Papers by Anders Segerstedt
Operational Research, Aug 12, 2020
Estimations of the amount of lithium-ion batteries reaching their end-of-life in 2025 and the amo... more Estimations of the amount of lithium-ion batteries reaching their end-of-life in 2025 and the amount being recycled indicates large deviations. To enable an efficient recycling process a well-defined and efficient supply chain network for the recovery of discarded lithium-ion batteries must be put in place. This includes analyzing the needs and restrictions of such a network. The aim of this paper is to provide decision support tools, to analyze input, and optimize a future supply chain for discarded lithium-ion batteries. A mixed integer programming model is developed and applied to the Swedish market. The findings show that several aspects will affect a reverse supply chain for discarded lithium-ion batteries, many of which are still uncertain and hard to predict.
International Journal of Production Economics, Dec 1, 2017
Cover-Time Planning, or Takt Planning, is presented. It is a system for calculating material requ... more Cover-Time Planning, or Takt Planning, is presented. It is a system for calculating material requirements and start of purchases and production. Requested production rates of sales items, or alternative prefabricated modules in stock, are "broken down", exploded, to create the need for components, for all underlying items (articles) in the Bill of Material. Inventory and already ordered replenishments are compared with the item's desired production rate. How long already made actions are expected to cover the desired expected sales and production rates is compared with the item's lead time; if a forward future shortage is likely the article is signalled for a refill. With examples is described how make-to-order production is done easily. The method is a type of reorder point system, but with time instead of quantity as decision variable. Unlike a traditional reorder point system increases and decreases of production can be planned. Future work load in various production sections can be estimated. It is described how an "Available-to-promise"-system should be designed and used. Cover-Time Planning (CTP) is a complete alternative to Materials Requirements Planning (MRP). CTP responds faster than MRP, since MRP for each structural level uses a batch size to "break down" and to magnify the need at the underlying level. In the end a large material acquisition needs to be ordered maybe just to build a single end item. CTP uses the end item requirement rates on all structural levels shifted with the lead times, when customer demand changes, the entire production chain react simultaneously.
Godkänd; 2015; 20150915 (andbra
Godkänd; 2011; 20110407 (ysko
Operations and Supply Chain Management: An International Journal, 2014
An accurate cost analysis is necessary to evaluate changes in a supply chain; this article shows ... more An accurate cost analysis is necessary to evaluate changes in a supply chain; this article shows how a rather simple framework can be used when evaluating changes in a supply chain. The framework is built on a Supply Chain Cost (SCC) model and customer service measurements, delivery precision and leadtime. Both suggested changes in a supply chain and already executed changes can be evaluated by the framework. Two different examples from the company Ericsson are presented to illustrate the framework, which is a 5 step analysis model. The existing, or pre-existing, supply chain is analysed, described and defined. The SCC and performance measures are measured and/or estimated. Improvements are designed and defined. The same measures as before are measured again. The measures from before and after the change of the supply chain are evaluated to decide if the changes are improvements or not. Cutting costs in one area of the supply chain can be a mistake if not the total supply chain is considered and the total SCC. Considering both the SCC part and customer service measures present a wider understanding of the change. It is shown that SCC can be used as a tool to identify cost savings and evaluate if a change project will, or has, resulted in the cost savings the project aims for. Rough standard costs measures should be avoided instead actual costs should be used as much as possible. The used framework hopefully stimulate to similar analyses in other companies with other supply chains.
International Journal of Logistics Systems and Management, 2013
This article describes the findings and results from an improvement project concerning a producti... more This article describes the findings and results from an improvement project concerning a production line at an Ericsson plant in Sweden. The article is a type of a case study that describes activities and discussions in an improvement project. A value stream mapping showed that only a few percent of the throughput time was really adding value to the customer. In an improvement project the involvements of all employees are important. Interviewing and education of workers/operators lead to that they also contribute with suggestions to improve the production flow. Value stream mapping though often classified as a lean technique is a technique for improvements of most kind of productions, here it is applied to a situation that must be classified more agile than lean. A selection of generated, and rather general, solutions were implemented: reduced buffers; more of a 'one-piece' flow; a reduced waiting time by adding work tasks; a more levelled manufacturing and efficient flow was created by a recombination of processes and a reallocation of work tasks. Our article hopefully stimulates students and practitioners to find improvement activities in similar situations and projects.
In this paper, a heuristic method is presented which gives a novel approach in solving joint repl... more In this paper, a heuristic method is presented which gives a novel approach in solving joint replenishment problems. Our heuristics is from the beginning a basic spreadsheet model that solves the JRP in an iterative procedure. The principle of the recursion procedure is to find a balance between the replenishment-and inventory holding cost for the different items by adjusting the replenishment frequencies. The heuristic is also tested according to an extensive test template, with a great amount and variety of problems. The method shows pleasing results concerning the closeness to optimality and performs well in comparison with many other heuristics.
