Using feature-based product modelling to integrate design and rapid prototyping

Rapid prototyping (RP) provides a means of producing physical models directly from computer aided design (CAD) data. The aim of this research was to determine the most effective method of integrating RP into the design process. A review of the links between design and RP was undertaken. This revealed that RP is a technology which can benefit several key areas of engineering design. Many computer tools were identified which supported the designer's use of RP but most of these relied on using CAD geometry alone. Using this incomplete set of design information hindered the integration of RP into the design process. A hypothesis was formulated which stated that a feature-based product modelling methodology was needed to enable RP to become an integrated part of the design process. To demonstrate the validity of the methodology, it was embodied in a design support system (DSS) for rapid prototyping. The DSS requirements were determined through a survey of designers using RP, and a full specification for the system was defined. A demonstration version was implemented using a relational database coupled with a CAD system. The demonstration DSS enabled feature-based geometry and non-geometric information to be integrated within a single product model. An application program was developed which used the product model data to optimise the orientation of an RP model in order to meet the differing surface finish requirements for each feature in a component. This example use of the system illustrated the benefit of using a feature-based product model to optimise the designer's use of RP. Future work needed to improve the DSS to a state where it would be ready for development into a commercial package was identified. Finally, conclusions were drawn as to how all the objectives were met and summarising the original contribution to knowledge made by the research

Using feature-based product modelling to integrate design and rapid prototyping

Rapid prototyping (RP) provides a means of producing physical models directly from computer aided design (CAD) data. The aim of this research was to determine the most effective method of integrating RP into the design process. A review of the links between design and RP was undertaken. This revealed that RP is a technology which can benefit several key areas of engineering design. Many computer tools were identified which supported the designer's use of RP but most of these relied on using CAD geometry alone. Using this incomplete set of design information hindered the integration of RP into the design process. A hypothesis was formulated which stated that a feature-based product modelling methodology was needed to enable RP to become an integrated part of the design process. To demonstrate the validity of the methodology, it was embodied in a design support system (DSS) for rapid prototyping. The DSS requirements were determined through a survey of designers using RP, and a full specification for the system was defined. A demonstration version was implemented using a relational database coupled with a CAD system. The demonstration DSS enabled feature-based geometry and non-geometric information to be integrated within a single product model. An application program was developed which used the product model data to optimise the orientation of an RP model in order to meet the differing surface finish requirements for each feature in a component. This example use of the system illustrated the benefit of using a feature-based product model to optimise the designer's use of RP. Future work needed to improve the DSS to a state where it would be ready for development into a commercial package was identified. Finally, conclusions were drawn as to how all the objectives were met and summarising the original contribution to knowledge made by the research

The investigation of a method to generate conformal lattice structures for additive manufacturing

Additive manufacturing (AM) allows a geometric complexity in products not seen in conventional manufacturing. This geometric freedom facilitates the design and fabrication of conformal hierarchical structures. Entire parts or regions of a part can be populated with lattice structure, designed to exhibit properties that differ from the solid material used in fabrication. Current computer aided design (CAD) software used to design products is not suitable for the generation of lattice structure models. Although conceptually simple, the memory requirements to store a virtual CAD model of a lattice structure are prohibitively high. Conventional CAD software defines geometry through boundary representation (B-rep); shapes are described by the connectivity of faces, edges and vertices. While useful for representing accurate models of complex shape, the sheer quantity of individual surfaces required to represent each of the relatively simple individual struts that comprise a lattice structure ensure that memory limitations are soon reached. Additionally, the conventional data flow from CAD to manufactured part is arduous, involving several conversions between file formats. As well as a lengthy process, each conversion risks the generation of geometric errors that must be fixed before manufacture. A method was developed to specifically generate large arrays of lattice structures, based on a general voxel modelling method identified in the literature review. The method is much less sensitive to geometric complexity than conventional methods and thus facilitates the design of considerably more complex structures. The ability to grade structure designs across regions of a part (termed functional grading ) was also investigated, as well as a method to retain connectivity between boundary struts of a conformal structure. In addition, the method streamlines the data flow from design to manufacture: earlier steps of the data conversion process are bypassed entirely. The effect of the modelling method on surface roughness of parts produced was investigated, as voxel models define boundaries with discrete, stepped blocks. It was concluded that the effect of this stepping on surface roughness was minimal. This thesis concludes with suggestions for further work to improve the efficiency, capability and usability of the conformal structure method developed in this work

New Trends in 3D Printing

A quarter century period of the 3D printing technology development affords ground for speaking about new realities or the formation of a new technological system of digital manufacture and partnership. The up-to-date 3D printing is at the top of its own overrated expectations. So the development of scalable, high-speed methods of the material 3D printing aimed to increase the productivity and operating volume of the 3D printing machines requires new original decisions. It is necessary to study the 3D printing applicability for manufacturing of the materials with multilevel hierarchical functionality on nano-, micro- and meso-scales that can find applications for medical, aerospace and/or automotive industries. Some of the above-mentioned problems and new trends are considered in this book

