Additive manufacturing

Reverse Engineering and Rapid Prototyping are consolidated practices in the industrial product design process. In any case, best practices should be set up according to the type of product and of objectives. This paper presents the results of a product re-engineering application in the field of high quality stainless steel cutlery. This activity included a re-modeling of a basis-shape that reproduces at best the original shape of a cutlery set designed in the Thirties for Alessi, which is still considered to be very fashionable. The shape of the manufactured physical pieces of cutlery has changed in time in respect to the original design, mainly because of some problems related to their manufacturing, which has been transferred from the central plant to other branches. We have obtained the digital model of the pieces of cutlery on the basis of the analysis of the available original 2D drawings, and of the laser scanning and subsequent re-engineering design of the available manufactured objects. Particularly complex activity was the removal of the shapes deviations due to the different forming techniques used in the various production factories. At the end of the reconstruction activity, physical prototypes of the new models were produced by means of a sintering process in order to evaluate and compare them to the original ones. © The Eurographics Association 2007.

The work presented in this paper is focused on the finite element modelling (FEM) of the failure behaviour of lattice composite hollow structures that have been subjected to an external hydrostatic pressure. Furthermore, the development of an experimental procedure to measure the aforementioned resistance, and to test the FEM model is also presented. Carbon fibres composite hollow cylinders with a lattice structure and with different geometries were produced and tested. In order to develop a design tools for such structures, all the experiments performed were computer simulated using finite element modelling. The results obtained with FEM simulation provide further insight to analyze and investigate the failure mechanism. The elastic instability of the studied structures was therefore analyzed and the influence of element geometry on the collapsing resistance thereof was considered. As a result of the study it has been possible to locate three different failure modes which where strictly related to the length of the cylinders. Both the shape of the broken tube and the lever of failure stresses were correctly predicted by the FEM model. © 2005 Elsevier Ltd. All rights reserved.

Keywords: Buckling analysis , Composite tubes , FEM modelling , Lattice structures

Product design and optimisation today involves so many fields of expertise, many of which are in rapid evolution, that it can be very difficult for the designer to manage them. This paper describes the development of the DGLs (Design Guidelines), a knowledge-based tool that could be of great help to designers and engineers in modifying their products to get compatibility with different manufacturing and verification technologies. The current release of the DGLs, heavily influenced by the adoption of some ISO-GPS (Geometrical Product Specification) concepts, has been validated using the Rapid Prototyping technique called FDM (Fluid Deposition Modelling) and the CMM (Coordinate Measuring Machine) verification technique. © Springer-Verlag London Limited 2007.

Keywords: Design Guidelines , Geometrical Products Specifications (GPS) , ISO Technical Committee 213 (ISO/TC 213) , Knowledge based systems (KBS) , Rapid Prototyping

Repairing severe human skull injuries requires customized cranial implants. Trauma, cranial tumors, infected craniotomy bone flaps and neurosurgical external decompression are the main causes for large cranial defects. The success of the reconstructive cranial surgery depends on diverse aspects regarding the preoperative evaluation of the defect, the design and manufacturing of the implant and the execution of the operation. Currently, the design of membranes is mainly a manual work, even with the use of CAD facilities, and results in a time-consuming and user-dependent skull reconstruction. This paper presents an automated design methodology for custom-made cranioplasty plates in a PHANToM®-based haptic environment and the possibility to manufacture the same using Solid Freeform Fabrication technologies.

Keywords: Custom-made cranial plates , Haptic environment , PHANToM®-based tools , Solid freeform fabrication

The paper presents an innovative approach totally based on digital data to optimize lower limb socket prosthesis design. This approach is based on a stump's detailed geometric model and provides a substitute to plaster cast obtained through the traditional manual methodology with a physical model, realized with Rapid Prototyping technologies; this physical model will be used for the socket lamination. The paper discusses a methodology to reconstruct a 3D geometric model of the stump able to describe with high accuracy and detail the complete structure subdivided into bones, soft tissues, muscular masses and dermis. Some different technologies are used for stump acquisition: non contact laser technique for external geometry, CT and MRI imaging technologies for the internal structure, the first one dedicated to bones geometrical model, the last for soft tissues and muscles. We discuss problems related to 3D geometric reconstruction: the patient and stump positioning for the different acquisitions, markers' definition on the stump to identify landmarks, alignment's strategies for the different digital models, in order to define a protocol procedure with a requested accuracy for socket's realization. Some case-studies illustrate the methodology and the results obtained. © 2006 SPIE-IS&T.

