Influence of Elastomer Layers in the Quality of Aluminum Parts on Finishing Operations

In finishing processes, the quality of aluminum parts is mostly influenced by static and dynamic phenomena. Different solutions have been studied toward a stable milling process attainment. However, the improvements obtained with the tuning of process parameters are limited by the system stiffness and external dampers devices interfere with the machining process. To deal with this challenge, this work analyzes the suitability of elastomer layers as passive damping elements directly located under the part to be machined. Thus, exploiting the sealing properties of nitrile butadiene rubber (NBR), a suitable flexible vacuum fixture is developed, enabling a proper implementation in the manufacturing process. Two different compounds are characterized under axial compression and under finishing operations. The compression tests present the effect of the feed rate and the strain accumulative effect in the fixture compressive behavior. Despite the higher strain variability of the softer rubber, different milling process parameters, such as the tool feed rate, can lead to a similar compressive behavior of the fixture regardless the elastomer hardness. On the other hand, the characterization of these flexible fixtures is completed over AA2024 floor milling of rigid parts and compared with the use of a rigid part clamping. These results show that, as the cutting speed and the feed rate increases, due to the strain evolution of the rubber, the part quality obtained tend to equalize between the flexible and the rigid clamping of the workpiece. Due to the versatility of the NBR for clamping different part geometries without new fixture redesigns, this leads to a competitive advantage of these flexible solutions against the classic rigid vacuum fixtures. Finally, a model to predict the grooving forces with a bull-nose end mill regardless of the stiffness of the part support is proposed and validated for the working range.This research was funded by Basque Government (Eusko Jaurlaritza) under the ELKARTEK Program, SMAR3NAK project, grant number KK-2019/00051

The fiscal transformation of the Spanish Carrera de Indias in the 17th century: a reinterpretation

This article examines the fiscal transformation of Spain's trade with Spanish America during the 17th century. It analyses the taxation of trade combined with the evolution of the Hispanic Monarchy's long-term domestic debt. To this end, the author looks at the almojarifazgo de Indias (main customs duty), its juro (annuity) obligations and the evolution of the transatlantic trade. He argues that the fall in customs revenue and the increasing non-payment of the juros issued against the almojarifazgo were neither a consequence of the alleged crisis of the Carrera de Indias nor of the higher incidence of fraud. The Crown was not interested in exerting greater fiscal pressure on the trade or fighting fraud at the customs houses of Seville and Cadiz as the increased tax revenue would have gone entirely to service the unpaid juros. Instead, the fiscal burden shifted towards extraordinary contributions that were free of juro obligations.The financial support received from the Spanish Ministerio de Ciencia e Innovación (pro- ject entitled «Crisis fiscal y declive económico en la Monarquía Hispánica, 1550-1700», PID2020-118287GB-100) and the Basque Government (Consolidated Research Group IT897-16 UPV-EHU) is gratefully acknowledged

Hardness, grainsize and porosity formation prediction on the Laser Metal Deposition of AISI 304 stainless steel

The presented numerical model solves the heat and mass transfer equations in the Laser Metal Deposition process and based on the evolution of the thermal field predicts the grainsize, the resulting hardness and evaluates the pores formation probability in an AISI 304 stainless steel. For this purpose, in a first step, the model calculates the shape of the deposited material and the variations of the temperature field. In a second step, and based on the evolution of the thermal field, the model calculates the resulting hardness of the deposited material, the grainsize and the porosity formation probability after the deposition process. Numerical results are experimentally validated, and good agreement is obtained. Consequently, besides predicting the geometry of the resulting part and the evolution of the thermal field, the developed model enables to evaluate the quality of the deposited material. Therefore, the optimum process conditions and strategy when depositing AISI 304 stainless steel can be determined without initial trial-and-error tests.“LaCaixa” foundation . In addition, this work has been founded by the H2020- FoF13-2016 PARADDISE project (contract No.: 723440). This work has been also carried out in the framework of the DPI2016-79889-R – INTEGRADDI project, funded by the Spanish Ministry of Industry and Competitiveness

Effects of Gravity and Non-Perpendicularity during Powder-Fed Directed Energy Deposition of Ni-Based Alloy 718 through Two Types of Coaxial Nozzle

The consequences of gravity and the nozzle inclination angle in the powder-fed Directed Energy Deposition (DED) process were examined in this study. We also sought to define guidelines and manufacturing strategies, depending on the DED system configuration and the nozzle type. To do so, two nozzle types were used: a continuous coaxial nozzle with a slit of 0.5 mm and a four-stream discrete coaxial nozzle. Although the main effects of the configurations and the nozzles are well-known, their effects on the clad characteristics and the deposition strategy are as yet unclear. In this paper, measurements of a single clad and the effects of different deposition strategies on cladding applications and inclined walls are presented, and the consequences for manufacturing processes are discussed. Based on a complete study of a single clad, working vertically, five different tilted deposition strategies were applied: three to a single clad and two to an inclined wall. The results for both the single clad and the inclined wall reflect a pattern of changes to height, width, area, and efficiency, at both small and large nozzle angles and deposition strategies. The inclined wall presents a maximum horizontal displacement that can be reached per layer, without geometrical distortions. The amount of material per layer has to be adapted to this limitation.This research was funded by the European Commission through the project "PARADDISE: a Productive, Affordable and Reliable solution for large scale manufacturing of metallic components by combining laser-based Additive and Subtractive processes with high Efficiency” (Grant Agreement 723440), an initiative of the Public–Private Partnership “Photonics and Factories of the Future”. This research was also funded by European Institute of Innovation & Technology (EIT), through the project "DEDALUS: Directed Energy Deposition machines with integrated process ALgorithms Under dedicated monitoring and control System” (ID 20094), and by the vice-counseling of technology, innovation and competitiveness of the Basque Government (Eusko Jaurlaritza), under the ELKARTEK Program, PROCODA project, grant number KK-2019/00004

