Environmental comparison of MESO-CLAD® process and conventional machining implementing life cycle assessment

CLAD^® process (Direct additive laser manufacturing, Construction Laser Additive Directe in French) allows the direct manufacturing of small parts, and especially in case of complex shapes, giving equivalent properties with traditional processes such as conventional machining or casting techniques. Present environmental considerations are very important for updates in legislation or in order to make economic allowances. A specified mechanical Ti₆Al₄V part is used as a support and SimaPro software allows to perform Life Cycle Assessment. This study suggests that the absence of chips production, which represents up to 80% of the titanium consumption, provides to CLAD^® process an unquestionable advantage. This process requires longer times of execution, which increase additional energy consumptions, and the comparison of this process with conventional machining demonstrates that damages to resources and to human health are highly reduced. In both cases a large part of the environmental impacts are due to the powder elaboration. Finally, CLAD^® process can add shapes on machined/casted parts and it is possible to consider the manufacture of a mechanical part via a hybrid process.     

A design for the additive manufacture of functionally graded porous structures with tailored mechanical properties for biomedical applications

CAD/CAM-based layered manufacturing and additive manufacturing techniques of metals have found applications in near-net-shape fabrication of complex shaped parts with tailored mechanical properties for several applications. Especially with the onset of newer processes such as electron beam melting (EBM) and direct metal laser sintering (DMLS), revolutionary advances may be achieved in material substitution in the medical implant industry. These processes must be suitably developed and tested for the production of medical grade substitutions. In this article, we discuss a design process for creating periodic cellular structures specifically targeted for biomedical applications. Electron beam melting is used to fabricate the parts. Evaluation of the mechanical properties is performed and compared with design parameters. Compression tests of the samples show effective stiffness values ranging from 0.57 (±0.05) to 2.92 (±0.17) GPa and compressive strength values of 7.28 (±0.93) to 163.02 (±11.98) MPa. Substituting these values for simulation of biomechanical performance of patient-specific implants illustrates the compatibility and matched functional performance characteristics of highly porous parts at a safety factor of 5 and an effective reduction in weight. These developments are unique for the construction of maxillofacial and craniofacial implants. The novel design strategy also lends itself very well to metal additive manufacturing technologies. Implants designed and fabricated with this design strategy and manufacturing process would have mechanical properties equivalent to the part they replace and restore better function and esthetics as against the currently used methods of reconstruction. Suitable examples of a titanium porous cranioplasty plate and a sandwich structure are illustrated.     

A review of process development steps for new material systems in three dimensional printing (3DP)

Three dimensional printing (3DP) is a method for direct digital manufacturing that provides capabilities for creating a wide range of part geometries (including internal channels) in a broad variety of materials, including just about anything that is available as a spreadable powder. Taking advantage of the full variety of materials requires development of specific implementations of 3DP. This paper organizes the process of 3DP implementation into five steps (powder formulation, binder method selection, binder formulation and testing, printing process specification, and post-processing specification) and presents a review of the literature relevant to each step in 3DP implementation.     

Robotic Manipulation of Highly Irregular Shaped Objects: Application to a Robot Crucible Packing System for Semiconductor Manufacture

The basic technology for a robotic system is developed to automate the packing of polycrystalline silicon nuggets into a fragile fused silica crucible in Czochralski (melt pulling) semiconductor wafer production. The highly irregular shapes of the nuggets and the packing constraints make this a difficult and challenging task. To address this task, key research areas are identified, developed, and integrated. In this system, nuggets are grasped by a three-cup suction gripper and manipulated with a seven-degree-of-freedom SCARA manipulator. An optical 3-D vision system, based on active laser triangulation, measures nugget and crucible profiles. A model-free Virtual Trial and Error packing algorithm determines optimal nugget placement in real time. A hybrid position-force control scheme has been implemented and tested for physical nugget placement. The simulation and laboratory tests show that the system has the capabilities of meeting high production rates, achieving high process constraints, and maintaining cost effectiveness that exceed levels obtained with manual packing. The results suggest that model-less robotic sensor control systems can be effective in manufacturing applications. The key contribution of this paper is to show that robot systems can be effectively used to manipulate highly irregular shaped objects in the context of real commercial manufacturing processes.     

Additive manufacturing based on optimized mask video projection for improved accuracy and resolution

Additive manufacturing (AM) processes based on mask image projection such as digital micro-mirror devices (DMD) have the potential to be fast and inexpensive. More and more research and commercial systems have been developed based on such digital devices. However, the accuracy and resolution of the related AM processes are constrained by the limited number of mirrors in a DMD. In this paper, a novel AM process based on the mask video projection has been presented. For each layer, a set of mask images instead of a single image are planned based on the principle of the optimized pixel blending. The planned images are then projected in synchronization with the small movement of the building platform. A mask image planning method has been presented for the formulated optimization problem. Experimental results have verified that the mask video projection process can significantly improve the accuracy and resolution of built components.     

