mixed integer program (MIP). An iterative based heuristic optimizing algorithm incorporating the MIP is developed. The control algorithm is compared with another job shop control system where only the input is assumed variable. The two systems are compared by computer simulation and results indicate significant improvements for most of the performance measures evaluated. Significant reductions in the mean and variance of the manufacturing lead time with a better distribution among its parts were also achieved. / Ph. D.

Dissertation (PhD)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Silver/Zinc batteries are extensively used for applications where a power source with a high energy density is needed. A reactor was developed to manufacture the zinc electrodes for these batteries. The parameters for the control of this reactor were identified. The interaction and relationships between the set of parameters were established and quantified. The novel design of the reactor includes features such as continuous replenishment of the constituting chemicals, parallel flow of the plating fluid, inert anodes and a serial electrical layout. The controlling parameters consist of both chemical and physical parameters. They are - zincate concentration, hydroxyl concentration, density, temperature, flow rate of the plating fluid, and current density. The unique solubility characteristics of zinc oxide in potassium hydroxide lend themselves to a novel approach for the determination of the zincate concentration in· the plating solution. A set of conditions for the manufacturing of electrodes, with the required characteristics, was identified. The requirements are densely packed zinc dendrite morphology with high porosity and mechanical stability. The designed reactor complies with the industries safety requirements. The batteries were successfully applied in their operational domain (torpedoes) after this extensive research project was completed. / AFRIKAANSE OPSOMMING: Silwer/Sink batterye word intensief aangewend in gebruike waar 'n kragbron met hoë energie digtheid benodig word. 'n Reaktor is ontwikkel wat die sink elektrodes van die tipes batterye vervaardig. Die veranderlikes vir die beheer van die reaktor is bepaal. Die interaksie en verwantskap tussen die stel veranderlikes is verkry en gekwantifiseer. Die unieke ontwerp van die reaktor het die volgende karakteristieke, nl. aaneenlopende vervanging van die chemikalië verbruik, parallelle vloei van die plateringsvloeistof, inerte anodes en elektriese uitleg in serie. Die chemiese en fisiese veranderlikes is beide beherende veranderlikes. Hierdie fisiese en chemiese veranderlikes wat die proses beheer is die sinkaat konsentrasie, hidroksiel konsentrasie, digtheid, temperatuur, vloeitempo van die plateringsvloeistof en die stroomdigtheid. Die unieke oplossingskarakteristieke van sinkoksied in kalsium· hidroksied leen hom tot die unieke proses om die sinkaat konsentrasie in die plateringsvloeistof te bepaal. 'n Steloperasionele kondisies vir die vervaardiging van die elektrodes met die spesifieke spesifikasies soos verlang, is geïdentifiseer. Hierdie kondisies is die diggepakte sinkdendriet morfologie met 'n hoë porositeit en meganiese stabiliteit. Die ontwerpte reaktor voldoen aan die industriële veiligheidsvereistes en die ergonomiese maatstawwe. Die batterye is suksesvol gebruik in hulle industriële aanwending as gevolg van die suksesvolle afhandeling van die stuk navorsing.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009. / This thesis details the conceptual design of a fixture-based, reconfigurable, automated spot welding system aimed at manufacturing various sub-assemblies of circuit breakers. The welding operations are currently done using manual welding equipment, making this stage of the assembly process highly labour intensive. A range of product models and variants are assembled in quantities requiring frequent change-overs. Low-cost automation within a developing country’s manufacturing industry, more specifically within the Republic of South Africa, is the target context. The chosen design restriction, of incorporating a part fixturing design approach, distinguishes this research from F. S. D. Dymond’s work, who addressed the same problem while restricted to a fixtureless assembly approach. A conceptual layout design was developed to address part feeding, manipulation, transportation, fixturing and welding requirements, for an entire breaker model range. A simulation model for three possible layouts of the selected conceptual design provided a means to investigate each layout’s ability to tolerate and balance variation in production requirements, and to establish objective comparative performance data. This showed that the optimal configuration consists of four single loop layout systems. The thesis concludes that the final concept possesses the flexibility to produce the primary product range. Reconfiguration for production beyond this range is assisted by the modular nature of the layout. Ultimately, a reconfigurable design should focus on a properly selected base of core product ranges, providing an expandable and reusable system. The system can be supported by manual assembly stations which handle highly variant, incompatible product ranges.