2. Joanes de Matet-en gutuna

Joannes de Matet-en gutuna, edizio honetako 16.a (TNA, HCA 30/264). [image 1] Argazkiak: Xabier LAMIKIZ

Un "cuento ruidoso": confidencialidad, reputación y confianza en el comercio del siglo XVIII

Este trabajo aborda el estudio de tres conceptos que incidían de manera fundamental en el comportamiento económico y social de los comerciantes del siglo XVIII: confidencialidad, reputación y confianza. El estudio está dividido en tres partes. En primer lugar se define y analizan los tres conceptos en el contexto del comercio del siglo XVIII. Seguidamente se presentan la metodología y las fuentes documentales que se emplearán para conocer el funcionamiento cotidiano de los tres conceptos. Finalmente, la tercera y más sustancial parte está dedicada al caso de Juan de Eguino y su viaje de negocios a la Lima virreinal; Eguino era un comerciante establecido en Cádiz que se vio obligado a viajar al Perú tras convencerse de que sus dos socios de Lima le estaban engañando

Analysis of Alloy 718 surfaces milled by abrasive waterjet and post-processed by plain waterjet technology

This work analyzes the surfaces obtained in Alloy 718 when they are milled by Abrasive Waterjet (AWJ) at different conditions. This analysis revealed that all surfaces have a homogeneous roughness in the transversal and the longitudinal directions, present embedded abrasive particles and have hardened about 50% with respect to the untreated bulk Alloy 718. On the other hand, Plain Waterjet (PWJ) technology was used for removing the abrasive particles embedded in surfaces of Alloy 718 milled previously by AWJ technology. The effect of this process on the surface characteristics is also analyzed. For all tested conditions, this technology removed all the particles embedded in the surface. In addition, the PWJ technology process in general smoothened the surfaces produced by AWJ milling and it also released near-surface stresses.The authors acknowledge the support of the Ministry of Economy and Competitiveness of the Spanish Government for support of project EVOCA II (reference DPI2013-45308-P)

Latest Developments in Industrial Hybrid Machine Tools that Combine Additive and Subtractive Operations

Hybrid machine tools combining additive and subtractive processes have arisen as a solution to increasing manufacture requirements, boosting the potentials of both technologies, while compensating and minimizing their limitations. Nevertheless, the idea of hybrid machines is relatively new and there is a notable lack of knowledge about the implications arisen from their in-practice use. Therefore, the main goal of the present paper is to fill the existing gap, giving an insight into the current advancements and pending tasks of hybrid machines both from an academic and industrial perspective. To that end, the technical-economical potentials and challenges emerging from their use are identified and critically discussed. In addition, the current situation and future perspectives of hybrid machines from the point of view of process planning, monitoring, and inspection are analyzed. On the one hand, it is found that hybrid machines enable a more efficient use of the resources available, as well as the production of previously unattainable complex parts. On the other hand, it is concluded that there are still some technological challenges derived from the interaction of additive and subtractive processes to be overcome (e.g., process planning, decision planning, use of cutting fluids, and need for a post-processing) before a full implantation of hybrid machines is fulfilledSpecial thanks are addressed to the Industry and Competitiveness Spanish Ministry for the support on the DPI2016-79889-R INTEGRADDI project and to the PARADDISE project H2020-IND-CE-2016-17/H2020-FOF-2016 of the European Union's Horizon 2020 research and innovation program

Le Dauphin itsasontziaren testuinguru historikoa : Louisbourgeko euskaldunak, ekonomia atlantiarra eta gerra (1713–1758)

1. Le Dauphin itsasontzia 1757ko apirilaren 9an Britainia Handiko hiru gerra-ontzik Atlantikoa zeharkatzen ari zen Le Dauphin zeritzon itsasontzi frantsesa harrapatu zuten. Baionatik atera eta Louisbourgerako norabidea zeraman Le Dauphin-ek. Britainiarrek itsasontzia ez ezik barnean zeraman guztia bahitu zuten, dokumentu mordoa barne. Dokumentuon artean euskaraz idatzitako 50 eskutitz zeuden, Lapurdiko 48 bizilagunek Louisbourg aldean zeuden 45 pertsonari bidaliak. Zazpi Urteko Gerraren (1756..