Study on Parametric Optimization of Fused Deposition Modelling (FDM) Process

Rapid prototyping (RP) is a generic term for a number of technologies that enable fabrication of physical objects directly from CAD data sources. In contrast to classical methods of manufacturing such as milling and forging which are based on subtractive and formative principles espectively, these processes are based on additive principle for part fabrication. The biggest advantage of RP processes is that an entire 3-D (three-dimensional) consolidated assembly can be fabricated in a single setup without any tooling or human intervention; further, the part fabrication methodology is independent of the mplexity of the part geometry. Due to several advantages, RP has attracted the considerable attention of manufacturing industries to meet the customer demands for incorporating continuous and rapid changes in manufacturing in shortest possible time and gain edge over competitors. Out of all commercially available RP processes, fused deposition modelling (FDM) uses heated thermoplastic filament which are extruded from the tip of nozzle in a prescribed manner in a temperature controlled environment for building the part through a layer by layer deposition method. Simplicity of operation together with the ability to fabricate parts with locally controlled properties resulted in its wide spread application not only for prototyping but also for making functional parts. However, FDM process has its own demerits related with accuracy, surface finish, strength etc. Hence, it is absolutely necessary to understand the shortcomings of the process and identify the controllable factors for improvement of part quality. In this direction, present study focuses on the improvement of part build methodology by properly controlling the process parameters. The thesis deals with various part quality measures such as improvement in dimensional accuracy, minimization of surface roughness, and improvement in mechanical properties measured in terms of tensile, compressive, flexural, impact strength and sliding wear. The understanding generated in this work not only explain the complex build mechanism but also present in detail the influence of processing parameters such as layer thickness, orientation, raster angle, raster width and air gap on studied responses with the help of statistically validated models, microphotographs and non-traditional optimization methods. For improving dimensional accuracy of the part, Taguchi‟s experimental design is adopted and it is found that measured dimension is oversized along the thickness direction and undersized along the length, width and diameter of the hole. It is observed that different factors and interactions control the part dimensions along different directions. Shrinkage of semi molten material extruding out from deposition nozzle is the major cause of part dimension reduction. The oversized dimension is attributed to uneven layer surfaces generation and slicing constraints. For recommending optimal factor setting for improving overall dimension of the part, grey Taguchi method is used. Prediction models based on artificial neural network and fuzzy inference principle are also proposed and compared with Taguchi predictive model. The model based on fuzzy inference system shows better prediction capability in comparison to artificial neural network model. In order to minimize the surface roughness, a process improvement strategy through effective control of process parameters based on central composite design (CCD) is employed. Empirical models relating response and process parameters are developed. The validity of the models is established using analysis of variance (ANOVA) and residual analysis. Experimental results indicate that process parameters and their interactions are different for minimization of roughness in different surfaces. The surface roughness responses along three surfaces are combined into a single response known as multi-response performance index (MPI) using principal component analysis. Bacterial foraging optimisation algorithm (BFOA), a latest evolutionary approach, has been adopted to find out best process parameter setting which maximizes MPI. Assessment of process parameters on mechanical properties viz. tensile, flexural, impact and compressive strength of part fabricated using FDM technology is done using CCD. The effect of each process parameter on mechanical property is analyzed. The major reason for weak strength is attributed to distortion within or between the layers. In actual practice, the parts are subjected to various types of loadings and it is necessary that the fabricated part must withhold more than one type of loading simultaneously.To address this issue, all the studied strengths are combined into a single response known as composite desirability and then optimum parameter setting which will maximize composite desirability is determined using quantum behaved particle swarm optimization (QPSO). Resistance to wear is an important consideration for enhancing service life of functional parts. Hence, present work also focuses on extensive study to understand the effect of process parameters on the sliding wear of test specimen. The study not only provides insight into complex dependency of wear on process parameters but also develop a statistically validated predictive equation. The equation can be used by the process planner for accurate wear prediction in practice. Finally, comparative evaluation of two swarm based optimization methods such as QPSO and BFOA are also presented. It is shown that BFOA, because of its biologically motivated structure, has better exploration and exploitation ability but require more time for convergence as compared to QPSO. The methodology adopted in this study is quite general and can be used for other related or allied processes, especially in multi input, multi output systems. The proposed study can be used by industries like aerospace, automobile and medical for identifying the process capability and further improvement in FDM process or developing new processes based on similar principle

Polymers and Their Application in 3D Printing

Dear Colleagues, Fused filament fabrication, also known as 3D printing, is extensively used to produce prototypes for applications in, e.g., the aerospace, medical, and automotive industries. In this process, a thermoplastic polymer is fed into a liquefier that extrudes a filament while moving in successive X–Y planes along the Z direction to fabricate a 3D part in a layer-by-layer process. Due to the progressive advances of this process in industry, the application of polymeric (or even composite) materials have received much attention. Researchers and industries now engage in 3D printing by implementing numerous polymeric materials in their domain. In this Special Issue, we will present a collection of recent and novel works regarding the application of polymers in 3D printing

