SolidWorks钣金零件设计(五)——实体和钣金混合建模方法

从SolidWorks 2010版本开始,SolidWorks允许用户在多实体环境下设计钣金零件.即在一个钣金零件内部,用户可以建立多组不同材质、不同厚度的钣金部分,各个钣金部分可以单独展开.如图1所示,在当前的钣金零件中存在多个部分,每个部分可以代表整组钣金组件的一个焊接单元(实体).在FeatureManager设计树中,每个钣金特征对应一个钣金实体,在"切割清单"文件夹中显示了零件中的实体.SolidWorks 2011进一步丰富了多实体钣金零件的设计,用户可以在钣金零件中添加焊缝等特征,完成的焊缝显示在"焊接文件夹"中,并可用于工程图中的焊接表.     

基于关键特征相对位置关系的钣金零件检索算法

针对二维钣金类CAD零件相似性的检索,提出一种适用于钣金展开件的相似性检索算法.在分析钣金零件形状特点的基础上,选取设计过程中常用的36种关键特征,建立了关键特征的位置关系模型.该模型以构建关键特征之间的相对位置三角形为基础,具有坐标系无关和旋转无关的特性;以关系模型为依据,提出了钣金件关键特征的相对位置检索算法,并通过实例计算了不同钣金零件之间的相似度.实验结果表明,文中算法是有效的,可满足钣金零件的检索要求,具有实用价值.     

交互式计算机辅助服装排料系统的设计及实现

文中从多边形的特点出发，设计并实现了一个以多边形靠拢处法，多边形重叠检测算法和分段移动算法等技术的基础的交互式计算机辅助服装排料系统。     

一种分阶段优化的排料算法

提出一种基于分阶段优化的排料算法.在算法的第一阶段,在排料前先估算本阶段用到的原板材尺寸和数量,将权重因子超过阅值的待排件均匀分布在其上.在排料过程中再根据待排件权重因子和组合因子动态调整空闲区域的排料布局,从而可大幅度降低排料算法复杂度,提高板材利用率.在第二阶段,将剩余待排件合理排放在原板材上,在排料即将结束时,可根据相邻因子确定排料布局以减少废料碎片.生产实践表明,这样研制出的排料系统利用率高、布局合理,能满足工业上的一刀切要求.     

一种实用的铁制工艺品排料方案的设计与实现

根据铁制工艺品企业的需求,结合前人提出的求解矩形Packing问题的贪心算法和矩形排料的十字线法,本文设计实现了一种实用的铁制工艺品排料方法。实验结果表明,本文所实现的排料方法运行速度较快,具有较强的可用性和实用性。系统已在有关企业投入试用。     

二维不规则形状自动排料算法的研究与实现

针对二维不规则形状自动排料问题,给出了解决自动排料的求解思路,并对自动排料的主要算法作出了研究和改进,以便更好地提高算法效率及可靠性。     

排料算法优化

用计算机进行计算、优化排料是剪、冲裁等材料加工过程中非常值得关注的问题。对贵金属、特种材料和高档装饰材料等,提高它们的利用率具有明显的经济效益。 排料优化问题依照算法和材料的不同可分为矩形板排料和连续带排料两大类。在剪裁加工中材料大多为矩形板材,常采用矩形板材优化排料算法。有时还要把冲剪顺序、冲剪方式等作为附加条件考虑在优化过程中。这类优化过程中按工件形状又分为两类：复杂工件排料、矩形工件排料。矩形板材排料过程中工件种类多,尺寸各异。 在连续冲裁加工中材料大多为宽度给定的连续带,工件种类单一。按照…     

改进的蚂蚁算法在矩形优化排料中的应用

矩形件优化排料问题是一类具有NP完全难度的组合优化问题.将改进的蚂蚁算法应用到矩形件优化排料问题求解中,优化试验结果表明可获得比基本蚂蚁算法更好的效果,为矩形件优化排料这类NP完全问题提供了新的思路和方法.     

