3,803 research outputs found
Energy saving opportunities in direct drive machine tool spindles
No full textThe aim of the work is to carry out a comprehensive assessment of the energy saving opportunities linked to the introduction of direct drives solutions in machine tool spindle systems. Although there is a clear industrial trend towards the replacement of the traditional motor-transmission based spindle solutions, there is a lack of scientific studies focused on the associated energy-related aspects. For this purpose, two spindle units characterized by similar performances were analyzed from the energy consumption, losses and efficiency perspective. Empirical spindle system energy models were developed exploiting experimental tests performed on a motor test bench used for reproducing different machining conditions. The identified models were used to estimate the energy savings that can be achieved substituting the traditional gearbox-based solution with the novel direct-drive spindle. The analysis was carried out considering a realistic production scenario for the machine equipped with the analyzed spindle. It was demonstrated that about 7% of the energy absorbed by the overall machine can be saved and that this improvement accounts for the 147% of the requested cutting energy. For sake of generality, the analysis was repeated considering different production scenarios and ways of using the machine. It can be concluded that the achievable energy savings are even robust to the change of the executed machining operations
Motivi letterari nei libri per l’infanzia di Paolo Di Paolo
No full textThe article, organised in the form of a discussion, aims to analyse the themes and motifs of Paolo Di Paolo’s works that are addressed to young audiences. The author has recently published a large number of volumes directed just at younger readers. When beholding the titles that constitute the author’s bibliography, the reader is struck by Di Paolo’s predisposition to transform literary classics: as much in Giacomo il signor bambino as in the edition of the Divina Commedia, the author’s goal is to try to reach his new readers. Therefore, Di Paolo proves to be a prolific author of the genre; in fact, in his bibliography, volumes of fairy tales with a classic slant, such as La mucca volante, are listed as well.L’articolo contiene un’analisi di temi e di motivi delle opere di Paolo Di Paolo dirette al pubblico più piccolo. L’autore negli ultimi anni ha pubblicato un cospicuo numero di volumi indirizzati, infatti, proprio ai lettori più giovani. Ciò che stupisce scorgendo i titoli che costituiscono la bibliografia dell’autore, è la predisposizione a trasformare i classici della letteratura: tanto in Giacomo il signor bambino quanto nell’edizione della Divina Commedia l’obiettivo è cercare di raggiungere i lettori più giovani. Di Paolo si dimostra, quindi, un autore prolifico del genere, tant’è che nell’elenco non mancano volumi fiabeschi dal taglio classico come La mucca volante. Analizzare le opere giovanili dello scrittore costituisce un fatto inedito
Tube bending machine modelling for assessing the energy savings of electric drives technology
No full textThe aim of the work is to carry out a comprehensive analysis of the energy saving opportunities offered by the introduction of electric drives in the rotary-draw tube bending technology. Although there is a clear industrial trend towards the replacement, especially for low tonnage forming machines, of the traditionally adopted hydraulic drives, there is a lack of scientific research that has studied its implications on energy consumption. For this purpose, an energy model for tube bending machines was developed. The parameters of the model were identified exploiting experimental power measurements performed on both a hybrid hydraulic-electric and a fully electric machine. The energy saving analysis was carried out through the updated energy models. For sake of generality, the analysis was extended considering various tube material-diameter combinations and different machine working conditions. The results showed that relevant energy savings can be obtained and that the improvements are affected by the machine throughput. It was also observed that the minimum achievable energy saving is significantly higher (at least three times) than the energy share for processing the tube. An efficiency analysis of both types of machines was also reported. The introduction of the electric drives allows increasing the machine efficiency up to 50 percentage points. This achievement slightly decreases with the increment of the rotary-draw bending machine throughput
Development of a generalized process-based observer for indirect monitoring of cutting force and tool vibration in milling
No full textIn machining processes, cutting forces and vibration measurements are essential to allow cutting process and tool conditions
monitoring. Moreover, in order to get information about the quality of the milled part, the amplitude of the tool tip vibration
would be very useful. Since both the measurements are extremely complicated especially in an industrial scenario, in this study,
an in-process model-based estimator of cutting forces and tool tip vibration was designed and properly tested. Although in the
specific literature some cutting force observers, based on Kalman’s filter theory, were developed, a general cutting force observer
that is suitable for working in any cutting condition is still missing. Indeed, one of the limitations of the existing approaches is
connected to the capability of estimating the cutting forces/vibrations even when the regenerative chatter affects the cutting. This
drawback is mainly due to the fact that the model typically used for developing the observer considers only the machine
dynamics, but it does not consider the coupling with the cutting process. In order to overcome this shortcoming, in this paper an
observer based on a combined machine tool dynamics-cutting process model was conceived. In fact, even the contribution due to
the regeneration phenomenon was considered in the observer development. The innovative observer was tested through
simulations of stable and unstable cuttings. The estimating properties were compared to the ones achievable using the approach
already adopted in the literature. The observed results confirmed the enhancement of the observer monitoring skills in milling
operations affected by regenerative chatter
Energy assessment of different cooling technologies in Ti-6Al-4V milling
No full textManufacturing craves for more sustainable solutions for machining heat-resistant alloys. In this paper, an assessment of different cooling lubrication approaches for Ti6Al4V milling was carried out. Cryogenic cutting (liquid nitrogen) and conventional cooling (oil-based fluid) were assessed with respect to dry cutting. To study the effects of the main relevant process parameters, proper energy models were developed, validated and then used for comparing the analysed cooling lubrication strategies. The model parameters were identified exploiting data from specifically conceived experiments. The power assessment was carried out considering different perspectives, with a bottom-up approach. Indeed, it was found that cryogenic cooling, thanks to a better tribological behaviour, is less energy demanding (at least 25%) than dry and conventional cutting. If the spindle power is considered, lower saving percentages can be expected. Cryogenic cooling showed its best energy performance (from 3 to 11 times) with respect to conventional cutting if the machine tool perspective is analysed. Considering even the primary energy required for producing the cutting fluids, the assessment showed that cryogenic cooling requires up to 19 times the energy required for conventional cutting
A new receptance coupling substructure analysis methodology to improve chatter free cutting conditions prediction
No full textThe cutting process stability depends on machine tool dynamics that is strongly influenced by the tool. Receptance coupling substructure analysis (RCSA) can be used to estimate the tool tip dynamic compliance and consequently the chatter free cutting conditions when the machine is equipped with a tool that has not been previously tested. This methodology can be particularly useful on real shop-floors where a lot of different tool-tool holder configurations are generally used. RCSA typically combines experimental dynamic compliance measurements performed on a machine equipped with a selected tool and the finite element (FE) models of both the already tested tool and the new ones. This paper presents a new receptance coupling substructure analysis (RCSA) approach that overcomes the drawbacks in the estimation of the receptances that contain rotational and moment contributes. This indeed often limits the accuracy of the RCSA techniques presented in other scientific works. The proposed formulation allows to better estimate both the matrices of receptances of the spindle-tool holder assembly and the tool-tool holder connection stiffness. Those quantities are used, together with the FE model of the new tool, to predict the unknown tool tip dynamic compliance. Some useful guidelines to implement the proposed RCSA are also defined: they allow to manage the procedure accuracy considering the experimental methodology typically used to measure dynamic compliances. The proposed innovative RCSA is experimentally tested and validated. © 2013 Elsevier Ltd
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