An Information Modelling Framework to Support Intelligent Concurrent Design and Manufacturing of Sheet Metal Parts

Sharing of information is an important issue in supporting integrated and rapid product development. The use of information modelling technology is a promising approach for solving the problems of the intensive sharing of information in a concurrent and rapid product development cycle. This paper explores the definition and the structure of a framework of information modelling for the concurrent design and manufacturing of sheet metal parts. This framework aims to build an information bridge to fill the gap between the sheet metal part design and manufacturing systems. It is based on abstract handling principles of entities called zero thickness and zero bend radius principles. Based on this framework, information models can be built for information sharing by different systems. Knowledge bases that support intelligent concurrent design and manufacturing can also be created. In this paper, a two-branch tree based stepping-structure information modelling methodology for sheet metal parts is described, and a case study is given.     

An Intelligent Knowledge-Based System for Product Cost Modelling

An intelligent knowledge-based system for product cost modellingis presented in this paper. The developed system has the capability of selecting a material, as well as machining processes and parameters based on a set of design and production parameters; and of estimating the product cost throughout the entire product development cycle including assembly cost. The proposed system is applied without the need for detailed design information, so that it can be used at an early design stage, and, consequently, redesign cost and longer lead time can be avoided. Hybrid knowledge representation techniques, such as production rules, frame and object oriented are employed to represent manufacturing knowledge. Fuzzy logic-based knowledge representation is applied to deal with uncertainty in the knowledge of cost model to generate reliable cost estimation. This paper deals with cost modelling of both a machining component and an injection moulding component, which is a process that gives high production rates, excellent quality and accuracy of products, and low manufacturing cost. Based on the analysis of the moulded product life cycle, a computer-based cost model was developed which integrated the relationship between cost factors, product development activities, and product geometry. The estimated cost included the costs of material, mould and processing. The system has been validated through a case study.     

基于特征信息建模技术

提出一种新的基于特征信息建模方法,该方法能在多级抽象层次上完备地描述产品信息,并提供良好的产品数据表达和数据转换机制,使CAD/CAM集成和并行设计的实现成为可能。笔者运用这种建模技术研制了板材折弯FMC运行控制软件自动生成系统,在产品信息集成与共享基础上,该系统集设计、分析、工艺规划、制造过程于一体,并具有良好的总体结构。     

Challenges of manufacturability and product data management in bending

Effective production in a networking environment of sheet metal products needs accurate and relevant PDM (product data management) data, appropriate modeling of components supported by local and global network solutions, and utilization of advantages of feature-based modeling. To enable these aspects of effective production in sheet metal production, it is necessary to evaluate the integration of DFMA (design for manufacturing and assembly) and PDM. This paper aims at identifying the challenges of DFMA and PDM integration through recognizing possible malfunctioning parts of their integration. The observations are based on sheet metal specimens in which the DFMA and PDM aspects are visible in punching and bending. This study will focus on five issues that are included either in DFMA or PDM, or both: the effects of different calculation methods for the flattened length, utilization viewpoints of global or local manufacturability guidelines, assembly conditions, options to tune the manufacturing process instead of changing the product geometry, and possible additional requirements given by the customers. Based on practical design and manufacturing tests, it has become evident that one option to improve the quality of analyzed sheet metal parts is to further develop the integration of DFMA features with the workshop’s cutting and punching parameters. As one possible improvement to these kinds of integration tasks of DFMA and PDM, it is suggested that the responsibilities for developing DMFA and PDM applications with proper design parameters could be analyzed more deeply between persons working with information exchange, product design, software design, or production machine design.     

Ideal stretch forming for minimum weight axisymmetric shell structures

A companion paper “Minimum Weight Design of Axisymmetric Shell Structures” by Richmond and Azarkhin describes the design of axisymmetric thin-walled structures and parts that can support specified loads with minimum material. The result is an optimum shape and thickness distribution in the final part when the strength of the material is assumed to be uniform. Here, we demonstrate the application of ideal forming theory to design sheet stretching processes that can produce the optimum shapes and thickness distributions from flat sheets of uniform thickness. Specific designs are achieved for producing minimum weight shell structures that will support a specified uniform pressure assuming both the Mises and the Tresca yield criteria along with the rigid-perfectly plastic flow condition. In the case of the Tresca yield condition, the optimum structure is a spherical shell segment with uniform thickness, and an associated ideal stretching process is hydraulic bulging. Because the effects of strain hardening have been neglected in the structural optimization theory, it has been possible here to design the minimum weight structure and its forming process sequentially. In subsequent work, we plan to include the effects of strain hardening on the shell strength, which will then require coupled design of the structure and its forming process. Also extension of these methods to three-dimensional geometries will be considered.     

