Economic and Performance Analysis of Dual-Bay Vertical Lift Modules

Poster

Economic and Performance Analysis of Dual-bay Vertical Lift Modules

Warehouse picking is one of the most time and cost consuming activities in a warehouse, often requiring the presence of human operators, who travel within the aisles to retrieve the items needed by the customers. Several studies demonstrate that the travelling activity can represent even the 50% of the total picking time, with a subsequent creation of a separate storage and picking area for small objects. In the last years, new solutions for order picking systems have been developed, especially for small items. One of these solutions requires Vertical Lift Modules (VLMs), storage columns with extractable trays. In this paper, the employ of dual-bay VLMs, compared to a carton racks warehouse, has been analysed from an economic point of view. Some mathematical formulations have been developed, to estimate the total annual cost and the respective convenience limits of both systems, according to their productivity. Moreover, some useful guidelines for practitioners are derived

preventing ergonomic risks with integrated planning on assembly line balancing and parts feeding

In this paper, we advise to perform assembly line balancing simultaneously with decision-making on parts feeding. Such integrated planning may open additional potential to reduce labour costs. Additional planning flexibility gained with the integrated planning may be used to mitigate ergonomic risks at workplaces. We formulate the integrated assembly line balancing and parts feeding planning problem, propose a mixed-integer model and compare integrated planning to a common hierarchical planning approach in a detailed case study on the assembly of a self-priming pump. Our case study illustrates that workplaces with high ergonomic risks may emerge even in productions that involve handling parts and workpieces of low weights and avoid static and awkward postures. We also show that the proposed integrated planning approach may eliminate excessive ergonomic risks and improve productivity indicators simultaneously

Efficacy and limits of sildenafil citrate in patients with arterial erectile dysfunction: role of peripheral arterial disease and cardiovascular comorbidities

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Sviluppo e caratterizzazione di uno schema di multiplazione di sensori interferometrici in fibra ottica

L'obiettivo di questa tesi è di illustrare, sviluppare, caratterizzare e sperimentare uno schema di multiplazione di sensori interferometrici in fibra ottica. Lo schema analizzato si basa sulla trasmissione di due segnali ottici (ottenuti dal filtraggio dello spettro d'uscita di un amplificatore all'erbio) a lunghezza d'onda diversa in una configurazione interferometrica di tipo Mach-Zehnder. A seguito di una vibrazione, in un canale si propaga il segnale retro-diffuso per effetto Rayleigh e nell'altro si propaga il segnale riflesso dall'estremità della fibra di sensing: elaborando ed analizzando i segnali dei due canali si può localizzare il punto in cui è stato generato il disturbo. Il primo capitolo consiste in una panoramica sui sensori in fibra ottica, in particolare quelli distribuiti, per poi presentare lo stato dell'arte dei sensori vibrazionali in fibra. Nel secondo capitolo vengono descritti la struttura e il principio di funzionamento del sensore proposto descrivendo in particolar modo gli amplificatori e i filtri che lo costituiscono; vengono inoltre presentate le varie configurazioni del sensore testate. Il terzo capitolo consiste, invece, nell'elaborazione dei dati raccolti e, quindi, nell'analisi delle prestazioni del sensore. Nel quarto capitolo, infine, vengono riassunti i punti principali del lavoro svolto e vengono discussi i risultati ottenuti sottolineando i punti di forza, i problemi e i possibili sviluppi futuri dello schema propost

Modelling time efficiency of cobot-supported kit preparation

Kitting – meaning to supply assembly with components in pre-sorted kits – is widely seen as beneficial for assembly quality and efficiency when there is a multitude of component variants. However, the process by which kits are prepared – the kit preparation – is labour intensive, and kit errors are problematic at assembly processes. The use of robotics to support kit preparation has received some attention by researchers, but literature is lacking with respect to how collaborative robots – cobots – can support kit preparation activities. The purpose of this paper is to identify the potential of a cobot to support time-efficient batch preparation of kits. To address the purpose, the paper presents a mathematical model for estimation of the cycle time associated with cobot-supported kit preparation. The model is applied in a numerical example with experimental data from laboratory experiments, and cobot-supported kit preparation is compared with manual kit preparation. The findings suggest that cobot-supported kit preparation is beneficial with diverse kits and smaller components quantities per SKU (Stock Keeping Unit) and provides less variability of the outcome, when compared to manual kit preparation. The paper reveals several insights about cobot-supported kit preparation that can be valuable for both academics and practitioners. The model developed can be used by practitioners to assess the potential of cobots to support kit-batch preparation in association with assembly, spare parts, repair and maintenance, or business to business industry

Throughput models for a dual-bay VLM order picking system under different configurations

Purpose Vertical lift module (VLM) is a parts-to-picker system for order picking of small products, which are stored into two columns of trays served by a lifting crane. A dual-bay VLM order picking (dual-bay VLM-OP) system is a particular solution where the operator works in parallel with the crane, allowing higher throughput performance. The purpose of this paper is to define models for different operating configurations able to improve the total throughput of the dual-bay VLM-OP system. Design/methodology/approach Analytical models are developed to estimate the throughput of a dual-bay VLM-OP. A deep evaluation has been carried out, considering different storage assignment policies and the sequencing retrieval of trays. Findings A more accurate estimation of the throughput is demonstrated, compared to the application of previous models. Some use guidelines for practitioners and academics are derived from the analysis based on real data. Originality/value Differing from previous contributions, these models include the acceleration/deceleration of the crane and the probability of storage and retrieve of each single tray. This permits to apply these models to different storage assignment policies and to suggest when these policies can be profitably applied. They can also model the sequencing retrieval of trays