Browsing by Keyword "Vibration assisted drilling"
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Item Evaluation on advantages of low frequency assisted drilling (LFAD) aluminium alloy Al7075(2020) Veiga, Fernando; Suárez, Alfredo; Del Val, Alain Gil; Penalva, Mariluz; de Lacalle, Luis Norberto Lopez; Tecnalia Research & Innovation; FABRIC_INTELDrilling operation of dissimilar stack materials is a crucial assembly operation in airframe manufacturing; this is due to both the number of holes drilled in an aircraft structure and the fact that this is an operation performed in the finishing phase of the manufacturing chain. This paper aims to evaluate an alternative strategy for conventional drilling and peck drilling, which are now the most widespread solutions used for drilling aluminium alloys. The alternative approach proposed by this paper consists of low frequency assisted drilling (LFAD) performed into frequencies vibrations (between 50 to 100 Hz). In this paper, the chip formation process of drilling assisted by low-frequency vibrations of FC/Al stack material has been analytically modelled and compared with the conventional drilling of aluminium. Results show chip segmentation during the drilling operation resulting in less temperature increasing, avoiding problems in the final geometrical quality of the hole, and burr formation.Item Low frequency vibration assisted drilling of PC1000 polycarbonate(2019) Alonso, Unai; Goirigolzarri, Borja; Ostra, Txomin; de Lacalle, L.N. Lopez; FABRIC_INTELA challenge in drilling polymers is their very low melting point, especially when holes with a large length-to-diameter ratio are required. One opportunity to avoid chip accumulation is the use of low vibration assisted drilling. In the present work, the comprehensive knowledge acquired from the machining of metals is transferred to drilling of polycarbonate PC1000. The first research objective of this work was to evaluate if the kinematic models proposed in literature could predict the onset of discontinuous chip generation. To do so, a series of drilling tests were performed with a MITIS tool holder varying vibration amplitude and hole length. During the tests, thrust force and workpiece temperature were registered and, afterwards, hole diameter and surface roughness were measured. The results showed that a kinematic model can be useful to predict the onset of discontinuous chip generation. It was also concluded that surface roughness increases with vibration amplitude until the onset of chip breakage is reached. Furthermore, a correlation between temperature and surface roughness was detected. Regarding cutting forces, a relationship was observed between the thrust force signal amplitude and the amplitude vibration of the MITIS tool-holder. This correlation could be useful to calibrate other future designs of tool holders.