Semi-automatic Design for Disassembly Strategy Planning: An Augmented Reality Approach

Abstract The mounting attention to environmental issues requires adopting better disassembly procedures at the product's End of Life. Planning and reckoning different disassembly strategies in the early stage of the design process can improve the development of sustainable products with an easy dismissing and recycling oriented approach. Nowadays many Computer Aided Process Planning software packages provide optimized assembly or disassembly sequences, but they are mainly based on a time and cost compression approach, neglecting the human factor. The environment we developed is based upon the integration of a CAD, an Augmented Reality tool, a Leap Motion Controller device, see-through glasses and an algorithm for disassembly strategies evaluation: this approach guarantees a more effective interaction with the 3D real and virtual assembly than an approach relying only on a CAD based disassembly sequence planning. In such a way, the operator may not test in a more natural and intuitive way automatic disassembly sequences, but he/she can also propose different strategies to improve the ergonomics. The methodology has been tested in a real case study to evaluate the strength points and criticalities of this approach

FEM ANALYSIS AND EXPERIMENTAL TESTS ON A DEVICE FOR POURING CONCRETE

Aim of the paper is the prediction of the on-service behaviour of an articulated device for pouring concrete composed of five arms. Experimental tests have been performed on a prototype of the equipment made on Weldox 900E steel, while a parallel finite element analysis has been made on a virtual model of the device. Comparison of experimental tests and numerical analysis allows to gain a deep insight on the performance of the apparatus. A virtual model of the apparatus has been developed by a 3D CAD modeller and analyzed through FEM numerical programs in both static and dynamic conditions. During dynamic simulation, accurate evaluation of all loadings and constraints have been made and a modal analysis has been performed on the whole structure to identify critical frequencies. Test plans have been devised to assess performance of the articulated device in both static and dynamic conditions by instrumenting the prototype of the equipment with rectangular rosettes. During quasi-static tests, a series of known discrete loads (up to roughly 1800 N), measured by a dynamometer, has been applied at the end of the fifth arm of the structure. Deflections at the end of the fifth arm, corresponding to each applied load, have been measured by a laser device, utilizing, as reference, the configuration at rest of the structure. Strains are measured by the strain gages of each rosette. Dynamical tests have been performed, by simulating experimentally concrete pouring. During both static and dynamic tests, the 3D strain state and the 2D plane stress state can be derived in each site where rectangular rosettes have been located. Principal stresses, principal strains, direction of the principle strains and stresses, Mohr stress and strain circles have been recorded and compared with those predicted through the finite element analysis. Comparison between numerical and experimental results has been carried out. A very good correlation has been obtained for static loading to assess the soundness of the virtual model. Both experimental tests and numerical simulation in the on-service condition allow to identify the more dangerous resonance frequencie

The Re-use of Free-form Surface Features by MRA Representation

Il riutilizzo di features di superfici complesse (free-form surface features) (FFF), generate in sessioni di modellazione precedenti e poi trasferite su modelli geometrici con base diversa, è un campo di ricerca attualmente molto attivo e vivace. Infatti i benefici di creare una libreria di features per superfici che possa essere impiegata in modellazioni successive è un obiettivo attraente, soprattutto in confronto allo sviluppo che ha avuto la modellazione per feature nel campo del sistemi CAD per la meccanica. Il punto chiave è la formulazione completamente diversa del modello geometrico: nel caso dei solidi si tratta di un albero CSG (Constructive Solid Geometry), mentre le superfici free-form vengono definite attraverso la loro parametrizzazione e il griglia di controllo che, pur garantendo ottima modifica locale, ne impedisce un approccio di modellazione globale. In questo articolo verrà esposto l’applicazione della teoria dell’Analisi in Multi-risoluzione (MRA) mediante wavelets come strumento per la ricerca e l’estrazione di form features da superfici complesse, nonché il possibile modo di riutilizzo delle suddette a sessioni di modellazione completamente diverse. I risultati ottenuti dagli esempi realizzati sono stati più che soddisfacenti, avendo dimostrato la capacità di questo metodo di estrarre form features e riapplicarle a superfici diverse con minimo sforzo computazionale

CAD-CAM integration for 3D Hybrid Manufacturing

Hybrid Manufacturing (HM) is oriented to combine the advantages of additive manufacturing, such as few limits in shape reproduction, good customization of parts, distributive production, minimization of production costs and minimization of waste materials, with the advantages of subtractive manufacturing, in terms of finishing properties and accuracy of dimensional tolerances. In this context, our research group presents a design technique that aims to data processing that switches between additive and subtractive procedures, to the costs and time of product-manufacturing optimization. The component prototyping may be performed combining different stages (ad-diction, gross milling, fine milling, deposition\u2026) with different parameters and head/nozzles and is able to work with different materials either in addictive, either in milling. The present paper is dedicated to introduce different strategies, or in other terms, different combinations of machining features (addictive or deductive) and differ-ent materials to complete a prototype model or mold. The optimization/analysis piece of software is fully integrated in classic CAD/CAM environment for better supporting the design and engineering processes