Layout Planning Technology of Cellular Manufacturing System Based on Process Interconnection Analysis

With sustaining change of production mode,layout planning is no longer a thing built once for all.Cellular layout(CL) is becoming a hotspot in the research field of manufacturing system layout.Traditional researches on layout planning are mainly concentrating on aspects of layout arithmetic,style and evaluation,etc.Relatively seldom efforts are paid to CL and its specific problems as cell formation(CF),equipment sharing and CL analysis.Through problem analyzing of layout in cellular manufacturing system(CMS),research approach of cell formation,interactive layout and layout analysis threaded with process interconnection relationship(PIR) is proposed.Typical key technologies in CL like CF technology based on similarity analysis of part processes,interactive visual layout technology,layout evaluation technology founded on PIR analysis and algorithm of cell equipment sharing are put forward.Against the background of one enterprise which encounters problems of low utility of key equipments and disperse material logistic,an example of four-cell layout is given.The CL adjustment and analysis results show that equipment with high level of sharing degree should be disposed around the boundary of its main cell,and be near to other sharing cells as possible; process route should be centralized by all means,so equipment adjustment is to be implemented along direction that route intersection can be decreased; giving consideration to the existence of discrete cell,logistic route and its density should be centralized to cells formed.The proposed research can help improve equipment utility and material logistic efficiency of CL,and can be popularized to other application availably.

Influence of manufacturing process-induced geometrical defects on the energy absorption capacity of polymer lattice structures

Modern additive manufacturing processes enable fabricating architected cellular materials of complex shape,which can be used for different purposes.Among them,lattice structures are increasingly used in applications requiring a compromise among lightness and suited mechanical properties,like improved energy absorption capacity and specific stiffness-to-weight and strength-to-weight ratios.A dedicated modeling strategy to assess the energy absorption capacity of lattice structures under uni-axial compression loading is presented in this work.The numerical model is developed in a non-linear framework accounting for the strain rate effect on the mechanical responses of the lattice structure.Four geometries,i.e.,cubic body centered cell,octet cell,rhombic-dodecahedron and truncated cuboctahedron 2+,are investigated.Specifically,the influence of the relative density of the representative volume element of each geometry,the strain-rate dependency of the bulk material and of the presence of the manufacturing process-induced geometrical imperfections on the energy absorption capacity of the lattice structure is investigated.The main outcome of this study points out the importance of correctly integrating geometrical imperfections into the modeling strategy when shock absorption applications are aimed for.

Design of Cellular Manufacturing Systems Considering Dynamic Production Planning and Worker Assignments

This article presents a comprehensive mathematical model for the design and analysis of Dynamic Cellular Manufacturing Systems （DCMS）. The proposed DCMS model considers several manufacturing attributes such as multi period production planning, dynamic system reconfiguration, duplicate machines, machine capacity, the available time for workers, worker assignments, and machine procurement. The objective is to minimize total costs; consisting of holding cost, outsourcing cost, inter-cell material handling cost, maintenance and overhead cost, machine relocation cost. While a study of published articles in the area of Cellular Manufacturing Systems （CMS） shows that workforce management issues have not sufficiently been addressed in the literature, the model presented also incorporates CMS workforce management issues such as salaries, hiring and firing costs of workers in addition to the manufacturing attributes. In-depth discussions on the results for two numerical examples are presented to illustrate applications of the proposed model. The model developed aims to raise the envelope by expanding and improving several CMS models previously presented in the literature.

Modeling the Scheduling Problem in Cellular Manufacturing Systems Using Genetic Algorithm as an Efficient Meta-Heuristic Approach

This paper presents a new,bi-criteria mixed_integer programming model for scheduling cells and pieces within each cell in a manufacturing cellular system.The objective of this model is to minimize the makespan and intercell movements simultaneously,while considering sequence-dependent cell setup times.In the cellular manufacturing systems design and planning,three main steps must be considered,namely cell formation(i.e,piece families and machine grouping),inter and intra-cell layouts,and scheduling issue.Due to the fact that the cellular manufacturing systems problem is NP-Hard,a genetic algorithm as an efficient meta-heuristic method is proposed to solve such a hard problem.Finally,a number of test problems are solved to show the efficiency of the proposed genetic algorithm and the related computational results are compared with the results obtained by the use of an optimization tool.

