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Article
Publication date: 26 October 2018

Luca G. Campana, Paolo Di Barba, Fabrizio Dughiero, Michele Forzan, Maria Evelina Mognaschi, Rudy Rizzo and Elisabetta Sieni

In electrochemotherapy, flexible electrodes, composed by an array of needles, are applied to human tissues to treat large surface tumors. The positioning of the needles in…

Abstract

Purpose

In electrochemotherapy, flexible electrodes, composed by an array of needles, are applied to human tissues to treat large surface tumors. The positioning of the needles in the tissue depends on the surface curvature. The parallel needle case is preferred, as their relative inclinations strongly affect the actual distribution of electric field. Nevertheless, in some case, small inclinations are unavoidable. The purpose of this paper is to study the electric field distribution for non-parallel needles.

Design/methodology/approach

The effect of electrode position is evaluated systematically by means of numerical models and experiments on phantoms for two different angles (5° and 30°) and compared with the case of parallel needles. Potato model was used as phantom, as this tissue becomes dark after few hours from electroporation. The electroporation degree was gauged from the color changings on the potatoes.

Findings

The distribution of electric field in different needle configuration is found by means of finite element analysis (FEA) and experiments on potatoes. The electric field level of inclined needles was compared with parallel needle case. In particular, the electric field distribution in the case of inclined needles could be very different with respect to the one in the case of parallel needles. The degree of enhancement for different inclinations is visualized by potato color intensity. The FEA suggested that the needle parallelism has to be maintained as possible as if the tips are closer to each other, the electric field intensity could be different with respect to the one in the case of parallel needles.

Originality/value

This paper analyzes the effect of inclined electrodes considering also the non-linearity of tissues.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 38 no. 1
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 16 June 2021

Mattia Mele, Giampaolo Campana and Gian Luca Monti

The amount of radiated energy is known to be a crucial parameter in powder-bed additive manufacturing (AM) processes. The role of irradiance in the multijet fusion (MJF…

Abstract

Purpose

The amount of radiated energy is known to be a crucial parameter in powder-bed additive manufacturing (AM) processes. The role of irradiance in the multijet fusion (MJF) process has not been addressed by any previous research, despite the key role of this process in the AM industry. The aim of this paper is to explore the relationship between irradiance and dimensional accuracy in MJF.

Design/methodology/approach

An experimental activity was carried out to map the relationship between irradiance and dimensional accuracy in the MJF transformation of polyamide 12. Two specimens were used to measure the dimensional accuracy on medium and small sizes. The experiment was run using six different levels of irradiance. For each, the crystallinity degree and part density were measured.

Findings

Irradiance was found to be directly proportional to part density and inversely proportional to crystallinity degree. Higher irradiance leads to an increase in the measured dimensions of parts. This highlights a predominant role of the crystallisation degree and uncontrolled peripherical sintering, in line with the previous literature on other powder-bed AM processes. The results demonstrate that different trends can be observed according to the range of sizes.

Details

Rapid Prototyping Journal, vol. 27 no. 6
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 19 November 2020

Mattia Mele, Giampaolo Campana and Gian Luca Monti

Multi-jet fusion (MJF) process is based on a polymeric powder bed that is heated and irradiated by infra-red lamps. The layer under construction is jetted with inks to…

Abstract

Purpose

Multi-jet fusion (MJF) process is based on a polymeric powder bed that is heated and irradiated by infra-red lamps. The layer under construction is jetted with inks to provide the desired heat management conditions for selective melting. Depending on several process variables, manufactured parts can exhibit lifting of the borders of the top surface of the shape under construction. This phenomenon is related to the capillarity effect. As a result, the top surface of MJF-manufactured parts can present a peculiar convex shape. This study aims to propose a solution that instead induces the capillarity effect outside of the part under construction.

Design/methodology/approach

A specific design is developed to avoid the capillarity effect in MJF. It is based on an analytical model that was previously developed by the authors to estimate the shape and extent of the capillary on top surfaces of benchmark components. The proposed methodology is established by the predicted calculation of maximum values of capillarity rise and length, and safety factors. A fin-shaped geometry is designed to avoid the capillarity effect. An experimental campaign is implemented to verify the effectiveness of the proposed solution. Prototypes are manufactured by an HP MultiJet 4200 in the original design and the so-called finned-riser design, by adding a well-dimensioned appendage on the top surface to shift the capillarity effect outside the border of the part under construction. Measurements are done by a CAM2 ScanArm contactless measuring system to achieve the real shape of top surfaces. Geomagic Control X software by 3D systems is used to evaluate the quality of measured surfaces in comparison with the expected geometry of the top plane of the benchmark.

Findings

The investigated approach involves adding an auxiliary finned-shape appendage, which acts similarly to the risers in foundry technology, to the top surface of the part that is being produced by MJF technology. The procedure and rules for determining the dimensions of the fin are established based on physical considerations and process modelling. The method is then applied to a prototype part, which is designed to highlight the effectiveness of the finned-riser design for improving the dimensional accuracy of the top surfaces of products manufactured by the MJF process. Experimental measurements of top surfaces of the original benchmark are compared to the same ones in the case of the finned-riser benchmark. Reported results are satisfactory, and the capillary effect occurred in the fins outside the border edges of the part. Further developments are planned to extend the proposed design.

