Papers by Author: Luis Norberto López de Lacalle

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Authors: Francisco Javier Campa, Luis Norberto López de Lacalle, Aitzol Lamikiz
Abstract: Ever increasingly, universities have to face the demands of their students regarding tools and methods to complete their education in preparation for the industrial environment. On the other hand, the university has to meet a Research and Development function oriented to the improvement of the competitiveness of that environment. These are two different functions that the university must unite to offer an optimum service. Hence, the university needs tools that can meet this dual function: teaching and researching. This paper proposes the concept of a “Glass Machine” as a dual purpose approach based on the adaptation of machine tools to satisfy that dual function. This concept has been applied to a machine tool by means of two machines: a turn-milling centre and a feed-drive test bench, which have been used for practices in the subjects of 4th and 5th year of Industrial Engineering, allowing at the same time the usual research activity of the High Performance Machining Team. In short, this work is about the optimization of the available resources of the university, thus satisfying the needs of the students and the industrial environment.
Authors: A.I. Fernández-Abia, J. Barreiro, Luis Norberto López de Lacalle, Gorka Urbikain Pelayo
Abstract: Behavior of austenitic stainless steels is not well known and these materials are still considered as difficult to machining materials. Moreover, the continuous increment of cutting speeds and other cutting parameters derived from last technological advances in tool material makes it more difficult to understand the behavior of these materials in high performance machining. A mechanistic model is presented in this paper for cutting force prediction of austenitic stainless steels turned at very high cutting speeds (up to 750 m/min). The developed model allows the estimation of cutting forces in turning when the cutting action occurs on the side cutting edge and nose radius edge for general turning tools. A tool-part geometrical model is proposed and the cutting force coefficients have been calculated by means of characterization tests.
Authors: Soraya Plaza, N. Ortega, Ainhoa Celaya, Jose Antonio Sánchez, Luis Norberto López de Lacalle, Borja Izquierdo
Abstract: The European Higher Education Area has entailed some upheaval since it has involved deep changes in university education. Among the subjects taught in technical education such as Manufacturing Technologies, which involve strong experimental contents, the use of specific tools is helpful for better understanding of such subjects. This article highlights the need for the use of simulation tools in the field of manufacturing processes. The student may achieve optimal understanding and learning from them. They can understand, in a more visual way, complex phenomena that govern different processes and the influence of key variables. Applications related to sheet metal forming, forging and casting processes are presented. The main objective is to enable students to better understand the phenomena that govern the processes of moulding and forming, with the invaluable help of simulation software. The final aim is to ensure that the student reaches an optimum knowledge of moulding and forming processes using simulation software.
Authors: Jose Antonio Sánchez, Luis Norberto López de Lacalle, N. Ortega, Aitzol Lamikiz, Soraya Plaza
Abstract: The paradigm the new European Higher Education Area places us in together with the teaching/learning guidelines and models demands the teacher adapt his/her function considering new methods which locate the students in the centre of this process. In this context the experience of the subject ‘Advanced forming and moulding techniques’ taught in 5th course of the Industrial Engineering qualification at the Bilbao Engineering Faculty (UPV/EHU), is presented. This subject must be taken by students opting for intensification in Mechanical Manufacturing. The subject is taught over tour months with 30 students per group on average, where a methodology based on Scoring Rubrics was set up.
Authors: Francisco Javier Campa, Luis Norberto López de Lacalle, S. Herranz, Aitzol Lamikiz, A. Rivero
Abstract: In this paper, a 3D dynamic model for the prediction of the stability lobes of high speed milling is presented, considering the combined flexibility of both tool and workpiece. The main aim is to avoid chatter vibrations on the finish milling of aeronautical parts, which include thin walls and thin floors. In this way the use of complex fixtures is eliminated. Hence, an accurate selection of both axial depth of cut and spindle speed can be accomplished. The model has been validated by means of a test device that simulates the behaviour of a thin floor.
Authors: Luis Norberto López de Lacalle, Adrián Rodríguez, Aitzol Lamikiz, Ainhoa Celaya
Abstract: In this paper the ball burnishing as a finishing process for sculptured surfaces is studied. This technique is a quick, easy and economical process for a significant improvement of high-end parts. Aiming at the burnishing of complex parts, different strategies are possible. In this case two strategies are presented: continuous burnishing (CB) using 5-axis interpolation and patch burnishing (PB) using 3+2 axis interpolation. Two parts have been previously machined in five-axis and then finished using ball burnishing techniques. The first one is an AISI 1045 hemisphere and the second one is a DIN 1.2379 part (64 HRC). Surface quality has been evaluated for both strategies obtaining a significant improvement of surface roughness and hardness.
