1,720,966 research outputs found
Operational space efficiency (OpSE): a structured metric to evaluate the efficient use of space in industrial workstations
No full textPurpose: This paper proposes a new metric, named Operational Space Efficiency (OpSE), intended to diagnose and quantify the inefficient use of floor space for stocking materials in industrial workstations. OpSE presents a formulation analogous to the well-known Overall Equipment Effectiveness and can be obtained as the product of three distinct indicators: Standard Compliance Effectiveness, Standards Selection Effectiveness and Design Space-usage Effectiveness. Design/methodology/approach: This indicator scrutinizes how usefully floor space in workstations is used to temporarily stock materials in the form of raw materials, semi-finished products, parts and components. It is suited for analyzing fixed-position layouts as well as product layouts typical of repetitive manufacturing settings, such as assembly lines in the automotive sector. The proposed indicator leverages an appropriate loss structure that features those factors affecting floor space utilization in workstations with regard to supplying and stocking materials. Findings: An Italian manufacturer in the field of electro-technology was used as an industrial case study for the application of the methodology. The application shows how the three indicators work in practice, the effectiveness of OpSE and the methodology as a whole, in diagnosing floor space usage inefficiencies and in properly addressing improvement actions of the internal logistics in industrial settings. Originality/value: The paper scrutinizes some important Key Performance Indicators (KPIs) dealing with space usage efficiency and identifies some significant drawbacks. Then it suggests a new, inclusive structure of losses and a KPI that not only measures efficiency but also allows to identify viable countermeasures
A continuous review, (Q, r) inventory model for a deteriorating item with random demand and positive lead time
Get PDFIn this paper, a single-product, single-location inventory system is considered. A fraction of the stock is lost every time unit, i.e., inventory experiences continuous decay. Demand is uncertain and replenishments require a positive lead time. Shortages are allowed and backorders-lost sales mixtures are considered. Inventory is reviewed continuously and a (Q, r) policy is applied. The problem is to find the order quantity and the reorder point that minimize the long-run expected total cost per time unit. It is known, in literature, that approaching this problem is a very difficult task. Moreover, very little research has been performed in this regard, although improvement of continuous review policy in an inventory system is a vital issue in ERP solutions, in particular for Industry 4.0. The cost model is developed by making some simplifying hypotheses and assuming that the dynamics of inventory level (i.e., stock on hand minus backorders) is captured through an Itō diffusion. An iterative method is proposed to minimize the cost function. Numerical experiments are performed to investigate the efficiency of the proposed model. Comparisons with an estimate of the optimal policy and with a former heuristic model are given. Results show that the model developed in this work should provide a very good approximation of the optimal policy over a reasonably wide range of parameter values. A sensitivity analysis is finally carried out in order to draw some managerial insights
Work In Next Queue CONWIP
No full textThe present paper is aimed at showing, through a simulative approach, that the adoption of a suitable dispatching rule allows to improve the single-loop CONstant Work In Process (CONWIP) control mechanism within Make To Order MTO) production systems, balancing the workload among the workstations, reaching a performance level that outperforms standard CONWIP and leans towards that of the corresponding m-CONWIP system. The benefits that may derive from the adoption of a single-loop CONWIP for the design/management of production systems are obvious, being true that (i) m-CONWIP systems are complex to design and optimize, (ii) the single-loop CONWIP systems can be designed with simpler approaches and that (iii) single-loop CONWIP systems remain easier to manage than the m-CONWIP systems. Thus, the well-known Work In Next Queue (WINQ) rule has been adjusted and used within a single-loop CONWIP model, to guarantee that items are favored within those routings for which higher capacity is available in the succeeding work centers. Its performance has been then compared respectively to that of the standard, FIFO-based, CONWIP system and that of an extremely efficient m-CONWIP system. It is known that the workload balancing capability of pull systems not only depends on the configuration of the system itself. It is also subjected to the variability in the order arrival pattern and of the processing times. These parameters have been therefore opportunely considered. Also, the number of available cards represents, along with the loading rule, the most important control parameter. It can be easily determined both in the standard and the WINQ-based CONWIP, whereas it represents a significant issue within the m-CONWIP systems. Thus, to optimize the number of cards within the m-CONWIP model a Genetic Algorithm (GA) has been opportunely configured.
