Alessandro Persona

Waste collection multi objective model with real time traceability data.

Waste collection is a highly visible municipal service that involves large expenditures and difficult operational problems, plus it is expensive to operate in terms of investment costs (i.e. vehicles fleet), operational costs (i.e. fuel, maintenances) and environmental costs (i.e. emissions, noise and traffic congestions). Modern traceability devices, like volumetric sensors, identification RFID (Radio Frequency Identification) systems, GPRS (General Packet Radio Service) and GPS (Global Positioning System) technology, permit to obtain data in real time, which is fundamental to implement an efficient and innovative waste collection routing model. The basic idea is that knowing the real time data of each vehicle and the real time replenishment level at each bin makes it possible to decide, in function of the waste generation pattern, what bin should be emptied and what should not, optimizing different aspects like the total covered distance, the necessary number of vehicles and the environmental impact. This paper describes a framework about the traceability technology available in the optimization of solid waste collection, and introduces an innovative vehicle routing model integrated with the real time traceability data, starting the application in an Italian city of about 100,000 inhabitants. The model is tested and validated using simulation and an economical feasibility study is reported at the end of the paper.

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.

Consignment stock of inventories in the presence of obsolescence

The Consignment Stock (CS) inventory policy is becoming an important strategy that companies adopt to face new manufacturing and supply chain management challenges. A CS policy implies great collaboration between the buyer and supplier, pushing them towards a complete exchange of information and a consistent sharing of management risks. In such a context, the effects of the obsolescence of products have to be carefully evaluated since they fall onto both actors, causing an increase in total supply chain costs. This paper proposes an analytical model able to take into account the effects of obsolescence in a supply chain managed with a CS policy. The deterministic single-vendor, single-buyer CS model is used as a base to develop the proposed model. A comparison with a non-obsolescence optimal solution available in the literature is presented. Moreover, the stochastic behaviour of the product lifetime estimation is also taken into consideration. Results demonstrate that the effects of obsolescence can consistently influence the global optimum condition.

TPM: situation and procedure for a soft introduction in Italian factories

Personalization of products, mix variability and short time to market are the most important factors that have forced companies to a new form of organization during past years. A very common reply to this question is a lean organization based on flexibility of productive lines, reduction of storage and integration among company sections. In this context, quite differently from a traditional system, the maintenance function must work efficiently. Also the maintenance division must contribute to the success of the factory. Aims to introduce a methodology for a soft and tenable application of the principles of total productive maintenance (TPM) in Italian factories. The first step of the study is an explanation of the actual situation, usually based on traditional or on productive maintenance. After a brief introduction, focuses on TPM links with productive maintenance in order to suggest a method for TPM. Concludes with a real application of TPM in a big factory, with a description of a world leader in plant manufacturing for the ceramics industry.

Kanban number optimisation in a supermarket warehouse feeding a mixed-model assembly system

Following just-in-time principles, a growing number of manufacturers are adopting the so-called supermarket concept. Supermarkets are decentralised storage areas scattered throughout the shopfloor that serve as an intermediate store for parts required by nearby assembly lines. From these stores, a certain number of handling operators deliver parts from the supermarket to, and collect empty bins from, assembly stations. Finally, they return to the supermarket and are refilled for their next tours. The assembly stations are typically refilled from the supermarket through the constant replacement of the consumed parts pulled by the kanban system. Considering a mixed model assembly system composed of different assembly lines, feeding problems can occur as an effect of the replenishment lead time, of the production mix variation, of the commonality between the different models assembled. The aims of this paper are (i) to highlight how the supermarket/multi-mixed assembly-line system presents specific attributes that prohibit the simple application of well-known kanban dimensioning formulations and (ii) to provide an innovative procedure to optimally set all decision variables related to such a feeding system.

An integrated reference model for production planning and control in SMEs

Versatile manufacturing (VM) companies typically manufacture high variety, mainly customised products in relatively low volumes, competing for each order with other supplier companies on the basis of price, technical expertise, delivery time and punctuality. The research presented in this study is included in a wide cross‐disciplinary project which involved seven research centres. In particular, this paper aims at identifying the general requirements and guidelines for the definition of an integrated model of the order to delivery cycle in a VM environment, which can particularly be suitable for the small‐medium enterprise needs. A number of guidelines emerged, mainly in the areas of customer requirements definition and commercial configuration of customer order, supply and production planning, and intermediate and final project evaluation.

Framework for designing a flexible cellular assembly system

Modern manufacturing companies have to face competition in a turbulent world market that requires them to improve their operating performances according to increasingly differentiated products with shorter life cycles, low volumes and reduced customer delivery times. The aim of the present paper is to develop a conceptual framework for the simultaneous design and control of a flexible, agile reconfigurable and robust assembly system in conjunction with the analysis and optimization of product, process, system structure, material-handling devices and plant layout. An effective solution for reconfigurability and agility in assembly to order and batch-type systems is a modular semi-automatic approach based on cellular flexible facilities: modularity, automation and human skills are combined to gain the advantages of mass production. Families of parts are produced in flexible cells, i.e. groups of various machines and resources that are physically close together and process one or more families of similar parts. The proposed approach is based on a multistage iterative procedure that integrates different supporting decision techniques and tools such as design for assembly, group technologies and cellular manufacturing. An application to the optimization of a semi-automatic flexible assembly system is illustrated: the system performances of example alternative solutions are presented and compared.

Sustainable SC through the complete reprocessing of end-of-life products by manufacturers: A traditional versus social responsibility company perspective

Every item produced, transported, used and discarded within a Supply Chain (SC) generates costs and creates an impact on the environment. The increase of forward flows as effects of market globalization and reverse flows due to legislation, warranty, recycling and disposal activities affect the ability of a modern SC to be economically and environmentally sustainable. In this context, the study considers an innovative sustainable closed loop SC problem. It first introduces a linear programming model that aims to minimize the total SC costs. Environmental sustainability is guaranteed by the complete reprocessing of an end-of-life product, the re-use of components, the disposal of unusable parts sent directly from the manufacturers, with a closed loop transportation system that maximizes transportation efficiency. Secondly, the authors consider the problem by means of a parametrical study, by analyzing the economical sustainability of the proposed CLSC model versus the classical Forward Supply Chain model (FWSC) from two perspectives: Case 1, the ‘traditional company perspective’, where the SC ends at the customers, and the disposal costs are not included in the SC, and Case 2, the ‘social responsibility company perspective’, where the disposal costs are considered within the SC. The relative impact of the different variables in the SC structure and the applicability of the proposed model, in terms of total costs, SC structure and social responsibility, are investigated thoroughly and the results are reported at the conclusion of the paper.

Simulation performance in the optimisation of the supply chain

Purpose – Recently, material flows have been viewed as an integral part of the overall manufacturing system and a critical factor in SCM. Static approaches and theoretical models are ineffective in considering all variables and constraints involved in complex instances: these often require a lot of computing time and present poor flexibility in terms of model changes. VIS approach is a valid way to support design and management decisions in order to achieve the integrated optimisation of the whole chain, but literature does not discuss difficulties and time required in applying it, or its related costs.Design/methodology/approach – Discrete/continuous hybrid simulation tools are used in order to model and simulate several operating conditions in combination with different system configurations.Findings – The discussion of the industrial cases shows the importance of simulation in supporting decisions concerning the design and management of supply chains in their great complexity and in a stochastic compet...