The objective of this research project was to identify the limitations associated with schedule-based Material Requirements Planning (SBMRP) and to present a knowledge-based expert system (KBES) approach to solve these problems. In SBMRP, the basic strategy is to use backward or forward scheduling based on an arbitrary dispatching rule, such as First-In First-Out. One of the SBMRP weak points is that it does not use such job information as slack times, due dates, and processing times, information which otherwise is important to good scheduling decisions. In addition, the backward scheduling method produces a better schedule than the forward scheduling method in terms of holding and late costs. Dependent upon job characteristics, this may or may not be true and should be tested. This study focused on the means to overcome these two weak points by the use of a KBES. Heuristic rules were developed through an experiment-based knowledge acquisition process to generate better schedules, rather than relying solely upon forward or backward scheduling. Scheduling performance was measured, based on the minimization of the sums of holding and late costs. Due to complexities of the problem, heuristic methods were used rather than analytic methods. In particular, five loading rules were selected, based upon their close relationship to selected job characteristics, including processing times and due dates. Combined loading methods (CLMs) were developed to obtain better performance, derived by combining the two existing SBMRP scheduling strategies with five loading heuristic rules. This resulted in the generation of 10 CLMs for further evaluation. Since this study proposed a new approach, an expert human scheduler was not available. To overcome this problem, knowledge acqusition through computer experimentation (KACE) was utilized, based upon an architecture of five components: job generator, scheduler, evaluator, rule generator (an extended version of ID3), and the KBES. The first three components were used to generate a large number of examples required by the rule generator to derive knowledge. This derived knowledge was incorporated into the KBES. Experimental results indicated that the KBES outperformed the two existing SBMRP methods. Based on sensitivity analysis, the KBES exhibited robust performance with regard to every job parameter except number of parts. As the number of parts was increased, KBES performance was subject to degradation since the possibility of interactions or conflicts between parts tended to increase, resulting in shifting the threshold ratio of total available time to total processing time. Thus, it is strongly recommended that a new KBES capable of accommodating 30 parts or more should be developed using the KACE method. / Graduation date: 1991

Examensarbetet är utfört på Lifco Dental, som är ett distributionsföretag i Enköping undervårterminen 2013 och omfattar 30 högskolepoäng. Lifco Dentals huvudsakliga verksamhet ärlagerhantering av tandläkarartiklar och det rör sig om cirka 40 000 artiklar i varierandestorlek.Examensarbetet avser i första hand styrning av lagerhållning och artikelplacering. Andraområden som har bearbetas är ergonomi och personalfrågor. Arbetet kretsar kring följandeforskningsfrågor;1. Enligt vilka principer kan man placera artiklar?2. Hur kan man utforma arbetssättet på lager både kostnadseffektivt och ergonomiskt?3. Hur kan materialflödet effektiviseras?från källor som artiklar, litteratur, internet och direktkontakt med personal har samlats in.Behandling av information har baserats på författarnas tidigare kunskaper och vägledning avhögskolans handledare.Valda vertyg och metod är; Read a Plant, värdeflödeskartläggning, spagettidiagram,Paretodiagram, 5-Varför, benchmarking och intervjuer av personal, säljbolag och tandläkare.Dessa verktyg har hjälpt att analysera nuläget i verksamheten och identifiera slöserier samtförbättringsområden. En del verktyg har varit mer relevant för att kunna besvaraforskningsfrågorna.Bäst artikelplacering torde uppnås med ABC-principen. Undersökning av tre identifieradeergonomiska riskmoment gjordes enligt arbetsmiljöverkets bedömningsmall, vilket påvisadeatt man genom att ha rätt resurser, hjälpmedel och klara direktiv kan undvika skador. Dettakan man åstadkomma bland annat genom visuellt ledningssystem och investering i nyaergonomiska verktyg. Resultatet från värdeflödeskartläggning och paretodiagram tyder påbristande fördelning av resurser och identifierar flaskhalsar i flödet. En kontrolleradfördelning av anpassade resurser reducerar ojämnheter och underlättar styrningen.Författarna har baserad på analysen rekommenderat principer för artikelplacering ochlagerflöde samt rekommendationer kring personalmotivering, engagemang och ergonomi. / This Master of Science thesis has been conducted at Lifco Dental, a logistics company inEnköping, Sweden, during the spring term of 2013, encompassing 30 credits. Lifco Dental’score operation is logistics and inventory management of dental products, a sum total ofapproximately 40,000 articles in various sizes.The thesis is primarily concerned with inventory management and article placement. Otherareas of interest have been ergonomics and human resource management. The main researchareas have been;1. According to which principles can articles be placed?2. How can the inventory be managed to be cost efficient and have good ergonomics?3. How can material flows be streamlined?Information from sources such as articles, literature, the internet and direct interaction withemployees has been gathered. This information has been processed based on the authors’prior experience as well as extensive guidance from the MDH supervisor.The authors´ chosen tools and methods have been Read a Plant; Value Stream Mapping;Spaghetti diagram; Pareto diagram; 5Why; benchmarking and interviews with employees,sales staff and dentists. These tools and methods have aided us in analyzing the current stateof operations and in identifying waste as well as areas of opportunity. Some tools have provenmore relevant than others in producing relevant research answers.Optimal article placement can be achieved with the ABC principle. Studies of threeergonomically problematic operations, utilizing templates provided by Arbetsmiljöverket,showed that correct resources and aids as well as clear directives reduces the risks of injuries.This can be achieved by deploying a visual management system and more ergonomical toolsand aids. Results from the Value Stream Mapping and Pareto diagram suggest deficiencies inthe allocation of resources and identifies bottlenecks in the material flow. Controlledallocation of resources reduces inbalances and enhances control.Based on the analysis the authors have recommended principles for article placement andinventory flow as well as recommendations regarding staff motivation, commitment andergonomics.

