1,720,996 research outputs found
Approximated closed-form minimum-cost solutions to the (S - 1, S) policy with complete backordering
No full textA study on the importance of selection rules within unbalanced MTO POLCA-controlled production systems
No full textThe present paper is aimed at investigating, through simulation, the behaviour of the POLCA method when a Make-to-Order (MTO) production system is highly unbalanced, in terms of both routings and times. In particular, the study is addressed to verify (i) the effective capability of the POLCA method to improve the uncontrolled system and (ii) the impact of how orders are processed at each workstation, to show that POLCA performance can be further improved in such circumstances by adopting an appropriate selection rule. Germs and Riezebos (2010) proved that POLCA is very effective in reducing the Total Throughput Time (TTT) with respect to the corresponding unconstrained production systems. Owing to this, it appears evident that POLCA represents a valuable and effective Make-to-Order (MTO) production control method. However, they only considered balanced systems, hence some observations must be carefully addressed. In fact, often, in real world applications, the systems to be controlled are designed to process units with very different routings, each with significantly different probability to occur
Computer-Aided Activity Planning (CAAP) in Large-Scale Projects With an Application in the Yachting Industry
No full textThe present paper provides the schema for an innovative and
modular computer-based approach to the planning of activities in largescale projects. Such projects are characterized by tens of thousands of tasks, which are consequently burdensome and difficult to plan manually. This is true to the point that in many shipyards only a low level of detail is used and poor planning is generally performed. The proposed approach is called Computer-Aided Activity Planning (CAAP), and an application in the yachting industry is shown to demonstrate its effectiveness. In particular, the so-called outfitting planning problem is faced. The CAAP system, taking into account the available shipyard resources and the knowledge on the building rules is able to automatically define, sequence, and schedule the activities of the whole outfitting process acting as a "planning configurator". Moreover, it allows the industry-specific knowledge to be stored, maintained and shared within the (extended) organization. Owing to these "building blocks", plans can be defined accurately and in a shorter time starting from pre-defined templates, with particular impact on lead times whenever variations to complex projects are needed. Finally, to verify the actual capabilities of the approach, the CAAP was implemented within a prototypical software called NautiCAAP
Stochastic Theory of Tool-Life - Theoretical developments on the injury theory
No full textThis paper aims at presenting a revisited and extended version of the injury theory, originally developed by Ramalingam and Watson (1977) and Ramalingam (1977). This theory allows deriving tool-life distributions when either a single catastrophic event or a gradual and cumulative wear process terminates the tool useful life. Since these models cover great importance in tool-life modelling, this paper would contribute in this direction with further observations and results, giving special attention to the mathematical formulation. In particular, besides deriving known results following a different approach, we extend the theory to the case of multiple machines with both single- and multi-tool configurations. Moreover, as examples we derive different expressions of the tool-life distribution in the cases studied related to particular formulations of the injury rate
A fuzzy multi-criteria approach for critical path definition
No full textThis paper focuses on the identification of the critical path in complex projects networks. To extend the capabilities of the traditional project-scheduling approaches an innovative framework is presented, which integrates Fuzzy Logic and Multi Criteria Decision Making (MCDM) techniques. The aim is to determine the critical path taking into account not only the expected duration of the tasks, but also additional critical parameters such as: 'duration variability', 'costs', 'shared resources', 'risk of major design revisions' and 'external risks'. To this scope, all the previously mentioned parameters are evaluated following a mathematical approach based on Fuzzy Logic and are aggregated using the 'Technique for Order Preference by Similarity to Ideal Solution' (TOPSIS) to de. ne the resulting critical path. An example concerning an engineering project is also presented to better explain the potentials and the capabilities of the proposed approach
An Integer Linear Programming Approach to Maintenance Strategies Selection
No full textPurpose - The paper presents a RCM embedded integer linear programming approach (suited to the budget monetary resources allocation task) to the maintenance strategies mix selection for an industrial plant equipments.
Design/methodology/approach - The developed approach allows to determine the optimal maintenance strategies mix for a set of equipments in a more quantitative way than the classic RCM approach. The proposed model takes into account, for each potential failure determined using the FMECA and for each admissible strategy, the costs and the potential RPN reduction. Finally, an industrial case concerning an Italian paper-mill plant is reported to demonstrate the effectiveness of the approach presented.
Findings - The paper finds that the application of the proposed approach allows to optimally allocate the budget monetary resources, determining which suitable maintenance practice apply to each failure, taking into account the costs of each strategy and the potential reduction of the RPN.
