Consensus tree method for generating master assembly sequence

An assembly process plan for a given product provides the sequence of assembly operations, their times as well as the required tools and fixtures for each operation. Much research has been done on automating and optimizing assembly sequence generation as the most important part of an assembly process plan. A novel method for generating the assembly sequence of a given product based on available assembly sequence data of similar products is presented. The proposed method uses a binary tree form to represent the assembly sequences of an existing family of products. A Genetic Algorithm is employed to find the consensus tree that represents the set of all assembly sequence trees with minimum total dissimilarity distance. This is similar to defining Generic Bill-of-Material. The generated consensus tree serves as a master assembly sequence for the product family. The assembly sequence for a new product variant that falls within, or significantly overlaps with, the scope of the considered family of products can be directly extracted from the derived master assembly sequence tree. The developed method is demonstrated using a family of three control valves. This novel method greatly simplifies and enhances automatic assembly sequence generation and minimizes subsequent modifications, hence, reduces assembly planning cost and improves productivity.     

Local order scheduling for mixed-model assembly lines in the aircraft manufacturing industry

Multi-variant products to be assembled on mixed-model assembly lines at locations within a production network need to be scheduled locally. Scheduling is a highly complex task especially if it simultaneously covers the assignment of orders, which are product variants to be assembled within a production period, to assembly lines as well as their sequencing on the lines. However, this is required if workers can flexibly fulfill tasks across stations of several lines and, thus, capacity of workers is shared among the lines. As this is the case for final assembly of the Airbus A320 Family, this paper introduces an optimization model for local order scheduling for mixed-model assembly lines covering both assignment to lines as well as sequencing. The model integrates the planning approaches mixed-model sequencing and level scheduling in order to minimize work overload in final assembly and to level material demand with regard to suppliers. The presented model is validated in the industrial application of the final assembly of the Airbus A320 Family. The results demonstrate significant improvement in terms of less work overload and a more even material demand compared to current planning.     

基于子装配的装配序列规划方法研究

为了提高复杂机械产品装配序列规划的效率,提出了基于子装配的装配序列规划方法.建立了基于有向约束图的装配模型,并给出了基于子装配的装配序列规划系统框架,从而将产品装配序列规划问题转化为子装配的装配序列规划问题;给出了子装配的相关定义,并从稳定性和干涉性两个方面设计了子装配的识别方法;最后,给出了系统算法流程图,并通过电机车轴承箱装配实例验证了该算法的有效性.     

Incorporating expedited time and cost of the end product into the product structure diagram

This paper presents an algorithm for determining expedited time and cost of the end product in the product structure diagram (PSD) using critical path method (CPM) and time-costing method. The classical PSD provides essential information for the consequent material requirement planning (MRP). Such information includes the parent–child relationship between the end item and its components at each level, the number of components required at the child level in order to produce one unit at the parent level, and the number of periods required for production of each component. Selecting an appropriate acquisition method (either manufacturing process or speed of assembly or specific supplier) for each component is one of the early tasks faced by a product/process design team and it is critical because that the resulting decisions are then translated into the PSD and its subsequent material requirement planning. In this study, we propose a step-by-step decision procedure using the CPM and time-costing method for determining the optimal component procuring alternatives when expediting end product's completion time is desired. A numerical example demonstrates its practical usage.     

Modular design for increasing assembly automation

Modular design can address the need for a high number of product variants and further allow a higher degree of automation in the assembly line. A framework is developed for the simultaneous modular product design and the design of automated manufacturing system. Product designs are optimized for automation using Design Structure Matrix and Modular Function Deployment. Alternative production systems are designed and accessed based on the analysis of assembly steps hierarchically. The implementation of the framework on the design of a production system for furniture assembly, able to handle multiple variants with a large number of components, is demonstrated.     

Development of new concepts and software tools for the optimization of manual assembly systems

Due to growing numbers of differing products and variants, assembly systems with optimized manual workstations have become an efficient alternative to highly automated but less flexible production systems. Especially in the final stage of the product assembly, the flexibility of human employees enables them to meet the requirements for assembling various products and changing volumes. In order to create highly efficient production systems based on human work, it is necessary to develop innovative concepts for the design and organization of manual assembly structures. Another major issue is the development of software tools allowing the facility planner to simulate and optimize the complete design of the assembly structure such as the material flow or manual workstations, e.g. with respect to ergonomics, before construction. These requirements have led to a comprehensive research framework for manual assembly systems.     

