1,721,004 research outputs found
Preface [Selected Topics in Manufacturing]
No full textThis book presents selected contributions on a wide range of scientific and technological areas covered by AITeM (the Italian Association of Manufacturing). It discusses the following topics: additive manufacturing, advanced and unconventional machining and processes, material removal processes, foundry and forming, tools and machine tools, assembly/disassembly, joining materials and material properties, quality metrology and material testing, manufacturing systems engineering, sustainable manufacturing, smart manufacturing and cyber-physical systems, education in manufacturing and human factors, industrial applications. Written by young AITeM associates, the contributions reflect the multifaceted nature of the research in manufacturing, which takes advantage of emergent technologies and establishes interdisciplinary connections with various scientific and technological areas to move beyond simple product fabrication and develop a complex and highly interconnected value creation processes ecosystem pursuing high-value-added products to compete globally
Lead Time Analysis of Manufacturing Systems with Time-Driven Rework Operations
No full textProducts whose quality features deteriorate with the time they spend in the manufacturing system are common in industry. Usually, they are perishable products that loose their performance or value whenever their sojourn time in the system exceeds a certain threshold. A typical example is the food industry where such products need to be identified and scrapped. In other cases, perishable products can be reworked for restoring their functions when their sojourn exceeds a threshold. For instance, automotive painting processes suffer of dust settling on parts before the drying process and semiconductor wafers risk contamination between the cleaning and heating processes. This work develops an analytical method to evaluate the performance of systems with rework operations triggered by an extended residence time. The approach is based on the exact computation of the lead time distribution in production lines featuring general markovian machines. By exploiting the developed method, specific production policies aiming at minimizing the rework rate and maximizing the effective throughput in such systems are investigated. The method is validated within a real case showing high benefits through industrial applications
Scheduling Remanufacturing Activities for the Repair of Turbine Blades: An Approximate Branch and Bound Approach to Minimize a Risk Measure
Full text linkRefurbished products are gaining importance in many industrial sectors, specifically high-value products whose residual value is relevant and guarantee the economic viability of the remanufacturing at an industrial level, e.g., turbine blades for power generation. In this paper we address the scheduling of re-manufacturing activities for turbine blades. Parts entering the process may have very different wear state or presence of defects. Thus, the repair process is affected by a significant degree of uncertainty. To cope with this, the proposed approach pursues robust schedules minimizing the risk associated to a timely completion time. An approximate branch and bound algorithm is developed grounding on the estimation of the lower bound of the makespan. The viability and efficiency of the approach is assessed through computational experiments grounding on the industrial case under study and a comparison is operated among alternative scheduling approaches
Preface
No full textThis book presents selected contributions on a wide range of scientific and technological areas covered by AITeM (the Italian Association of Manufacturing). It discusses the following topics: additive manufacturing, advanced and unconventional machining and processes, material removal processes, foundry and forming, tools and machine tools, assembly/disassembly, joining materials and material properties, quality metrology and material testing, manufacturing systems engineering, sustainable manufacturing, smart manufacturing and cyber-physical systems, education in manufacturing and human factors, industrial applications. Written by young AITeM associates, the contributions reflect the multifaceted nature of the research in manufacturing, which takes advantage of emergent technologies and establishes interdisciplinary connections with various scientific and technological areas to move beyond simple product fabrication and develop a complex and highly interconnected value creation processes ecosystem pursuing high-value-added products to compete globally
Energy Efficient State Control of Machine Tool Components: A Multi-sleep Control Policy
No full textEnergy efficient control policies that switch off/on machine tools aim to reduce the energy consumed while not producing parts. Commonly, a transitory is required before resuming the service; thus, to switch off/on the machine might be not advantageous. This paper analyzes a time-based threshold policy that disables/enables machine components with separated control commands instead of controlling the whole machine simultaneously. According to the subset of controlled components, multiple sleeping states and transitory duration can be defined. Machine idle times are assumed stochastic and the expected value of the energy consumed per produced part is reduced while assuring a certain target of machine utilization. A simulation optimization algorithm is used to search for the optimum. The analysis is based on two real CNC machining centers. Potential benefits are compared to state-of-the-art policies and discussed for a set of realistic numerical cases representing several production environments
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Development of Single Point Exposure Strategy to Suppress Vapour Formation During the Laser Powder Bed Fusion of Zinc and Its Alloys
No full textThe conventional scanning strategies based on linear trajectories in Laser Powder Bed Fusion (LPBF) are highly limited for processing novel materials. In order to manage the energy input and exploit a higher feature resolution, novel scan strategies are required, capable of exploiting the flexibility enabled by the fast modulation capabilities of contemporary fiber laser sources. Zinc and its alloys are among these challenging materials for LPBF aimed to be used in customized biodegradable implants. LPBF of Zn is notoriously difficult to process due to excessive vaporisation which generates high porosity. Accordingly, in this study an innovative LPBF processing strategy based on Single Point Exposure (SPE) was developed. The control over the energy input via single spot exposure allowed to suppress excessive vapour and spark formation typical to Zn alloys. The dynamics of the novel process and its parameters were investigated employing open LPBF platforms and high-speed imaging. Fully dense struts with diameters lower than 300 μm were achieved to produce Zn alloy lattice structures, confirming the effectiveness of the innovative SPE strategy for high precision deposition of challenging materials
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