Authors: Francisco Javier Campa, Luis Norberto López de Lacalle, Gorka Urbicain, Aitzol Lamikiz, Sébastien Seguy, Lionel Arnaud
Abstract: A common problem in the aeronautical industry is the chatter vibration due to the lack of dynamic stiffness in the milling of thin walls and thin floors. The present work proposes a method for chatter avoidance in the milling of flexible thin floors with a bull nose end mill. It allows the calculation of the thickness previous to finish milling or the minimum dynamic stiffness that the floor must have to avoid the chatter vibration appearance. To obtain these values, the stability model algorithm has been inverted to estimate the thickness or the dynamic stiffness required in a floor to allow a stable milling. This methodology has been validated satisfactorily in several experimental tests.
Authors: Jose Antonio Sánchez, Luis Norberto López de Lacalle, Aitzol Lamikiz
Abstract: The use of Electrical Discharge Machining (EDM) for the manufacturing of moulds and dies is generally accomplished by using different cutting regimens, from roughing to finishing, until the specified surface finish and dimensional tolerances are met. Multistage planetary EDM can be used to simplify the production process. Benefits such as the reduction of machining time, the need for less electrodes, electrode wear minimization and the improvement of the final surface finish of the component can be obtained. Design of multistage planetary EDM strategies requires a sound knowledge of the optimum radius for each orbit that assures surface roughness and dimensional accuracy together with a minimum machining time. Therefore, it is necessary to know the “exact” value of the gap at each stage. In this paper the influence of different process variables on the design of multistage planetary EDM strategies is analyzed.
Authors: M. Arsuaga, Luis Norberto López de Lacalle, R. Lobato, G. Urbikain, F. Campa
Abstract: Boring operations of deep holes with a slender boring bar are often hindered by the precision because of their low static stiffness and high deformations. Because of that, it is not possible to remove much larger depths of cuts than the nose radius of the tool, unlike the case of turning and face milling operations, and consequently, the relationship between the cutting force distribution, tool geometry, feed rate and depth of cut becomes non-linear and complex. This problem gets worse when working with a rotating boring head where apart from the cutting forces and the variation of the inclination angle because of shape boring, the bar and head are affected by de centrifugal forces. The centrifugal forces, and therefore the centrifugal deflection, will vary as a function of the rotating speed, boring bar mass distribution and variable radial position of the bar in shape boring. Taking in to account all this effects, a load and deformation model was created. This model has been experimentally validated to use as a corrector factor of the radial position of the U axis in the boring head.
Authors: Luis Norberto López de Lacalle, Gorka Urbikain Pelayo, Ibon Azkona, Victor Verbiţchi, Radu Cojocaru, Lia Nicoleta Boţilă, Cristian Ciucă, Ion Aurel Perianu, Miomir Vlascici
Abstract: Coating of steel with aluminium alloy is needed for the execution of a functional layer for corrosion protection. Some experiments have been performed on square-section tubes (50 mm x 50 mm) of S235 steel, according to EN 10 025, to be coated with 1 mm thick sheets of EN AW 5754 aluminium alloy that have been previously bended as U shaped profiles. A new experimental model of specialized equipment has been used for certain experiments to make these functional layers of aluminium alloy on steel. Firstly, friction drilling and threading by form tapping, followed by screws-mounting without nuts have been used to make such joints. Several holes have been executed by a Ø4.3 friction drilling tool, then an M5 form tap was used for threading. For friction drilling, tools with 90% tungsten carbide content and 1 micron grain size were applied. By threading, TiN coated form taps have been used. Secondly, overlap friction stir welding (FSW) has been applied, to make a functional layer of aluminium alloy on a 50 mm x 50 mm S235 steel tube. The wings of the U profiles were overlapped. A quenched FSW tool, own-made of C 45 grade steel, EN 10083, has been used for these joining tests. The joining parameters are mentioned for each process. The run of each joining process is described and the joint test samples are presented. The appearance of the screw-mounted functional layers is appropriate. The metallographic analysis has revealed adequate form of the burr formed below the hole. The burr height is 2.5 – 3.2 mm. The pattern of the M5 thread is appropriate. No defects have been detected on the holes and threads. The appearance of the FSW functional layers is adequate. Metallographic analysis shows that FSW joints of the overlapped aluminium alloy sheets are adequate, because there is no gap between these sheets. There is only a narrow gap between the aluminium alloy bottom sheet and the wall of the steel tube, which proves an appropriate positioning of the two metals. No defects were detected, except for a weld flaw, as a small and isolated cavity, with a section less than 0.1 mm2, considered within the acceptance limit, according to EN 25239-5. The U shaped sheets of aluminium alloy are firmly fixed on the square steel tube, for both coating types. The mentioned processes are proposed to increase productivity in industrial technologies for series production. The processes addressed in this paper are more rapid than conventional processes. Adequate preparation of the parts to be welded, mechanization and automation allow repeatability and quality. The target applications are coated structure elements for devices, appliances, tools, welded structures or automobiles. The involved industrial areas of the applications are: manufacturing, electro-technique, construction and automotive industries. The presented processes are ecological, because they do not need lubricants or other toxic substances and do not produce chips or harmfull substances.
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