Damage evolution in creep bulging of thin sheet metal

The creeping motion of thin sheet metal, damaged by artificial cavities is observed in bulging tests and simulated ‘semi’-analytically. The sheet metal satisfies Norton’s Law for secondary creep and is subjected to a bi-directional stretch. The stretch is produced by creep bulging through elliptical dies with the virtue of sustaining nearly uniform background stress ratio for each aspect ratio of the die axes. In order to reach large deformations with significant shape evolution of the cavities, the tests were conducted at superplastic conditions. The sheet is double layered (only one layer is cavitated) made of Tin–Lead (50–50 Pb–Sn). The measured damage growth is compared to an approximate simulation. The simulation of the damage evolution, throughout its time history, makes repeated use of a so-called “Green-function solution” for the motion of a single isolated cavity in an infinite viscoplastic continuum. The solution is modified from Muskhelishvili’s elastic solution by replacing the elastic shear modulus by a “viscous-like” variable (“plastic shear modulus”) which depends (non-linearly) on the evolved average strain-rate. Similarly, the stresses in the ligaments between cavities were averaged to approximate the local stress concentrations. Due emphasis is given to the rotation of each elliptical cavity, beside its expansion (contraction) and elongation.     

Configuration-oriented product modelling and knowledge management for made-to-order manufacturing enterprises

In made-to-order (MTO) manufacturing enterprises (ME), product architectures are usually modularised and components standardised. Product configuration is a key technology for order realisation in MTO–ME and is a typical knowledge-based application. Through a configuration process, product modules or components are selected and assembled according to customer requirements. Product configuration relates to a great deal of knowledge that represents complexity relations among components or modules, such as configuration rules and assembly constraints. Traditional product modelling techniques are focused mainly on physical product modelling and geometric representation, which makes them insufficient to help in the product configuration process. This paper discusses configuration-oriented product modelling and knowledge management for MTO–ME. A general process of product configuration modelling is proposed. The configuration model represents a product family from which a specific configuration solution or product variant can be derived. Actually, configuration modelling is a process which captures and represents product knowledge. In this paper, product knowledge is organised and managed through a knowledge component (KCOM) that includes configuration rules and constraints. A KCOM-based product knowledge representation model is presented. Finally, a PDM system is extended to support product modelling and knowledge management for MTO configurable products .     

G180型柴油机油箱冲压成形过程研究

首先叙述了钣金冲压过程中出现缺陷的影响因素,以G180型柴油机油箱为例,具体介绍了其选材、模具设计、工艺等设计制造过程,并着重分析了其在冲压制造过程中所存在的问题及解决办法,为其他板料冲压制造提供了设计素材和处理出现缺陷的经验。     

A resource-based modelling approach to support responsive manufacturing systems

The manufacturing industry faces the challenge of responding quickly to the ever-changing requirements of customers. A key factor in these highly competitive environments is an ability for companies to master key production system dynamics such as change in the product types and variants and production quantities that they make, with high quality, low cost, and fast delivery. A novel approach to modelling manufacturing systems is introduced which is based on the provision of means for explicitly representing and computer executing dynamic producer units (DPUs). DPUs are defined as re-usable, change capable components of a manufacturing enterprise and have been described in the present authors’ previous publications. DPU concepts were conceived to support (1) the design of change capable manufacturing systems that can realise families of similar products in varying quantities and mixes and (2) the re-configuration of manufacturing systems in cases of withdrawal of a product family and introduction of a new one. To achieve this, a generic manufacturing system model is required to facilitate the systematic and timely alteration of production system designs and production plans. DPU modelling concepts facilitate these alterations through explicitly specifying the need for change capabilities so that rapid and cost-effective changeover responses can be made when production requirements change. This paper presents how DPU modelling concepts can be applied with reference to an industrial case study and describes a change decision-making framework in the form of a taxonomy and enabling tools.     

