Alberto Boschetto

3D roughness profile model in fused deposition modelling

Purpose – The paper aims to predict the surface roughness of fused deposition modelling prototypes. Since average roughness is not comprehensive, this study aims to extend the characterization to all the roughness parameters obtainable by a profilometric analysis.Design/methodology/approach – A theoretical model of the 3D profile is supplied as a function of process parameters and part shape. A suitable geometry was designed and prototyped for validation. Data were measured by a profilometer and complemented by microscopic analysis. A methodology based on the proposed model was applied to optimise prototype fabrication in two practical cases.Findings – The proposed profile is effective in describing the micro‐geometrical surface of fused deposition modelling prototypes. The third dimension enables the calculation of amplitude, spatial and hybrid roughness parameters.Research limitations/implications – Because of mathematical assumptions and technological aspects, the validity of the model presents limitat...

Surface improvement of fused deposition modeling parts by barrel finishing

Purpose – The purpose of this paper is to study the integration between this technology and barrel finishing (BF) operation to improve part surface quality. Fused deposition modeling (FDM) processes have limitation in term of accuracy and surface finishing. Hence, post-processing operations are needed. A theoretical and experimental investigations have been carried out. Design/methodology/approach – A geometrical model of the profile under the action of machining is proposed. The model takes into account FDM formulation and allows to predict the surface morphology achievable by BF. The MR needed in the model is obtained by a particular profilometer methodology, based on the alignment of Firestone–Abbot (F–A) curves. The experimental performed on a suitable geometry validated geometrical model. Profilometer and dimensional measurements have been used to assess the output of the coupled technologies in terms of surface roughness and accuracy. Findings – The coupling of FDM and BF has been assessed and chara...

Thickening of surfaces for direct additive manufacturing fabrication

Purpose – The purpose of this paper is to propose a new way of prototyping surfaces, taking the mathematical background into account, without involving drawing environments.Design/methodology/approach – The authors thicken surfaces from a mathematical point of view to obtain solids. Next they look for an operative procedure to build virtual models and interchange files. The authors build a sample of Enneper thickened surface by fused deposition modelling and verify the prototype by reverse engineering techniques.Findings – The authors provide a formulation able to thicken surfaces in mathematical terms. An operative procedure generates virtual solids and interchange files in the same environment. The approximations necessary for additive fabrication, such as triangulations and mesh geometry, can be chosen at this stage.Research limitations/implications – The approach is useful at the product/process development stage, in which surfaces are delivered by theoretical analysis. At this stage a prototype can g...

Deburring of Sheet Metal by Barrel Finishing

In sheet metal processes the burrs cannot be completely eliminated during the process but can be minimized by optimization of the process parameters. Hence the deburring often becomes an essential secondary operation. Most of the deburring operations are hand-made and therefore several manufacturers tend to eliminate these tedious and labor-intensive operations due to time and cost issues. Moreover, clamping problems can arise which, together with the deburring forces, can induce dimension alterations and local deformations, particularly for thin sheets. Barrel finishing is an old technique commonly used to improve the surface roughness of complicated parts, but can find interesting applications also in the deburring. Aim of this work is to present an experimental investigation on the deburring of sheet metal performed by barreling. A technological model has been developed in order to assess the height of the burr as a function of the initial burr and of the working time.

Corner Shaping by Barrel Finishing

Corner shaping is a necessary operation in manufacturing of most mechanical components. Edge radiusing is the principal way to reduce stress concentration in components like gear, crank shaft, ball bearing, to permit assembly and disassembly of parts, to avoid local damage and to reduce the possibility of hurting the operators. Often precise values of corner radius are specified in component design. Deterministic operations such as chipping, plastic deformation and non traditional ones such as electro discharge machining, abrasive jet deburring are well established technology. Yet, sometimes, it results not economic or even impossible to perform these operations due to the complicated part geometry, difficulty in part clamping and tool path, large number of parts to be produced. Barrel finishing is technique able to improve the roughness of parts of complicated shape by means of a soft mechanical action over the surface performed by abrasive media. The main features of this technology is that the parts do not need to be fixed. Radiusing is, in turn, a potential application area for barrel finishing which has been investigated in this paper. Experimental tests were conducted on finished specimens with sharp corners in order to achieve information about corner radius evolution as a function of the time for different set parameters. The radius values have been assessed by analyzing the acquired profiles with a proprietary fitting procedure. It has been found a square root relation between radius and working time and, by assessing the influence of single parameter, a radiusing model has been proposed.Copyright

Workpiece and media tracking in barrel finishing

The 2D kinetics of the workpiece during barrel finishing operation is studied. A particle image tracking technique was applied to a transparent thin barrel in order to acquire the position of the part within granular flow in rolling regime. The use of industrial near shape media leads to an intrinsic difficulty to trace the part position. The achieved trajectories permit to calculate the active working time, part density distribution, the media velocity gradient and the workpiece to media velocity gradient. These information are useful to calculate the total sliding and to get information about strain stress over part in order to investigate operation efficiency.