Hybrid Make-To-Stock (MTS)-Make-To-Order (MTO) manufacturing is a well known policy that captures the benefits of both MTS and MTO policies. This manufacturing policy is adopted by many manufacturing firms because it allows for production based on customer specifications while keeping short response times. We study a hybrid MTS-MTO manufacturing system which consists of two processing stages and an intermediate buffer between these two stages. We propose two separate scenarios for ordering and replenishment of components from the first stage which will give more realistic guidance for practitioners. The first scenario is batching customer orders before being released to the first stage. The second scenario is batch replenishment of common components from the first stage. Most existing MTS-MTO models focus on one-for-one ordering and replenishment strategies. We enhance these models by introducing a batch ordering policy to account for economies of scale in ordering when there is an ordering cost associated with each order placed for common components. We use queueing theory to model the system behavior and use the matrix-geometric method to evaluate system performance under the new ordering policy. Afterwards, we develop an optimization model with the objective to minimize the system overall costs. The purpose of our optimization model is to find the optimal intermediate buffer size and the optimal order quantity for the system. In the second scenario, we introduce the batch replenishment policy from stage 1. This policy is suitable when stage 1 and stage 2 are physically distant and there is a shipping cost incurred when components are transferred from stage 1 to stage 2. The decision variables in this model are the intermediate buffer size and the shipping quantity. We show that the base stock policy is sub-optimal when there is an ordering cost incurred for ordering components. The savings from adopting the batch ordering policy are high and the response time for most customer orders is not affected. When there are shipping costs and shipping time between the two stages, we show that the right selection of the system decision variables can have a large impact on the total cost incurred by the system.

Detta examensarbete har ägt rum vid Produktionsverkstad 1 (PV1) på Wexiödisk AB där diskmaskiner av huvtyp tillverkas. Syftet med detta examensarbete har varit att undersöka vilka lagerstyrningsmodeller som är lämpliga för att styra avdelningens materialflöden med. Arbetet har genomförts i två steg. Först behandlades artiklar unika för produkterna vid PV1, därefter artiklar gemensamma med andra produkter. Enligt modeller ur relevant litteratur utformades förslag på hur dessa kunde appliceras praktiskt. Förslagen presenterades och diskuterades med berörd personal som valde Tvåbingesystem 2. Ett test gjordes enligt principen ”den japanska sjön” vilket innebar lägre lagernivåer i lastbärarna. De problem som uppstod noterades. Resultatet blev att antalet artiklar som plockades i veckosatser minskades vilket skapat underlag för att minska administrationen av tillhörande plocklistor. Plockvagnen har kunnat tas bort vilket frigjort yta vid monteringsavdelningen. Förutsättningar finns att slå samman två plocklistor till en och därmed förenkla arbetet för förrådspersonalen. / This degree project has been performed at Production unit 1 (PV1) at Wexiödisk AB, where hood type washing machines is manufactured. The purpose of this project has been to investigate which inventory control models that could be suitable to control the section’s material supplies. The work has been accomplished in two steps. At first, items unique to products manufactured at PV1 were treated, followed by items common with other products. According models in relevant literature, suggestions were made to how the models could be applied practically. The suggestions was presented to and discussed with the parties concerned who chose Two-bin system 2. A trial was carried out according to the principle of “the Japanese river” which implied lowered inventory levels. The problems that occurred were noted. The result was that the number of items that was weekly picked and distributed was reduced which has created a basis to also reduce the administration of the systems picking lists. The item wagon has been removed which has cleared floor space at the assembly section. Conditions have been created to merge two picking lists into one and thereby simplify the work for the inventory staff.