Industriell logistik, ETS, Luleå tekniska universitet Denna skrift är en sammanfattning och aktue... more Industriell logistik, ETS, Luleå tekniska universitet Denna skrift är en sammanfattning och aktuell konklusion av vårt studiebesök vid hemtjänsten i Jokkmokk 10 och 11 december 2013. Tanken var att vi eventuellt med ruttplanering skulle minska bilkörningen och energiförbrukningen. Vår slutsats är att enkla tumregler och uppföljningar, som presenteras nedan, i det system som redan finns, är att föredra jämfört med dyr avanserad datoriserad ruttplanering. Vi kommenterar historisk utveckling, systemleverantörers ansvar, matdistribution, andra system för hemtjänst mm.
Supply Chain Management: An International Journal, 2004
Polarica is a company in northern Europe buying, refining and selling wild berries and other spec... more Polarica is a company in northern Europe buying, refining and selling wild berries and other specialty foods. During the last couple of years the volume of wild berries, mostly blueberries, has increased a lot. This expansion forces Polarica to consider investments in freezing‐in capacity and cold‐storage capacity. A simple heuristic model was constructed, from which it was concluded that additional volumes of frozen blueberries require more storage facilities and it was also recommended that the location should be based on load‐distance analysis. The way this problem is tackled and solved can be copied and hopefully it presents ideas for other similar studies.
Production Planning & Control, 2002
The paper presents the main routines of production and inventory control at ABB Motors, VaÈ stera... more The paper presents the main routines of production and inventory control at ABB Motors, VaÈ steraÊ s and Volvo Wheel Loaders, Eskilstuna. The primary interest is to present how Material Requirements Planning (MRP) is used in these two companies. If the number of end items is large, the company assembles-to-order or makes-to-order then additions to pure MRP seem to be necessary. ABB Motors and Volvo Wheel Loader use: planning bills, a normal bill of materials with `adding bills of materials', a master production schedule planning system with an available-to-promise function and a home-made `system' for modules available-to-promise. One important measure for the both companies is the accumulative lead-time. An increase of the Master Production Schedule in a shorter time than the accumulative lead-time is avoided, because it will lead to suggestions of purchase in past time periods and therefore most probably to future material shortages.
A variant of the Clark and Wright's saving method is presented. Only the first calculated pa... more A variant of the Clark and Wright's saving method is presented. Only the first calculated pairs of saving are used, also when complements or additions are searched for to an already decided route. The variant is simple, very fast and it shows promising results. Therefore it is suitable for the introduction of the topic and importance of efficient vehicle routing. Efficient distributions and collections are important because they consume less recourses and energy; it makes the world more sustainable. (Authors of textbooks in logistics and operations management are free to incorporate this search method in their next edition; we can also provide additional small numerical examples suitable for students to solve in an examination.)
International Journal of Production Research, 2006
For a company's long-term profitability, most important processes are the way it starts parts of ... more For a company's long-term profitability, most important processes are the way it starts parts of the manufacturing process before the customer order arrives and the way it determines and promises delivery quantities and times for the customer orders. In practical computer applications Material Requirement Planning and/or Reorder point systems are the base techniques mostly used. This article presents Cover-Time Planning, a variant of a reorder point system. Cover-Time Planning (CTP) is developed with a forward-looking forecasted demand rate and the decision variable is "time", instead of "quantity" for an ordinary reorder-point system. MRP and CTP are introduced and compared through a numerical example. MRP and CTP must treat practical "make-to-order"; therefore, this paper discuss available-to-promise, planning bills, and other help systems for practical applications of Master Production Scheduling. The paper presents how and why, in practice, a Master Production Scheduling system with an available-topromise function should be used and how this system should be designed. It is also argued that a fully Enterprise Resource Planning (ERP) system cannot only be created by MRP, but also by CTP.
International Journal of Production Research, 2009
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific r... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
International Journal of Production Research, 2004
Subsequent to the publication of Segerstedt (2004), in which the concepts of Segerstedt (1999) we... more Subsequent to the publication of Segerstedt (2004), in which the concepts of Segerstedt (1999) were developed to consider multi-level production, the author has been made aware of a paper (Goyal, 1975) that includes a clear and straightforward treatment of the ELSP problem, and contains a successful heuristic that finds the best known solution to the Bomberger (1966) problem. Readers interested in Segerstedt (2004) may find Goyal (1975) and also Goyal (1973 (a), 1973 (b), 1984) and Brander et al. (2004) interesting.
