Alberto Regattieri

Performance Measurement In Supply Chain: New Network Analysis And Entropic Indexes

Industrial organisations must supply a variety of products and services, meet the needs of fragmented customer expectations, and cope with the consequences of the globalisation of world markets, all of which are producing significant levels of complexity. This study develops a new quantitative measurement of complexity for a supply network based on network analysis, which is often used to study natural ecosystems, focusing in particular on the concept of entropy of information. The research reports advances in both theory on the supply network analysis problem and on its application to industrial contexts. Eight indexes based on entropy are presented. These measures provide a meaningful analysis of the level of complexity in the whole supply network mapping the exchanges of goods between the different actors in the network. The impact of possible modifications of the structure can simply be evaluated using these tools, providing a simple evaluation of the different scenarios. The proposed method takes a holistic point of view to tackle the problem of supply network optimisation. A real world application of the developed new methodology is presented.

A multiple single-pass heuristic algorithm solving the stochastic assembly line rebalancing problem

Assembly line rebalancing is a problem companies are frequently confronted with as continuous changes in product features and volume demand caused by the volatility of modern markets result in re-definition of assembly tasks and line cycle time fluctuations. Consequently, managers are forced to adjust the balancing of their lines in order to adapt to the new conditions while trying to minimise both increases in completion costs and costs related to changes in task assignment. In particular, when modifications are made to line balancing, costs are incurred for operator training, equipment switching and moving, and quality assurance. The stochastic assembly line rebalancing problem is essentially composed of a multi-objective problem in which two joint objectives, total expected completion cost of the new line and similarity between the new and the existing line, must be optimised. Consequently, this paper presents a multiple single-pass heuristic algorithm developed for the purpose of finding the most complete set of dominant solutions representing the Pareto front of the problem. The operative parameters of the heuristic are set as a result of a great deal of experimentation. Moreover, a multi-objective genetic algorithm is developed and then compared with the proposed heuristic in order to demonstrate its effectiveness. Finally, an illustrative case study is presented.

Buffer size design linked to reliability performance: A simulative study

Material flow along a Flow Production Line may be disrupted by machine failures or variable processing times. In particular, Automatic Flow Production Lines are often affected by the presence of micro-down-times (i.e. speed losses due to work-pieces blocking or congestion, momentary stiff or stuck pieces on machines, etc.), which can penalize the productivity of the system and increase losses in availability for the whole plant. Moreover, micro-breakdowns cause inability of the system not to respond to sudden changes in demand due to capacity restrictions. Intermediate buffers built between the various machines in an asynchronous automatic (or semi-automatic) production line may increase the reliability of the whole system by limiting the consequences of micro-downtime, and saving companies from making inadequate purchases of oversized equipment. In this paper a new efficiency simulative study for the allocation of storage capacity in serial production lines is developed and a new experimental cross matrix is provided as a tool to determine the optimal buffer size. Thus, this research studies the relationship of machines availability and buffers size, in order to stress a new paradigm: the buffer design for availability (BDFA). Using a simulation approach, this paper describes the effects of workstation reliability parameters on buffer capacity level, developing a set of simple guidelines to support and help designers and practitioners in the rapid and robust buffer design issue.

Similarity-based storage allocation rules in an order picking system: an application to the food service industry

Todays distribution warehouses often need to process a far higher volume of smaller orders of multiple products which considerably increases logistics costs. They use the so-called order picking (OP) systems where products have to be picked from a set of specific storage locations by an OP process usually driven by production batches or customer orders. The OP is often very labour-intensive and its efficiency largely depends on the distance the order pickers have to travel, which therefore needs to be minimised. Minimising this distance is affected by several factors e.g. facility layout, shape of storage area, and especially the storage assignment strategy. Products that are frequently ordered together in multi-item, less than unit load customer orders should be stored near each other: this is the correlated storage assignment strategy. This study develops, tests and compares a set of different storage allocation rules based on the application of original similarity coefficients and clustering techniques. Lastly, a case study demonstrates the effectiveness of the proposed rules in minimising logistic costs.

