A review of synthesis methods for additive manufacturing

With the design freedoms afforded by additive manufacturing (AM) processes, an increasing interest in shape synthesis methods has led to a variety of advances in topology optimisation methods and associated synthesis technologies. In this paper, we identify research issues related to the application of AM to shape synthesis methods, review recent advances in topology optimisation, and outline a vision for future synthesis capabilities.     

Rapid additive manufacturing of functionally graded structures using simultaneous wire and powder laser deposition

Laser additive fabrication allows the manufacturing of functionally graded structures that are not possible using conventional subtractive manufacturing. Laser deposition of injected powders with varying compositions, layer-by-layer, is often used for the building up of functionally graded fully dense structures or materials. This approach, however, has some drawbacks: the un-used powders (normally 60-80%) cannot be recycled as they will be contaminated by the powder mixture. In addition, multiple passes are needed to develop functionally graded structures. This paper reports the feasibility and characteristics of using simultaneous powder and wire feeding laser deposition to produce functionally graded structures in a single step. This approach has been shown to eliminate the above problems associated with powder feed laser deposition. In this work, copper powder and nickel wire have been used to deposit functionally grated copper/nickel/iron structures on H13 tool steel. A 1.5-kW diode laser is used for the build-up process. Electron probe microanalysis (EPMA), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and optical microscopy are used to analyse the deposited materials in terms of morphology, composition distributions, microstructures and phases formed. Successful deposition of functionally graded Cu-Ni-Fe structures has been demonstrated. Comparisons are made with the dual powder feed deposition process, which shows the inclusion of un-melted Ni powders in the Cu layer as a result of melting temperature difference of the two materials.     

Rapid additive manufacturing of functionally graded structures using simultaneous wire and powder laser deposition

Laser additive fabrication allows the manufacturing of functionally graded structures that are not possible using conventional subtractive manufacturing. Laser deposition of injected powders with varying compositions, layer-by-layer, is often used for the building up of functionally graded fully dense structures or materials. This approach, however, has some drawbacks: the un-used powders (normally 60–80%) cannot be recycled as they will be contaminated by the powder mixture. In addition, multiple passes are needed to develop functionally graded structures. This paper reports the feasibility and characteristics of using simultaneous powder and wire feeding laser deposition to produce functionally graded structures in a single step. This approach has been shown to eliminate the above problems associated with powder feed laser deposition. In this work, copper powder and nickel wire have been used to deposit functionally grated copper/nickel/iron structures on H13 tool steel. A 1.5-kW diode laser is used for the build-up process. Electron probe microanalysis (EPMA), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and optical microscopy are used to analyse the deposited materials in terms of morphology, composition distributions, microstructures and phases formed. Successful deposition of functionally graded Cu–Ni–Fe structures has been demonstrated. Comparisons are made with the dual powder feed deposition process, which shows the inclusion of un-melted Ni powders in the Cu layer as a result of melting temperature difference of the two materials.     

Application of additive manufacturing techniques in sports footwear

Additive manufacturing (AM) enables faster prototype development for design visualisation, performance studies and personalisation in the sports footwear industry. Among the available AM techniques, stereolithography (SLA), PolyJet (PJ), selective laser sintering (SLS) and three-dimensional printing (3DP) have been used for sports footwear prototyping. A five-point scoring system was used to rate the performance of AM techniques in four important characteristics namely accuracy, surface finish, range of materials supported and building time. Key elements of AM-based footwear personalisation and customisation methodology were also discussed.     

A new methodological framework for design for additive manufacturing

Additive manufacturing (AM) offers numerous benefits for innovative design solutions. However, engineers are currently not supported in identifying and incorporating these potentials systematically in their design solutions. In this paper, previous Design for Additive Manufacturing (DfAM) approaches are first reviewed comprehensively and classified into distinct categories according to their main purpose and application. They are then analysed further by being related to conventional design methodologies like VDI 2221. Since previous DfAM approaches only provide selective assistance at single steps in the product development process, a new framework for DfAM is proposed. Existing methods and tools, both from DfAM and from general design methodologies, are integrated into the modular framework structure. A concept for using the framework is presented to provide design engineers with continuous support in all product development phases, thereby fostering the complete exploitation of AM potentials and the development of AM-conformal designs.     