自动排料中关键算法的研究

通过基于演化计算的全局搜索,寻找零件在排料时的最优次序及各自的最佳旋转角度,并采用最低最左原则(BL,Bottom-Left)实现自动排料.文中通过对自动排料中排料件图形的表示及数据结构描述,以及关键算法的实现讨论,将在处理不规则多边形的排料优化问题中判断点是否在多边形内部的通用方法射线法与多边形的单调性相结合,提出一种改进算法,并通过实验获得了较好的结果和性能.     

求解板材排料问题的新方法

§１．引言 板材排料问题是家具、包装、地毯等行业常见的一个问题．它是指将一批不同种类的待排矩形件全部排放在给定的板材上,使排料所用的板材数量尽可能地少,即板材的利用率尽可能地高．实质上是一个组合优化的二维布局问题,从计算复杂性来看,是一个ＮＰ完全问题,但至今还没有找到解决该问题的有效多项式时间算法．寻求其近似最优解的近似算法是目前解决该问题的途径之一． 国内外已有不少学者在布局问题方面作了一些研究．如有用模拟退火算法解决大规模排料问题,但其解过分依赖于模拟退火算法冷却进度表的参数的选取,而且该算法…     

Ship part nesting by pattern recognition and group arrangement

The automatic nesting for a computer-aided manufacturing (CAM) system in shipbuilding industry requires more constraints than in other fields such as automobile, clothes and shoes. The nesting software has more influence on the productivity of shipbuilding industry, being equipped with such functions as automated operation, user-friendly interface, generation of stable cutting data and draft, and synchronization with enterprise resource planning (ERP). Many algorithms have been developed to increase the utilization rates of sheet metal plates and decrease scrap ratios. However, the minimization of the computational time and scrap ratio has not been fulfilled yet because of inherent constraints in nesting processes. To increase the efficiency of the part nesting in shipbuilding industry, this study presents pattern recognition and group arrangement method. The form features of ship parts are recognized and classified into pre-defined patterns by using the ray projection method. Then, the parts are grouped based on grouping rules. The proposed method has been validated with actual ship parts.     

Genetic Algorithm Coding Methods for Leather Nesting

The problem of placing a number of specific shapes in order to minimise waste is commonly encountered in the sheet metal, clothing and shoe-making industries. The paper presents genetic algorithm coding methodologies for the leather nesting problem which involves cutting shoe upper components from hides so as to maximise material utilisation. Algorithmic methods for computer-aided nesting can be either packing or connectivity driven. The paper discusses approaches to how both types of method can be realised using a local placement strategy whereby one shape at a time is placed on the surface. In each case the underlying coding method is based on the use of the no-fit polygon (NFP) that allows the genetic algorithm to evolve non-overlapping configurations. The packing approach requires that a local space utilisation measure is developed. The connectivity approach is based on an adaptive graph method. Coding techniques for dealing with some of the more intractable aspects of the leather nesting problem such as directionality constraints and surface grading quality constraints are also discussed. The benefits and drawbacks of the two approaches are presented.     

An integrated knowledge based system for sheet metal cutting–punching combination processing

Cutting and punching are two important processes in the sheet metal industry; the former is flexible in processing whilst the latter is effective in production. To combine the advantages of both, the so-called combination machines that combine the cutting and punching processes are used in sheet metal processing. To support such machines, this paper presents an integrated knowledge based CAD/CAM system for sheet metal cutting–punching combination processing. The whole system consists of five functional modules, i.e., modeling, nesting, process planning, NC-programming and simulation and reporting module. These modules share a unified objected-oriented data structure, so they are integrated seamlessly in terms of data processing. The knowledge base is the core of the integrated system, based on which, the system runs in an efficient and intelligent manner. This system has been successfully applied in industry, and an application example is demonstrated.     