工艺规划为核心的产品协同研发生产平台

为实现具有市场竞争力产品的高端研发,并具备较高的质量及成本控制能力,文中提出构建以工艺规划为核心的产品数字化研发生产平台的解决思路.平台框架包含计算机辅助设计、产品数据管理、计算机辅助工艺规划和协同制造模块;通过工艺与设计、生产两端的数据共享,实现设计、工艺数据和生产的高效协同;通过工艺规划方案的功能描述,展现了一个为...     

汽车覆盖件冲压成形仿真研究进展

汽车覆盖件冲压成形仿真技术的发展,突破了原有汽车冲压件模具及工艺设计的设计方法,对保证工件质量、减少材料消耗、缩短产品开发周期、降低制造成本具有重要意义.概述了目前汽车覆盖件冲压成形仿真所涉及到的热点领域,如摩擦与接触、回弹分析、模具系统和工艺参数、材料屈服模型和板料形状设计,讨论了这些领域的研究进展和进一步研究的发展方向.     

An Automated Progressive Process Planning and Die Design and Working System for Blanking or Piercing and Bending of a Sheet Metal Product

This paper describes the development of a computer-aided design and manufacturing system for irregular-shaped sheet metal products for blanking or piercing and bending operations. The approach is based on knowledge-based rules. Knowledge for the system is formulated from plasticity theories, experimental results and the empirical knowledge of field experts. This program for the system has been written in AutoLISP using AutoCAD and on SmartCAM using a personal computer and is composed of nine modules, which are input as shape treatment, flat pattern-layout, production feasibility check, blank-layout, strip-layout, die-layout, data-conversion, modelling, and post-processor modules. Based on knowledge-based rules, the system is designed by considering several factors, such as material and thickness of product, complexities of blank geometry and punch profile, diameter and material of a wire, and the availability of a press. This system is capable of unfolding formed sheet metal to give a flat pattern and automatically accounts for the adjustment of bending allowances to match tooling requirements by checking dimen-sions and generating NC data automatically according to the drawings of the die-layout module. Results obtained using the modules enable the designer and manufacturer of blanking or piercing and bending dies to be more efficient in this field.     

Substepping algorithms with stress correction for the simulation of sheet metal forming process

The finite element analysis of the sheet metal forming process involves various nonlinearities. To predict accurately the final geometry of the sheet blank and the distribution of strain and stress and control various forming defects, such as thinning, wrinkling and springback, etc., the accurate integration of the constitutive laws over the strain path is essential. Our objective in this paper is to develop an effective and accurate stress integration scheme for the analysis of three-dimensional sheet metal forming problems. The proposed algorithm is based on the explicit “substepping” schemes incorporating with the stress correction scheme. The proposed algorithms have been implemented into ABAQUS/Explicit via User Material Subroutine (VUMAT) interface platform. The algorithms are then employed to analyze a typical deep-cup drawing process and the accuracy of these algorithms has been compared with the implicit “return” algorithm and explicit forward algorithm. The results indicate that the explicit schemes with local truncation error control, together with a subsequent check of the consistency conditions, can achieve the same or even better level of accuracy as “return” algorithm does for integrating large plastic problems like sheet metal forming process.     

A manufacturability advisor for spun and rollformed sheet metal components

In today’s manufacturing scenario, accounting for manufacturability considerations at the product design stage is not an option but a necessity. When CAD/CAM tools are used to reduce design lead times, accounting for manufacturing process related considerations implicitly is often difficult. Availability of manufacturability advisor systems that analyze part geometry and other product related information for ease of manufacturing could be a solution to this problem. The purpose of a manufacturability assessment is to give feedback to the designer in order to make the product/process more effective. Present research is concerned with the development of an automated manufacturability advisor for sheet metal components. Unlike most of the work done in the past that concentrated on bending and other forming processes, present work deals with sheet metal components manufactured by two different processes, namely “spinning” and “rollforming”. Effectiveness of the proposed manufacturability advisor is demonstrated by taking the number of industrial parts as examples.     

Buckling phenomena related to rolling and levelling of sheet metal

The paper deals with analytical and numerical considerations of buckling phenomena in thin plates or strips under in-plane loads which typically appear during rolling and levelling, i.e. straightening by stretching, of sheet metal. Buckling due to self-equilibrating residual stresses, caused by the rolling process, in eventual conjunction with global tensile stresses (denoted as “rolling buckling”) as well as buckling during the levelling process (denoted as “stretching buckling” or “towel buckling”) are considered. Analytical estimates are derived and compared against results of numerical simulations and field observations. Mode jumping by varying the global strip tension is explained on the basis of the derived analytical solutions. It is shown how from the waves, i.e. height and length, observed on the strip sliding over or lying on a rigid plane one can provide information about the distribution of the differences in the plastic strains over the width of the strip which lead to the buckled configuration. And, vice versa, knowledge of the plastic strain distribution can be used for estimating the expected wave heights representing a measure for the geometrical quality of the rolled product. The influence of the dead weight of the strip on the post-buckling pattern is also discussed on the basis of non-linear analyses.     

