Industrial Additive Manufacturing: A manufacturing systems perspective

As Additive Manufacturing becomes increasingly prevalent in commercial manufacturing environments, the need to effectively consider optimal strategies for management is increased. At present most research has focused on individual machines, yet there is a wealth of evidence to suggest competitive manufacturing is best managed from a systems perspective. Through 14 case studies developed with four long-established Additive Manufacturing companies this paper explores the conduct of Industrial AM in contemporary manufacturing environments. A multitude of activities, mechanisms, and controls are identified through this detailed investigation of Additive Manufacturing operations. Based on these empirical results a general four component Industrial Additive Manufacturing System is developed, together with the identification of potential strategic opportunities to enhance future manufacturing.     

A new Steiner patch based file format for Additive Manufacturing processes

Additive Manufacturing (AM) processes adopt a layering approach for building parts in continuous slices and use the Standard Tessellation Language (STL) file format as an input to generate the slices during part manufacturing. However, the current STL format uses planar triangular facets to approximate the surfaces of the parts. This approximation introduces errors in the part representation which leads to additional errors downstream in the parts produced by AM processes. Recently, another file format called Additive Manufacturing File (AMF) was introduced by ASTM which seeks to use curved triangles based on second degree Hermite curves. However, while generating the slices for manufacturing the part, the curved triangles are recursively sub-divided back to planar triangles which may lead to the same approximation error present in the STL file. This paper introduces a new file format which uses curved Steiner patches instead of planar triangles for not only approximating the part surfaces but also for generating the slices. Steiner patches are bounded Roman surfaces and can be parametrically represented by rational Bezier equations. Since Steiner surfaces are of higher order, this new Steiner file format will have a better accuracy than the traditional STL and AMF formats and will lead to lower Geometric Dimensioning and Tolerancing (GD&T) errors in parts manufactured by AM processes. Since the intersection of a plane and the Steiner patch is a closed form mathematical solution, the slicing of the Steiner format can be accomplished with very little computational complexity. The Steiner representation has been used to approximate the surfaces of two test parts and the chordal errors in the surfaces are calculated. The chordal errors in the Steiner format are compared with the STL and AMF formats of the test surfaces and the results have been presented. Further, an error based adaptive tessellation algorithm is developed for generating the Steiner representation which reduces the number of curved facets while still improving the accuracy of the Steiner format. The test parts are virtually manufactured using the adaptive Steiner, STL and AMF format representations and the GD&T errors of the manufactured parts are calculated and compared. The results demonstrate that the modified Steiner format is able to significantly reduce the chordal and profile errors as compared to the STL and AMF formats.     

Adaptability analysis of design for additive manufacturing by using fuzzy Bayesian network approach

The rapid development of Additive Manufacturing (AM) has been conspicuous and appealing towards manufacturing end-use products and components over the past decade. The continual advancement of AM has brought many advantages such as personalization and customization, reduction of material waste, cutting off the existence of special tooling during fabrication, etc. However, the AM approach has its limitations, such as a lack of knowledge of AM process activities and the progressive industrialization of AM, which makes the design process activities unstable, unpredictable, and have a limited effect. The concept of “design for AM (DFAM)” is increasing, which means we have the opportunity to concentrate almost totally on product functioning. Therefore, the entire design paradigm must be revised to accommodate new production capabilities, geometries, and parameters to avoid molding or machine tooling technology constraints. Few studies have attempted to provide systematic and quantitative knowledge of the relationship between these elements and the feasibility of the design process, making it difficult for designers to assess and control AM industrialization. For this reason, DFAM is needed to reform AM from rapid manufacturing to a mainstream manufacturing method. This paper put forward a framework based on the Fuzzy Bayesian Network (FBN) for DFAM decision-making. Twenty impact factors were encapsulated from experts’ experience and existing literature to investigate the potential adaptability of DFAM. The proposed approach uses expert knowledge and Fuzzy Set Theory (FST) presented with Triangular Fuzzy Numbers (FFN) to perceive the uncertainties. The Bayesian Network (BN) captures the causal relationships and dependencies among the impact components and analyzes the DFAM adaptability for robust probabilistic reasoning. A robot arm claw was used to show the effectiveness of our approach. The results showed that FBN could be used to guide DFAM adaptability in the manufacturing industry.     

