Thesis (M.Eng.)(Mechanical)--University of Pretoria, 2006. / Includes summaries in English and Afrikaans. Includes bibliographical references.

Syfte – Syftet med denna studie är att undersöka hur lagerstyrning av reservdelar inom hjälpmedelsförsörjning kan effektiviseras. Metod och genomförande – Den valda strategin för att uppfylla studiens syfte omfattades av att genomföra en fallstudie i samarbete med Hjälpmedelscentralen på Länssjukhuset Ryhov i Jönköping. Empiri från fallstudien har erhållits genom intervjuer och dokumentationsstudier. Insamlad data har analyserats gentemot det teoretiska ramverket och därmed genererat studiens resultat. Resultat – Studiens resultat visar inledningsvis på att rörlighet, volymvärde och kritiskhet är viktiga aspekter att beakta vid lagerstyrning av reservdelar inom hjälpmedelsförsörjning. Rörlighet och volymvärde har utgjort kriterier för en sortimentsövergripande ABC-klassificering, vilket resulterade i tre segment. Ett av dessa segment, kundorder, har så pass låg rörlighet att det ansågs lämpligt att endast beställa dessa reservdelar då behov uppstår. För de övriga segmenten bör lagerstyrningen utföras med beställningspunktsystem, dock med en viss skillnad när det gäller styrningens intensitet. Vidare anses det lämpligt att, för enskilda reservdelar, göra kvalitativa bedömningar avseende kritiskhet. Detta ska säkerställa att kritiska reservdelar får en mer uppmärksammad styrning för att därmed, i större utsträckning, undvika bristsituationer. Implikationer – I denna studie har det fastställts hur lagerstyrning av reservdelar inom hjälpmedelsförsörjning kan effektiviseras. För verksamheter som vill åstadkomma detta är det dock nödvändigt att identifiera de aspekter som, för verksamheten i fråga, är mest väsentliga. Vidare krävs det att tillgång till nödvändigt dataunderlag säkerställs. Begränsningar – Fallstudiedesignen utgjordes av en enfallsstudie där endast en analysenhet undersöktes. I och med att olika verksamheter har olika förutsättningar för lagerstyrning hade det varit lämpligt att inkludera fler fallverksamheter i undersökningen. Detta hade resulterat i en högre grad av generaliserbarhet. / Purpose – The purpose of this study is to investigate how to achieve efficient inventory management of spare parts in the health care sector. Methodology – To meet the purpose of the study a case study has been conducted in collaboration with Hjälpmedelscentralen at Länssjukhuset Ryhov in Jönköping. The empirical data have been obtained by methods such as interviews and documentation studies. By analysing empirical data in comparison with the theoretical framework the findings of the study was generated. Findings – Initially, the findings of the study implies that aspects such as usage frequency, annual dollar volume and criticality are important to consider in inventory management of spare parts in the health care sector. Usage frequency and annual dollar volume have been used as criteria for an assortment wide ABC-classification which resulted in three segments. One of these segments, customer order, has a very low usage frequency. Therefore it was considered appropriate to only order these spare parts when an actual need has occurred. The inventory management of the remaining segments should be carried out with a reorder point system. However, there is a certain difference regarding the intensity of the management between the two segments. Furthermore, it’s appropriate to conduct a classification based on criticality. This should ensure that critical spare parts get more attention and hence decreasing the risk of shortage. Implications – In this study, it has been determined how to achieve efficient inventory management of spare parts in the health care sector. For those who aim to do this it’s necessary to identify the aspects that are most important for the particular business. Furthermore, it’s important that these businesses ensure the availability of necessary data. Research limitations – The conducted case study was designed as a holistic single case study. Since businesses differ from each other it would have been appropriate to conduct a multiple case study. As a result of this, a higher degree of generalisation could have been achieved.