EVOLUTIONARY ALGORITHMS WITH PREFERENCE FOR MANUFACTURING CELLS FORMATION

Due to the combinatorial nature of cell formation problem and the characteristics of multi-objective and multi-constrain, a novel method of evolutionary algorithm with preference is proposed. The analytic hierarchy process （AHP） is adopted to determine scientifically the weights of the sub-objective functions. The satisfaction of constraints is considered as a new objective, the ratio of the population which doesn＇t satisfy all constraints is assigned as the weight of new objective. In addition, the self-adaptation of weights is applied in order to converge more easily towards the feasible domain. Therefore, both features multi-criteria and constrains are dealt with simultaneously. Finally, an example is selected from the literature to evaluate the performance of the proposed approach. The results validate the effectiveness of the proposed method in designing the manufacturing cells.

Surface texture evaluation of additively manufactured metallic cellular scaffolds for acetabular implants using X.ray computed tomography

The surface topography of acetabular implants plays a key role in providing cell attachment and proliferation.The measurement and characterisation of the surface texture of the cellular scaffold layer on the acetabular cup are very difficult due to the 3D nature of scaffold geometry.It is proposed to use X-ray computed tomography(XCT)to measure the surface texture of an electron beam melting-produced titanium acetabular cup.The surface texture of its cellular scaffold is evaluated using the newly developed 3D surface texture parameters,which allows surface characterisation on 3D triangular mesh surfaces.Four commonly used height parameters,i.e.the arithmetical mean height Sa,the root mean square height Sq,the skewness Ssk and the kurtosis Sku,are calculated from surface patches extracted from the XCT scanned triangular mesh surface.In addition,the surface peak density and pit density,which are more related to cell communication and proliferation,are estimated based on the 3D watershed segmentation.The Wolf pruning with an empirical threshold 12μm is used to control the over-segmentation.

CMS环境下基于智能优化算法的单元间布局问题研究

研究了单元制造系统(CMS)设计中单元间布局设计问题,从单元制造系统的实际出发,提出了一种基于割树(Slicing-tree)的单元间布局设计模型。该模型考虑了单元形状约束、单元I/O点位置优化等诸因素对布局结果的影响。针对基于割树的描述形式,采用遗传算法求解,提出了一种新的割树编码方案,克服了以往编码方案易产生非法子串、不能覆盖整个解空间以及实现困难等缺点。计算结果表明,该算法是有效的、可行的。

中国羊绒及其制品贸易格局波动影响因素分析——基于CMS模型实证研究

我国是羊绒生产、加工、消费第一大国和羊绒产品贸易大国。根据UNComtrade相关数据,采用修正CMS模型分析我国原绒进口、无毛绒进出口和羊绒制品出口波动成因。研究发现,竞争效应是推动我国原绒进口增长主要因素,产品效应次之,增长效应作用最小;增长效应是我国无毛绒进出口贸易增长主要因素,竞争效应逐渐增强出口增长作用,产品效应对无毛绒进口增长贡献率较小且呈下降趋势,而对其抑制作用显著;增长效应是我国羊绒制品出口贸易增长主要因素,竞争效应贡献率较高且不断增加,而产品效应影响则越来越小。

橡胶型CM发泡特性的探讨

以橡胶型氯化聚乙烯(CM)为基材,采用OBSH作为发泡剂,研究了各种因素对CM发泡特性的影响。结果表明:DCP用量为3.5份,在170℃下发泡,其硫化胶的发泡性能较好;填料和增塑剂的品种和用量对CM的发泡性能的影响较大;填料采用CaCO3(用量为20份)、增塑剂为环氧大豆油和变压器油时,硫化胶的发泡性能较好。