Keywords: 3D geometrical model , Human body scanning , Lower limb prosthesis , Medical imaging , Rapid prototyping , Reverse engineering

Considering the whole product life-cycle, product model is usually defined during the design phase, given a set of requirements and constraints belonging to the same domain. The use of different manufacturing and verification technologies may, however, profoundly affect the characteristics of the product, so that a re-design phase is often necessary. In previous work, a Knowledge Based System named Design GuideLines (DGLs) was developed, aiming to help the designers make the product model compatible with the requirements and constraints of the specific manufacturing and verification domains. During the DGLs development, the possibility emerged to exploit them in order to identify possible relations among product features. This aspect seems very important, further helping the designer to better understand the consequences of the modifications suggested by the DGLs and applied to the product model during the re-design phase. The present work aims to identify these relations among product features. The result of DGLs exploitation has been critically analyzed to highlight the link between manufacturing characteristics and product features, and, further, among features themselves. Unpredictable relations among the product features, given a particular Rapid Prototyping technology as manufacturing technology, have been discovered and exploited. Copyright " 2006 by ASME.

Keywords: Fluid deposition modeling , Knowledge based systems , Process parameters , Product features , Rapid prototyping

The aim of this study is to apply and validate a general-purpose working methodology, derived from the analysis of processes which come from two different domains (the field of medicine and the preservation of cultural heritage), in the investment casting process. CSCW methods and tools have proven to be the best 'gluing tool to bond the different activities, and thus heavily exploited during the customization of the general-purpose working methodology. This paper describes a case study performed in an industrial sector and related to the investment casting application field. It was chosen to test methodology and to demonstrate its wide applicability. The case study involved the realization of a centrifugal pump impeller, where the application of this CSCW-based methodology has delivered important results such as the reduction of product development time and the drastic reduction of production costs.

Keywords: CSCW , IDEF modelling , Rapid prototyping , Virtual team-working

The paradigm of Mass Customisation (MC) is today fundamental for the European fashion industry. Footwear industry is still labour intensive and companies need solution to reduce costs and remain competitive in the global market. In particular, specialized companies that produce customized medical shoes prescribed for people with feet malformations deal with small batches or unique pairs. This work presents some approaches and low-cost solutions related to foot measurement and CAD data elaboration for facilitating the diffusion of "made-to-measure" products. An integrated process made of hardware devices and customized software is explored and described aiming to increase production efficiency and reduce costs.

Keywords: 3D design tools , 3D foot measurement , Mass customization , Personalised shoes

In a Design For Manufacturing context, Rapid Prototyping techniques are some way still considered as “new technologies”: the peculiar characteristics of the manufacturing processes are not widely known and may deeply affect the final product functionality. A Knowledge Based System, the Design Guidelines — DGLs, was developed by our Research Group at the University of Udine; it evaluated the products design, in order to verify its feasibility by DMLS (Direct Metal Laser Sintering) Rapid Prototyping technique. During the evaluation process, the DGLs also keep into consideration the aspects relating the verification step, according to the ISO-GPS principles, thus enhancing the completeness of the tool. Aim of this work was to customise the DGLs for design optimisation in FDM (Fused Deposition Modelling), also evidencing the critical aspects and proposing alternative solutions. The contents and structure of the customised version of DGLs are presented in this work.

Keywords: Fused deposition modelling , Knowledge-based systems , Rapid prototyping

The purpose of the present work was to develop a tool for preoperatively planning the Total Hip Replacement (THR). Starting from the MR images, the 3D surface model of both the pelvis and the femur was built and the surgical operation was virtually performed. Data coming from gait analysis were added to visualize the physiologic movement of the hip joint. The resulting triangular mesh was sufficiently accurate to allow the building of the stereolithographic model of the joint by means of rapid prototyping technique. The plastic bones allow the user to have an enhanced vision of the surgical procedure to be performed. © 2005 CARS and Elsevier B.V.

Keywords: Magnetic resonance imaging , Rapid prototyping , Surgical planning , Total hip replacement

The three-dimensional printing technology (3DP™) is a rapid prototyping process in which powdered material is deposited in layers and selectively joined with binder. The most common deposition method used in this rapid prototyping approach is the drop on demand. However, continuous jet deposition results in an order of magnitude increase in printing speed and that it is gaining popularity. A key component of a continuous deposition printhead is the catcher, which collects droplets that are not meant to hit the powder bed. Current catching systems face problems such as trapped air, and crystallisation that result in unwanted droplets hitting the powder bed. This work looks at redesigning the catcher, and addresses new control algorithms required for proper binder deposition. A mathematical model for binder flight trajectory is developed and validated by experiment. © 2004 Elsevier B.V. All rights reserved.

Keywords: Process simulation , Rapid prototyping , Three-dimensional printing

This article presents the use of stereolithography in oral implantology. Stereolithography is a new technology that can produce physical models by selectively solidifying an ultraviolet-sensitive liquid resin using a laser beam, reproducing the true maxillary and mandibular anatomic dimensions. With these models, it is possible to fabricate surgical guides that can place the implants in vivo in the same places and same directions as those in the planned computer simulation. A 70-year-old woman, in good health, with severe mandibular bone atrophy was rehabilitated with an overdenture supported by 2 Branemark implants. Two different surgical planning methods were considered: 1) the construction of a surgical guide evaluating clinical aspects, and 2) the surgical guide produced by stereolithographic study. The accuracy of surgical planning can reduce the problems related to bone density and dimensions. Furthermore, the stereolithographic study assured the clinicians of a superior location of fixtures in bone. Surgical planning based on stereolithographic technique is a safe procedure and has many advantages. This technologic advance has biologic and therapeutic benefits because it simplifies anatomic surgical management for improved implant placement. Copyright © 2004 by Lippincott Williams & Wilkins.