The following thesis counteracts the relationship of Supply Chain Design (SCD) and web-sales[1], and concentrates on the overall aim of “How to re-design Supply Chains more effective when a web sales portal is applied?”. In order to clarify this aim, following four research objectives are set: How does e-commerce connect to Supply Chain Design in general? What is required for a successful implementation of e-commerce? What are the costs and benefits by implementing e-commerce? Which potential risk factors in correspondence of the implementation of             e-commerce may influence the whole SCD and e-commerce interaction process?  Previous studies have not discussed the interaction of e-commerce and supply chain design on operational level at all, which accounts for a large portion of interests these days. When looking at the research objectives they have been solved in three process steps. First of all the general connection of e-commerce and Supply Chain Design had been analysed through an extensive literature review in form of i.e. suitable books and research papers. Results demonstrated that e-commerce helps to support and manage supply chain activities by offering relevant information. The connection between e-commerce and SCD insists of a close gearing. E-commerce helps to support and manage supply chain activities by offering relevant information about what kind of product is demanded, what is available in warehouses, which products are in the manufacturing processes, and which products will enter the physical facilities and customer sites. Following, research objectives two to four had been identified for which a literature review has created a firm basis on the status quo of current research studies. Combined with findings of developing a web-sales implementation plan for a leading group in power and automation technologies this work-out has been used as empirical research on how a real life company is carrying out these objectives. This plan had been worked out on-side the company, data has been obtained through interviews, observations, and internal system data. Requirements for a successful implementation of e-commerce are seen in strategic and organisational planning activities, as well as specific platform conditions. Concerning costs and benefits, monitoring and evaluating improvements, increasing customer satisfaction, and reducing order-cycle times stay in contrast to incidental fixed and variable costs which had been demonstrated through a detailed break-even analysis. Potential risk factors which had been identified can be countervailed through an appropriate risk management. Thirdly, the overall research question of “How to re-design Supply Chains more effective when a web sales portal is applied?” had been solved based on intermediate results of step one and two, combined with the project work-out, providing informative and sufficient data. The result is that in a first step a clear picture of which products and spare parts will be sold has to be defined. Secondly a precisely inventory management - discussing which parts to hold in stock, where to stock them, and how much to hold in stock - needs to be worked out. And thirdly, after analysing the possible and most plausible inventory strategy, possible distribution varieties need to be analysed. The most appropriate solution for the case company is represented in an Inventory-Distribution-Matrix. This research study has created a basis for the business unit of Power Electronics to improve possible efficiency. The knowledge and implementation steps operated for this implementation plan can be used for other business units in Switzerland and can be seen as a decision maker. Therefore this work-out has generated an enormous benefit for the case company. Instead of acting instinctively, decisions are based on qualitative and quantitative methodologies, data collection methods and data analysis techniques, and therefore follow a process strategy. [1]“Web-sales” in this context is associated with selling and buying information, products, or services via computer networks (Strader & Shaw, 1997), in this research study it is identical to “E-commerce”.

In this dissertation, we consider a multi-item two-echelon inventory distribution system in which the central warehouse operates with (Q, R) policy, and each local warehouse implements base-stock policy. The objective is to find the policy parameters minimizing the relevant system-wide costs subject to an aggregate mean response time constraint at each facility. We first propose an exact solution procedure based on a branch-and-price algorithm to find the relevant policy parameters of the system considered. Then, we propose four alternative heuristics to find the optimal or near-optimal policy parameters of large practical-size systems. The first heuristic, which we call the Lagrangian heuristic, is based on the simultaneous approach and relies on the integration of a column generation method and a greedy algorithm. The other three heuristics are based on the sequential approach, in which first the order quantities are determined using a batch size heuristic, then the reorder levels at the central warehouse and the basestock levels at the local warehouses are determined through the same method used for the Lagrangian heuristic. We also propose a lower bound for the system-wide cost. Later, we extend our study to compound Poisson demand. The performance of the Lagrangian heuristic is found to be extremely well and improves even further as the number of parts increases. Also the computational requirement of the heuristic is quite tolerable. This makes the heuristic very promising for large practical industry-size problems. The performance of the sequential heuristics is also satisfactory, but not as much as the Lagrangian heuristic.

