Browsing by Author "Tabernero, I."
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Item An approach to thermal modeling of laser polishing process(2009) Ukar, E.; Lamikiz, A.; Tabernero, I.; Liebana, F.; Del Pozo, D.; COMPOSITE; SGPolishing operation of die and molds represents up to 30% of the total manufacturing cost, since it is a high added value operation that is necessary carried out manually by qualified personnel. There are several alternatives to hand operations, such as abrasive automated methods operated by robots, ball burnishing or laser polishing process in order to reduce operation time and costs. The presented article proposes a laser based polishing operation which consists in the application of a laser beam in a very controlled way. The radiated energy melts a microscopic layer which flows and re-solidifies smoothing the topographic irregularities of the surface resulting in a reduction of the initial roughness. The article presents, in addition to some experimental results of laser polishing process, a thermal model developed based on the finite difference method. The model is able to take into account different types of lasers; in particular, simulations for a CO2 laser and a high power diode laser have been carried out. As the model gets the full map of temperatures in 3D, it is possible to predict the melted material layer thickness, which is a crucial parameter in the laser polishing process. Finally, two types of validation tests are presented: First, some tests measured by pyrometers on the test part surface. Secondly, the comparison of a series of metallographic analysis on W.-Nr.1.2379 tool steel, where the metallurgical changes caused by the laser radiation can be observed with the thermal field estimated by the model.Item An industrial approach of laser polishing with different laser sources: Industrielle Methode zum Laserpolieren mit verschiedenen Laserstrahlquellen(2015-07-01) Ukar, E.; Lamikiz, A.; Liébana, F.; Martínez, S.; Tabernero, I.; COMPOSITESurface finishing of dies and molds is one of the most interesting applications of laser polishing process. Because of the variety of materials used in die and mold manufacturing, as well as the different surface topographies, in each case, it is necessary to use appropriate process parameters. The presented work focuses on the study of laser polishing process on three commonly used materials in the manufacture of dies and molds, such as tool steels AISI D2 and AISI P20, ductile cast iron GGG70L and LaserForm ST-100, a specific material developed for plastic injection mold making. Experimental studies were carried out determining the influence of the energy density on the roughness reduction rate. A key point that has a direct impact on the resulting surface roughness is the initial surface finishing of the material before laser polishing. In order to determine the degree of influence, experimental studies were conducted on two steels, AISI H13 and AISI P20, which are typically used in mold making industry. The experimental tests showed that a random distribution of peaks and valleys allows more homogenous material melting and gives as result a smoother surface after laser polishing.Item Parameter optimization for mould and die recovering using laser cladding(2009) Tabernero, I.; Lamikiz, A.; Ukar, E.; Arregi, B.; Figueras, J.; Soriano, C.; EXTREMATIn the last years the laser cladding has become an important technology that has been studied by several industries as automotive or aeronautical. Therefore, although this technology was used initially for coatings, actually it is being used for repairing or even direct manufacturing of high added value parts. In this paper, the application of laser cladding for repairing a GGG70L stamping die is presented. The first step is to present the methodology used to obtain the optimum conditions for AISI 316L stainless steel clads on structural steel (DIN C45). The next section shows a deeper study about the capacity of the process to fill standard geometries on DIN C45 and DIN 1.2379. Finally, a nodular cast iron GGG70L stamping die is repaired using laser cladding process. The parameters and strategy used for the repairing have been obtained on previous sections. Furthermore, in the final section a powder concentration model is presented as the first step to create a complete model that simulate the three stages of laser cladding: interaction between powder and laser beam, creation of melt pool and generation of clad geometry.Item Parameter study on laser surface finishing with 2D scan head(2012) Ukar, E.; Tabernero, I.; Liebana, F.; Saitua, I.; Villaseca, R.; Sobrado, J.; COMPOSITEIn recent years laser polishing is becoming an alternative for automated surface finishing of dies and molds. This process involves melting and subsequent solidification of the material. Depending on the initial topography, the energy density necessary to reduce surface asperities can cause excessive heat damage, and thus, limit the applicability of the process. The work presented here focuses on the use of a high quality laser beam, with a spot diameter below 50 microns driven by a 2D scanner for processing of materials typically used in dies and mold manufacturing. So, the highly focused beam ensures minimal thermal damage, and the scan head allows high productivity rates. A new processing strategy based on two stages surface processing was developed to process topographies with strong directionality.Item Parameter study on laser surface finishing with 2D scan head(Trans Tech Publications Ltd, 2012) Ukar, E.; Tabernero, I.; Liebana, F.; Saitua, I.; Villaseca, R.; Sobrado, J.; COMPOSITEIn recent years laser polishing is becoming an alternative for automated surface finishing of dies and molds. This process involves melting and subsequent solidification of the material. Depending on the initial topography, the energy density necessary to reduce surface asperities can cause excessive heat damage, and thus, limit the applicability of the process. The work presented here focuses on the use of a high quality laser beam, with a spot diameter below 50 microns driven by a 2D scanner for processing of materials typically used in dies and mold manufacturing. So, the highly focused beam ensures minimal thermal damage, and the scan head allows high productivity rates. A new processing strategy based on two stages surface processing was developed to process topographies with strong directionality.