Determining the economic lot size has always represented one of the most important issues in production planning. This problem has long attracted the attention of researchers, and several models have been developed to meet requirements at minimum cost. In this paper we explore and discuss the evolution of these models during one hundred years of history, starting from the basic model developed by Harris in 1913, up to today. Following Harris's work, a number of researchers have devised extensions that incorporate additional considerations. The evolution of EOQ theory strongly reflects the development of industrial systems over the past century. Here we outline all the research areas faced in the past by conducting a holistic analysis of 219 selected journal papers and trying to give a comprehensive view of past work on the EOQ problem. Finally, a new research agenda is proposed and discussed.
Worldwide, production systems are demanding new procedures and tools towards responsible inventory management, both in theory and in practice. In real industrial environment, manual fmaterial handling activities such as loading/unloading and stocking/picking operations are performed daily when a purchase/production material order is processed into industrial plants, and can be source of work-related musculoskeletal disorders. Only in the last four years, environmental and social aspects of the production systems have been progressively introduced in lot-sizing international theory, mostly in order to address the increasing request of 'sustainability' in modern society. Research in the lot-sizing area is fundamentally driven by the first basic model and by a large set of succeeding incremental steps, developed in order to better reflect real industrial problems and constraints. The social impact of economic order quantity policies has not been thoroughly investigated and is often discussed only via a descriptive approach. This work develops a new two-step approach capable of considering the social impact of lot-sizing procedures in terms of 'ergonomics' along with traditional annual logistic costs. Such approach divides the lot-sizing decisions in two main types: 'In-house', where the most influential decision variable is the size of the packaging units to move within the plant; 'In-bound', where the optimal number of ergonomic bins to purchase per order determines the minimum total cost. The outcome is what is defined as the 'ergonomic lot-size', which permits companies to reduce the ergonomic risks for their workers, while continuing to be profitable and efficient in assembly line part feeding
The recent changes in customers' orders, which on one hand are becoming more frequent and on the other require smaller quantities of several products, inevitably impact the job of warehouse picking managers, who find themselves in the necessary position to satisfy a high pick volume in a short time window. Moreover, warehouse manual picking is traditionally characterized by a high human factor impact; which derives that improving such a system requires a reduction of both orders processing time and human possible errors. In this sense, a possible strategy can be the development and employment of technological systems able to support operators during their picking tours. The aim of this study is to present a new pick-to-light design solution capable of driving different operators through their activities, preventing or reducing errors by a new real-time control and alert system, based on the main potentialities of the RFID technology. After the description of the technical characteristics and of the operation of the new solution, a qualitative comparison with other existing paperless picking systems is also proposed.
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