关于现代模具制造的研究

此文构造了面向工艺过程规划的现代模具制造框架,并与传统模具制造相对比,总结出现代模具制造的主要特点,存在的问题及相应对策。     

泰州石化水污染治理达标整体技术设计总结

泰州石化总厂的污水处理工程为例，介绍现有的炼油企业通过合理系统划分，将高、低浓度污水分质处理，并采取适当的污水处理方法(隔离式BAF及膜法A／O等)，实现全厂污水达标排放。     

Advanced process systems design technology for pollution prevention and waste treatment

The paper presents a generic process synthesis and optimisation tool suitable to take up applications in the design of waste treatment systems and in pollution prevention. The main component of the technology is a generalized process synthesis representation for simultaneous consideration of reaction and separation in multiphase systems that is amenable for stochastic optimisation. The flexibility of the representation allows applications to overall process synthesis problems as well as to decomposed reactor, reactive separation and mass exchange network design problems. Applications of the synthesis framework to waste water treatments processes using activated sludge and to natural gas sweetening in hybrid membrane-adsorption processes are presented. The paper highlights the use of the systematic technology in environmental systems design and shows how novel designs of improved performance as well as optimal design knowledge can be revealed using the systematic design framework. Context abstract: Environmental process systems for waste treatment and pollution prevention become increasingly complicated to design. There is a strong need for technology that provides systematic decision support to the process synthesis team in order to enable the timely selection of processes that operate close to the performance limits of the system under consideration. Conventional, optimisation-based process design technology is severely limited by the number of design decisions they can support simultaneously as well as by the increasingly complex process models required for the meaningful mathematical representation of environmental process systems. We have devised an optimisation-based process design methodology for integrated reaction and separation systems that overcomes major limitations of existing tools. This paper illustrates the use of this technology to provide systematic decision-support to the environmental process systems designer.     

Improvement of welding heat source models for TIG-MIG hybrid welding process

Tungsten inert gas-metal inert gas (TIG-MIG) hybrid welding process is an effective way to improve welding productivity and quality due to advantages of the two processes. Mathematical analysis is crucial to fundamentally understand this synergetic welding process. In this study, based on experimental visualization of arc behaviors, some assumptions are proposed to deduce adaptive plane and volumetric heat source models separately for each involved welding method first. The influence of torch angles on distribution of temperature and geometry of weld bead are calculated and compared with experimental results. It shows that this developed algorithm of heat source can be employed to accurately predict welding process whether the electrode gun is slanted backward or forward to the direction of welding. Then TIG-MIG hybrid welding process is simulated and analyzed without considering the attractive or repulsive force of two arcs. The characteristic of TIG-MIG welding process is discussed compared to single MIG. It lays the foundation for the further research on the interaction of the two arcs during TIG-MIG hybrid welding.     

摩托车棘轮起动齿轮冷挤压齿工艺及模具设计

摩托车的棘轮、起动齿轮是起动器的重要组成部分,其制造精度高,工艺复杂。此文从工艺性分析、坯料选择、设备选型等方面阐述了两齿轮冷挤压齿成形工艺,对冷挤压模具结构、齿模设计补尝作了详细介绍。     

Application of vibration in the laser powder deposition process

Laser powder deposition (LPD) has been used for a few decades as a technique that is unique in the application of complex geometry part manufacturing, high-value parts repairing, and surface modification. However, improving the buildup quality of LPD process is still a challenge because of the presence of defects. In this paper, the effect of in-process vibration frequency on the buildup properties of LPD is studied. Experimental results show that the vibratory energy has a significant effect on reducing porosity. Up to an 80% reduction in the porosity and the maximum defect size can be obtained by choosing the appropriate vibration parameters. In addition, a more homogeneous microstructure is achieved that results in less deviation in hardness throughout the buildup.     

Reformulation of matrix-based LCI: from product balance to process balance

A recent paper in this journal points out that the ISO standards for LCA ignore the situation of internally recurring unit process in life cycle inventories. The paper also presents a way to solve this problem, using a set of simultaneous equations with one equation for each unit process and one variable for each product. The authors appear to be unaware of existing approaches towards this problem in which a set of simultaneous equations is used, but with a reverse set-up: one equation for each product and one variable for each unit process. This paper reviews the existing literature and contrasts it with the newly proposed method. It is concluded that the presentation of the new method is unclear in certain parts, and that its realm of application is probably restricted to product systems with mono-functional processes.     

