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复杂曲面是数控加工中的一种类型,在数控系统加工前,商业软件会将复杂曲面离散成海量直线段逼近,但相邻直线段间速度的不连续性严重影响曲面加工质量,因此常采用轨迹段间插入直线或曲线来改善速度的连续性。基于已有轨迹段间插入圆弧的转接算法,提出一种基于公差的改进圆弧过渡路径规划算法,在保证转接轨迹精度的同时提高了转接速度。进一步,采用一种加速度连续、加加速度有界的7段S形加减速曲线,实现了刀具路径速度规划及插补。基于上述算法进行了曲线加工验证实验,实验结果表明,所提算法能够在达到同等加工精度条件下,显著提升轨迹段间的转接速度(的连续性),提高复杂曲面加工效率。 相似文献
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非圆曲线的逼近法数控加工 总被引:1,自引:0,他引:1
以椭圆形零件的数控加工为例,阐述了逼近法在非圆曲线形零件数控加工中的应用。由于一般数控机床的编程代码只具有直线插补和圆弧插补功能,因此对于非圆曲线的数控加工大多采用小段直线或小段圆弧去逼近轮廓曲线,完成数控编程。 相似文献
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提出一种精确计算插补步长的双NURBS曲线随动插补算法。首先由曲面数控加工的离散刀位数据分别拟合出刀尖点和刀轴点NURBS曲线,并建立两条曲线插补参数间的随动关系模型;然后采用辛普森积分法计算出曲线的总弧长,进行插补运动的加减速规划;再以刀尖点NURBS曲线为基准确定插补参数,采用辛普森法确定各插补周期的进给步长及插补点坐标;最后依据随动关系模型获得刀轴点NURBS曲线对应的插补参数,完成曲面加工刀路规划的刀具位姿插补。仿真实验表明,与同一参数插补法相比,参数随动法可以获得更加稳定的等距效果,便于实时控制插补过程中的刀轴位置和姿态。 相似文献
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普通的数控系统只具有直线和圆弧插补功能,对于凸轮这类轮廓中含有非圆曲线的零件不能直接进行数控加工,需要先通过一定的插补拟合算法用直线或者圆弧来代替轮廓中的非圆曲线.本文重点研究了近似双圆弧插补算法的原理和控制方法,通过具体实例比较了近似双圆弧插补算法与双圆弧插补算法的优缺点. 相似文献
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一种数控自动编程直线插补的新算法 总被引:2,自引:0,他引:2
本文给出了一种根据零件加工精度的要求 ,对三次B样条列表曲线进行直线插补、自动生成变步长刀位轨迹的算法 ,简称自适应算法。该算法可根据曲线曲率大小 ,自动改变步长 ,同时逼近误差满足要求。该算法稳定、可靠 ,便于在列表曲线、列表曲面的数控加工中推广应用 相似文献
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B样条列表曲线直线插补的自适应算法 总被引:1,自引:0,他引:1
给出了一种根据零件加工精度要求,对三次B样条列表曲线进行直线插补,自动生成变步长刀位轨迹的算法,简称自适应算法。该算法当列表曲线曲率大时,使步长变小,反之使步长变大,同时使逼近误差满足要求。该算法稳定、可靠,便于在列表曲线、列表曲面的数控加工中推广应用。 相似文献
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REN Kun FU Jianzhong CHEN Zichen 《机械工程学报(英文版)》2008,21(2):23-26
To avoid suffering gouge and transient overshooting in high speed cutting machining, a novel parametefized curve interpolator model with velocity look-ahead algorithm is proposed. Based on a prearrangement step interpolation algorithm for parameterized curves and considering high curvature points, parameterized curve tool path is divided into acceleration segments and deceleration segments by look-ahead algorithm. Under condition of characteristics of acceleration and deceleration stored in control system, deceleration before high curvature points and acceleration after high curvature points are realized in real-time in high speed cutting machining. Based on new parameterized curve interpolator model with velocity look-ahead algorithm, a real cubic spline is machined simulativly. The simulation results show that velocity look-ahead algorithm improves velocity changing more smoothly. 相似文献
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Xiaohui Zhang Dong Yu Taotao Song 《The International Journal of Advanced Manufacturing Technology》2012,62(9-12):1179-1189
The existing interpolation algorithm cannot meet the need of high-speed and high-accuracy machining of a free-form surface. So this paper proposed a correcting and compressing interpolation algorithm. Depending on the distance and angle evaluated from the adjacent command points, the machining path of free form can be divided into two machining types. For those regions where the accurate figure is critical such as corners, the convention linear interpolation is performed exactly between the adjacent command points. For those regions having a large radius of curvature where the smooth figure is critical, firstly, the interior point selection method based on circle transition is derived to reduce the tolerance between the machining path and the original surface; secondly, the interior point correction method based on the least-square method is proposed to reduce the calculation error and round-off error in the interior point and estimate the first- and second-order derivative vectors of the interior point; thirdly, the shape-defining point is selected by the bend direction of the machining path and fitted to a quintic spline curve which has the C2 continuity; fourthly, the fitting accuracy controlling method is proposed to ensure the machining accuracy; lastly, the curve interpolation is performed on the fitted smooth curve. Machining tests carried out on a vertical machining center show that the proposed algorithm can improve the machining efficiency and machining quality of a free-form surface. 相似文献
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An adaptive feedrate scheduling method of dual NURBS curve interpolator for precision five-axis CNC machining 总被引:1,自引:1,他引:0
Yuwen Sun Yurong Bao Kaixuan Kang Dongming Guo 《The International Journal of Advanced Manufacturing Technology》2013,68(9-12):1977-1987