制造业信息化建设

推进制造业信息化是落实"以信息化带动工业化"战略、走新型工业化道路的重要举措。推进制造业信息化是《国家中长期科学和技术发展规划纲要》提出的重要任务;是面向国民经济建设主战场,整合科技资源、实施"以信息化带动工业化"战略、走新型工业化道路的重要举措;是推进经济结构调整和经济增长方式转变的重要手段。制造业信息化将信息技术、自动化技术、现代管理技术与制造技术结合应用,推进设计制造数字化、生产过程智能化和企业经营管理信息化。用高新技术改造和提升制造业,促进制造业研发设计、生产制造、企业管理和市场营销的变革,带动产品设计和制造模式的创新、企业管理和经营模式的创新以及企业间协作模式的创新,是新时期我国制造业适应全球竞争环境、生存和发展的必由之路,对提升我国制造业的自主创新能力和市场竞争能力具有重要意义。     

增材再制造产业的现状与发展

增材再制造基于增材制造技术,能实现零部件损伤部位尺寸恢复和零部件性能恢复或提升,是一种颠覆性新加工技术.该技术对关键产业起到赋能作用,能够促进产业高质量发展.针对金属增材再制造技术,具体阐述了激光增材再制造、电弧增材再制造和电子束增材再制造技术的工艺特点,并详细地分析了增材再制造技术在钢铁冶金、船舶、航空航天、电力、交...     

基于构件的可重构制造执行系统研究

制造执行系统是实现企业信息集成的关键技术，是企业信息化工程领域的研究热点之一。分析了制造执行系统的定义和功能，并提出基于软件构件的可重构制造执行系统的软件体系结构和实现方法。可重构制造执行系统的开发与运行实践表明，可重构制造执行系统的软件开发效率高、周期短、可扩展性好。     

An Improved Two-Level Support Structure for Extrusion-Based Additive Manufacturing

Extrusion-Based Additive Manufacturing is one of the most commonly used Additive Manufacturing techniques. However, the technique requires that the overhang features in a model should be provided with supports from below. The added supports contribute to a major source of material waste during the manufacturing process. In order to save support materials, considering 3D printing directions as a constraint of adding supports, we propose a two-level support structure where Level 1 consists of a truncated beam-structure and Level 2 consists of a slim tree-shaped structure. The main contribution of this paper is the modification of the shape of Level 1 support and optimization of the topologies of the tree-supports in Level 2. The approach developed in this paper leads to material savings up to 31.01% and printing time savings up to 13.10% in comparison to the existing literature. Several comparison experiments were conducted on benchmark models to validate the developed approach and have been reported in this paper.     

A review on wire arc additive manufacturing: Monitoring,control and a framework of automated system

Wire arc additive manufacturing technology (WAAM) has become a very promising alternative to high-value large metal components in many manufacturing industries. Due to its long process cycle time and arc-based deposition, defect monitoring, process stability and control are critical for the WAAM system to be used in the industry. Although major progress has been made in process development, path slicing and programming, and material analysis, a comprehensive process monitoring, and control system are yet to be developed. This paper aims to provide an in-depth review of sensing and control design suitable for a WAAM system, including technologies developed for the generic Arc Welding process, the Wire Arc Additive Manufacturing process and laser Additive Manufacturing. Particular focus is given to the integration of sensor-based feedback control, and how they could be implemented into the WAAM process to improve its accuracy, reliability, and efficiency. The paper concludes by proposing a framework for sensor-based monitoring and control system for the GMAW based WAAM process. This framework provides a blueprint for the monitoring and control strategies during the WAAM process and aims to identify and reduce defects using information fusion techniques.     

"虚拟制造"重振武汉制造业

虚拟制造模式为企业和地区经济带来了又一次跨越式发展的契机。本文分析了武汉市制造业的现状、优势和不足，结合虚拟制造理论，从政府和企业两个角度阐述了如何利用虚拟制造的思想重振武汉制造业。     

Investigation of humping phenomenon for the multi-directional robotic wire and arc additive manufacturing

Wire Arc Additive Manufacturing (WAAM) is a promising technology for fabricating medium to large scale metallic parts with excellent productivity and flexibility. Due to the positional capability of some welding processes, WAAM is able to deposit parts with overhanging features in an arbitrary direction without additional support structures. The dimensional quality of the overhanging parts may however deteriorate due to the humping effect, which appears as a series of periodic beadlike protuberances on the weld deposits. There has been significant research on the humping phenomenon in the downhand welding, but it is doubtful whether the existing theories of humping formation can be applied in the positional deposition during WAAM process. This study has therefore provided an experimental work to investigate the formation of the humping phenomena in the positional deposition during additive manufacturing with the gas metal arc welding. Firstly, the mechanism of humping formation was analysed to explain humping occurrence for positional deposition. Then, the mechanism was validated through experiments with different welding parameters and positions. Finally, a series of guidelines are summarised to assist the path planning and process parameter selection processes in multi-directional WAAM.     

