Balancing mixed-model assembly lines: a computational evaluation of objectives to smoothen workload

Mixed-model assembly lines are widely used in a range of production settings, such as the final assembly of the automotive and electronics industries, where they are applied to mass-produce standardised commodities. One of the greatest challenges when installing and reconfiguring these lines is the vast product variety modern mixed-model assembly lines have to cope with. Traditionally, product variety is bypassed during mid-term assembly line balancing by applying a joint precedence graph, which represents an (artificial) average model and serves as the input data for a single model assembly line balancing procedure. However, this procedure might lead to considerable variations in the station times, so that serious sequencing problems emerge and work overload threatens. To avoid these difficulties, different extensions of assembly line balancing for workload smoothing, i.e. horizontal balancing, have been introduced in the literature. This paper presents a multitude of known and yet unknown objectives for workload smoothing and systematically tests these measures in a comprehensive computational study. The results suggest that workload smoothing is an essential task in mixed-model assembly lines and that some (of the newly introduced) objectives are superior to others.     

Sequencing mixed-model assembly lines to minimise the number of work overload situations

The mixed-model sequencing problem is to sequence different product models launched down an assembly line, so that work overload at the stations induced by direct succession of multiple labour-intensive models is avoided. As a concept of clearing overload situations, especially applied by Western automobile producers, a team of cross-trained utility workers stands by to support the regular workforce. Existing research assumes that regular and utility workers assemble side-by-side in an overload situation, so that the processing speed is doubled and the workpiece can be finished inside a station's boundaries. However, in many real-world assembly lines the application of utility workers is organised completely differently. Whenever it is foreseeable that a work overload will occur in a production cycle, a utility worker takes over to exclusively execute work, whereas the regular worker omits the respective cycle and starts processing the successive workpiece as soon as possible. This study investigates this more realistic sequencing problem and presents a binary linear program along with a complexity proof. Different exact and heuristic solution procedures are then introduced and tested. Additional experiments show that the new model is preferable from an economic point of view whenever utility work causes considerable setup activities, for example walking to the respective station.     

装配干扰的控制：Fuzzy—Petri网络系统帮助调整装配计划

复杂产品单件或小批量装配的流程，经常会受到许多干扰的影响。因此，装配管理人员必须使根据生产能力得出的中期装配计划不断更新，适应实际的装配流程，以确保达到预期的生产目标。一种干扰管理系统已经投入使用，以支持对生产有影响的决策。这一系统目前在克姆尼茨工业大学和亚琛工业大学机床和企业管理实验室（ＷＺＬ）的合作下应运而生。为了制定现行的装配计划，采用了以Ｆｕｚｚｙ－Ｐｅｔｒｉ网络为知识基础的专家系统，该系     

支持设计过程的装配可行域划分和零件定位求解

提出了支持设计过程的六种装配约束 ,根据装配约束的结合条件划分出装配可行区域、装配可能区域和装配不可行区域 .在装配可行区域的零件的位置是直接确定的 .在装配可能区域零件的位置要根据它们的约束组合条件和几何数据进行解释 ,然后计算零件的位置和方向 .在装配不可行区域 ,零件的位置不能求解 .装配可行区域的划分和零件位置的确定可以极高的效率支持产品的设计过程     

基于映射的产品装配建模技术研究

根据自顶向下的设计要求,提出基于映射技术的功能模型向装配模型的转换方法.通过信息实例化及规则表达,保证了映射技术的可行性.通过建立不同的实例库和Mapping表,较好实现了模型信息的转换.通过功能单元映射为装配单元,功能间约束映射为装配连接特征以及装配关系,实现了设计约束的自顶向下传递和功能设计与结构设计的集成.利用二叉树对模型交互进行装配序列化处理,保证了装配模型结构的完整性与可装配性.通过开发原型系统验证了该方法的可行性.     

Balancing parallel two-sided assembly lines

Two-sided assembly lines are usually designed to produce large-sized products such as automobiles, trucks and buses. In this type of production line, both left-side and right-side of the line are used. In parallel assembly lines, one or more product types are produced on two or more assembly lines located in parallel to each other. Both production lines have several serious practical advantages. For this purpose, in this paper, two or more two-sided assembly lines located in parallel to each other are considered and a tabu search algorithm which combines the advantages of both types of production lines is developed. To assess the effectiveness of the proposed algorithm, a set of test problems are solved. The proposed algorithm is illustrated with two examples, and some computational properties of the algorithm are given.     

Meeting demand variation using flexible U-shaped assembly lines

Nowadays, companies must be able to provide a higher degree of product customisation to fulfil the needs of the increasingly sophisticated customer demand. This can only be achieved by having flexible production systems, able to cope with extended product ranges and with the uncertainty and variability of demand in the current market environment. The purpose of this paper is to present a contribution related to facilities design that accounts for this issue, by presenting flexible U-shaped line configurations for an assembly system. In this type of line, whenever the production volume or product mix changes, the only modification in the line will be the number of operators working in the line, as the physical workstations remain fixed. The relevance of the problem is stated and a heuristic procedure, based on ant colony algorithms, developed to address this problem is described. The results of the application of the proposed procedure to an assembly line of a major manufacturer of electronic security systems are reported.     