International Journal of Production Research, 2010
This paper presents a new method to describe, analyse and estimate production system performances... more This paper presents a new method to describe, analyse and estimate production system performances. According to current literature, the basic performance measures are WIP (Work-in-Process), lead time and throughput. These are also in this article used as performance measures. Continual trade-offs between different performances are necessary to stay competitive in today's market. Different performances are archived by adjusting system parameters. Knowledge about relations between system parameters and system performances in existing systems, and about system performances of not yet implemented system alternatives, is essential for business. Queuing theory and simulation can estimate system performances of not yet implemented systems and help the decision makers, but when the complexity increases queuing theory becomes very difficult and heavy to use. A single simulation presents limited information. Multiple simulations are necessary to ensure that the best alternative is chosen. A high number of simulations demand a lot of computer time and resources. Reduction of runs is desirable even with cheaper computer equipment. Currently, traditional two-dimensional charts are the only tools to present and analyse system performances. This article presents a new surrogate model for easier estimation and presentation of system performances, their internal relations, and relations to the system parameters. With the new surrogate model, system performances based on simulations are presented as positions in a three dimensional environment. Parametric curves and surfaces of Bezier type are generated and adapted to these positions. System performances of other system alternatives are then estimated. The number of simulation calculations can thereby be moderated. The method is illustrated with a small production line system.
International Journal of Production Economics, 2014
This article provides a short historical overview from Harris and his Economic Order Quantity (EO... more This article provides a short historical overview from Harris and his Economic Order Quantity (EOQ) formula to the Economic Lot Scheduling Problem (ELSP). The aim is to describe the development of the ELSP field from the EOQ formula to the advanced methods of today in a manner that suits master and graduate students. The article shows the complexities, difficulties and possibilities of scheduling and producing several different items in a single production facility with constrained capacity. The items have different demand, cost, operation time and set-up time. Set-up time consumes capacity and makes the scheduling more complicated. Idle time makes the scheduling easier but is bad from a practical point of view since it creates unnecessary costs due to low utilisation of the facility. A heuristic solution method is used on a small numerical example to illustrate different solution approaches. The solution method creates a detailed schedule and estimates the correct set-up and inventory holding cost even if the facility works close to its capacity.
International Journal of Production Economics, 2014
We explore the issue of supply chain coordination by considering trade credit and its risk. It sh... more We explore the issue of supply chain coordination by considering trade credit and its risk. It shows that, in a retailer-manufacturer system, the manufacturer may deliver less than the retailer's order quantity when the payment is delayed, and the manufacturer's risk aversion makes this result hold in a wider range. These findings are different from the common sense believed in the retailer-manufacturer coordination literature, which suggests the manufacturer to entice the retailer to enlarge the lot size. The manufacturer's decision of decreasing the order quantity prevents the supply chain from operating in the optimal situation. In order to coordinate supply chain, we propose a modified quantity discount based on both order quantity and advance payment which means the manufacturer offers quantity discount if the retailer pays part of the payment in advance and enlarges her order quantity. The ranges of advance payment ratio and the quantity discount are derived. Numerical examples are used to demonstrate the conclusions.
International Journal of Production Economics, 2013
Organisations focus on reducing costs in their supply chains to increase net income. In order to ... more Organisations focus on reducing costs in their supply chains to increase net income. In order to reduce costs a company needs to know how to measure Supply Chain Cost (SCC). This paper is concerned with SCC and how measurements of SCC are and can be used in industry. The paper describes a suggested model for measuring SCC. Representatives from 30 companies in 10 different business sectors are interviewed about how they measure costs in their supply chains compared against this model. The focus is also on identifying the difference between SCC based on estimated standard cost compared to actual cost. A case study describes and shows the difference between measuring SCC based on calculated standard cost and measuring it based on actual cost. Our studies show that general thorough cost and supply chain analyses in many companies can be improved and further developed.
International Journal of Production Economics, 2007
In this paper, a heuristic method is presented which gives a novel approach to solve joint replen... more In this paper, a heuristic method is presented which gives a novel approach to solve joint replenishment problems (JRP) with strict cycle policies. The heuristic solves the JRP in an iterative procedure and is based on a spreadsheet technique. The principle of the recursion procedure is to find a balance between the replenishment and inventory holding costs for the different items by adjusting the replenishment frequencies. The heuristic is also tested according to an extensive test template and shows pleasing results. It also performs well in comparison with many other heuristics.
International Journal of Production Economics, 2004
This paper considers an inventory control system, primarily for a finished goods inventory. The p... more This paper considers an inventory control system, primarily for a finished goods inventory. The purpose is to create a procedure that can handle both fast-moving items with regular demand and slow-moving items. The suggested procedure should be easy to implement in a modern computerized ERP-system. Essentially, the system is a periodic review system built around a Croston forecasting procedure. An Erlang distribution is fitted to the observed data using the mean and variance of the forecasted demand rate. According to probabilities for stock shortages, derived from the probability distribution, the system decides if it is time to place a new order or not. The Croston forecasting method is theoretically more accurate than ordinary exponential smoothing for slow-moving items. However, it is not evident that a Croston forecasting procedure (with assumed Erlang distribution) outperforms ordinary exponential smoothing (with assumed normal distribution) applied in a ''practical'' inventory control system with varying demand, automatically generated replenishment, etc. Our simulation study shows that the system in focus will present fewer shortages at lower inventory levels than a system based on exponential smoothing and the normal distribution.
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Papers by Anders Segerstedt