Thesis (MBA)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: This document describes the different possibilities of Low Cost Intelligent Automation (LCIA)and process analysis for companies in the processing industry. These techniques can be used in production and assembly to reach a higher productivity and to maintain the company's competitiveness. Productivity is very important for any company, because it influences the profit. LCIA means using cheap solutions to automate processes in assembly and production. Cheaper machines payoff much faster. This is important, because life cycles are becoming shorter and shorter. With LCIA more manual processes can be automated. This is an advantage especially in countries with high labour costs. Process analysis helps to optimise processes in a company. To reach this goal it is essential to analyse processes systematically. This helps to gather detailed information about manufacturing defects and where they originated from. With these information it is much easier to eliminate the source of error and to reduce the number of defective products. Less errors in a production process lead to higher quality and productivity. The company "Festool GmbH Deutschland" serves as an example for using the described methods. The presented examples for LCIA are simple solutions to automate manual processes in the assembly division. The process of a fully automated machine serves as an example to illustrate the different aspects of a process analysis in this company. The methodologies presented in this document can be used to achieve improvements especially in productivity. Therefore any company coming from a labour intensive industry should think about integrating LCIA and process analysis into their continuous improvement strategy. / AFRIKAANSE OPSOMMING: Hierdie dokument beskryf die verskillende moontlikhede van Lae Koste Intellegente Automasie (LKIA)en die proses analise vir maatskappye in die vervaardiging industrie. Hierdie metodes kan gebruik word in produksie en montering om hoër produktiwiteit te verkry sowel as die maatskapy se mededingendheid te handhaaf. Produktiwiteit is baie belangrik vir enige maatskappy, want dit beïnvloed die winsgewindheid. LKIA beteken die gebruik van goedkoop oplossings om prosesse te automatiseer in montering en produksie. Goedkoper masjiene word vinniger afbetaal. Dit is belangrik, want die lewenssiklus van beide produkte en masjiene word al korter. Met LKIA kan meer handprosesse ge-automatiseer word. Dit is 'n voordeel veral in lande met hoë arbeidskostes. Proses analise help om die prosesse in 'n maatskappy te optimiseer. Om hierdie doel te bereik is dit belangrik om prosesse sistematies te analiseer. Bogenoemde help om gedetaileerde informasie in te samel rondom vervaardigings defekte sowel as die oorsprong daarvan. Met hierdie informasie is dit makliker om die oorsprong van foute uit te skakel en om die getal foutiewe produkte te verminder. Minder foute tydens die vervaardigings proses ly tot 'n hoër kwaliteit en produktiwiteit. Die maatskappy "Festool GmbH Deutschland" dien as 'n voorbeeld vir die gebruik van die beskryfde metodes. Die voorgestelde voorbeelde vir LKIA is eenvoudige oplossings om die handprosesse in die monterings afdeling te outomatiseer. Die proses van 'n ten volle ge-automatiseerde masjien, dien as 'n voorbeeld om die verskillende aspekte van proses analise in hierdie maatskappy te illustreer. Die metodologie wat gebruik is in die dokument, kan gebruik word om verbeteringe veral in produktiwiteit te bewerkstellig. Dus kan enige firma in 'n arbeidsintensiewe industrie gebruik maak van die integrasie van LKIA en proses analise in sy deurlopende verbeterings strategie.

Thesis (PhD)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Some concepts of manufacturing on their own playa decisive role in manufacturing like Integration, Intelligence and Remote Monitoring. They have been tried and tested with great success in various applications in manufacturing. However, very little has been written on the synergy that is created when all three is deployed in one system. It is the aim of this work to survey the attributes of each of these key concepts, to compare them on the grounds of applicability and to study the effects when combined into one system. Final conclusions are made after the hypotheses have been validated with the aid of an experimental model. The first objective of this work is to show how many techniques such as expert systems, fuzzy logic, neural networks and genetic algorithms are used to enable systems to perform intelligently. It is accepted that the competitiveness, growth and profitability of a company in future may depend on the level of its system intelligence. This is so because an intelligent system is able to act appropriately under rapidly changing conditions of customer customisation and demands on quicker throughputs. A further objective of this work is to show how integration adds the element of synergy to a system. This is done by showing several ways of achieving integration by non-technological means like departmental consolidation, plant consolidation, product rationalisation, more flexible working practices, etc. There are as many options for integration by technical means as well, ranging from group technology to process or transfer lines, and from flexible automation such as robots through to hard automation using special-purpose machinery and transfer lines. The third objective is to show how remote monitoring enhances the capabilities of manufacturing systems by synergising with the other two key concepts. With the technology of intelligent manufacturing and integration, larger and more complex manufacturing