Practical implications - The proposed model permits to assign (during the budget monetary resources allocation task) to each failure the optimal strategy, among a set of suitable maintenance practices, considering the costs and the estimated RPN reduction.
Originality/value - The paper proposes a completely new RCM embedded approach to the maintenance strategies selection, in order to optimally allocate the budget monetary resources. This model overcomes the limits of the traditional RCM approach, taking into account quantitative aspects, i.e. the compatibility constraint between failures and policies, the maintenance strategies costs, and the RPN estimated reduction
A standard agreement for vendor managed inventory
No full textPurpose – The purpose of this paper is to define the standard structure of a vendor managed inventory (VMI) agreement, which can be used as a guideline for the early definition of the agreement.
Design/methodology/approach – Starting from an industrial application of relevance, the information flow and the technical details, which are to be defined before the operation startup, are identified and discussed. These data are used as the key points for the definition of the basic frame of the agreement. A particular emphasis is given to the “Technical Specification” and the “Service Level Agreement” sections.
Findings – It is shown that a VMI agreement should be arranged into parts dealing with the generic and legal sides of the agreement, whereas the technical aspects and the relation-specific topics should be addressed in the annexes. This increases the flexibility of the agreement in that, as the VMI relationship evolves over time, changes will affect only the annexes leaving the main body of the agreement unaltered.
Practical implications – The proposed agreement has a flexible structure and can be easily adopted by the personnel involved to correctly define and implement VMI in several industrial fields.
Originality/value – By approaching VMI from a practical point of view, this paper identifies the main issues that must be covered in the agreement to fit the needs of both parties and to assure benefits on both sides
Overall Equipment Effectiveness of a Manufacturing Line (OEEML): an integrated approach to assess systems performance
No full textPurpose - Overall equipment effectiveness (OEE) is the key metric to measure the performance of individual equipment. However, when machines operate jointly in a manufacturing line, OEE alone is not sufficient to improve the performance of the system as a whole. The purpose of this paper is to show how to overcome this limitation, by presenting a new metric (overall equipment effectiveness of a manufacturing line OEEML) and an integrated approach to assess the performance of a line. Design/methodology/approach An alternative losses classification structure is developed to divide the losses that can be directly ascribed to equipment, from the ones that are spread in the line. Starting from this losses classification structure, an approach based on OEE is developed to evaluate the criticalities and the effectiveness of the line. Findings This method has been applied to an automated line for engine basements production. Results show that OEEML successfully highlights the progressive degradation of the ideal cycle time, explaining it in terms of: bottleneck inefficiency, quality rate, and synchronisation-transportation problems. Research limitations/implications OEEML alone fails to explain to which extent effectiveness is supported by in process-inventories and should be integrated with additional metrics to estimate the inventories-related costs. Practical implications OEEML provides practitioners with an operative tool useful to highlight the points where the major inefficiencies take place and to foresee the potential benefits of corrective actions. Originality/value In relation to other methodologies, OEEML presents two main advantages: it detects and quantifies the line's critical points and it can be applied even in presence of buffers, without underestimating the efficiency of the syste
A note on "A Multiple-Vendor Single-Buyer Integrated Inventory Model With a Variable Number of Vendors"
No full textIn this technical note, an alternative solution procedure to the model that developed is presented. In particular, we take into account the same assumptions, but the total cost function is reformulated, i.e., the step-type discontinuity is replaced by a logistic approximation and the total costs of the system are computed on the whole set of preselected suppliers. Subsequently, we show that the total cost function possesses some properties in terms of convexity and continuity that allow the exploitation of standard constrained nonlinear minimization algorithms. Finally, tests conducted on the same set of problems that originally considered illustrate the good performances of the solution procedure developed in this note
Redesign of Supply Chain in Fashion Industry based on Strategic Engineering
No full textThis paper proposes the innovative approach of Strategic Engineering to Fashion Industry in order to redesign the Supply Chain of Medium Size Enterprises active in high quality Made in Italian women's footwear and how this innovative approach could support enhancements and improvements over multiple target functions. The paper introduces the approach and proposes the framework as example of how combining Modeling and Simulation, Artificial Intelligence and Data Analytics in closed loop with real data it could be possible to support Decision Makers in re-engineering processes and redesigning business models even in Small Medium Size Enterprises devoted to high quality production. (C) 2022 The Authors. Published by Elsevier B.V
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