A review: additive manufacturing for active electronic components

Fabrication of fully functional devices is one of the ultimate goals of additive manufacturing technology. In order to achieve this goal, a critical step is to fabricate electronic components using fully additive methods. Although there are still numerous roadblocks that need to be overcome towards this goal, research activities in the field of additive manufacturing for electronic components in general, and for active components in particular, are progressing at a considerable pace and have been achieving significant successes. The purpose of this review is, therefore, to consolidate recent developments in this exciting field. Such developments include fully additive manufacturing methods for active components such as transistors, light-emitting diodes, and batteries. We discuss and compare the advantages, as well as disadvantages, of these methods. We also discuss major challenges that need to be addressed in the roadmap for additive manufacturing of active components.     

A tensor-based hierarchical process monitoring approach for anomaly detection in additive manufacturing

Additive manufacturing (AM) is a technology that enables the creation of complex shapes with advanced structural and functional properties. It has transformed the traditional manufacturing operations into a more flexible and efficient process, reshaping the whole value chain and allowing new levels of product customization. AM is a layer-by-layer manufacturing process, in which materials are deposited in each layer to create the object of interest. Due to the layer-wise nature of the process, anomalies and defects might occur within each layer, across several layers or throughout the whole sample. An accurate and responsive detection strategy that enables the detection of various types of anomalies is essential for ensuring the quality and integrity of the manufactured product. In this paper, a hierarchical in situ process monitoring approach, namely, a three level monitoring strategy, is proposed to detect local, layer-wise, and sample-wise anomalies using thermal videos acquired during the manufacturing process. The proposed approach integrates hierarchical low-rank tensor decomposition methods with statistical monitoring techniques to effectively detect anomalies at different levels, namely, the within-layer level, the layer level, and the sample level. Simulations are used to evaluate the performance of the method and compare with existing benchmarks. The proposed approach is also applied to thermal videos acquired during the laser powder bed fusion (L-PBF) process to illustrate its effectiveness in practice.     

Material characterisation and process development for chocolate additive layer manufacturing

This paper describes the development of a novel fabrication method known as chocolate additive layer manufacture (ChocALM). The system has been developed for the layer-by-layer manufacture of creative and personalised three dimensional (3D) chocolate products. This study investigates the material and property behaviour of a commercial chocolate. Deposition experiments have been carried using the newly developed ChocALM system to illustrate the effects of the deposition parameters on the geometrical accuracy and dimension of the deposited chocolates. The results revealed that process parameters such as extrusion rate, nozzle velocity and nozzle height are critical for successful deposition of chocolate and the optimisation of these parameters enables the ChocALM system to create 3D chocolates with appropriate quality.     

Optimal design for additive manufacturing of heterogeneous objects using ultrasonic consolidation

Rapid prototyping (RP) technologies, such as Laser Engineering Net Shaping (LENS®) and Ultrasonic Consolidation (UC), can be used to fabricate heterogeneous objects composed of more than one material, wherein spatially varied microscopic structural details produce continuously or discretely changing mechanical or thermal properties on a macroscopic scale. These objects are engineered to achieve a potentially enhanced functional performance. Past research on the design of such objects has focused on representation, modeling, and desired functional performance. However, the inherent constraints in RP processes, such as system capability, size and shape of raw materials, and processing time, lead to fabricated objects that may not meet the designer's original intent. To overcome this situation, the research presented in this paper focuses on developing an approach— Design for Additive Manufacturing (DfAM)—to implement identified manufacturing constraints into the design process. Previous work has applied DfAM to the design of heterogeneous objects fabricated using the LENS® process. Two manufacturing constraints for this process, namely the achievable volume fractions and the processing time, were identified and incorporated into the DfAM. In this paper, the DfAM approach is extended to the design and manufacture of heterogeneous objects for the UC process. Constraints on the possible volume fraction values and on the gradient material direction are two identified manufacturing limitations, which are incorporated into the design process. An element-based finite element (FE) representation is extended to model layered heterogeneous objects. Each element is composed of metal foils of different materials according to specific design parameters. An evolutionary-based optimizer is used for its ability to handle the type of multi-modal problems encountered in the design of heterogeneous objects. The multi-criteria design problem, consisting of finding the optimal material composition along the build direction, that satisfies the functions of minimum weight and structural deformation, is implemented and solved. A three-dimensional I-beam made of two materials—aluminum for lightweight and steel for better strength characteristics—is used to illustrate the DfAM approach and its implementation for the design of heterogeneous objects using the UC process.     