Södra Interiör har en anläggning i Kallinge där man tillverkar golv och paneler av furu. I takt med att produktionen har ökat har även lagernivåerna ökat vilket har ökat risken för att fel råvara används till fel produkt. Syftet med examensarbetet är att ta fram ett arbetssätt som minskar risken för att fel råvara används. Studien visar att något måste göras för att säkerställa att rätt råvara används till rätt produkt. Lagernivån och informationskvaliteten är andra problem som identifierats. Nyckelbegreppen för att lösa problemen är ordning och reda, information, framförhållning och utrymme. Förbättringsförslagen har olika karaktär, där vissa förbättringar kan göras omgående med små resurser medan andra tar längre tid och kräver större resurser. De viktigaste förbättringsförslagen handlar om att skapa mer utrymme i lagret, tydligare uppmärkning av virkespaketens innehåll och bättre informationskvalitet. / Södra Interiör has a plant in Kallinge which manufactures flooring and panels of pine. As production has increased, inventory levels has increased. This has increased the risk that wrong raw material is used for the wrong product. The purpose of this study is to develop an approach that reduces the risk that wrong materials are used. The study shows that something must be done that ensure that correct materials are used for the right product. Stock level and information quality are other concerns identified. Key concepts to solve problems are: well organized, information, advanced planning and space. Improvement proposals are different in nature, where some improvements could be made immediately with few resources, while others take more time and require more resources. The main suggestions for improvement is about creating more space in the warehouse, clearly mark up of the timber package contents and better information quality.

Hybrid Make-To-Stock (MTS)-Make-To-Order (MTO) manufacturing is a well known policy that captures the benefits of both MTS and MTO policies. This manufacturing policy is adopted by many manufacturing firms because it allows for production based on customer specifications while keeping short response times. We study a hybrid MTS-MTO manufacturing system which consists of two processing stages and an intermediate buffer between these two stages. We propose two separate scenarios for ordering and replenishment of components from the first stage which will give more realistic guidance for practitioners. The first scenario is batching customer orders before being released to the first stage. The second scenario is batch replenishment of common components from the first stage. Most existing MTS-MTO models focus on one-for-one ordering and replenishment strategies. We enhance these models by introducing a batch ordering policy to account for economies of scale in ordering when there is an ordering cost associated with each order placed for common components. We use queueing theory to model the system behavior and use the matrix-geometric method to evaluate system performance under the new ordering policy. Afterwards, we develop an optimization model with the objective to minimize the system overall costs. The purpose of our optimization model is to find the optimal intermediate buffer size and the optimal order quantity for the system. In the second scenario, we introduce the batch replenishment policy from stage 1. This policy is suitable when stage 1 and stage 2 are physically distant and there is a shipping cost incurred when components are transferred from stage 1 to stage 2. The decision variables in this model are the intermediate buffer size and the shipping quantity. We show that the base stock policy is sub-optimal when there is an ordering cost incurred for ordering components. The savings from adopting the batch ordering policy are high and the response time for most customer orders is not affected. When there are shipping costs and shipping time between the two stages, we show that the right selection of the system decision variables can have a large impact on the total cost incurred by the system.

Title: Inventory Control of WEEE (Waste of Electronic and Electrical Equipment) Reverse Logistics in parts of China  --The HEA (household electrical appliances) manufacturers’ perspective   Background: With economic development, the requirement of public for enterprises and products has become increasingly rational. Price is no longer the only consideration of public, they also pay attention to other factors, such as energy conservation. The manufacturers face enormous challenges because of the late start of products recycling in China. So enterprises start to build their own recycling logistics system in order to have more competitive for themselves.   Purpose: The purpose is to describe the methods of inventory controls in the case HEA manufacturers and the problems of inventory controls, find out what problems exsist in the case manufacturers, then analyze what are the origins of these issues for HEA manufacturers as well as propose how these issues can be alleviated, and what methods would be suitable. By solving these research questions, the thesis tries to offer some suggestions about inventory control improvement not only to the cases, but also wider to the whole HEA manufacturers in China.   Method: Multiple - case study as research method has been applied. Specifically, two case companies, Chinese HEA manufacturers, have been selected. Two telephone focused interviews combined with open-ended interviews have been conducted with two related managers. The empirical evidence has been analyzed by using with-in case study and cross-case analysis method, then model analysis is applied.     Results, conclusion: First, the methods are not good enough in the two case companies, a new model is built to help inventory control in the case companies. Second, from external and internal perspective, the origins to cause the problems are a lot, but the main causes are environmental factors, and in busy seasons of these companies. Besides, for doing reverse logistics is a capital costing job, none of the enterprises would like to step in. and reverse logistics is in an uncertainty environment, doing so need to make sure everything clearly and orderly, or costs will be a large amount. The best way of improving inventory control of WEEE reverse logistics in China is that the enterprises standing together to restore the orders.   Limitations and drawbacks: For one thing, there are not enough previous studies references in China, this brought some difficulties of supporting the view points in the thesis. Two empirical cases are not persuasive enough to represent the whole China due to the limitation of the authors’ knowledge and the huge area of China. Nevertheless, the ideal model in model analysis is not that complicated, which means, for more complex problems and processes, the model would be lame.

