Robust uniform triangulation algorithm for computer aided design

This paper presents a new robust uniform triangulation algorithm that can be used in CAD/CAM systems to generate and visualize geometry of 3D models. Typically, in CAD/CAM systems 3D geometry consists of 3D surfaces presented by the parametric equations (e.g. surface of revolution, NURBS surfaces) which are defined on a two dimensional domain. Conventional triangulation algorithms (e.g. ear clipping, Voronoi-Delaunay triangulation) do not provide desired quality and high level of accuracy (challenging tasks) for 3D geometry. The approach developed in this paper combines lattice tessellation and conventional triangulation techniques and allows CAD/CAM systems to obtain the required surface quality and accuracy. The algorithm uses a Cartesian lattice to divide the parametric domain into adjacent rectangular cells. These cells are used to generate polygons that are further triangulated to obtain accurate surface representation. The algorithm allows users to control the triangle distribution intensity by adjusting the lattice density. Once triangulated, the 3D model can be used not only for rendering but also in various manufacturing and design applications. The approach presented in this paper can be used to triangulate any parametric surface given in S(u,v) form, e.g. NURBS surfaces, surfaces of revolution, and produces good quality triangulation which can be used in CAD/CAM and computer graphics applications.     

基于板料网格变形的翻边工序修边线确定方法

车身零件翻边前一般有修边工序,需要准确的修边线,否则翻边后零件达不到零件尺寸要求。为减少修边模的开发周期和成本,提出一种基于板料网格变形的修边线确定方法。在零件毛坯上蚀刻上正方形网格,进行翻边前的一些工序;根据估计的修边线,得到翻边前的零件形状,测量出翻边前在修边区域上各网格点的坐标;对零件进行翻边,测量出翻边前后在修边区域上各网格点的坐标;根据翻边前后的零件网格以及翻边后零件的边缘线,通过翻边前后网格比例变形关系确定出翻边前修边线位置。如果试冲零件边缘线有误差,可反复采用这种方法优化修边线。这种方法可在模具调试或在仿真中采用。采用一个汽车地板零件的修边线确定算例,验证了上面提出的方法的可行性。     

Efficacy of trimming chilled beef during fabrication to control Escherichia coli O157:H7 surrogates on subsequent subprimals

Effectiveness of trimming external carcass surfaces from subprimals during fabrication to reduce Escherichia coli O157:H7 surrogates was evaluated. Carcass sides (n = 10 sides) were inoculated along the hide pattern opening before entering the blast chill cooler with a gelatin slurry containing a bacterial cocktail of three rifampicin-resistant, nonpathogenic E. coli biotype I strains. Following a 48 h chill, sides were fabricated to produce eight subprimals. Microbiological samples were taken from the original carcass fat surface area, initial lean surface area, trimmed fat surface area (where applicable), and trimmed lean surface area (where applicable). Newly exposed lean surfaces had lower (P < 0.05) counts of rifampicin-resistant E. coli than did the external fat surfaces. However, fat and lean surfaces that were not inoculated became contaminated during the fabrication process. Trimming external surfaces reduced levels of pathogens, but under normal fabrication processes, pathogens were still spread to newly exposed surfaces.     

吹氩站多功能精炼技术开发

二炼钢厂吹氩站改造后。钢水吹氩精炼更加能够满足实际生产需要。经过1年多的开发，吹氩站具有以下多种功能：钢包CAS吹氩、微调钢水中[Si]、[Mn]、[Ti]、[Nb]、微调钢水温度、喂铝线微调[Als]、喂碳线微调[C]、出钢前试气提高钢包底吹氩成功率，节约了生产成本缩减工序时间。     

轿车内饰装配质量控制技术

轿车内饰装配质量直接影响车内美观性、乘员舒适性及车体安全性 ,传统样架检验难以定量描述内饰装配偏差 ,而CMM测量数据缺乏空间直观性 ,现提出通过二维图纸或CMM测量数据反求技术建立零部件三维模型 ,利用虚拟装配技术仿真三维实体装配 ,定量装配偏差 ,控制轿车内饰装配质量 ,并以地毯总装过程中出现的地毯腾空缺陷为例 ,通过CMM测量、统计分析、反求技术及虚拟装配等技术进行地毯装配质量管理与控制     

一种通过激光修调产生精确时钟的方法

文章介绍了一种通过修调,可在片内得到精确时钟的方法。该方法由于内部集成了检测电路,只需通过判断pad的输出结果即可得到修调状态,因此可应用于大规模工业化生产。在文章中给出了修调值的选取方法,同时还讨论了影响修调精度的因素。     

一种用于开关电源的多模式振荡器

基于0.25 μm BCD工艺,设计了一种应用于开关电源的多模式环形振荡器,具有结构简单、三种模式可选、可修调的特点。电路通过模式切换生成可调电流的方式对电容充放电,产生不同频率的斜坡及方波信号。测试结果表明:在-40 ℃~125 ℃温度范围内,振荡器主振荡模式输出范围为483.9~518.6 kHz,与固定频率(500 kHz)的最大偏移率为3.72%,电阻频率调节模式输出范围为25 kHz~2.5 MHz,同步模式下可调同步频率范围为40 kHz~4 MHz。目前,该振荡器已被成功应用于一种DC-DC开关电源芯片中。     

TRIZ-based trimming for process-machine improvements: Slit-valve innovative redesign

This paper proposed a TRIZ-based integrated trimming process to resolve a process-machine problem by re-designing the problematic processing machine. Applied on a slit-valve failure of chemical vapor deposition equipment in one of major Taiwanese foundry companies, the proposed problem solving process successfully identified the critical key disadvantages of the problem and solved the slit-valve failure with breakthrough results. A number of solutions were generated by the integrated process which involves a number of TRIZ tools. This paper describes only the solution by the trimming process. Unlike the great majority of engineers use “addition” or “substitution” methods to resolve problems, the proposed trimming process used “subtraction” method to solve problem. The integrated systematic method can be used to address any process-machine related problems. The main contributions of this paper include: (1) Establishing an integrated TRIZ-based trimming process to resolve process-machine related problems capable of breakthrough problem solving and/or significant cost savings; (2) solving the slit-valve problem with 83.3% component count reduction, 95% component cost reduction, 99% operational energy reduction, and completely designed-out the original failure mode. The results have been converted into a patent pending approval.     

新研制的MJK194×3型数控双圆锯片裁边机

新研制出的裁边机采用微机控制的步进电机摇尺，设激光锯口指示器辅助检测的毛边板板宽检测工位，板材横、纵向自动进料装置，便携数控摇尺器等。裁边工序损耗较旧的裁边机减少约１／４。     

Crack deviation during trimming of aluminium automotive sheets

Crack propagation and deviation during trimming of aluminium sheet metal have been analysed experimentally and modelled by a finite element analysis (FEA). The experimental results may be summarized as follows. Two crack propagation mechanisms operate in aluminium sheet metal, i.e. either between adjacent voids or by multiple coalescence of micro-cracks. A fracture process-zone may be identified for both mechanisms. Outside this fracture process-zone, no damage is observed. The particular crack propagation mechanism does not influence the crack path. A mechanical model based on a two steps analysis is presented. In the first step, the overall stress strain field prior to cracking is determined by an explicit Arbitrary Lagrangian Eulerian (ALE) formulation based FEA. In the second step, dedicated to crack propagation, no remeshing is used. A cumulative damage model based on the equivalent plastic strain increment is shown to be very efficient. The damage variable is interpreted as bifurcation in the direction of the maximum plastic strain rate. Finally, the applications show the possibility of trimming aluminium sheet metal without sliver generation.