Optimal design for additive manufacturing of heterogeneous objects using ultrasonic consolidation

Rapid prototyping (RP) technologies, such as Laser Engineering Net Shaping (LENS®) and Ultrasonic Consolidation (UC), can be used to fabricate heterogeneous objects composed of more than one material, wherein spatially varied microscopic structural details produce continuously or discretely changing mechanical or thermal properties on a macroscopic scale. These objects are engineered to achieve a potentially enhanced functional performance. Past research on the design of such objects has focused on representation, modeling, and desired functional performance. However, the inherent constraints in RP processes, such as system capability, size and shape of raw materials, and processing time, lead to fabricated objects that may not meet the designer's original intent. To overcome this situation, the research presented in this paper focuses on developing an approach— Design for Additive Manufacturing (DfAM)—to implement identified manufacturing constraints into the design process. Previous work has applied DfAM to the design of heterogeneous objects fabricated using the LENS® process. Two manufacturing constraints for this process, namely the achievable volume fractions and the processing time, were identified and incorporated into the DfAM. In this paper, the DfAM approach is extended to the design and manufacture of heterogeneous objects for the UC process. Constraints on the possible volume fraction values and on the gradient material direction are two identified manufacturing limitations, which are incorporated into the design process. An element-based finite element (FE) representation is extended to model layered heterogeneous objects. Each element is composed of metal foils of different materials according to specific design parameters. An evolutionary-based optimizer is used for its ability to handle the type of multi-modal problems encountered in the design of heterogeneous objects. The multi-criteria design problem, consisting of finding the optimal material composition along the build direction, that satisfies the functions of minimum weight and structural deformation, is implemented and solved. A three-dimensional I-beam made of two materials—aluminum for lightweight and steel for better strength characteristics—is used to illustrate the DfAM approach and its implementation for the design of heterogeneous objects using the UC process.     

Selective laser melting raw material commoditization: impact on comparative competitiveness of additive manufacturing

The paper analyses the impact of cheaper metal powder supplies on the comparative competitiveness of additive manufacturing (AM). By utilising two case studies, we compare the economic impact of an innovative titanium extraction method on Selective Laser Melting (SLM) and conventional methods of machining and casting. A switch-over analysis identifies the production quantities above which conventional manufacturing is more cost competitive than additive manufacturing. This analysis is performed for current raw material as well as cheaper raw material supply. The results illustrate the improved comparative competitiveness of SLM as the titanium supply is commoditised and more readily available in powder form. The responsiveness of the supply chain is improved as the switch-over point between SLM and conventional methods increases. Moreover, as the raw material supply chain for titanium is transformed through the use of this novel extraction method, the manufacturing supply chain is simplified.     

Informing additive manufacturing technology adoption: total cost and the impact of capacity utilisation

Informing Additive Manufacturing (AM) technology adoption decisions, this paper investigates the relationship between build volume capacity utilisation and efficient technology operation in an inter-process comparison of the costs of manufacturing a complex component used in the packaging industry. Confronting the reported costs of a conventional machining and welding pathway with an estimator of the costs incurred through an AM route utilising Direct Metal Laser Sintering (DMLS), we weave together four aspects: optimised capacity utilisation, ancillary process steps, the effect of build failure and design adaptation. Recognising that AM users can fill unused machine capacity with other, potentially unrelated, geometries, we posit a characteristic of ‘fungible’ build capacity. This aspect is integrated in the cost estimation framework through computational build volume packing, drawing on a basket of sample geometries. We show that the unit cost in mixed builds at full capacity is lower than in builds limited to a single type of geometry; in our study, this results in a mean unit cost overstatement of 157%. The estimated manufacturing cost savings from AM adoption range from 36 to 46%. Additionally, we indicate that operating cost savings resulting from design adaptation are likely to far outweigh the manufacturing cost advantage.     