Integration of Product Design and Assembly Planning in the Digital Factory

As assembly process planning fulfils the main function of connecting product design to production simulation and thus, the production system itself, a feasible software solution is needed to support this process. Thus, a novel concept is presented that aims at improving the integration of digital product design and assembly planning by introducing a consistent data structuring. This approach helps to reduce redundant tasks and supports the continuous data exchange. It is based on the use of assembly features, i.e. pre-defined geometry elements that contain additional technological information.The prototypical implementation of the concept focuses on the use of commercially available software tools, expanding them with additional functionality for the application of assembly features. The feature-based concept has been tested with a scenario from the automotive supplier industry. For the considered assembly, a comparison between the conventional and the feature-based planning approach is presented in the paper. It points out that the major advantages of the developed concept can be seen in an improved data consistency as well as a higher level of efficiency within the planning activities.     

以客户需求为驱动的婴儿推车快速设计平台的开发与实现

以快速设计思想为指导,对以实现客户需求为驱动的婴儿推车快速设计平台展开了系统性研究与开发.论述了以客户需求为驱动的设计平台特性、快速设计平台的主界面设计、客户产品需求定制的实现和基于配置与变型方法的快速设计的实现.为了选取产品实例库中与客户需求匹配程度高、产品族各模块间的装配契合度好的模型,高效实现配置设计和变型设计,提出多子装配体的检索装配算法.     

Quality-driven Sequence Planning and Line Configuration Selection for Compliant Structure Assemblies

Assembly sequence planning is an integral part of a new product and process development. However, currently there are very few available approaches to evaluate the impact of assembly sequences on product quality. This paper develops a methodology for Quality-driven Sequence Planning (Q/SP) with consideration to product dimensional quality based on the following three steps: (1) Sequence generation for predetermined line configurations using /(-piece mixed-graph representation of assembly; (2) Dimensional quality model of variation propagation for assembly processes with compliant parts; and (3) Evaluation of sequences based on the multivariate process capability index. The methodology is illustrated using an industrial case study.     

Augmented Reality Aided Assembly Design and Planning

This paper presents a methodology that integrates the assembly Product Design and Planning (PDP) activities with the Workplace Design and Planning (WDP) activities to improve the efficiency and quality of assembly design and planning at the early design stage. This methodology is implemented in an augmented reality (AR) assembly environment, where engineers can design and plan a product assembly and its assembly sequence through manipulating virtual prototypes in a real assembly workplace. In this AR environment, WDP information are fed back to the designers and engineers in real-time to aid them in making better decisions in assembly design and planning.     

Appropriate Human Involvement in Assembly and Disassembly

Product assembly as well as disassembly is often carried out by workers who have been trained and are flexible with respect to the different variants, delivery dates and changing lot sizes. Though there has been a strong tendency to mechanize and automate production during the last years many operations in assembly and disassembly are still very often performed manually. Furthermore there might be an increase in manually operated assembly or disassembly as a result of product equipment investments with shorter usage time. This keynote paper deals with the state of practice as well as the tendencies in product and production technology and the influence of markets. Another question is going to be the use of information technology on the shop floor level and between the shop floor and other levels within a company as well as the customers. Therefore industrial engineering is increasingly dealing with the influence of organization and structuring of production processes.     

柔性装配系统规划设计研究

在系统研究柔性装配系统规划设计内容的基础上,从产品的整个生命周期出发,建立了柔性装配系统并行设计 整体约束网络模型,最后根据系统设计因素多且相互制约的特点,提出结合领域知识和遗传算法的人机一体优化策略对柔性装配系统进行规划设计。     

Human Hybrid Robot: a new concept for supporting manual assembly tasks

Due to the volatile conditions in today’s production, flexible assembly systems are required. However, current plants are often custom-made which are designed for a fix product spectrum. Especially for the assembly of unique products or products with a small-scale lot size and large-scale lot size with a high diversity of variants, many manufacturing steps are difficult or non economic to automate. Thus, a large part of the manufacturing processes is to be performed manually. These can be supported by assistance systems, but appropriate systems are seldom available. A new approach for supporting manual assembly tasks is the hybridization of biological and technical systems, a so-called “Human Hybrid Robot” (HHR). The kinematic chains of human, machines and tools are configured task-depended in serial and parallel arrangement. By doing so, the individual skills are used optimally. Main focus of this concept is improving the assembly accuracy and error prevention to boost the overall quality of the assembly processes. This paper presents the theoretical concept. Possible applications and realization of exemplary components are outlined to show the potential of HHR.     