我国制造业的CM模式

从循环经济的理论出发，采用主成分分析法计算了2001—2004年我国制造业细分行业的循环制造业指数CMI，并且采用面板数据的方法分析了我国制造业循环经济发展的影响因素。研究表明，科技创新和技术消化吸收能力对循环制造模式具有促进作用，而国有化程度高和外商投资比重大的行业则不利于循环制造模式的推广。

Hall-Petch relationship in selective laser melting additively manufactured metals:using grain or cell size?

The mechanical properties of many materials prepared by additive manufacturing technology have been greatly improved.High strength is attributed to grain refinement,formation of high density dislocation and existence of cellular structures with nanoscale during manufacturing.In addition,the super-saturated solid solution of elements in the matrix and the solid solution segregation along the wall of the cellular structures also promote the improvement of strength by enhancing dislocation pinning.Hence,the existence of cellular structure in grains leads to differences in the prediction of material strength by Hall-Petch relationship,and there is no unified calculation method to determine the d value as grain size or cell size.In this work,representative materials including austenite 316L SS were printed by selective laser melting(SLM),and the strength was predicted.The values of cell size and grain size were substituted into Hall-Petch formula,and the results showed that the calculation error for 316L is increased from 4.1%to 11.9%.Therefore,it is concluded that the strength predicted by grain size is more accurate than that predicted by cell size in additive manufacturing materials.When calculating the yield strength of laser additive manufacturing metal materials through the Hall-Petch formula,the grain size should be used as the basis for calculation.

Current status,enablers&barriers of implementing cellular manufacturing system in Indian industries

The cellular manufacturing （CM） has been proved as a well-known manufacturing strategy that helps to improve manufacturing efficiency and productivity by utilizing the philosophy of group technology. Large num- ber of papers has been published in the area of design issues of CM system. Unfortunately, the issues related to acceptability of CM in Indian industries are typically not examined rigorously as technical issues. This paper pre- sents the results of a survey carded out to find the status, enabler and barrier of implementing CM system in Indian industries.

Fatigue behavior of Ti-6Al-4V cellular structures fabricated by additive manufacturing technique

Porous titanium and its alloys have been considered as promising replacement for dense implants, as they possess low elastic modulus comparable to that of compact human bones and are capable of providing space for in-growth of bony tissues to achieve a better fixation. Recently, the additive manufacturing(AM) method has been successfully applied to the fabrication of Ti-6 Al-4 V cellular meshes and foams.Comparing to traditional fabrication methods, the AM method offers advantages of accurate control of complex cell shapes and internal pore architectures, thus attracting extensive attention. Considering the long-term safety in the human body, the metallic cellular structures should possess high fatigue strength.In this paper, the recent progress on the fatigue properties of Ti-6 Al-4 V cellular structures fabricated by the AM technique is reviewed. The various design factors including cell shapes, surface properties, post treatments and graded porosity distribution affecting the fatigue properties of additive manufactured Ti-6 Al-4 V cellular structures were introduced and future development trends were also discussed.

增材制造316L不锈钢组织结构特征与硬化机理

通过电弧送丝技术(WAAM)、激光同轴送粉(DED)以及激光选区熔化(SLM)增材制造技术制备出含有不同胞晶/枝晶尺寸的316L不锈钢,揭示了枝晶/胞状结构的形成及对力学性能的影响。结果表明:WAAM、DED和SLM试样的胞晶/枝晶尺寸依次减小,对应的冷却速率依次增大。同时,在WAAM和DED样品中枝晶/胞晶间区域发现骨状δ铁素体以及Cr、Mo的富集,但在SLM样品中未观察到以上现象,这主要是因为SLM过程中的高冷却速率显著抑制了δ铁素体的形成和元素偏析。WAAM、DED、SLM样品的显微硬度依次增加,其硬化机制与凝固胞状结构尺寸密切相关,且增材制造过程的热应力导致的高密度位错也对硬度有一定贡献。