轻型汽车和汽车塑料配件涂装工艺过程的VOCs组分特征

通过采集和分析珠江三角洲(以下简称“珠三角”)地区轻型汽车和汽车塑料配件涂装工艺过程的VOCs样品,识别了上述两个行业不同涂装工艺过程的VOCs组分特征.结果表明:芳香烃(56.4%~75.5%)和OVOCs(11.0%~35.7%)为轻型汽车涂装工艺占比最大的两种VOCs组分;烷烃和烯炔烃在烘干工艺所占比重要高于喷涂工艺;1,2,4-三甲苯为电泳和面涂烘干工序的主要VOCs组分,间/对-二甲苯、乙酸丁酯、丙二醇甲醚醋酸酯分别为中涂、面涂和中涂烘干工序的主要VOCs组分.汽车塑料配件涂装工艺不同工序的VOCs组成相似,芳香烃(53.3%~58.3%)和OVOCs(40.9%~45.8%)为主要VOCs组成,甲苯、乙酸乙酯、乙酸丁酯等为主要VOCs组分.不同废气治理设施对汽车塑料配件涂装工艺VOCs组分会造成一定的影响.活性炭吸附治理设施处理后的主要VOCs组分为甲苯、乙苯和邻二甲苯等芳香烃组分,水喷淋治理设施则为乙酸乙酯、乙酸丁酯和丙二醇甲醚醋酸酯等OVOCs类组分.通过与其他研究对比,丙二醇甲醚醋酸酯作为原辅料和废气中的主要组分之一,在以往研究中并未识别出来,表明针对测试对象的原辅料与工艺信息的现场调研是开展VOCs组分特征及成分谱研究的基础工作,建议未来该方面研究加强对前期调研工作的重视.此外,建议关注行业发展趋势给VOCs成分谱研究带来的影响.     

机械零件的粉末冶金成形方法

此文主要介绍了几种较实用和新发展的机械零件的粉末冶金成形方法,包括Olivetti法,螺旋形状零件成形法,粉末注射成形,组合烧结成形,粉末锻造和旋转锻造。     

成都市典型工艺过程源挥发性有机物源成分谱

选取成都市人造板、医药制造和化工制品等工艺过程源典型企业,通过采样瓶和SUMMA罐采样及GC-MS和国标分析方法,获取了人造板等行业各生产工艺环节的挥发性有机物(VOCs)排放组分特征.其中,人造板生产工艺分为制胶、调胶、分选和热压,医药制造分为生产车间和废水处理.结果表明,人造板和医药制造VOCs贡献组分以OVOCs为主,占VOCs总排放的50%以上.甲醛制造有组织和无组织排放组分差异较大,有组织以OVOCs为主而无组织以卤代烃为主.涂料制造VOCs排放与其原辅料相关性较高,VOCs排放组分以芳香烃和OVOCs为主.人造板各工艺环节除调胶外,最主要的VOCs组分均为甲醛,其排放占比达到50%以上.医药制造各工艺环节的首要VOCs组分均为乙醇,1,4-二烷、乙酸乙酯和甲苯等亦为主要组分.甲醛制造以丙酮和乙醇等组分为主.涂料制造主要以间,对-二甲苯等芳香烃为主.以臭氧生成潜势表征人造板、医药制造和化工的VOCs污染源反应活性,结果表明不同行业VOCs组分对反应活性的贡献类似,均主要以甲醛、乙醇等OVOCs和部分芳香烃等高活性组分为主.应对工艺过程源等行业分环节监管,并重点关注臭氧生成潜势较大的VOCs组分,分析行业排放特征和化学机制,从源头控制O3生成.     

基于通勤时间距离的LE污水处理过程故障检测方法

污水处理过程的性能监测与故障诊断,对于保障污水处理过程正常运行及保证出水质量达标具有重要意义.针对污水处理过程数据具有非线性、不确定性及且易受随机噪声影响等特征,提出了一种新的基于通勤时间距离的LE流形学习算法实现对复杂过程数据的特征提取.改进算法采用通勤时间距离方式进行样本间的相似度衡量并构造邻域图,理论分析和仿真测试表明改进算法可有效克服基本LE算法的邻域参数敏感问题并提高了算法的鲁棒性.将基于通勤时间距离的LE流形学习算法用于污水处理过程故障检测建模,在低维流形子空间构造综合统计量进行过程监测.应用结果表明,与基于PCA方法和LE方法的故障检测模型相比,基于改进算法的故障检测模型可及时探测故障的发生,具有较低的故障漏报率和故障误报率.为污水处理等复杂工业过程的故障监测提供了一种可行的解决方案.     