Inventory management policies of two independent dealers in a service parts system with transshipment is studied in this thesis. Dealers can collaborate by pooling inventory or service. Revenue is shared in transshipment, can sometimes be contrary to profit maximization of one of the parties albeit sum of profits is increased. To assess the benefits of inventory pooling under equilibrium strategies, and the effect of competition on profits, a Markov Decision Process is formulated. A simpler variant of the optimal four-index threshold policy is used to characterize the production, service and transshipment related inventory decisions. A game theoretical approach as well as notions from policy iteration is taken to find the best response policy and equilibrium policies of the dealers. Numerical study is conducted to investigate the effect of cost, revenue and demand parameters, as well as dealer asymmetricities on benefit of pooling, service levels and transshipment flows. Analysis shows that commission schemes fairly allocating transshipment value to the players, high customer traffic intensities, and low transshipment costs are most suited environments for pooling. System centralization is beneficial when the inventory holding costs are high, transshipment costs are low, customer traffic intensities are high or the commission structure is distracting a party. Competition, within the experimental settings, dampens about 45% of the benefits of pooling.

Capacity pooling in production systems, in the form of production capacity or inventory pooling, has been extensively studied in the literature. While production capacity pooling has been proven to be beneficial, the impact of inventory pooling has been less significant. These results cannot be easily extended to repairable systems due to fundamental differences between repairable and production systems. For one thing, in repairable systems, the demand rate is a function of the number of operational machines, whereas it is exogenous and constant in production systems. In this Thesis, to serve different fleets of machines possibly at different locations, we study whether repair shop pooling is more cost effective than having dedicated on-site repair shops for each fleet. In the first model, we consider transportation delays and related costs, which have been traditionally ignored in the literature. We include on-site spare-part inventories that operate according to a continuous-review base-stock policy. Our numerical findings indicate that when transportation costs are reasonable, repair shop pooling is a better alternative. Next, we model a pooled repair shop that fixes failed components from different k-out-of-n:G systems. We permit a shared spare parts inventory serving all systems and/or reserved spare parts inventories for each system; we call this a hybrid model. The destination for a repaired component can be chosen either on a first-come-first-served basis or by following a static priority rule. Our findings show that both hybrid policies are more cost effective than having separate repair shops and inventories for each system. We propose implementing the multilevel rationing (MR) policy in systems with shared inventory. The MR policy prioritizes classes, and stops serving a class from inventory if the inventory level is below the inventory threshold identified for that class. When there is no inventory, the repaired component is sent to the highest priority class among those with down machines. To approximate the cost of the MR policy, we study an M/G/1//N queueing system serving multiple classes of customers with an unreliable server. Our numerical findings indicate that the MR policy performs as well as the epsilon-optimal policy and outperforms the hybrid policies.

Capacity pooling in production systems, in the form of production capacity or inventory pooling, has been extensively studied in the literature. While production capacity pooling has been proven to be beneficial, the impact of inventory pooling has been less significant. These results cannot be easily extended to repairable systems due to fundamental differences between repairable and production systems. For one thing, in repairable systems, the demand rate is a function of the number of operational machines, whereas it is exogenous and constant in production systems. In this Thesis, to serve different fleets of machines possibly at different locations, we study whether repair shop pooling is more cost effective than having dedicated on-site repair shops for each fleet. In the first model, we consider transportation delays and related costs, which have been traditionally ignored in the literature. We include on-site spare-part inventories that operate according to a continuous-review base-stock policy. Our numerical findings indicate that when transportation costs are reasonable, repair shop pooling is a better alternative. Next, we model a pooled repair shop that fixes failed components from different k-out-of-n:G systems. We permit a shared spare parts inventory serving all systems and/or reserved spare parts inventories for each system; we call this a hybrid model. The destination for a repaired component can be chosen either on a first-come-first-served basis or by following a static priority rule. Our findings show that both hybrid policies are more cost effective than having separate repair shops and inventories for each system. We propose implementing the multilevel rationing (MR) policy in systems with shared inventory. The MR policy prioritizes classes, and stops serving a class from inventory if the inventory level is below the inventory threshold identified for that class. When there is no inventory, the repaired component is sent to the highest priority class among those with down machines. To approximate the cost of the MR policy, we study an M/G/1//N queueing system serving multiple classes of customers with an unreliable server. Our numerical findings indicate that the MR policy performs as well as the epsilon-optimal policy and outperforms the hybrid policies.