Eco-friendly additive manufacturing of metals: Energy efficiency and life cycle analysis

Additive manufacturing (AM) of metal materials has attracted widespread attention and is shifting the conventional manufacturing landscape toward free-form processes. With increasing concerns about global sustainability, eco-consideration is highly encouraged to be integrated into AM processes. This review provides a comprehensive and timely discussion on the life cycle of metal parts fabricated through AM. The energy consumption required for raw metal material extraction and subsequent AM processes is analyzed. The eco-design and energy efficiency of metal AM are evaluated to reveal the role of manufacturing methods, machine subsystems, and post-processing modes in the eco-integration. AM-induced supply chain management, utilization, and recycling of the printed metal structure are also analyzed. Finally, a comprehensive life cycle assessment regarding the environmental, social, and economic impacts of metal AM is also addressed. Future directions of AM are also briefly discussed to provide insight and vision on the emerging field of additive eco-manufacturing.     

网络化制造环境下一种面向能力的制造资源模型

制造资源管理是网络化制造中重要的一环。针对现有模型中共享资源在实现可行性方面存在的不足，提出建立一种面向能力的制造资源模型，并以XML格式进行描述。在此基础之上，建立了基于制造特征的任务定义模型。     

制造执行系统的功能设计

制造执行系统是制造企业信息集成系统的关键使能技术,而制造执行系统的功能设计是设计一个高质量制造执行系统的基础。该文基于制造执行系统的活动模型,设计制造执行系统的功能模块。这些功能模块体现了制造执行系统的功能需求。     

A novel approach for multi-agent-based Intelligent Manufacturing System

In the recent years, the competition of shortening the development cycle of new products is more and more fierce. Given the shortcomings of traditional scheduling algorithm in Intelligent Manufacturing, the architecture of multi-agent-based Intelligent Manufacturing System is put forward, which represents the basic processing entity. The architecture is based on the methodology of multi-agent systems (MAS) in distributed artificial intelligence (DAI). The multi-agent system has some common characteristics, such as distribution, autonomy, interaction and openness, which are helpful to transform the traditional architecture into a distributed and cooperative architecture in an Intelligent Manufacturing System. To develop a multi-agent-based scheduling system for Intelligent Manufacturing, it is necessary to build various functional agents for all the resources and an agent manager to improve the scheduling agility. In this paper, the proposed architecture consists of various autonomous agents that are capable of communicating with each other and making decisions based on their knowledge. The architecture of Intelligent Manufacturing, the scheduling optimization algorithm, the negotiation processes and protocols among the agents are described in detail. A prototype system is built and validated in an illustrative example, which demonstrates the feasibility of the proposed approach. The experiments prove that the implementation of multi-agent technology in Intelligent Manufacturing System makes the operations much more flexible, economical and energy-efficient.     

Optimal part orientation in Rapid Manufacturing process for achieving geometric tolerances

Rapid Manufacturing (RM) processes have evolved from the Rapid Prototyping (RP) paradigm and are increasingly being used to manufacture parts, tools and dies in addition to prototypes. The advantages of RP methods to produce complex shapes without the use of specialized tooling can naturally be extended to RM processes. For RM to be accepted as a mainstream manufacturing process, parts created by RM have to consistently satisfy critical geometric tolerances specifications for various features of the part. This paper investigates the relation between cylindricity tolerance, one of the key form tolerances, and part build orientation in layered manufacturing. The effect of build orientation on cylindricity error is analyzed by three methods: first by a simple analytic method, second by simulating the manufactured surface using a CAD (Computer Aided Design) file of the part and third by using an STL (Stereolithography) file. The mathematical relationship between cylindricity error and part orientation in a RM process is modeled and critical feasible regions for cylinder build orientation are calculated. A graphical technique for calculating the optimal build orientation for a part with multiple cylindrical features is also developed and presented in this paper. This method is tested and validated with the help of a test case and the results are provided in the paper.     