Non-uniform rational b-spline (NURBS) tool path is becoming more and more important due to the increasing requirement for machining geometrically complex parts. However, NURBS interpolators, particularly related to five-axis machining, are quite limited and still keep challenging. In this paper, an adaptive feedrate scheduling method of dual NURBS curve interpolator with geometric and kinematic constraints is proposed for precision five-axis machining. A surface expressed by dual NURBS curves, which can continuously and accurately describe cutter tip position and cutter axis orientation, is first used to define five-axis tool path. For the given machine configuration, the calculation formulas of angular feedrate and geometric error aroused by interpolation are given, and then, the adaptive feedrate along the tool path is scheduled with confined nonlinear geometric error and angular feedrate. Combined with the analytical relations of feed acceleration with respect to the arc length parameter and feedrate, the feed profiles of linear and angular feed acceleration sensitive regions are readjusted with corresponding formulas and bi-directional scan algorithm, respectively. Simulations are performed to validate the feasibility of the proposed feed scheduling method of dual NURBS curve interpolator. It shows that the proposed method is able to ensure the geometric accuracy and good machining performances in five-axis machining especially in flank machining. 相似文献
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X. Zhiming C. Jincheng F. Zhengjin 《The International Journal of Advanced Manufacturing Technology》2002,20(4):270-276
This paper presents a real-time interpolation algorithm for NURBS curves. In contrast to the existing linear and circular
interpolators, the proposed interpolator can maintain small contour errors and feedrate fluctuations. Feedrate components,
acceleration components and the servomotor driving force for each axis are precalculated from the given curve shape and themachine
tool dynamic properties. As a sudden change in the geometrical properties of the tool path can increase contour errors and
cause a sudden change of driving force of each servomotor, a new strategy of variable feedrate machining based on the geometrical
properties of tool path is suggested. Real-time performance measurement of this interpolator is performed to demonstrate its
practical feasibility. 相似文献
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The design of a NURBS pre-interpolator for five-axis machining 总被引:1,自引:1,他引:0
Wei Li Yadong Liu Kazuo Yamazaki Makoto Fujisima Masahiko Mori 《The International Journal of Advanced Manufacturing Technology》2008,36(9-10):927-935
A non-uniform, rational B-spline (NURBS) interpolator has great advantages for free-form surface machining compared to the conventional linear/circular interpolator. However, the existing NURBS interpolators can only handle the NURBS trajectory given in a customized NURBS G code. Also, it is limited to three-axis applications. In this paper, a NURBS pre-interpolator with three function options is proposed for a computer numerical control (CNC) system so that the NURBS interpolator can be thoroughly applied for five-axis machining. The first function is called the NURBS converter function, which is used to convert a series of linear/circular segments exactly into a NURBS curve. The second function is the NURBS smoother function, by which, a series of linear segments are fitted to a NURBS curve. The third option provides two kinds of NURBS G codes definition, by which, the NURBS trajectory with five axes can be represented directly. Upon using the three options of the NURBS pre-interpolator, a unified NURBS curve can be obtained for further interpolation. Two actual machining cases are conducted to evaluate the feasibility of the proposed pre-interpolator. 相似文献
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基于凸轮磨削过程中恒磨削力要求恒线速度的加工机理,通过三次参数样条方程得到凸轮的理论曲线,采用微直线段取代微弧进给,得到砂轮轴心轨迹曲线的插补方法。分析了凸轮磨削精度、进给速度与插补参数之间的关系,实现凸轮曲线的高精度等速实时插补。该方法还可以推广到一般加工平面封闭曲线的CNC机床。 相似文献
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基于机床混合模型的参数曲线高速插补速度极值分析 总被引:1,自引:1,他引:0
参数曲线高速数控插补时,进给速度规划需要综合考虑机床动力学特性和曲线几何特征的限制。通过建立机床进给系统的机电混合模型,给出了参数曲线高速插补进给速度的机床动力学约束条件。以此条件为基础,采用“速度-加速度”相平面分析法导出了速度极值曲线解析表达式。与实时插补弦高误差约束下的速度极值曲线表达式相比,二者具有一致性。通过机床动力学约束下的速度极值曲线最大实时插补弦高误差估计,可简化插补进给速度规划约束条件。研究结果表明,给出进给速度极值解析曲线是有效的,可为参数曲线高速插补进给速度优化规划提供理论分析依据。 相似文献