Dissertation (Ph.D.) -- Worcester Polytechnic Institute. / Keywords: Computer aided manufacturing planning; Object-oriented systems analysis (OSA); Feature; manufacturing resource capability; setup planning; multi-part fixture Includes bibliographical references (p.146-154).

[pt] O dinamismo dos mercados vem se intensificando, em face da globalização, dos avanços tecnológicos e das mudanças sociais. Consequentemente, as empresas necessitam se adaptar tempestivamente para se manter competitivas, ou podem vir a desaparecer. Neste contexto, inovações disruptivas são cada vez mais frequentes. Assim é o caso da manufatura aditiva, conhecida popularmente por impressão 3D. Tratam-se de tecnologias com potencial disruptivo que vai além do paradigma de produção, influenciando a logística, a sociedade, os mercados e múltiplos setores, tais quais o de saúde, o de defesa, o automotivo, o de construção civil e até mesmo o de alimentos. Nesta vertente, o presente trabalho busca verificar o potencial disruptivo das tecnologias de manufatura aditiva, iniciando pelo aprofundamento no conhecimento sobre estas tecnologias. Em seguida, é feita análise sobre a gestão das cadeias de suprimentos atual e as implicações das tecnologias de manufatura aditiva sobre a gestão das cadeias de suprimentos. Por fim, o estudo confronta o potencial disruptivo da manufatura aditiva com a cadeia de suprimentos de sobressalentes da Marinha do Brasil, no intuito de aprimorar aquela cadeia de suprimentos, buscando, naquelas tecnologias, solução para as dificuldades enfrentadas pela Esquadra do Brasil. / [en] The dynamism of markets has been intensifying by the globalization, the technological advances and the social changes. Consequently, companies need to adapt timely to remain competitive, or may disappear. In this context, disruptive innovations are becoming more frequent. This is the case of additive manufacturing, popularly known as 3D printing. These are technologies with disruptive potential that goes beyond the production paradigm, influencing logistics, society, markets and multiple sectors, such as health, defense, automotive, civil construction and even food. From this point, this work seeks to verify the disruptive potential of additive manufacturing technologies, starting with the deepening of the knowledge about these technologies. Next, it is analyzed the management of current supply chains and the implications of additive manufacturing technologies on supply chain management. Finally, the study confronts the disruptive potential of additive manufacturing with the Brazilian Navy s supply chain of spare parts, in order to improve that supply chain, searching solutions to the difficulties faced by the Brazilian Fleet in those technologies.

Esta dissertação tem como objetivo desenvolver uma sistemática de auxílio à tomada de decisão na definição das estratégias de suprimento de peças sobressalentes no âmbito da manutenção industrial. Para atingir este objetivo, inicialmente, foram realizadas revisões da literatura para identificar os critérios utilizados na definição das estratégias de suprimento e, também, as variáveis de decisão utilizadas na definição dessas estratégias. Essas variáveis foram divididas em quatro classes: sistema/equipamento, peça, suprimento e estocagem. Em seguida foram elaborados dois questionários fechados, o primeiro a respeito das características e o segundo a respeito das variáveis de decisão de suprimento das peças sobressalentes. Estes questionários foram aplicados na caracterização das peças de dois equipamentos instalados em uma planta petroquímica. As respostas do questionário de critérios foram avaliadas possibilitando a identificação de lacunas existentes na estratégia atualmente adotada pela empresa em relação a algumas peças, além de apontar algumas oportunidades de otimização de estoques. / This essay aims to develop a systematic to support spare parts provision decisionmaking in industrial maintenance. To achieve this goal, initially, literature reviews were conducted to identify the criteria used in the definition of supply strategies and also the decision variables used in the definition of these strategies. These variables were divided into four classes: system / equipment, spare part, supply and storage. Two closed questionnaires were developed. The first one was about the characteristics and the second one was about the decision variables of spare parts supply. These questionnaires were applied to characterize the parts of two equipment installed in a petrochemical plant. The characteristics questionnaire answers were evaluated, enabling the identification of gaps in the strategy currently adopted by the company for some parts, while pointing out some inventory optimization opportunities.