A Short Review on 4D Printing

Additive Manufacturing can be described as a process to build 3D objects by adding layer-upon-layer of material, the material traditionally being plastics, metals or ceramics, however ‘smart’ materials are now in use. Nowadays, the term “3D Printing” has become a much-used synonym for additive manufacturing. The use of computing, 3D solid modeling applications, layering materials and machine equipment is common to majority of additive manufacturing technologies. Advancing from this 3D printing technology, is an emerging trend for what is being termed “4D printing”. 4D printing places dependency on smart materials, the functionality of additive manufacturing machines and in ingenious design processes. Although many developments have been made, limitations are still very much in existence, particularly with regards to function and application. The objective of this short review is to discuss the developments, challenges and outlook for 4D printing technology. The review revealed that 4D printing technology has application potential but further research work will be vital for the future success of 4D printing

A Guide to Additive Manufacturing

This open access book gives both a theoretical and practical overview of several important aspects of additive manufacturing (AM). It is written in an educative style to enable the reader to understand and apply the material. It begins with an introduction to AM technologies and the general workflow, as well as an overview of the current standards within AM. In the following chapter, a more in-depth description is given of design optimization and simulation for AM in polymers and metals, including practical guidelines for topology optimization and the use of lattice structures. Special attention is also given to the economics of AM and when the technology offers a benefit compared to conventional manufacturing processes. This is followed by a chapter with practical insights into how AM materials and processing parameters are developed for both material extrusion and powder bed fusion. The final chapter describes functionally graded AM in various materials and technologies. Throughout the book, a large number of industrial applications are described to exemplify the benefits of AM

A Guide to Additive Manufacturing

This open access book gives both a theoretical and practical overview of several important aspects of additive manufacturing (AM). It is written in an educative style to enable the reader to understand and apply the material. It begins with an introduction to AM technologies and the general workflow, as well as an overview of the current standards within AM. In the following chapter, a more in-depth description is given of design optimization and simulation for AM in polymers and metals, including practical guidelines for topology optimization and the use of lattice structures. Special attention is also given to the economics of AM and when the technology offers a benefit compared to conventional manufacturing processes. This is followed by a chapter with practical insights into how AM materials and processing parameters are developed for both material extrusion and powder bed fusion. The final chapter describes functionally graded AM in various materials and technologies. Throughout the book, a large number of industrial applications are described to exemplify the benefits of AM

Infrared stereolithography

Tese de doutoramento em Ciência e Engenharia de Polímeros e CompósitosStereolithography is an important rapid prototyping process that creates three-dimensional solid objects in a multi-layer procedure. This technology involves the curing or solidification of a liquid photo or thermo sensitive polymer through the use of an irradiation light source, which supplies the energy needed to induce a chemical reaction, bonding large numbers of small molecules and forming a highly cross-linked polymer. This reaction determines the resin morphology that, in turn, defines the physical, electrical, and mechanical properties of the cured material. The cure reaction is highly exothermic and, the temperature and the reaction rate can vary considerably within the curing material due to polymers low thermal conductivity. The main goal of this thesis is to study the process of microstereolithography by infrared radiation and the corresponding polymeric systems. Thermal effects were used over an appropriated polymeric resin to induce a phase change in the material, known as cure reaction, and consequently to obtain solid shapes or patterns. Cure kinetics was characterised and the effects of resin composition were determined. The knowledge of parameters and material composition influence over the process is of great importance to predict both the final geometry and mechanical properties.A estereolitografia é um importante processo de prototipagem rápida que permite criar objectos sólidos tridimensionais através de um processo camada a camada. Esta tecnologia envolve a cura ou solidificação de uma resina polimérica líquida, termo ou foto sensível através da utilização de uma fonte de irradiação, que fornece a energia necessária para provocar uma reacção química, ligando um grande número de pequenas moléculas e levando à formação de um polímero altamente reticulado. Esta reacção determina a morfologia de resina que, por sua vez, define as propriedades físicas, eléctricas e mecânicas do material curado. A reacção de cura é altamente exotérmica e a temperatura e velocidade da reacção podem variar consideravelmente no interior do material curado devido à baixa condutividade térmica dos polímeros. O objetivo principal deste trabalho é estudar o processo de micro estereolitografia por radiação infravermelha e os sistemas poliméricos correspondentes. Efeitos térmicos foram utilizados sobre uma resina polimérica apropriada para induzir uma mudança de fase no material, conhecido como reacção de cura, e, consequentemente, para obter formas ou padrões sólidos. A cinética da cura foi caracterizada e os efeitos da composição da resina foram determinados. O conhecimento da influência dos parâmetros e da composição do material no processo é de grande importância para prever a geometria final e as propriedades mecânicas