Keywords: Anatomic models , Jaw atrophy , Rapid prototyping , Surgical planning

Objectives: To create and to spread a new interactive multimedia instrument, based upon virtual reality technologies, that allows both the running simulation of machines and equipment and the reproduction via Web of complex three-dimensional (3D) anatomical models such as the skull. Methods: There were two main aspects of the project, one of design engineering and the other biomedical engineering, for the creation of "artificial" and anatomical objects. The former were made with 3D Studio Max R4 by Autodesk, San Rafael, CA, while the latter were created starting from real bones scanned with a CT system or a surface scanner and elaborated with different programs (3D Studio Max R4, Scenebuilder by Viewpoint, New York, NY and Spinfire by Actify, San Francisco, CA). The 3D models were to be integrated into web modules and had to respect file limits while preserving a sufficient definition. Two systems of evaluation were used, a questionnaire on a selected sample and an external evaluation by a different university. Results: The Viewpoint format offers the best interactivity and size reduction (up to 96% from the original 3D model). The created modules included production of radiological images, rapid prototyping, and anatomy. The complete "3D Distant Learning Prototype" is available at www.webd.etsii.upm.es. Conclusions: The software currently available permits the construction of interactive modules. The verification on the selected sample and the evaluation by the University of Naples show that the structure is well organized and that the integration of the 3D models meets the requirements.

Keywords: Distant learning , Rapid prototyping , Web 3D

A method to find optimal topology and shape of structures is presented. With the first the optimal distribution of an assigned mass is found using an approach based on homogenisation theory, that seeks in which elements of a meshed domain it is present mass; with the second the discontinuous boundaries are smoothed. The problem of the optimal topology search has an ON/OFF nature and has suggested the employment of genetic algorithms. Thus in this paper a genetic algorithm has been developed, which uses as design variables, in the topology optimisation, the relative densities (with respect to effective material density) 0 or 1 of each element of the structure and, in the shape one, the coordinates of the keypoints of changeable boundaries constituted by curves. In both the steps the aim is that to find the variable sets producing the maximum stiffness of the structure, respecting an upper limit on the employed mass. The structural evaluations are carried out with a FEM commercial code, linked to the algorithm. Some applications have been performed and results compared with solutions reported in literature. © 2003 Elsevier Science Ltd. All rights reserved.

Keywords: Genetic algorithms , Shape optimisation , Topology optimisation

When considering the use of rapid prototyping (RP), there are many questions a designer might ask. One such question is "what build orientation should be used to minimise the adverse effects of surface roughness?" At present, this decision is often made in an intuitive way or sometimes overlooked completely. This paper describes a methodology and software implementation that provides the designer with a computer graphics based visualisation of RP model surface roughness. This enables the build orientation to be determined as a result of increased designer knowledge. The surface roughness values were obtained through an extensive empirical investigation of several RP techniques. These are used as the database for a visualisation algorithm that represents varying surface roughness of the RP model as colour shading within a CAD image. The nature of the empirical measurements is analysed and the functionality of the software algorithm is described. Examples are given that demonstrate the use and benefits of the methodology. Finally, conclusions are drawn as to the significance of the work and future research directions are outlined. © 2002 Elsevier Science Ltd. All rights reserved.

Keywords: Material deposition , Rapid prototyping , Rapid technologies , Roughness visualisation , Surface roughness measurements

Within our approach we apply feature-based models and techniques, realized within typed attributed entity (TAE) structures. In particular, we are interested in the handling of additional fabrication relevant form structures and the automatic determination of fabrication parameters. To verify developed methodologies and to demonstrate the applicability of our taken approach, several selected parts, taken from precision machinery engineering and aerospace engineering were modeled and processed.

Due to life cycles of artifacts, which become shorter, rapid prototyping development and tight feedback among product requirements, design, and manufacturing are gaining increasing importance. Classical rapid prototyping technologies such as computer-numerically-controlled (CNC) machinery, which remain still time consuming and expensive, are getting superseded by a growing propensity to apply new solid freeform fabrication (SFF) technologies, which became commercially available since 1987. Although, being on the market for only less than a decade, remarkable progress in various directions such as accuracy, used materials, through-put, and equipment costs, has been achieved in SFF technologies. However, there are still several technological as well as methodological problems left. Within given scope, we would like to tackle some, taken from the methodological field, which seems still weakly developed compared to existing technology. Within our approach we apply feature-based models and techniques, realized within typed attributed entity (TAE) structures. In particular, we are interested in the handling of additional fabrication relevant form structures and the automatic determination of fabrication parameters. To verify developed methodologies and to demonstrate the applicability of our taken approach, several selected parts, taken from precision machinery engineering and aerospace engineering were modeled and processed. An implemented prototype environment and a stereolithography apparatus (SLA) were used for integrated knowledge handling, computation and SFF fabrication.