ORIGINAL ARTICLE Modelling micro geometrical profiles in fused deposition process A. Boschetto & V. Giordano & F. Veniali Received: 27 July 2011 /Accepted: 3 November 2011 /Published online: 19 November 2011 # Springer-Verlag London Limited 2011 Abstract Fused deposition modelling is an established additive manufacturing technique for creating function- al prototypes from three-dimensional computer-aided design models. Despite of the potential advantages of this technology, surface roughness is a substantial problem and some attempts have been made to predict the average roughness R a . As well known, the surface quality characterization of a part is not limited to R a but involves many other roughness parameters. The knowl- edge in advance of these parameters is a critical point especially in the product design stage both for rapid prototyping purpose and finished part manufacturing. In this work, a novel approach aimed to the geometrical description of roughness profile is reported. By means of an analytic formulation it is possible to calculate custom set of roughness parameters. An experimental analysis, based on design of experiments technique, is carried out to investigate the effects of several factors on shape profile. The achieved results permit to define the domain in which the presented model depends only on two parameters. A profilometric analysis has been performed on specimens properly designed to validate the method. Statistical tests show a good accordance with predicted 1 Introduction Rapid prototyping (RP) is a host of several technologies fabricating 3D solid models, from virtual data, without geometric restrictions. It emerged as a support, in concep- tualization stage, to realise complex shape parts without the use of specific tools, in a relatively fast way and with minimum human intervention [1]. In the last two decades the technology progressed from being a system to build prototypes in the product/design stages, to a constructive method for finished products. For this reason it is correct to refer to most of the RP systems as additive manufacturing (AM), a technology employed to produce shaped parts by stacking and bonding 2D layers in a given direction [2]. Fused deposition modelling (FDM) has grown to one of the most popular AM process. From 1996, applying new patented two-axis high-speed motion control systems, building speed increased by up to 500% [3]. FDM, developed by Stratasys, fabricates layer by layer components by applying acrylonitrile butadiene styrene (ABS) in filament form. The virtual model, converted in a Standard Triangulation Language (STL) format and oppor- tunely oriented [2], is sliced. After the toolpath creation, the plastic filament is fed from a coil into an extrusion head where it is heated and extruded through a small nozzle onto a base plate which lowers by the single layer thickness. Because overhanging features need to be braced, some support material is fed by another extrusion head and then removed in post processing operations. Both the base plate and the chamber, in which the process system is contained, are maintained at constant temperature, above the glass transition temperature of the ABS, so that the stresses relax and thermoplastic resin immediately solidifies by natural cooling after deposition, bonding to the underlying layer. A. Boschetto : V. Giordano (*) : F. Veniali Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, 00184 Roma, Italy e-mail: Veronica.Giordano@uniroma1.it Int J Adv Manuf Technol (2012) 61:945–956 DOI 10.1007/s00170-011-3744-1 values for the made assumptions and the calculated roughness parameters. Keywords Rapid prototyping . Additive manufacturing . Fused deposition modelling . Surface roughness . Profile model