1,721,252 research outputs found
A PERT model based on the Dampster and Shafer's theory of evidence – application to product development
No full textCOSTI DI ADEGUAMENTO ALLA DIRETTIVA ROHS - ANALISI SPERIMENTALE SUI PROCESSI PRODUTTIVI CARATTERIZZATI DA SALDATURA LEAD FREE
No full textIn diversi settori della produzione industriale si sta sempre piùaffermando l’esigenza di progettare e produrre prestandoattenzione all’impatto ambientale. In questo contesto si collocala direttiva RoHS (Restriction of the use of HazardousSubstances), finalizzata a ridurre o eliminare l’utilizzo di alcunesostanze definite come genericamente pericolose. Questo articolo affronta l’analisi sperimentale dei costi di adeguamento alla suddetta direttiva in un’impresa di piccole-medie dimensioni che realizza cablaggi su commessa, nella quale la direttiva ha significativamente modificato i cicli tecnologici di saldatura, che tradizionalmente venivano effettuati con leghe di saldatura al piombo ora bandite dal mercato. In particolare, si è focalizzata l’attenzione sulle voci di costo di adeguamento alla direttiva che sono risultate più significative: costi di modifica dei cicli tecnologici e costi di stoccaggio. I risultati ottenuti confermano l’elevata incidenza sui costi di produzione che la direttiva RoHS genera nel caso di una piccola-media impresa
CLUSTERING APPROACHES FOR MANAGING SIMILAR ITEMS IN THE FIELD OF IRREGULAR AND SPORADIC DEMAND PROFILES: EVIDENCE FROM AN EMPIRICAL COMPARISON
No full textManaging irregular and sporadic demand patterns is a fundamental task in several real life contexts, such as spare parts consumption, multi-echelon supply chains or start-up production. This work is a study of re-order policies and stock inventory management approaches aimed at optimizing pre-defined performance indexes. Specifically, given a firm operating in the field of electric resistance manufacturing, the focus is on the application of different item clustering methods, in order to define groups of items with similar behavior that require similar management approaches. The work offers a framework for the comparative evaluation of two different item clustering methods, by means of a simulative approach, available when product demand profiles are irregular and sporadic. In order to compare them, a multi-criteria technique is preferable because of the high uncertainty of the cost structure. Hence, after running the simulation, three Key Performance Indicators (KPI) are estimated: the average inventory level, the average number of backorders that occurred and the average number of emitted orders. Finally, some conclusions are drawn by defining a field of implementation for each clustering approach studied
Spare Parts Replacement Policy Based on Chaotic Models
Get PDFPoisson point processes are widely used to model the consumption of spare parts. However, when the items have very low consumption rates, the historical sample sizes are too small. This paper presents a modelling technique for spare parts policies in the case of items with a low consumption rate. We propose the use of chaotic models derived from the well-known chaotic processes logistic map and Hénon attractor to assess the behaviour of a set of five medium voltage motors supplying four drives in the rolling mill of a steelmaking plant. Supported by the chaotic models, we conclude that the company needs an additional motor to ensure full protection against shortages
The application of a Quality Function Deployment approach for the design of a B2B web platform
No full textDecision trees for supervised multi-criteria inventory classification
Get PDFA multi-criteria inventory classification (MCIC) approach based on supervised classifiers (i.e. decision trees and random forests) is proposed, whose training is performed on a sample of items that has been previously classified by exhaustively simulating a predefined inventory control system. The goal is to classify automatically the whole set of items, in line with the fourth industrial revolution challenges of increased integration of ICT into production management. A case study referring to intermittent demand patterns has been used for validating our proposal, and a comparison with a recent unsupervised MCIC approach has shown promising results
JOBS PRE-ALLOCATION ON PARALLEL UNRELATED MACHINES WITH SEQUENCE DEPENDENT SETUP TIMES: EVIDENCE FROM A LARGE EXPERIMENTATION
No full textIn this paper the problem of allocating and scheduling jobs on parallel unrelated machines is studied. Jobs are grouped in families of similar items. A sequence dependent setup is required between batches of jobs belonging to the same and different families, even if in the first case lower time is required. The size of batches is not known a-priori, hence the problem is divided in two different sub-problems: a) the allocation of volumes of work on each machine and b) subsequently the scheduling of
each item. The focus of the paper is on the first step and consequently on the pre-assignment problem. Three different solving approaches are implemented in several real-life case studies
On the Analysis of Effectiveness in a Manufacturing Cell: A Critical Implementation of Existing Approaches
Get PDFOEE (Overall Equipment Effectiveness) is a widely used indicator in the evaluation of effectiveness of manufacturing systems. However, several authors published alternative approaches for its computation, complicating the implementation step for practitioners. This study analyses the literature regarding OEE, selects four main methodologies for its evaluation and examines the underlying differences between them. A real life case study is analysed to illustrate problems arising during data collection and the differences in results obtained, together with traceable conclusions for improving the performance of production systems, both in traditional and in innovative industrial plants, following Industry 4.0 principles.OEE (Overall Equipment Effectiveness) is a widely used indicator in the evaluation of effectiveness of manufacturing systems. However, several authors published alternative approaches for its computation, complicating the implementation step for practitioners. This study analyses the literature regarding OEE, selects four main methodologies for its evaluation and examines the underlying differences between them. A real life case study is analysed to illustrate problems arising during data collection and the differences in results obtained, together with traceable conclusions for improving the performance of production systems, both in traditional and in innovative industrial plants, following Industry 4.0 principles
The "Glymphatic-Lymphatic System Pathology" and a New Categorization of Neurodegenerative Disorders
Get PDF- …
