Ivan Ferretti

Cost performance and bullwhip effect in a hybrid manufacturing and remanufacturing system with different control policies

In recent years, remanufacturing has emerged as an important research area. This requires developing methods and models in order to aid companies in systematically evaluating current as well as projected remanufacturing systems. This paper addresses the inventory control problem in a hybrid inventory system with manufacturing and remanufacturing options. In this study, by changing the definition of inventory position of the serviceable stock, we introduce a shift PULL inventory control policy, which is compared with PULL, DUAL, and Separate PULL control policies studied previously in the literature. Besides evaluating the economic consequences with different control policies, we also study system dynamic behaviour such as the bullwhip effect, in order to understand the advantages and disadvantages of different policies. After the experiments, we propose several management guidelines for such a hybrid inventory system. The major findings are: (1) separate PULL and DUAL can be good alternatives when the manufacturing lead time is significantly longer than the remanufacturing lead time; (2) shifted PULL exhibits a good performance when the two lead times differ slightly. Owing to the complexity in solving the optimization problem, a simulation approach is used.

A joint economic lot size model with third-party processing

A joint economic lot size model with third-party processing is studied.Aim of this work is to analyse the performance of different supply chain configurations.Results show that adopting a coordination policy between Vendor and Manufacturer can lead to a total cost saving.Results show that VMI with CS policy can additionally improve such results. This contribution presents a production-inventory model for a supply chain that incorporates three distinct entities a Vendor, a third-party external Manufacturer and a Buyer. The Vendor purchases raw materials from a supplier and performs preliminary manufacturing operations, the semi-finished goods are sent to a third-party Manufacturer for additional manufacturing operations then the products are sent back to the Vendor for final operations or assembly with other components and finally they can be sold to the customer. The study of this particular Supply Chain configuration has been inspired by an industrial case observed in the aeronautical sector.The aim of this work is to analyse the performance of different supply chain configurations with third-party processing for operations carried out by the Manufacturer. The first option is to consider a traditional production-inventory system where the Vendor and the Manufacturer follow a centralised traditional agreement policy. The second option involves a centralised Vendor Managed Inventory policy with consignment stock agreement between the Vendor and the Manufacturer. The objective is to determine the optimal lot size policy, i.e. traditional agreement or consignment stock agreement, in order to minimize supply chain total cost.Finished goods are assumed to have price-independent deterministic demand, while cost components are assumed to be constant over time. The analysis is carried out considering system total cost as the objective function to be minimized.

A Queuing Approach for Energy Supply in Manufacturing Facilities

Nowadays increasing energy efficiency is one of the main objectives of manufacturing systems so as to remain competitive despite of the foreseen increase in energy prices for the next years. We propose a novel queuing-based model for the appreciation of the energy consumption on a company base, so as to optimize the total energy costs due to electricity utilization.

Eco-efficient cold chain networks design

ABSTRACT The demand of food distribution across global supply chains is continuously growing and since this kind of deliveries need refrigeration, the growth will enormously increase the energy request and the associated carbon emissions. The aim of this study is to develop a model for the optimisation of eco-efficiency related to a typical refrigerated food distribution network design as a particular case of cold chain. Inventory holding, transportation and energy consumption cost components are included in the model for the evaluation of economic performance of the chain, while energy consumption for storage and transport activities is also considered to contribute to the environmental performance of the chain. In order to model a supply chain related to refrigerated food, the perishability of distributed products is also involved in the model, as it influences storage and distribution activities performances. A novel analytical model is developed for the economic and environmental evaluation of the considered chain. A numerical study that considers different alternative configurations of the distribution network for refrigerated green peas is presented and results are discussed considering the eco-efficiency of different alternatives. Finally, main limitations of the model and future developments are presented and discussed.

Supply chain network design under uncertain demand: robust and stable optimisation approaches

This paper is focused on the design of a supply chain taking into account the variability of the final customer demand: the traditional strategy for the network configurations so as to face such uncertainty, named robust approach, to seek the minimum expected total cost over the planning horizon. The novelty of this contribution resides in the investigation of an alternative way to face the uncertainty, named stable approach, which aim is to determine the minimum variability of transport and handling cost in the considered time horizon. The goal is the definition of the network configuration that can efficiently operate under the uncertainty of the customer demand, to this extent the solutions of the robust and the stable approaches have been compared. A numerical analysis has been performed over a realistic case study data and results of robust and stable and hybrid solutions have been reported.

Integrated Energy Value Analysis: A New Approach

The improvement of energy efficiency of 20 % is one of the three objectives of the EU Directive 20-20-20. To reach this goal, all production processes have to be analysed with reference to their energy consumption so as to identify actions aimed at removing or reducing energy wastes. From the Lean Production framework, the variation of the Value Stream Mapping (VSM), the Energy VSM (EVSM) is selected as a useful tool able to highlight the seven types of wastes identified by Ohno in Toyota Production System and energy wastes. This work aims at proposing a possible modification of the EVSM, which encompasses it within the Energy Audit and the Energy Balance Chart. The goal is to realize a deep energy analysis, highlighting energy wastes, in order to understand which corrective actions must be implemented or which corrections to energy reduction should be considered to reduce energy wastes.