共查询到20条相似文献，搜索用时 234 毫秒
1.
采用平底端刀五轴端铣加工模具曲面时,由于存在干涉和编程困难等问题,而大大影响其应用。对此,基于平底端刀端铣加工模具曲面的特点,将平底端刀五轴端铣加工模具曲面时的平底端刀和被加工曲面看作是一对互为共轭的空间啮合包络曲面,并用微分几何Frenet标架来描述数控加工的刀具轨迹,通过计算得到刀具轨迹的刀位点,从而设计平底端刀五轴端铣加工模具曲面的几何模型。 相似文献
2.
To improve the machining efficiency of large symmetrical freeform surface, this paper proposes a new machiningmethod: symmetrical machining (SM). Based on the concept of collision avoidance plane (CAP), collisions among cuttersor headstocks are avoided, and the area of machining residue is controlled effectively. Machining residue is eliminated dueto proper design of symmetrical tool in mechanism and control project. Taking 5-axis symmetrical machine with columnarheadstocks and flat cutters as example, this paper proposes collision avoidance algorithm. Finally, using a twin-skeg shipmodel surface as an example, the method is applied to avoiding collisions in original tool path. Simulation and real machiningresults show that the scheme is practical. Furthermore, the machining efficiency of SM is improved 85% more than that of thetraditional single cutter technology. 相似文献
3.
The methodology of 5-axis cutter selection to avert collision for free-form surface machining by flat-end cutters is presented.The combination of different cutters is adopt aiming at short machining time and high precision.The optimal small cutter is determined based on the geometric information of the points where a cutter most probably collide with the machined surface.Several larger cutters are slected to machine the surface in order to find the interference-free area.The difference of machining time for this area between the optimal small cutter and the large cutters is calculated.The functional relationship between the machining time and the radius of a cutter is established,by which the optimal number of cutters is obtained.The combination of cutters,which possesses the minimum overall machining time,is selected as the optimal cutter sizes.A case study has demonstrated the validity of the proposed methodology and algorithms. 相似文献
4.
Nicole DiDonato-Barnes Helenrose Fives Emily S. Krause 《Assessment in Education: Principles, Policy & Practice》2014,21(1):90-108
We investigated if instruction on a Table of Specifications (TOS) would influence the quality of classroom test construction. Results should prove informative for educational researchers, teacher educators, and practising teachers interested in evidenced-based strategies that may improve assessment-related practices. Fifty-three college undergraduates were randomly assigned to an experimental (exposed to the TOS strategy) and a comparison condition (no specific strategy support) and given materials for an instructional unit to use to construct a classroom test. Results of a multivariate analysis of covariance suggested that students exposed to the TOS strategy constructed a test with higher test content evidence but not response process evidence scores. Furthermore, we found that treatment participants were able to accurately complete the TOS tool and choose items that reflected the subject matter specified in the TOS tool. However, they experienced difficulty selecting items at the cognitive level specified in the TOS tool. 相似文献
5.
曲面重构是逆向工程的核心内容,目前大多数曲线曲面的研究都是围绕NURBS数学模型展开的。以NURBS数学模型为基础,对曲线曲面重构的方法、步骤、及其常见问题的分析处理进行了研究讨论,提出了曲线与点云相互结合重构曲面的方法,并进行了无动力排风扇叶片曲面的重构。结果表明,提出的方法是有效的和可行的,且具有一定的工程实用价值。 相似文献
6.
To improve polishing quality and cope with the shortage of skilled workers for aluminum wheel-hub surface polishing, an automatic surface polishing system with hierarchical control based on the teaching-playback method was presented. Multi-axis cutter location data （CL data） were generated with the teaching method. First, a helical tool path and a flexible polishing tool were adopted to achieve high quality and high efficiency; next, the initial irregular data were processed into continuous polishing CL data. The important factor affecting polishing quality, namely the interpolation cycle in the multi-axis CL data was calculated based on a constant removal rate. Results from polishing experiments show that the quality of automatic machine polishing is better and stabler than manual polishing. 相似文献
7.
LI Ya-juan WANG Guo-zhao 《浙江大学学报(A卷英文版)》2006,7(6):1084-1087
INTRODUCTION Modification of knots of a B-spline curve changes the shape of the curve. In some recent pub-lications (Juhász and Hoffmann, 2001; 2003; Hoff-mann and Juhász, 2004; Li and Wang, 2005), the authors studied the effect of the alteration of a single knot on the shape of the curve. Hoffmann (2004) and Li & Wang (2006) applied these theories into the constrained shape modification of B-spline and NURBS curves. Juhász (2001) and Hoffmann & Ju-hász (2005) studied the effe… 相似文献
8.
以汽车仪表盘为研究对象,通过激光扫描仪的非接触式测量获取零件曲面的点云数据,并利用Surfacer软件进行点云数据处理,且基于NURBS曲面重构理论进行零件曲面造型,最后利用Pro/Engineer软件完成汽车仪表盘的实体模型设计.与传统的设计方法相比,提高了工作效率,缩短了新产品的开发周期. 相似文献
9.