Designing production and service systems using queuing theory: principles and application to an airport passenger security screening system

Queues of people, products and machines frequently occur in many production and service systems, resulting in significant inefficiencies. This paper discusses the significant impact on these problems of the queuing theory introduced by Erlang and Kendall. A methodology based on the M/M/m queuing model (including a validation phase through a goodness-of-fit test) is proposed. This methodology makes parametric analyses of system performance according to the different possible ranges of input parameters. It helps solve several typical problems found in production systems (e.g., resource design, traffic and logistics analysis) and services (e.g., optimal design and management). There is a good tradeoff between the robustness of the results, coherence with real industrial systems and mathematical complexity. A real-world application involving the design optimisation of a passenger security screening system in an international airport is presented. In particular, the optimal number of security gates in the design is discussed.

Modelling the spare parts stock levels and its applications in industrial systems

This paper addresses a practical decision making by developing an innovative inventory and transportation cost model to determine the optimum number of the spare parts and its location in the warehouses subject to run-in, random and usage failure inside a maintenance network. The spare parts slow moving items inventory management is a complex problem. The demand is sporadic and difficult to forecast, the utilisation is specific, the part economic value is high, the failure causes system downtime costs and normally this complexity is compensated by overestimated the part inventories. The proposed procedure can be used to determine the spare parts stock level and allows to minimise a function cost sum of aggregate inventory costs and downtime production plant costs caused by the parts failure and transportation from the storage areas to the user or machines failed. Four real case studies from different industrial application projects are illustrated in order to demonstrate how to apply the proposed model into real world applications. The results and findings from such industrial applications are found useful to engineers and managers in industry.

Double pressing for porcelain stoneware tiles: an exploratory analysis

Purpose – Double pressing systems have recently been introduced to speed up and improve the pressing step of porcelain stoneware tiles. This paper aims to analyze double pressing systems using discontinuous pre‐compaction, both technically and economically. Two operative conditions are considered: the traditional forming of tiles during pressing is compared with the innovative production of a unique large‐sized slab, subsequently customized according to market requirements. Furthermore, manufacturing conditions are explored with infrequent or frequent production runs, due to increasingly smaller production batches, in order to evaluate which production process is more suitable when changing operative conditions are managed.Design/methodology/approach – The analysis is carried out experimentally, by collecting data in existing pilot plants, producing batches of products of different size and colour. Details are provided concerning the technical characteristics of the systems, along with costs per manufactu...

Innovative lay-up system in plywood manufacturing process

AbstractIn the traditional plywood manufacturing process, the lay-up stage absorbs approximately 24% of then total manufacturing costs. It usually requires axa0large amount of manpower and produces axa0significantn amount of waste material. Therefore, the authors have developed an innovative system based on axa0newn idea that reduces these values drastically. The solution is characterized by intensive use of flexiblen automation, and this breakthrough lay-up system technology is specifically discussed in relation to plywoodn manufacture. Since the new system was tested, it has been adopted and used by the European leader in poplarn plywood manufacturing.n Interesting results include productivity increases of up to 20%, axa0decrease in lay-up costsn of approximately 19% and axa0consumption of area reduced about 42%. Moreover, by reducing manpowern requirements, the new system generates axa0significant reduction in the number of problems relating ton product quality and operator safety, which is certainly not axa0trivial question in the traditional lay-upn system.n ZusammenfassungBei der konventionellen Sperrholzherstellung gehen 24% der gesamten Herstellungskosten zu Lastenn der Legephase. Hierzu wird in der Regel ein hoher Personalaufwand benötigt und eine erhebliche Mengen an Abfall wird produziert. Aus diesem Grunde wurde von den Autoren ein innovatives Verfahren entwickelt,n das auf einer neuen Idee basiert, mit der diese Faktoren erheblich reduziert werden. Die Lösung bestehtn im Einsatz flexibler Automatisierung. Dieses bahnbrechende Legeverfahren wird hier am Beispiel der Sperrholzherstellungn beschrieben. Inzwischen wurde dieses neue Verfahren vom führenden europäischen Hersteller vonn Pappelsperrholz übernommen und eingesetzt.n Zu den interessanten Ergebnissen zählen Produktivitätszunahmen von bis zu 20%, ein Rückgangn der Legekosten von ca. 19% und eine Reduktion der benötigten Fläche von ungefähr 42%. Außerdemn reduziert das neue Verfahren aufgrund des geringeren Personalbedarfs die bei dem traditionellen Verfahrenn bekannten Probleme hinsichtlich der Produktqualität und der Betriebssicherheit.n