systems are becoming a reality. However, the danger exists that the shop floor machine tools remain isolated islands of automation. Plant machinery needs to be networked into the enterprise-wide information system. The ability to monitor a variety of process parameters and alert plant staff to changing conditions can greatly reduce downtime. This lack of connectivity therefore represents a huge constraint as far as productivity is concerned. For this reason, there is a great interest to study remote monitoring, analysis and diagnostic systems for application in modem manufacturing. The major contribution of this work is to study the synergy that is created by combining the three key concepts into one system and to validate the findings with the aid of the experimental model. The meaning of validation is to make legally valid; to grant official sanction to; to confirm the validity of something or to declare something as true. To validate is to support or corroborate a theory on a sound or authoritative basis by experiments designed to show a hypothesis as being true. The components of the validation model are a neural network, a simulator, a decision evaluator or critic, and a teacher. The neural network is used to make the decisions. Its inputs are the system parameters and its outputs are a vector of values between 0 and 1, the highest value indicates the decision being made (winner takes all). The simulator executes the decision it obtains from the network and thus changes the state of the system. The evaluator looks at how the system changed due to the decision made by the network and decides whether it was a good or a bad decision. The teacher then adjusts the output of the network accordingly and trains the network with the adjusted outputs. The results of the validation experiments show that intelligence is used to train the model, integration is achieved by combining the elements of the model with the mobile robot and remote monitoring is done by the model to analyse the condition of the system and to react accordingly. The main objective of this work is clearly met in that synergy was shown to be created by the three key concepts. / AFRIKAANSE OPSOMMING: Aspekte soos Integrasie, Intelligensie en Afstandsmonitering speel 'n deurslaggewende rol in vervaardiging en is al op hulle eie met groot sukses in vele toepassings gebruik. Daar is egter nog nie veel aangeteken oor die sinergie wat ontstaan wanneer hulle tesame in een stelsel gebruik word nie. Dit is die doel van hierdie werk om die kenmerke van elk van hierdie sleutel aspekte na te vors, dit op grond van toepaslikheid met mekaar te vergelyk en die uitwerking te bestudeer wanneer hulle in een stelsel saamgevoeg word. Nadat die hipoteses met behulp van 'n eksperimentele model gevalideer is, word finale gevolgtrekkings gemaak. Die eerste doelwit van hierdie werk is om aan te toon dat verskeie tegnieke soos genetiese algoritmes en neurale netwerke gebruik word om stelsels meer kundig te laat optree. Dit word aanvaar dat die toekomstige mededingendheid en groei van ondernemings mag afhang van die stelsel intelligentheidsvlak. Dit is omdat intelligente stelsels gepas kan optree onder snel-veranderende omstandighede. 'n Verdere doelwit is om aan te toon hoe integrasie sinergie kan toevoeg tot 'n stelsel. Dit word gedoen deur verskeie metodes te bespreek van hoe om integrasie op 'n nie-tegniese vlak te bewerkstellig. Die tegniese metodes van integrasie word ook bespreek en sluit tegnieke soos groeptegnologie, aanpasbare outomatisasie en robotika in. Die derde doelwit is om aan te toon hoe afstandsmonitering as sleutel aspek die ander twee sleutel aspekte kan versterk. Die tegnologië van intelligente vervaardiging en integrasie maak die skepping van groter en meer kompleks vervaardigingstelsels nou moontlik. Die gevaar bestaan egter dat hierdie masjiene slegs eilande van outomatisasie sal bly indien hulle nie met behulp van netwerke in die onderneming se inligtingstelselopgeneem word nie. Die vermoë om prosesveranderinge te monitor kan lei tot verminderde staantyd van masjiene en kan dus produktiwiteit verhoog. Om hierdie redes is die toepassing van afstandsmonitering en -diagnosering belangrik vir toepassing in vervaardiging. Die belangrikste bydrae van hierdie werk is die studie van die sinergie wat ontstaan wanneer die drie sleutel aspekte in een stelsel gekombineer word en om die bevindinge te valideer met behulp van 'n eksperimentele model. Om te valideer beteken om iets geldig te verklaar of om die geldigheid van iets te bevestig. Dit beteken verder om 'n teorie te ondersteun of te staaf op 'n grondige en deskundige basis met behulp van eksperimente. Die validasie model bestaan uit 'n neurale netwerk, 'n simulator, 'n besluitevalueerder of beoordelaar, en 'n onderwyser (terugvoerder). Die neurale netwerk neem die besluite met die stelselparameters as inset en die uitset 'n vektor met waardes tussen 0 en 1. Die simulator voer die besluit uit en verander so die toestand van die stelsel. Die evalueerder bepaal hoe die stelsel verander het as gevolg van die besluit en bepaalook of dit 'n goeie of slegte besluit was. Die onderwyser verstel dan die uitset van die netwerk dienooreenkomstig en lei die netwerk op met die verstelde uitsette. Die resultate van die validasie eksperiment toon aan dat intelligensie gebruik word om die modelop te lei, integrasie behaal word deur die elemente van die model te kombineer met die mobiele robot en afstandsmonitering toegepas word deur die toestand van die stelsel te monitor en te analiseer. Die hoofdoelwit van hierdie werk word dus duidelik behaal deur die beskrywing van die sinergie wat ontstaan deur die kombinasie van die drie sleutel aspekte.