I ett litet företag finns en risk att ledningen fokuserar så mycket på kärnverksamheten att övriga administrativa verksamheter åsidosätts. Exempelvis finns det risk att företaget inte har full kontroll på sina lager. Syftet med den här uppsatsen är att beskriva och analysera värderingen och styrningen av lagret hos ett litet handelsföretag med butik och i förekommande fall ge förbättringsförslag. Vi har dels studerat lagar och rekommendationer avseende hantering av lager samt litteratur inom området lagerstyrning i handelsföretag. Dessutom har vi intervjuat företrädare för ett typiskt litet handelsföretag. Det undersökta företaget uppfyller gällande lagar och rekommendationer, men inte så mycket mer. Vidare använder sig företaget mestadels av känsla och erfarenhet i sin lagerstyrning. Förtaget använder alltså inte formella analyser och metoder i någon större utsträckning, om ens någon. Vi har några förslag på förbättringar i detta avseende. / In a small company there is a risk that the management focuses so much on the core business that other administrative tasks are ignored. For example, there is a risk that the company does not control its inventories efficiently. The purpose of this thesis is to describe and analyze the valuing and control of the inventory in a small retail company with a store and, where appropriate, give suggestions for improvement. We have studied laws and recommendations regarding inventory valuation and other literature regarding inventory control in retail companies. Additionally we have interviewed representatives for a typical small retail company. The investigated company does comply with applicable laws and recommendations, but not much more. Furthermore, the company uses mostly feel and experience in its inventory control. The company does not use formal inventory control in any great extent, if any. We have some suggestions for improvements in this regard.

This thesis studies inventory control with risk of major supply chain disruptions, specifically border closures and congestion. We first investigate an inventory system in which the probability distributions of order leadtimes are dependent on the state of an exogenous Markov process; we will model border disruptions via this exogenous process. We consider stationary, state-dependent basestock policies, which are known to be optimal for the system under study, and develop an expression for the long-run average cost of an arbitrary policy of this form. Restricting our attention to state-invariant basestock policies, we show how to calculate the optimal basestock (or order-up-to) level and long-run average cost. We provide a sufficient condition for the optimality of a state-invariant basestock policy and monotonicity results for the optimal state-invariant order-up-to level. We finally give the optimal state-invariant order-up-to level for a special class of supply states. Motivated by the possibility of port of entry closures in the event of a security incident, we specialize the previous model to a two-stage international supply chain. A domestic manufacturer orders a single product from a foreign supplier and the orders must cross an international border that is subject to closure. We first assume that border congestion is negligible. The manufacturer's optimal inventory policy and long-run average cost are analyzed. We present structural policy results and the results of a comprehensive numerical study that have important implications for business and for the cooperation between business and government in disruption management and contingency planning. Finally we extend the border closure model to include both border closures and the resulting congestion. We model the border processing system as a discrete-time, single-server queue with constant arrival rate and Markov-modulated service rate. A key task is the development of the leadtime distribution, which is more complex than in the previous model. We present the results of a comprehensive numerical study and provide managerial insights.

Studies in newsvendor decision-making have shown that human decisions systematically deviate from analytical solutions found in many utility models of the single period problem (SPP). Yet for the most part the impacts of this human decision bias in systems of newsvendor type products have not been investigated. We study bias in human decision-making to determine how different factors affect the performance of systems of newsvendor type products. We extended the state of the arts utility models of SPP to analyze the effects of individuals wealth on individual decision-making. Our theoretical and empirical results proved that individuals wealth significantly affected individual decision-making. Specifically, our analysis concluded that wealthier individual ordered more than poorer individual did when presented with the same investment opportunity. We created a human decision bias (HDB) model to include different newsvendor ordering policies that individuals could use to determine their order quantities. This model is set up to investigate individuals reliance on different ordering policies under different experimental conditions. We designed multi period newsvendor experiments to study effects of factors such as item profit margin, wealth, value of learning, and salvage value on decision-maker's order quantity. We found that wealth and profit margin factors significantly affected individual newsvendor decision-making. Learning, gender, and salvage value factor did not exhibit significant effects in our empirical studies. We designed multi period multi echelon newsvendor experiments to study effects of factors such as the relationship between newsvendors, item profit margin, and newsvendors' wealth on the performance of two-echelon newsvendors system. We found item profit margin, wealth, and relationship between supplier and retailer to significantly affect newsvendor decision-making. Finally, we present a case study of US fresh produce industry to illustrate the impacts of human decision bias on the performance of a supply chain system.