基于动态制造资源的产品工艺分工规划研究

针对制造企业联盟的产品工艺分工问题,研究并开发了基于动态制造资源的网络化产品工艺分工规划系统。论文阐述了工艺分工的设计方法,提出了逻辑制造单元、逻辑加工路线等新概念,并对产品工艺分工系统的体系结构与功能组成、基于动态制造资源的零件与逻辑制造单元建模方法、基于知识的逻辑加工路线设计及可执行加工路线生成方法进行了详细讨论。     

Assessment of reconfiguration schemes for Reconfigurable Manufacturing Systems based on resources and lead time

Reconfigurable manufacturing equipment is developed to meet the growing demand for more agile production. Agile manufacturing technology can improve the turnover of a company if it enables fast market introduction for volume production. Modular reconfiguration, defined as changing the structure of the machine, enables larger variation of products on a single manufacturing system; these solutions are called Reconfigurable Manufacturing Systems (RMS). The quality of RMS, and the required resources to bring it to reliable production, is largely determined by a swift execution of the reconfiguration process. This paper proposes a method to compare alternatives for the ways to implement reconfiguration. Three classes of reconfiguration are defined to distinguish the impact of the proposed alternatives. The procedure uses a recently introduced index method for development of RMS process modules, based on the Axiomatic Design methodology. Weighting factors are used to calculate the resources and lead time needed to implement the reconfiguration process. Application of the method leads to quick comparison of alternatives in the early stage of development. Successful execution of the method was demonstrated for the manufacturing process of a 3D measuring probe.     

Manufacturing systems: A knowledge- and optimization-based approach

Optimization approaches have traditionally been viewed as tools for solving manufacturing problems. The optimization approach is not suitable for many problems arising in modern manufacturing systems due to their complexity and involvement of qualitative factors. Expert systems appear to remedy the latter weakness of optimization approaches. The biggest disadvantage of expert systems in manufacturing environment is the slow response time. In this paper an integrand approach involving knowledge-based and optimization approaches is explored. The knowledge-and optimization-based approach is applied to solve two manufacturing problems: group technology (static problem) and scheduling (dynamic problem). The approach presented is illustrated with numerical example and computational results.The original version of this paper was presented at the 2nd International Symposium on Robotics and Manufacturing (ISRAM), Albuquerque, New Mexico 16–18 November 1988. The published proceedings of this meeting may be ordered from: CAD Laboratory for Systems/Robotics, EECE Dept, UNM, Albuquerque, NM 87131, U.S.A.     

Homogenization of material properties in additively manufactured structures

Additive manufacturing transforms material into three-dimensional parts incrementally, layer by layer or path by path. Subject to the build direction and machine resolution, an additively manufactured part deviates from its design model in terms of both geometry and mechanical performance. In particular, the material inside the fabricated part often exhibits spatially varying material distribution (heterogeneity) and direction dependent behavior (anisotropy), indicating that the design model is no longer a suitable surrogate to consistently estimate the mechanical performance of the printed component.We propose a new two-stage approach to modeling and estimating effective elastic properties of parts fabricated by fused deposition modeling (FDM) process. First, we construct an implicit representation of an effective mesoscale geometry–material model of the printed structure that captures the details of the particular process and published material information. This representation of mesoscale geometry and material of the printed structure is then homogenized at macro scale through a solution of an integral equation formulated using Green’s function. We show that the integral equation can be converted into a system of linear equations that is symmetric and positive definite and can be solved efficiently using conjugate gradient method and Fourier transform. The computed homogenized properties are validated by both finite element method and experiment results. The proposed two-stage approach can be used to estimate other effective material properties in a variety of additive manufacturing processes, whenever a similar effective mesoscale geometry–material model can be constructed.     

面向精益制造的生产执行系统销售模块功能设计

面向精益制造能力构建的企业生产执行系统（MES）在关键价值区域（生产）和层次（执行）,以小投入换大效益,为制造型企业信息化的全面实施打好基础。其中销售模块与传统erp销售功能相比,更注重利用mes的生产资源数据实时采集和反馈特点,让企业业务前端的销售管控更贴近服务于整个系统的即时高效运作。该文基于以上理念,详细阐述广义mes下销售模块的需求构建和策略设计。