胡世杰 《温州职业技术学院学报》2001,1(1):29-32
B665牛头刨床的刀架存在没有自动抬刀装置，没有自动垂直进给机构，以及刀架落刀等问题。本针对以上问题，根据具体生产实践，提出了一些行之有效的改进措施。 相似文献
10.
对非均匀有理B样条(NURBS)参数化特征设计和隐式代数曲面的原理实现曲面造型进行了介绍。在仿真的过程中运用CAD/CAM技术软件实现了凉亭顶部的设计,证实了在软件中运用非均匀有理B样条(NURBS)参数化特征设计在曲面造型方面是可行的,不仅拟合度好而且可以提高设计效率,并且可以使得图形更严密。 相似文献
11.
梁伟文 《深圳职业技术学院学报》2011,10(3):3-6
以Loop细分曲面为例,根据细分曲面的网格迭代特性,讨论了细分曲面的精加工刀具轨迹生成方法,对精加工时使用球头刀和刀具接触位置的偏移来生成刀具轨迹位置.在刀具轨迹生成过程中提出一种Z-map空间网格点存储技术,同时为了提高加工质量提出干涉检查和修正方法,并进行了实例验证.结果表明该类型刀具轨迹生成方法对于网格曲面的加工是可行、有效的. 相似文献
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13.
1 Introduction PlanardevelopmentofacurvedsurfaceisbroadlyusedinCAGDandCAD .Accordingtotheirdevelop ment ,surfacesaredividedintodevelopablesurfacesandnon developablesurfaces .Mostofcurvedsurfacesarenon developable ,butbroadlyusedinengineering ,suchasaircraftwings ,laminaofturbine ,fluidsur face .Howeverthedesignandhandlingofcurvedsur faceareverydifficult.Inordertopredigestthecom plexityofdesign ,planardevelopingisintroduced .Non developablesurfacescannotbedevelopedontoaplanewithoutstretch… 相似文献
14.
丁茹 《天津工程师范学院学报》2004,14(4):30-32
对NURBS(非均匀有理B样条)曲面的拟合算法和利用"权值"局部修改NURBS曲面的方法进行了研究,运用OpenGL技术实现了NURBS曲面的虚拟显示,通过血管的表面重建实验,验证了NURBS曲面拟合算法的正确性。 相似文献
15.
证明了M维欧氏空间中以正则单形的中心为球心的M维球面上任一点到各顶点及至各(M—1)维面距离平方之和均为不变量，从数量关系方面揭示了正则单形的一个性质．文末提出了一个猜想。 相似文献
16.
针对含自由曲面及标准解析曲面零件加工精度的高精度检测,本文提出一种形状公差评定的新方法——面向CAD模型的曲面形状误差检验。它实现了各种标准解析曲面和自由曲面形状的高精度检测,采用表达式精确地表示各种标准解析曲面和自由曲面;利用数据库技术研究CMM测量点云和CAD模型的最佳匹配算法;比较测量点云和CAD模型的法向偏移量即曲面形状误差,且用图形直观地显示出来。最后进行计算机仿真实验,实例验证算法可行性。 相似文献
17.
基于数控机床归参考点的故障诊断与排除 总被引：1，自引：0，他引：1
孙建仁 《实验室研究与探索》2004,23(5):36-37,76
采用分析举例的方法阐述了数控机床归参考点的基本方式，讨论只有做到机械上粗定位，电气上精定位，才能极大地降低归参考点故障的产生。数控机床归参考点故障只有在其确定的回参考点方式下准确诊断，并加以及时排除，才能进一步提高数控机床的开动率和可靠性。 相似文献
18.
The representation method of heterogeneous material information is one of the key technologies of het-erogeneous object modeling, but almost all the existing methods cannot represent non-uniform rational B-spline (NURBS) entity. According to the characteristics of NURBS, a novel data structure, named NURBS material data structure, is proposed, in which the geometrical coordinates, weights and material coordinates of NURBS heterogeneous objects can be represented simultaneously. Based on this data structure, both direct representation method and inverse construction method of heterogeneous NURBS objects are introduced. In the direct representation method, three forms of NURBS heterogeneous objects are introduced by giving the geometry and material information of control points, among which the homogeneous coordinates form is employed for its brevity and easy programming. In the inverse construction method, continuous heterogeneous curves and surfaces can be obtained by interpolating discrete points and curves with specified material information. Some examples are given to show the effectiveness of the proposed methods. 相似文献
19.
通过比较双圆弧弧齿锥齿轮齿面理论方程与加入刀位及刀位角误差后的齿面方程，应用网格模型和通过进一步的数值计算，进行了无误差的理论齿形和加入刀位及刀位角误差后所得到的实际齿形之间的定量分析，对刀位及刀位角误差对双圆弧弧齿锥齿轮的齿形以及传动的影响进行了初步研究。 相似文献
20.
吕凯 《通化师范学院学报》2013,(12):46-48
切削刀具的质量是机械加工设备长期有效运行的决定性因素.切削所产生的热量是铣刀片磨损和破损产生的重要因素,揭示刀具破损磨损的产生机理的重要手段是研究切削热和切削温度的变化规律.针对这一问题,用元胞自动机思想,建立以元胞自动机理论研究铣刀片在切削过程中温度影响的评价准则,来研究温度的变化对切削刀具的影响. 相似文献