Originality/value

MJF technology is attracting large interest from manufacturers to produce mass customised products. The quality of manufactured parts could be affected by peculiar defects related to process parameters. The present work aims to show a method to avoid the capillarity effect. It is based on an original analytical model developed by the authors and implemented successfully in the case of a benchmark geometry.

Details

Rapid Prototyping Journal, vol. 27 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 8 September 2021

Giampaolo Campana, Eckart Uhlmann, Mattia Mele, Luca Raffaelli, André Bergmann, Jaroslaw Kochan and Julian Polte

Support structures used in laser powder bed fusion are often difficult to clean from unsintered powder at the end of the process. This issue can be significantly reduced…

Abstract

Purpose

Support structures used in laser powder bed fusion are often difficult to clean from unsintered powder at the end of the process. This issue can be significantly reduced through a proper design of these auxiliary structures. This paper aims to investigate preliminary the airflow within differently oriented support structures and to provide design guidelines to enhance their cleanability, especially the depowdering of them.

Design/methodology/approach

This study investigates the cleanability of support structures in powder bed fusion technology. Digital models of cleaning operations were designed through computer-aided engineering systems. Simulations of the airflow running into the powder entrapped within the thin walls of auxiliary supports were implemented by computational fluid dynamics. This approach was applied to a set of randomly generated geometrical configurations to determine the air turbulence intensity depending on their design.

Findings

The results, which are based on the assumption that a relationship exists between turbulence and powder removal effectiveness, demonstrated that the maximum cleanability is obtainable through specific relative rotations between consecutive support structures. Furthermore, it was possible to highlight the considerable influence of the auxiliary structures next to the fluid inlet. These relevant findings establish optimal design rules for the cleanability of parts manufactured by powder bed fusion processes.

Originality/value

This study presents a preliminary investigation into the cleanability of support structures in laser powder bed fusion, which has not been addressed by previous literature. The results allow for a better understanding of the fluid dynamics during cleaning operations. New guidelines to enhance the cleanability of support structures are provided based on the results of simulations.

Details

Rapid Prototyping Journal, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 13 October 2020

Mattia Mele, Giampaolo Campana, Gregorio Pisaneschi and Gian Luca Monti

Multi jet fusion is an industrial additive manufacturing technology characterised by high building speed and considerable properties of the parts. The cooling phase…

Abstract

Purpose

Multi jet fusion is an industrial additive manufacturing technology characterised by high building speed and considerable properties of the parts. The cooling phase represents a crucial step to determine productivity, since it can take up to 4.5 times the building time. The purpose of this paper is to investigate into effects of cooling rate on parts manufactured by multi jet fusion. Crystallinity, density, distortions and mechanical properties of specimens produced through an HP multi jet fusion 4200 are examined.

Design/methodology/approach

An experimental activity is carried out on specimens cooled down at three different rates. Properties of the parts are analysed by means of differential scanning calorimetry, optical microscopy, three-dimensional scanning and tensile testing.

Originality/value

The present work makes a contribution to the body of knowledge providing correlations between the cooling phase of multi jet fusion and part properties. These results can be used to choose the right balance between production time and product quality.

Details

Rapid Prototyping Journal, vol. 26 no. 10
Type: Research Article
ISSN: 1355-2546

Keywords

Abstract

Details

Business Process Management Journal, vol. 25 no. 1
Type: Research Article
ISSN: 1463-7154

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Article
Publication date: 23 May 2008

Fiorenzo Franceschini, Maurizio Galetto, Luca Mastrogiacomo and Luciano Viticchiè

ISO 9000 and ISO 14000 standards certification is a phenomenon involving over the years a larger and larger number of companies and organizations. Looking at the empirical…

Abstract

Purpose

ISO 9000 and ISO 14000 standards certification is a phenomenon involving over the years a larger and larger number of companies and organizations. Looking at the empirical data, it is observed that the phenomenon is close to saturation in many countries. In Italy, on the other hand, there is an important increase in the number of certifications. The purpose of this paper is to pick out the different components and aspects which make Italian dynamics so particular.

Design/methodology/approach

In order to do that the single commodity sector was analyzed, studying certifications diffusion in terms of certified sites. With the aim of specializing the analysis within commodity sectors, this information has been compared with the Gross Domestic Product (GDP) percentage expressed by each sector.

Finding

The analysis shows that ISO certifications diffusion followed different dynamics depending on the commodity sectors. These reacted in different ways to the discontinuity of 2003, the year in which ISO 9000 standards changed from the 1994 to the 2000 version.

Research limitations/implications

Future research efforts will be directed at an in‐depth analysis of the differences between ISO 9000 and ISO 14000 certified and analogous non‐certified firms. This analysis will be performed using performance indices such as the number of employees, the profitability, the volume of business, etc.

Originality/value

The paper analyzes the dynamic of ISO 9000 and ISO 14000 certification diffusion in Italy in different commodity sectors. The term of comparison is given by the contribution given by each sector to the GDP.

Details

International Journal of Quality & Reliability Management, vol. 25 no. 5
Type: Research Article
ISSN: 0265-671X

Keywords

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