Papers by Author: Aitzol Lamikiz

Abstract: Present work deals with laser polishing process on GGG70L spheroidal cast iron, which is widely used in die making for the automotive industry. Free graphite in the structure of GGG70L makes difficult the polishing and surface roughness reduction because the high melting temperature. In this work a complete study is presented, where main process parameters are identified and free graphite is eliminated from surface. The quantification of surface improvement is presented in terms of resulting surface roughness, hardness, and heat affected layer thickness. Thus, using optimal parameters, laser polishing with 2D scan head gives satisfactory results on GGG70L cast iron with roughness reduction rates up to 80% and minimum mean roughness R_a of 0.5 μm.

Abstract: The best is to read these instructions and follow the outline of this text. The text area for your manuscript must be 17 cm wide and 25 cm high. The High Performance Manufacturing Group of the Faculty of Engineering of Bilbao has a workshop fully-equipped. In this way, these machine tools are valid both to support research carried out by the Group and also to improve teaching lessons, both theoretically and practically. In this paper, the case of a five-axis milling machine was presented and analyzed. Each year, the new students are taught to design various systems of the machine and they are also encouraged to make some practical tests. This dual use of machines is very useful since it allows to carry out high level researches, as well as to train new students in theoretical and practical issues.

Abstract: The main disadvantage for industrial application of new processes based on laser surface treatments, such as laser hardening, quenching or precipitation hardening, is the prior experimentation needed to determinate the optimum conditions for processes. The presented work is focused on the development of a tool based on a semi-empirical model to predict accurately the thermal field and thickness of the head affected zone in laser surface treatments in order to avoid the previous experimental setups of this processes. The conventional thermal models are focused on solving the differential equation of temperature field, considering the laser as heat source and thermal properties of each material. However, during the rapid heating treatment processes of metal surfaces are some unknown heat sinks such us metallurgical transformations or a changeable material absortivity that must be taken into account. The model has been adjusted and validated with experimental data for AISI 1045.

Abstract: In laser surface treatment the laser beam is used as energy source for surface modification improving aspects such as mechanical properties, tribology or surface texture. Modeling tools have special interest in processes with many variables, like laser surface processing, in order to minimize the tryout testing to find the optimal process parameters. The work presented here focuses on the prediction of the final topography in laser polishing process. By FFT analysis of the surface profile it is possible to get the different frequency components of the initial topography. On the other hand, thermal field simulation was carried out to evaluate the melt duration. Matching this with the spatial frequency damping during process, the reconstruction of the processed topography was obtained.

Abstract: The Abrasive Water Jet milling process is demonstrated to be an efficient technology for milling low machinability materials. Although its capability is demonstrated, the industrial application of this technology requires a depth control, for which a work focused in process modelling is needed. This research work introduces a model to predict the kerf shape in AWJ slot milling in Aluminium 7075-T651 in terms of four important process parameters: pressure, abrasive mass flow rate, stand-off distance and traverse feed rate. A hybrid evolutionary approach was employed for modelling the profile through two parameters: the maximum cutting depth and the full width at half maximum. Both the maximum depth and the width were also modelled as a function of aforementioned process parameters based on Analysis of Variance and regression techniques. Combination of two models resulted in an adequate strategy to predict the kerf shape for different machining conditions.

Abstract: The laser cladding process is based on the generation of a melt-pool in a substrate where a filler material is injected, generating a high quality clad with a minimum heat affected zone. This process is industrially used to generate coatings over wear or damaged surfaces, being an alternative to traditional deposition techniques. One of the most important aspects for its industrial application is to know the clad geometry in order to calculate the deposited layer thickness. This work presents a model in which, starting from the concentration of injected material and the melt-pool geometry, clad height is finally estimated. Both input variables are obtained by two previous validated models. On one hand, the melt pool is estimated by a thermal model based on the finite difference method, and on the other hand, concentration of injected material is provided by a particle concentration CFD model. This data is used in a mass balance over melt-pool area in order to estimate the deposited clad height.

Abstract: The adaptation of universities to the European Higher Education Area (EHEA) plays an essential role in society, creating new knowledge, transferring it to students by means of new and more active methodologies aimed at learning that will enable students to put everything they learn into practice. However, such methodologies are not equally applicable in all subjects. Subjects such as Manufacturing Technology, taught at different levels in both undergraduate and graduate levels, are descriptive to a great extent. This descriptive nature must be supported by new technologies if these subjects claim to be more attractive to students. In this paper some examples of successful case studies are presented. They represent the new way of understanding the teaching replacing the old concept of traditional classroom lecture by more interactive ones and, therefore, more attractive to students.

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.

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.

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.