Heuristic and genetic approach for nesting of two-dimensional rectangular shaped parts with common cutting edge concept for laser cutting and profile blanking processes

This paper presents a novel two-dimensional nesting strategy suitable for sheet metal industries employing laser cutting and profile blanking processes. The proposed nesting approach is developed by the combination of heuristic and genetic algorithms in order to generate an effective nested pattern, in such a way that, it minimizes the sheet material wastage and also the cutting tool path distance, while arranging a set of rectangular parts in a rectangular sheet. With the proposed bottom–left heuristic method, at first, the parts are considered in a specific sequence and orientation, and each part is translated to the feasible bottom left most position on the previously placed parts and then adjusted to form the common cutting edges with adjacent parts. Further, the heuristic algorithm ensures the formation of clusters, in which a group of parts share the cutting edges, for effective handling of parts while cutting. Finally the optimal and effective nested pattern is generated by the genetic evaluation process which reproduces several sets of nested patterns, before converging to the optimality. The effectiveness of the proposed work, in terms of utilization of sheet material, is demonstrated by comparing the results obtained from the literature. Furthermore the uniqueness of the present approach in enhancing the nested pattern efficiency and minimizing the tool path distance with common cutting edge concept is illustrated.     

Pattern nesting on irregular-shaped stock using Genetic Algorithms

Pattern nesting aims to position 2-D shapes on a sheet so as to achieve maximum usage of a stock, or equivalently to minimise wastage. There are different methods used on computer to lay out the positions of the shapes on the stock, such as linear programming and heuristic method. A recent approach attempts to use Genetic Algorithms (GAs) to solve the problem of pattern nesting. The successful development of using GAs to nest 2-D shapes on regular-shaped stock has proved the feasibility of using GAs to solve pattern nesting problem. This work presents a new method of solving the pattern nesting problem on irregular-shaped stock using GAs, known as the evolutionary boundary nesting algorithm. This approach further generalises the scope of the pattern nesting problem by allowing nesting on stocks of any shapes and sizes. This implies that the nesting algorithm can be used universally in any industry, such as the garment, shipbuilding and aerospace industry. Basically, the shapes are nested sequentially in the stock and the evolutionary boundary nesting algorithm uses GAs to find the best position to nest each shape along the boundary of the stock.     

Design considerations of flat patterns analysis techniques when applied for folding 3-D sheet metal geometries

This paper discusses a systematic approach to implement the principles of Flat Pattern Analysis FPA for folding sheet metal products. The paper starts by highlighting the needs for the vehicular structure forming process with respect to the main production line requirements through using Quality Function Deployment QFD matrix. Additionally, the potentials of fold forming for sheet metal parts in achieving the major production needs will then be benchmarked against other forming techniques through a decision making tool namely; the Analytical Hierarchy Process AHP. The study investigates the application of flat pattern tools for sheet metal products derived from analysis for thin or zero thickness sheets (i.e. paper origami). The analysis sets an approach to generate all possible configurations of flat patterns that result in a specific 3-D structure profile. Secondly, a set of optimality selection metrics are developed and applied to these configurations to help determine the most optimized flat pattern. These optimality measures are a metric based on compactness, a metric for nesting efficiency to describe the strip layout planning, and two measures to assess the manufacturing aspect i.e. bending operation in terms of number and orientation of bend lines.     

CAN——计算机辅助排样软件包

本文介绍一个实用的计算机辅助排样软件—CAN。该软件采用扫描探测排样算法,解决了具有任意形状的零件排样问题。同时,本文还提出了几点改进措施,提高了材料的利用率。     

Solution for textile nesting problems using adaptive meta-heuristics and grouping

 An optimal packing problem of non-convex polygons on a sheet is considered and applied to a textile nesting problem. We propose a procedure of grouping objects and adaptive meta-heuristics. The grouping procedure classifies objects into groups which are then allocated on the sheet using adaptive meta-heuristics. As a result, effectiveness of the meta-heuristics is improved. The performance of the proposed method is compared with other meta-heuristics using simulation experiments. The result shows that the present method is superior to cases where adaptive meta-heuristics without grouping are used.     

钣金件自动展开新方法

在对钣金件特征研究和"零厚度"假设的基础上,提出一种钣金件自动展开新方法.对钣金件进行特征分类,基于特征设计进行钣金件特征造型,并通过特征树的形式存储特征之间的关系,最后对特征树进行中序遍历得到钣金件的展开图.并将上述方法应用在SMCAD(Sheet-Metal CAD)系统中.结果表明,该方法能方便快捷的实现钣金件自动展开,并使钣金件设计和展开摆脱了对三维平台的依赖,展开过程更为简洁.