Line bending of Al 2 O 3 coated and uncoated aluminium thin sheets M. Barletta ⁎ , L. Casamichele, V. Tagliaferri University of Rome “Tor Vergata”, Department of Mechanical Engineering, Via del Politecnico, 1-00133 Rome, Italy Received 24 May 2005; accepted in revised form 12 December 2005 Available online 27 January 2006 Abstract A novel ‘hybrid’ forming process, consisting of a fluidized bed (FB) pre-treatment to coat with Al 2 O 3 and pre-curve aluminium thin sheets and of a diode laser forming to perform the proper line bending of FB pre-treated sheets, is defined and investigated in this paper. A comparison with the diode laser forming of untreated aluminium thin sheets is also carried out. An experimental investigation is performed varying, in the laser forming process, output power, scan speed and number of passes and, in the ‘hybrid’ process, besides the laser parameters, even the treatment time in the FB system. Consistent trends of bending angles according to laser operative parameters are achieved for both the forming processes. A significant saving of laser power necessary to form the specimens, an increase in maximum angles achievable as well as an improvement of aesthetic aspect of the final products characterize the ‘hybrid’ forming process, if compared with the laser forming process. As a result of dissimilar forming technologies, completely different bending mechanisms are highlighted, with the ‘hybrid’ forming giving rise to an unexpected inversion in bending direction. Finally, the opportunity for further applications of the ‘hybrid’ technology is also discussed, stating the basis for a wider industrial diffusion of the non-conventional forming technologies even for the manufacturing of basic commodities. © 2005 Elsevier B.V. All rights reserved. Keywords: Fluidized bed; Al 2 O 3 coating; Hybrid forming; Diode laser 1. Introduction Stiff market competition and continuously growing demand for improved product performance have led to the development of an ever-growing variety and quality of conventional (based upon traditional [1] and non-traditional mechanical systems [2– 4]) and unconventional (based upon ‘free contact’ systems [5,6]) shaping technologies. Mechanical forming of two- and three-dimensional shape can be relatively fast. It generally produces large deformations in a single or in a few of process steps [7,8], but it is often inaccurate due to variable ‘spring-back’ [7] and tool wear [8]. Unconventional shaping methods often result in high time and cost consuming procedures [9], which can also cause the degradation of strength [10] and several useful functional [11] and aesthetic properties of the processed parts [12]. Therefore, a real need to develop processes capable of providing adequate shaping rate, high shaping accuracy as well as minimum damage to the material properties does still exist. In addition to the above requirements, complexity of work surface shape and size, surface integrity, precision and miniaturization (i.e. micro- or nano-shaping) demands also play a vital role in forming technologies pushing towards the development of novel advanced shaping processes and strategies. In this context, a growing interest towards those shaping techniques able to gather the advantages of both conventional and unconventional shaping techniques has been arisen. Actually, such kind of processes do already exist [13,14] and are called ‘hybrid’ forming process as they use a combination of both contact and non-contact shaping techniques. Among such processes, a certain interest is paid upon those which make use of mechanical tools to produce a line bending and spatial forming of workpieces and of non-contact techniques, generally based upon a laser beam as energetic source, just to perform subsequent alignment operations or small regulations. Surface & Coatings Technology 201 (2006) 660 – 673 www.elsevier.com/locate/surfcoat ⁎ Corresponding author. E-mail address: barletta@mail.mec.uniroma2.it (M. Barletta). 0257-8972/$ - see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2005.12.013