A review of intelligent optimization for group scheduling problems in cellular manufacturing

Given that group technology can reduce the changeover time of equipment,broaden the productivity,and enhance the flexibility of manufacturing,especially cellular manufacturing,group scheduling problems(GSPs)have elicited considerable attention in the academic and industry practical literature.There are two issues to be solved in GSPs:One is how to allocate groups into the production cells in view of major setup times between groups and the other is how to schedule jobs in each group.Although a number of studies on GSPs have been published,few integrated reviews have been conducted so far on considered problems with different constraints and their optimization methods.To this end,this study hopes to shorten the gap by reviewing the development of research and analyzing these problems.All literature is classified according to the number of objective functions,number of machines,and optimization algorithms.The classical mathematical models of single-machine,permutation,and distributed flowshop GSPs based on adjacent and position-based modeling methods,respectively,are also formulated.Last but not least,outlooks are given for outspread problems and problem algorithms for future research in the fields of group scheduling.

基于元胞自动机的金属增材制造孔洞附近微观组织模拟

基于元胞自动机和粉末尺度的热流耦合模型,提出一种气孔处三维微观组织模拟方法。利用MATLAB构建元胞自动机模型,对增材制造钛合金Ti-6Al-4V的二维微观组织进行模拟,其模拟结果与实验结果吻合。通过FLOW-3D和EDEM软件联合仿真,利用有限体积法对三维多道次的粉末床熔融过程进行仿真,得到了温度场信息。将元胞自动机模型拓展到三维尺度,把得到的温度场数据导入元胞自动机模型,对孔洞位置处的微观组织进行数值模拟,得到了微观组织分布。该方法有助于构建金属增材制造工艺设计、缺陷表征、性能评价多尺度模型,以及用于晶粒、缺陷分布和疲劳寿命等信息预测。

浅析自动化封闭式细胞处理系统的模块化设计

本文从政策导向、行业指南的规划方向入手,在“质量源自设计”的理念下,根据细胞治疗产品生产制备环节对设备的功能需求,探讨自动化封闭式细胞处理系统的模块化设计思路。并结合目前市场上已有设备的功能使用情况,讨论符合GMP要求的自动化封闭式细胞处理系统发展趋势。

一种柔性路径下的跨单元调度方法

针对单元制造系统(Cellular manufacturing system,CMS)中需要多个单元协作完成的特殊工件,提出柔性路径下跨作业(Job shop)单元的特殊工件调度方法—基于信息素的方法(Pheromone-based approach,PBA).基于多Agent对单元制造系统建立模型,提出了冗余单元的概念,建立了多Agent之间的协商机制.同时通过建立Agent联盟,减少通信量的同时增强系统的鲁棒性和调度优化的全局性.实验结果表明,与常见的组合调度规则相比,本文提出的方法在5种性能指标上具有显著优势.

单元制造系统集成建模研究

单元制造作为一种先进制造模式包括单元构建、单元设计和单元管理三个方面。本文首先总结现有单元制造领域的研究现状和存在的问题。在此基础上 ,建立了同步优化单元构建、设备布置与成组排产的非线性规划模型 ,给出了基于遗传算法的模型求解方案。最后指出了今后研究的方向。

敏捷制造模式下的单元化制造

分析对生产组织和运行的要求，提出敏捷制造的组织和运行方式。在物理上，系统中的共享制造资源要按照成组技术进行组织和布局，而在生产组织上则要面向订单进行。对每一订单都要构成相应的虚拟单元（车间），它们具有自治性。在管理上，需要一种协调机制，来协调这些自治单元（车间）对公用的制造资源的分享。