基于搅拌摩擦的金属固相增材制造研究进展EI北大核心CSCD

基于搅拌摩擦的固相增材制造是大型轻质合金构件成形制造的新技术,已成为国内外先进成形制造领域研究的热点之一。本文对目前国内外基于搅拌摩擦的金属固相增材制造技术及其相关工艺机理的研究现状进行了分析和总结。常见的基于搅拌摩擦的固相增材制造技术可分为三类:基于搅拌摩擦搭接焊原理,使板材逐层堆积,从而获得增材构件的搅拌摩擦增材制造(friction stir additive manufacturing,FSAM)技术;采用中空搅拌头,通过添加剂(粉末或丝材)进行固相搅拌摩擦沉积的增材制造(additive friction stir deposition,AFSD)技术;采用消耗型棒材,通过棒材的摩擦表面处理,形成增材层的摩擦表面沉积增材制造(friction surfacing deposition additive manufacturing,FSD-AM)技术。重点分析了金属材料基于搅拌摩擦的固相增材制造技术的国内外研究与应用现状,对比了三类基于搅拌摩擦的固相增材制造技术的特征及其工艺优缺点。最后指出增材工艺机理、形性协同控制、外场辅助工艺改型、新材料应用和人工智能优化是基于搅拌摩擦的固相增材制造技术未来研究的重点方向。     

A quality management framework for implementing additive manufacturing of medical devices

This paper aims to provide a comprehensive review of the implementation of additive manufacturing (AM) for medical devices. A quality management framework is proposed with discussion on topics such as software and data input, product understanding, AM equipment qualification, process understanding and continuous process verification. The interplay between input materials, process controls, and final outcomes of AM were analysed in the framework of quality management. Opportunities and challenges in implementing AM for medical devices are discussed.     

Numerical comparison of lattice unit cell designs for medical implants by additive manufacturing

The aim of this study was to compare traditional strut-based lattices with minimal surface designs using morphological analysis and image-based simulations of design files. While the two types have been studied widely, no direct comparison has ever been done. Surprisingly, there are no major differences in performance between the two types generally, but minimal surface designs do outperform slightly on angular load simulation. However, minimal surface designs in this density range are shown to have very thin walls, potentially making their accurate production more challenging, or more suitable for applications where larger pore sizes and sheet thicknesses may be applicable. Interesting results such as dual pore size distributions and variations in tortuosity of pore networks are demonstrated, with differences between various designs. The results show that all the tested designs are suitable for bone implants, but the best design might be selected based on its specialised performance requirements.     

Volume modelling for emerging manufacturing technologies

The next generation manufacturing technologies will draw on new developments in geometric modelling. Based on a comprehensive analysis of the desiderata of next generation geometric modellers, we present a critical review of the major modelling paradigms, namely, CSG, B-Rep, non-manifold, and voxel models. We present arguments to support the view that voxel-based modellers have attributes that make it the representation scheme of choice in meeting the emerging requirements of geometric modelling.     

Design knowledge representation to support personalised additive manufacturing

ABSTRACT

This research aims to develop a set of new formal design representations that captures design requirements to improve the level of personalisation while taking advantage of the additive manufacturing (AM)-enabled design freedom. We propose a formal design process structure called design for AM-facilitated personalisation that merges design for personalisation and design for additive manufacturing. Also, we propose formal representations for an artefact–user interaction using finite state automata and goal-oriented user behaviours in the artefact use as formal language sets based on discrete event systems. By adopting the relational properties of affordance, effectivity, and preference, the proposed formal representations systemically link user behaviour-related artefact properties and user preferences to the design requirements for additive manufactured artefacts. This paper presents a case study of personalised chair design and a simulation of user behaviours in the chair–user interaction.     

焊接快速成形技术的发展现状

焊接快速成形技术是近几十年才发展起来的新型制造技术,具有高灵活性、低成本和高生产效率等优点,在军事、医疗、交通、教育等许多行业都得到了广泛应用。简单介绍了焊接快速成形技术的原理及特点,概述了以钨极氩弧焊、熔化极气体保护焊、等离子弧焊、激光焊、电子束焊为基础的焊接快速成形技术国内外的发展现状,指出了焊接快速成形技术在发展中存在的问题,并就关于成形精度、成形性能、成形材料的问题进行了分析。     

A review of printed passive electronic components through fully additive manufacturing methods

There have been significant advancements in the field of additive manufacturing in the past decades. Current technologies in this field allow fabrications of not only complex physical prototypes but also functional electronic components and circuitries. It is now possible to fabricate simple circuits embedded with several kinds of passive components, for example, resistors, capacitors, and inductors, which are the most fundamental building blocks of any electrical circuits. In order to aid future developments and integrations of printing electronics into a wider range of applications, this review attempts to provide an overview and the most recent developments of ‘fully additive’ printing techniques used for fabricating circuits and electronic components, including comparisons between their advantages and disadvantages. Each individual ‘fully additive’ printing technique is presented and discussed in detail. Potentials and challenges of additive manufacturing of electronics are also discussed.