基于产品配合图的装配顺序自动规划

装配顺序规划( ASP) 是基于装配建模的装配工艺顺序的自动规划生成, 是DFA( 面向装配的设计) 的关键技术之一。本文采用配合条件法进行装配顺序求解, 装配体采用其部件与部件间的配合关系来描述, 从部件间的配合关系可得到其装配体配合图。本文还在原算法的基础上添加了一些约束来降低算法的计算量, 使得算法更为简洁。该法在AutoCAD®设计平台上实现, 并采用装配体实例加以检验。     

Stochastic two-sided U-type assembly line balancing: a genetic algorithm approach

In this paper, a novel stochastic two-sided U-type assembly line balancing (STUALB) procedure, an algorithm based on the genetic algorithm and a heuristic priority rule-based procedure to solve STUALB problem are proposed. With this new proposed assembly line design, all advantages of both two-sided assembly lines and U-type assembly lines are combined. Due to the variability of the real-life conditions, stochastic task times are also considered in the study. The proposed approach aims to minimise the number of positions (i.e. the U-type assembly line length) as the primary objective and to minimise the number of stations (i.e. the number of operators) as a secondary objective for a given cycle time. An example problem is solved to illustrate the proposed approach. In order to evaluate the efficiency of the proposed algorithm, test problems taken from the literature are used. The experimental results show that the proposed approach performs well.     

Directed Assembly of Hybrid Nanomaterials and Nanocomposites

Hybrid nanomaterials are molecular or colloidal‐level combinations of organic and inorganic materials, or otherwise strongly dissimilar materials. They are often, though not exclusively, anisotropic in shape. A canonical example is an inorganic nanorod or nanosheet sheathed in, or decorated by, a polymeric or other organic material, where both the inorganic and organic components are important for the properties of the system. Hybrid nanomaterials and nanocomposites have generated strong interest for a broad range of applications due to their functional properties. Generating macroscopic assemblies of hybrid nanomaterials and nanomaterials in nanocomposites with controlled orientation and placement by directed assembly is important for realizing such applications. Here, a survey of critical issues and themes in directed assembly of hybrid nanomaterials and nanocomposites is provided, highlighting recent efforts in this field with particular emphasis on scalable methods.     

随机型双边装配线平衡问题的一种启发式算法

为有效求解随机型双边装配线第Ⅰ类平衡问题(STALBP 1),在分析双边装配线平衡特点的基础上,考虑各任务操作时间的随机性,提出了一种启发式算法。在该启发式算法中,假定各任务的操作时间服从正态分布,运用具有操作方位约束的任务优先分配等规则来进行任务的选择和分配,通过改变预设超限概率,在不同生产节拍下,分别得到不同的平衡方案。实例验证了算法的有效性。     

Strategy of Concurrent Optimization for an Assembly Sequence

An effective constraint release based approach to realize concurrent optimization for an assembly sequence is proposed. To quantify the measurement of assembly efficiency, a mathematical model of concurrency evaluation index was put forward at first, and then a technology to quantify assembly constraints was developed by application of some fuzzy logic algorithms. In the process of concurrent optimization of the assembly sequence, two kinds of constraints were involved. One was self-constraints of components, which was used to evaluate the assemble capability of components under the condition of full-freedom. Another was an assembly constraint between components represented by geometric constraints between points, lines and planes under physical restriction conditions. The concept of connection strength degree （CSD） was introduced as one efficient indicator and the value of it was evaluated by the intersection of the two constraints mentioned above. The equivalent constraints describing the connection weights between components were realized by a well designed constraints reduction, and then the connection weights based complete assembly liaison graph was applied to release virtual connections between components. Under a given threshold value, a decomposition and reconstituting strategy for the graph with the focus on high assembly concurrency was used to realize an optimized assembly concurrency evaluation index. Finally, the availability of the approach was illustrated in an example to optimize the assembly of a shift pump.     

Materials Fabricated by Micro‐ and Nanoparticle Assembly – The Challenging Path from Science to Engineering

We classify the strategies for colloidal assembly and review the diverse potential applications of micro‐ and nanoparticle structures in materials and device prototypes. The useful properties of the particle assemblies, such as high surface‐to‐volume ratio, periodicity at mesoscale, large packing density, and long‐range ordering, can be harnessed in optical, electronic, and biosensing devices. We discuss the present and future trends in the colloidal‐ assembly field, focusing on the challenges of developing fabrication procedures that are rapid and efficiently controlled. We speculate on how the issues of scalability, control, and precision could be addressed, and how the functionality of the assemblies can be increased to better match the needs of technology.     

直升机数字化装配工艺设计与三维AO构建

飞机装配工艺设计过程及工艺数据的组织管理是当前飞机数字化制造技术研究中的一个关键问题．在基于模型定义技术的基础上,提出了直升机数字化装配工艺设计与三维装配指令（assembly order, AO）构建的方法．通过对DPE软件进行客户化定制和脚本开发,优化了数字化装配工艺设计过程,实现了AO文本的自动输出,缩短了装配指令的编写周期;通过对DPE与3DVIA Composer软件的集成开发,实现了三维AO的构建,从而为装配现场可视化奠定了基础,较好地解决了传统装配指令对装配现场指导不生动、不直观等问题．     

面向虚拟装配的"顶点表示活动"网络排序装配顺序规划的研究

基于信息化制造这样一种新型制造模式，阐述了信息化制造的研究方向之一是虚拟装配技术，讨论了装配顺序规划的研究现状。研究了面向虚拟装配将顶点表示活动网络（Activity On Vertices，简称AOV网络）排序应用到装配顺序规划中的方法，探讨了AOV网络排序在减速器装配顺序规划中的应用。研究结果表明：该方法对于产品装配顺序规划的应用达到了预期的效果。