Progressive process design of door lock striker with double bosses by the wall-thickening process

Local thinning inevitably takes place in sheet metal forming. This can be prevented by the application of a compression load during wall-thickening forming, through which a part can become even thicker than the initial sheet material thickness. Wall-thickening forming is advantageous for the manufacturing of cup-shaped products and products with bosses. This study suggests a progressive process design procedure for the wall-thickening forming of a door lock striker with double bosses. The proposed procedure involves first drawing, redrawing, and upsetting. The design of the progressive process is performed with the suggested design procedure using finite element analysis. To verify the result of this study, an experiment for manufacturing door lock striker with double bosses was performed by the progressive process. The results of the experiment for the measurement of the thickness at the bosses showed good agreement with those of the finite element analysis. From the experimental result, double bosses with a thickness distribution of 2.25–4 mm can be manufactured from sheet metal with an initial thickness of 2 mm using wall-thickening forming, which results in an increase in the strength at the bosses by about 27 %.     

面向制造的成本计算系统开发

本系统采用ＶｉｓｕａｌＣ＋＋面向对象编程语言,利用三造型软件Ｓｏｌｉｄｗｏｒｋｓ作为开发平台,地其进行类库扩展,把产品的材料、重量、加工特征、成本等有铲属性以数据成员的形式表示,从而进行面向产品制造的成本计算。应用本系统,综合工厂生产实践的要求,在产品的设计阶段就可以初步计算出产品的制造成本,从而缩短了产品的开发周期。     

Study on practical application of a new seismic damper using a Zn–Al alloy with a nanocrystalline microstructure

Superplastic Zn–Al alloy has some excellent properties needed for a seismic damper, such as high ductility, low work hardening and no harmful metal to human health. In addition, superplastic materials with ultra-fined grains exhibit the high-strain-rate superplasticity and/or low-temperature superplasticity. Some investigations were carried out for nano-sized Zn–Al alloy in order to develop a high-performance seismic damper capable of replacing conventional dampers, such as low-yield-point steel. First, the design for appropriate structure as a damping device using superplastic Zn–Al alloy was discussed by FEM analysis. Secondly, a bulk Zn–Al alloy with nanocrystalline microstructure was manufactured by thermo-mechanical controlling process (TMCP) technology, and the tensile properties of this alloy were compared with that of low-yield-point steel. Then, the full-size cyclic testing of the damping device was carried out in order to evaluate the response for earthquake. As a result, an ecological and high performance seismic damper, the so-called “maintenance-free seismic damper”, has been successfully developed and put into actual use in a high-rise building.     

板料超塑胀形过程仿真及其应用

板料超塑胀形通常需要高温密闭环境,测试分析困难。本文在刚粘塑性有限元法的基础上开发了超塑胀形计算机仿真系统。应用仿真系统可对材料变形过程进行动态仿真,预测成形件壁厚分布,优化确定成形压力 时间曲线,为成形工艺设计提供有效分析工具。文中给出了“碗”形零件气压胀形仿真实例。     

Forming Machine Qualification by Analysis of Manufactured Parts Geometry: Application to Aluminium Forming Process

Today, manufacturing companies work in a concurrent engineering context. In this paper, we develop a methodology to validate the modelling of an aluminium forming process based on dimensional characterisation and finite element comparison. Generally, finite element modelling (FEM) is used to validate die design in parallel with an experimental process. In this work, we use FEM to design forming tools in a first step. In a second step, measurement in the three dimensions gives the sheet metal process machine tool errors, and it is necessary to integrate the reasons for these defects in the process of concurrent engineering in the field of metal forming. Finally, we conclude that multiscale models should be used to model the mechanical process ID="A1"Correspondance and offprint requests to: R. Bigot, LGIPM, EA 3096, ENSAM Metz, Technopole 2000, 4, rue Augustin Fresnel, 57078 Metz Cedex, France. E-mail: regis.bigot@metz.ensam.fr