Daria Battini

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.

Consignment stock inventory model in an integrated supply chain

The consignment stock (CS) is an innovative approach to manage inventories in which the vendor removes his inventory and maintains a stock of materials at the buyers plant. The aim of this paper is to promote a successful application and comprehension of the CS policy both in literature and practice. In this paper, we deal with a multi-echelon inventory system in which one vendor supplies an item to multiple buyers. The study develops a single-vendor and multi-buyer consignment stock inventory model in which many clients can establish a CS policy with the same vendor. The aim of the paper is to evaluate the real economical and logistic benefits from the point of view of both the partners and the whole supply chain, following the adoption of a CS policy. We determine the maximum and minimum inventory stock levels to store in the buyers’ plant warehouse and the optimal quantity delivered from the vendor to each buyer in order to minimise total supply chain costs. Space constraints in clients’ plant warehouse, stock-out risk due to the variability of consumption and obsolescence risk for the materials stored are also considered.

Consignment stock inventory policy: methodological framework and model

Consignment stock (CS) is an innovative approach to supply and stock management, based on a strong and continuous collaboration between vendor and buyer to create a ‘win-win’ situation, where both partners have equal gains. An analytic formulation of CS policy with obsolescence has been proposed in Persona et al. (2005). This article considers new critical factors (present in several industrial environments) providing a logical extension of the above mentioned study. The proposed methodology addresses, in particular, the design of a new stock policy in an industrial environment with demand variability, stock-out risk and limited warehouses space. The analytical model presented demonstrates that a traditional stock policy, such as the economic order quantity approach is always more expensive than the consignment stock approach. In addition, the benefits of the CS policy to the supply chain are consistently high including when applied to realities with high demand variation and space limitations.

Ergonomics in assembly line balancing based on energy expenditure: a multi-objective model

In many assembly systems, ergonomics can have great impact on productivity and human safety. Traditional assembly systems optimisation approaches consider only time and cost variables, while few studies include also ergonomics aspects. In this study, a new multi-objective model for solving assembly line balancing problem is developed and discussed in order to include also the ergonomics aspect. First, based on main features of assembly workstations, the energy expenditure concept is used in order to estimate the ergonomics level, thanks to a new technique, called Predetermined Motion Energy System, which helps rapidly estimate the energy expenditure values. Then, a multi-objective approach, based on four different objective functions, is introduced in order to define the efficient frontiers of optimal solutions. To complete the study, a simple numerical example for a real case is presented to analyse the behaviour of Pareto frontiers varying several parameters linked to the energy and time value.

Innovative real-time system to integrate ergonomic evaluations into warehouse design and management

Full-body integrated system for the real-time ergonomics evaluations.Integrated with many ergonomics assessment methodologies.Development of ad hoc tools for the real-time collected motion data.Available feedback both for the operators and for the engineers and managers.Applications in real warehousing environments. The present paper introduces an innovative full-body system for the real-time ergonomics evaluations of manual material handling in warehouse environments, where all parts of the body are interested during the activities execution. The system is based on inertial sensors with integrated compensation of magnetic interference and long wireless connection that permit its use also in heavy industrial applications. A specific set of tools has been developed in order to elaborate the collected motion data and give real-time evaluation and feedback of ergonomics based on the most used methodologies and extended with others advanced ad hoc tools, such as hands positions analysis, travel distance, time and methods collection calculations. The system has been applied to two different warehouses both for the re-design of the storage area and successively management of the typical warehousing activities, such as picking, packing and others, reducing the risk of musculoskeletal disorders and simultaneous increasing of productivity of systems.