CIMS中基于规则的产品数据管理的研究

随着企业信息化的快速发展,很多企业引入了CIMS,但是几个CIM组件之间庞大的数据交换成为难题.文章介绍了一种基于规则的产品数据管理方法,通过不同零件和不同BOM之间的数据交换动态地实现CIMS之间的数据管理,完成了不同CIM组件之间的数据交换,并且实现了对BOM工艺、加工计划的规划算法研究.该方法的实现可以把企业生产过程中所有与产品相关的信息和过程集成起来,统一管理,使产品数据在其生命周期内保持一致、及时更新.     

Crystallographic analysis of the FCC → BCC martensitic transformation in high-carbon steel

Based on the phenomenological crystallographic theory of martensitic transformations, the following crystallographic characteristics of the tetragonal martensite in high-carbon steel have been calculated: orientation relationships between the crystal lattices of the bct martensite and fcc austenite; the magnitude and direction of the macroscopic shear; the habit plane; the angle and the axis of rotation of the crystal lattice of the martensite. The calculation was performed for three variants of lattice deformation: Bain deformation; two-shear Kurdjumov-Sachs deformation; and the deformation we suggested upon the analysis of the fcc-bcc transformation. In the last variant, a minimum rotation of the crystal lattice of martensite is required; consequently, this variant is closest to the real mechanism of the martensitic transformation. An expression has been derived that describes the interrelation between the degree of tetragonality of the crystal lattice of martensite and the magnitude of the shear deformation of the lattice. It has been shown that the 12 crystal-lographically equivalent variants of shear upon the formation of the lattice of the tetragonal martensite form three groups in each of which the martensite has the same tetragonality axis. For each variant of the shear, we have two equivalent variants of deformation of the martensite with invariant lattice. This results in 24 variants of orientation relationships.     

A multi-agent architecture for plug and produce on an industrial assembly platform

Modern manufacturing companies face increased pressures to adapt to shorter product life cycles and the need to reconfigure more frequently their production systems to offer new product variants. This paper proposes a new multi-agent architecture utilising “plug and produce” principles for configuration and reconfiguration of production systems with minimum human intervention. A new decision-making approach for system reconfiguration based on tasks re-allocation is presented using goal driven methods. The application of the proposed architecture is described with a number of architectural views and its deployment is illustrated using a validation scenario implemented on an industrial assembly platform. The proposed methodology provides an innovative application of a multi-agent control environment and architecture with the objective of significantly reducing the time for deployment and ramp-up of small footprint assembly systems.     

Constraints analysis and evaluation of manual assembly

The use of integrated ergonomic constraints for the objective evaluation of manual assembly sequencing is proposed in this paper. Feasible assembly sequences are generated and evaluated by a new Liverpool assembly sequence planning (LASP) system in terms of product geometry, assembly workstation layout, operator characteristics and posture. Two new evaluation criteria, i.e., visibility, accessibility or both, are applied in the optimization of the assembly sequencing. With LASP, possible design faults and optimum assembly sequence with maximum visibility and/or accessibility score is obtainable during the design stage. An illustrative case study of an air conditioner assembly is also presented.     

Assembly system design and operations for product variety

Assembly is the capstone process for product realization where component parts and subassemblies are integrated together to form the final products. As product variety increases due to the shift from mass production to mass customization, assembly systems must be designed and operated to handle such high variety. In this paper we first review the state of the art research in the areas of assembly system design, planning and operations in the presence of product variety. Methods for assembly representation, sequence generation and assembly line balancing are reviewed and summarized. Operational complexity and the role of human operators in assembly systems are then discussed in the context of product variety. Challenges in disassembly and remanufacturing in the presence of high variety are presented. We then conjecture a future manufacturing paradigm of personalized products and production and discuss the assembly challenge for such a paradigm. Opportunities for assembly system research are summarized at the end of the paper.     

Open-architecture products

This paper defines open-architecture products (OAPs), a new class of products comprising a fixed platform and modules that can be added and swapped. Customers can adapt OAPs to their needs by integrating modules into the platform. Manufacturers will produce these platforms, while new small companies and customers will develop the modules, thus increasing employment and causing the economy to flourish. At the same time OAPs will provide consumers with the product they desire. Challenges include developing new OAP design software for non-professional designers and new assembly systems to facilitate economical assembly of a large number of product variants.