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Energy Cost Deployment (ECD): A novel lean approach to tackling energy losses
No full textConcerns regarding the environment have forced manufacturing organisations not only to aim for operational excellence but also to rethink how their operations and processes can become more environmentally sustainable. Companies need to decrease their unnecessary energy consumption while maintaining their productivity. Lean manufacturing is considered as one of the most influential energy management initiatives, since it increases the effective use of resources by identifying and eliminating losses. In this paper, a novel lean method called Energy Cost Deployment (ECD) is presented, whose objective are to classify, analyse, and eliminate energy losses within the factory. Modifying the well-known Manufacturing cost deployment, the novel ECD uses five matrices, which are built in sequence from the first one (i.e., A-matrix) to the last (i.e., E-matrix), in order to classify and analyse the causal factor of losses related to energy, with the focus on reducing and eliminating the greatest causal losses, and thus providing opportunities for greater efficiency. Each causal loss is quantified in monetary terms. Improvement techniques that deal with each causal loss are identified and then evaluated by means of a quantitative measure in order to find the preferable approaches. Finally, a practical decision procedure is used to select which improvement projects should be started, and hence which causal losses to tackle should be tackled, according to technical and economic factors. The effectiveness and practicality of the ECD method in tackling energy losses are illustrated using an industrial case study concerning a tissue-paper mill. Thanks to its structured stepby-step procedure, the ECD method improves the energy efficiency within a factory
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A lean approach to address material losses: materials cost deployment (MaCD)
No full textIn this paper, a novel lean approach to address material losses in production processes is presented. It is termed materials cost deployment (MaCD) and has the objective of identifying, analyzing, and reducing or eliminating material losses. Thanks to the modification of the manufacturing cost deployment framework, MaCD proposes an alternative structure for classifying and analyzing material losses, setting the focus on areas where the greatest losses are placed, and providing opportunities for greater efficiency and effectiveness in reducing and eliminating them. With the proposed approach, material losses within the factory are identified and classified into causal and resultant losses. Each loss is then quantified, also in monetary terms. The improvement actions to tackle each causal loss are identified and then evaluated by means of a quantitative measure in order to find the preferable ones. Finally, a practical decision procedure is applied to select which improvement interventions to start, and hence which causal losses to tackle, according to technical and economic factors. The effectiveness and practicality of MaCD in addressing material losses are shown by means of an industrial application concerning a European multinational group operating in the food and beverage industry
Project Time Deployment: a new lean tool for losses analysis in Engineer-to-Order production environments
No full textThis paper presents a novel lean tool called Project Time Deployment (PTD) whose objectives are to classify, analyse, and eliminate losses in order to reduce production lead time in Engineer-to-Order (ETO) environments. By combining two already known approaches, i.e. the Manufacturing Critical-path Time and the Manufacturing Cost Deployment, PTD identifies the critical losses affecting the project, focusing on the business processes where causal losses occur, and providing opportunities for greater efficiency and effectiveness by reducing or even eliminating them. In ETO projects, the lead time and respecting deadlines are of paramount importance and they are often threatened by several different losses that are difficult to compare. Companies thus need a tool to identify the losses and the tasks where they occur, quantifying them in terms of a single dimension: the time. PTD was designed using a methodology based on four steps: analysis of current solutions, concept design and prototype, proof of concept and validation, and definition of future researches. It was also validated in an industrial implementation concerning an Engineering, Procurement & Construction company operating in the steel industry, and led to an approximate 24% reduction in lead time
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