Order picking system design: the storage assignment and travel distance estimation (SA&TDE) joint method

Of all the warehouse activities, order picking is one of the most time-consuming and expensive. In order to improve the task, several researches have pointed out the need to consider jointly the layout of the warehouse, the storage assignment strategy and the routing policy to reduce travelled distances and picking time. This paper presents the storage assignment and travel distance estimation (SA&TDE) joint method, a new approach useful to design and evaluate a manual picker-to-parts picking system, focusing on goods allocation and distances estimation. Starting from a set of picking orders received in a certain time range, this approach allows to evaluate the combinations of product codes assigned to storage locations, aisles, sections or warehouse areas and to assess the most relevant ones, for the best location and warehouse layout, with the aim of ensuring optimal picking routes, through the application of the multinomial probability distribution. A case study is developed as well, in order to clarify the concept that underlies the SA&TDE joint method, and to show the validity and the flexibility of the approach, through the calculation of the saving at different levels of detail.

Estimating reliability characteristics in the presence of censored data: A case study in a light commercial vehicle manufacturing system

Abstract The reliability analysis of the critical components is the basic way to establish the efficiency of complex systems. For this issue, it is very important to select capable methods for service data collection as well as for analysis. The study introduces a framework defining a general approach for Failure Process Modeling (FPM). The paper also discusses the critical role of censored data and the need for a continuous and repetitive application of the proposed approach during the service life of systems. A case study in a light commercial vehicle manufacturing system is presented. The distributions of some reliability parameters of several critical components (i.e. reliability, hazard rate, etc.) have been estimated, repetitively during the system life, from the date of the initial installation onwards with a growing collection of time to failures. The relevant effect of the number of data, and in particular of censored data, on the robustness of reliability estimation and evaluation process is investigated.

A new methodological framework to implement an RFID project and its application

The introduction of new technologies in the industrial field has consistently seen the development of several different projects: some have been carried out successfully and others have encountered many difficulties, resulting in the failure of the projects. Often this is caused by the lack of the correct methodology to tackle the project and to understand how the new technology could be used in industrial applications. At present, radio frequency identification (RFID) technology represents a new tool of support for the automation of the processes and the improvement of the operating management of a system, being the missing link between the material flow and the information flow. RFID technology is used in a large number of possible applications, like product tracking, animal identification, inventory systems and others. However, in recent years, an inconsistent increase of such applications has been observed, due to the diverse information available on such technology and to the lack of a support method...

Inventory holding costs measurement : a multi-case study

Purpose – Logisticians in the worldwide industry are frequently faced with the problem of measuring the total cost of holding inventories with simple and easy-to-use methodologies. The purpose of this paper is to look at the problem, and in particular illustrate the inventory holding cost rate computation, when different kind of warehousing systems are applied. Design/methodology/approach – A multiple case study analysis is here developed and supported by a methodological framework directly derived from the working group discussions and brainstorming activities. Two different field of application are considered: one related to five companies with manual warehousing systems operating with traditional fork lift trucks; the other is among five companies operating with automated storage/retrieval systems (AS/RS) to store inventories. Findings – The multi-case study helps to understand how the holding cost parameter is currently computed by industrial managers and how much the difference between manual and aut...

Mixed model assembly system with multiple secondary feeder lines: layout design and balancing procedure for ATO environment

The constant research for efficiency and flexibility has forced assembly systems to change from simple/single assembly lines to mixed model assembly lines, while the necessity to reduce inventory has led the transition from single to multi-line systems, where some components are assembled in secondary lines, called feeder lines, connected to the main one by a ‘pull philosophy’. A possible approach to configure such an assembly system is to balance the main line first and use the retrieved cycle time to balance each feeder line separately, which is a questionable solution, especially if operators can perform tasks on both the feeder and the main line. Moreover for its complexity the mixed model balancing problem is usually solved transforming it into a single model by creating a single ‘virtual average model’, representative of the whole production mix. The use of a virtual average model assumes that the processing times of some models are higher or lower than the cycle time, which creates overload/idle time at the stations. This approach, especially in complex multi line production systems, largely reduces the assembly line productivity and increases the buffers dimensions. This paper faces the mixed model assembly line balancing problem in the presence of multiple feeder lines, introducing an innovative integrated main-feeder lines balancing procedure in case of unpaced assembly systems. The proposed approach is compared with the classical one and validated through simulation and industrial applications.