基于改进FWA-NN的污水处理过程溶解氧浓度预测

为实现对污水处理过程溶解氧质量浓度的实时准确预测,提出了一种改进的混沌烟花混合优化算法并构建了基于改进算法的神经网络在线软测量模型.结合污水处理过程的数据特征,定义了一项新的样本相似度衡量指标用于提取更具代表性的建模数据.在改进算法中,为提高基本烟花算法初始成员的质量,定义了一种改进的两级正弦混沌映射并利用混沌运动的遍历性精选烟花算法的初始群成员;通过融合混沌算法改进了基本烟花算法的搜索机制,基于设定准则将寻优过程分为两阶段并采用两分群同时进行.测试结果表明改进算法的收敛速度和收敛精度有较大程度提高.将改进的软测量建模方法和样本数据提取方法用于污水处理过程溶解氧质量浓度软测量建模,应用结果表明该模型的均方根误差和平均泛化误差分别为0.0175和0.0118,具有较强的泛化性能.     

精细化工园区工艺过程VOCs产生量核算方法

挥发性有机物(VOCs)是目前影响我国大气环境质量的关键污染物之一.工业源已成为中国最主要的VOCs排放源,其中化工行业的VOCs排放贡献尤为突出.化工企业已经大量集聚于化工园区内,因此化工园区的VOCs控制至关重要.本研究以典型精细化工园区——杭州湾上虞经济技术开发区为例,通过分析精细化工生产模式及VOCs产生原理,建立了基于工艺过程的VOCs产生量核算方法,对投料、升温、化学反应产生气体带出、清洗吹扫、真空抽气、泄压释放和蒸发逸散等生产过程的VOCs产生量进行了核算;同时运用化工流程模拟软件Aspen进行了前述生产过程VOCs产生量估算;运用2种方法对案例园区14种典型产品各工艺过程的VOCs产生特征进行了分析,并对两种方法的核算结果进行了比较.结果发现,除泄压释放环节外,两种方法的结果差异在±22%以内.进而对该园区典型企业的代表性产品进行计算方法应用,可得到精准的VOCs产生关键环节和组分.案例研究表明这一方法在定量的化工生产参数支持下估算精细化工工艺过程的VOCs产生量具有较好的精准性、简便性和可靠性.     

Economic-balance hybrid LCA extended with uncertainty analysis: case study of a laptop computer

The emergence of Life Cycle Assessment (LCA) on the global stage as a design and policy tool increases the importance of assessing and managing uncertainty. This article develops and implements uncertainty methods for hybrid LCA. Hybrid LCA combines a bottom-up construction of the supply-chain based on facility-level data on material/energy use with a top-down economic input-output (EIO) model to account for processes for which direct data were unavailable. For the bottom-up part of the LCA, we account for variability in process and usage pattern data by developing parameter ranges. For the EIO side we develop a method to assess price uncertainty. These methods are explored through a case study examining energy use and carbon dioxide emissions of manufacturing and use of a laptop computer, a 2001 Dell Inspiron 2500. Results show that manufacturing the computer requires 3010-4340 MJ of primary energy, 52-67% less than the energy to make a desktop computer, and emits 227-270 kg CO₂. The manufacturing phase represents 62-70% of total primary energy of manufacturing and operation. This indicates, as for desktop computers, that mitigating manufacturing energy use, for example through extending lifespan, can be an important strategy to manage the life cycle energy of laptop computers. Results also indicate that truncation error from excluded processes in the bottom-up process model is significant, perhaps particularly so due to complex supply chains of information technology products.     

National pathways to the Sustainable Development Goals (SDGs): A comparative review of scenario modelling tools

The recently-adopted global Sustainable Development Goals (SDGs) will have significant implications for national development planning in both developed and developing countries in the post-2015 period to 2030. Integrated, nationally-owned SDG strategies will be at the centre of national efforts to implement the new sustainable development agenda. The long-run processes and systems perspective that are inherent in the SDGs present complex analytical problems for policymakers and analysts. Scenario analysis and quantitative modelling will be important analytical tools to support national sustainable development planning, and there is an increasingly sophisticated suite of models available to decision makers. This paper reviews and assesses a broad range of different quantitative models that have the potential to support national development planning for the SDGs. The study develops a typology and inventory of 80 different models, and then reviews the comparative strengths, weaknesses and general utility of different models through an initial screening and subsequent multi-criteria analysis of short-listed models. Current gaps in model capabilities are highlighted in the context of providing analytical support for national development planning for the SDGs. While some existing models are particularly relevant, it is unlikely that an ideal model can analyse all SDG targets and variables of interest within a single modelling framework. Top-down ‘macro framework’ models are likely to be more useful for undertaking system-level or economy-wide scenario analysis driven by the national long-term goals and targets, and for exploring trade-offs and synergies among sectors. Bottom-up sectoral models will be able to support far more detailed option-level impact analysis of concrete interventions, technologies and investments. Combining both approaches within an analytical framework will provide a robust approach for analysis and decision-making. The results highlight a range of potential gaps in current modelling capabilities, and provide some new tools to assist with model selection.