Comparison Through Image Analysis Between Al Foams Produced Using Two Different Methods

Several methods are available for making metal foams. They allow to tailor their mechanical, thermal, acoustic, and electrical properties for specific applications by varying the relative density as well as the cell size and morphology. Foams have a very heterogeneous structure so that their properties may show a large scatter. In this paper, an aluminum foam produced by means of foaming of powder compacts and another one prepared via the infiltration process were analyzed and compared. Image analysis has been used as a useful tool to determine size, morphology, and distribution of cells in both foams and to correlate cell morphology with the considered manufacturing process. The results highlighted that cell size and morphology are strictly dependent upon the manufacturing method. This paper shows how some standard 2D morphological indicators may be usefully adopted to characterize foams whose structure derives from the specific manufacturing process.

Investigation via morphological analysis of aluminium foams produced by replication casting

Foams and porous materials with cellular structure have many interesting combinations of physical and mechanical properties coupled with low specific weight. By means of replication casting it is possible to manufacture foams from molten metal without direct foaming. A soluble salt is used as space holder, which is removed by leaching in water. This can be done successfully if the content of space holding fillers is so high that all the granules are interconnected. One of the main advantages of using the replication casting is a close control of pore sizes which is given by the distribution of particle sizes of the filler material. This contrasts with the pore size distribution of the materials foamed by other processes where a wider statistical distribution of pores is found. On the other hand, the maximum porosities that can be achieved using space holders are limited to values below 60%, whereas the other methods allow for porosities up to 98%. Temperature of the mould and infiltration pressure are critical process parameters: a typical problem encountered is the premature solidification of the melt, especially due to the high heat capacity of the salt. In this work foam properties such as cell shape, distribution and anisotropy and defect presence are investigated by using digital image processing technique. For this purpose replicated AlSi7Mg0.3 alloy foams are produced by infiltrating preforms of NaCl particles, varying the metal infiltration pressure and the mould preheating temperature. An original procedure based on image analysis has been set up to determine size, morphology and distribution of cells. The paper demonstrates that this methodology, coupled with microstructural analysis, is a useful tool for investigating the effects of process parameters on foam properties.

Design of a process for image improvement in digital cytology: a preliminary technology assessement

The work is focused on digital cytology, in particular on the introduction of the e-slides in the e-laboratory of cytology. The study has faced the problem of image-improvement in digital cytology, starting from the settling up of a significant application of digital cytology through the WEB up to the research and application of a suitable software environment. Thirty-eight snapshots have been selected from six e-slides relevant to cervico-vaginal cytology positioned at a web server. The software Mathematica has been selected due to its own characteristics and has been successfully used in a proposed process of image improvement applied on the snapshots with particular attention to (a) the focus emulation; (b) the visibility enhancement and (c) the feature recognition. The proposed methodology has been successfully investigated. It could be useful in tele-consulting, e-learning, in cooperative diagnosis and in the applications of image quality improvements. Furthermore, the methodology could be also usefu...

The focus emulation and image enhancement in digital cytology: an experience using the software Mathematica

The digital pathology is an image-based information environment enabled by computer technology that allows for the management of information generated from an e-slide. It embeds both the field of the digital cytology (D-CYT) and of the digital histology (D-HYST). When coming to D-CYT, basic problems due to the need of the technology emulate the focus function. This leads to an increase in the memory occupancy because a sample must be scanned with different levels of view, the so-called Z-stack. The study focuses on this basic problem in D-CYT. Eighteen snapshots have been selected from three cervico-vaginal e-slides. A table has been compiled with the information of the snapshots by means of coordinates, description of characteristics and objectives. The Mathematica software has been successfully used to improve the diagnostic content of the snapshots with particular attention to the emulation of the focus. The methodology could be useful in tele-consulting and in cooperative diagnosis because it could contemporarily allow the improvement of the diagnostic power combined with a decrease in the memory occupancy of exchanged snapshots.