球头铣刀铣削淬硬钢模具铣削力及模具加工误差研究

发布时间：2018-03-15 18:23

本文选题：淬硬钢模具　切入点：球头铣刀　出处：《哈尔滨理工大学》2017年博士论文　论文类型：学位论文

【摘要】：随着高速切削技术和硬切削技术的发展,具有高硬度、高韧性和高耐磨性的淬硬钢模具加工实现了以铣代磨,并以高精度和高效率的优势迅速成为汽车覆盖件模具加工的主要工艺方法。由于汽车覆盖件模具具有结构尺寸大、工作形面复杂、曲率变化频繁、表面质量和加工精度要求高等特点,使模具制造企业对自由曲面模具切削过程的控制及加工精度的保证面临很大的挑战。在自由曲面淬硬钢模具三轴球头铣削过程中,切削力方向多变,工艺系统呈署弱刚性,易引起切削过程稳定性下降,加工表面质量和加工精度下降,刀具寿命降低等问题。因此,研究自由曲面淬硬钢模具球头铣削过程的切削力、刀具变形、铣削稳定性、加工误差和补偿,以满足自由形面、高硬度、大尺寸模具的高精度高效率的生产需求,对推动汽车淬硬钢模具制造技术进步,促进高品质自由形面模具加工技术的发展和应用具有重要的现实意义。球头铣削自由曲面淬硬钢模具时,曲面曲率特征和加工倾角多变使瞬态切削力处于不稳定状态,多变载荷引起刀具变形和切削稳定性下降,同时,造成自由曲面的加工形貌和加工精度难以达到要求。本文针对自由曲面淬硬钢模具的球头铣削过程中存在的上述问题,进行球头铣刀铣削淬硬钢模具铣削力及模具加工误差研究,主要内容包括:针对曲面加工中前倾角、侧偏角、行距方向曲率和进给方向曲率引起铣削力方向和大小变化的问题,首先表征自由曲面曲率特征及加工倾角,根据球头铣刀切削刃几何形状,建立铣削过程中刀齿实际运动轨迹的三维摆线模型;基于三维摆线模型,考虑曲面加工前倾角、侧偏角、行距方向曲率和进给方向曲率,修正未变形切屑厚度模型,研究工件曲率和加工倾角对未变形切屑厚度的影响规律。建立考虑加工倾角和工件曲率的自由曲面瞬态铣削力模型,分析加工倾角和工件曲率对瞬态铣削力的影响规律。提出自由曲面瞬态铣削力预测方法,并进行实验验证,为刀具偏摆分析和动力学建模提供依据。基于自由曲面瞬态铣削力变化规律,采用有限元法分析球头刀偏摆,获得切削区部分切削刃变形分布规律;基于刀齿三维摆线运动轨迹,建立考虑切削刃不同位置变形的未变形切屑厚度模型,研究切削刃变形对未变形切屑厚度的影响规律。分析切削刃变形对刀工接触区域的影响规律,建立考虑切削区变形的自由曲面铣削力预测模型,并通过实验验证,为加工误差提供理论依据。自由曲面球头铣削的未变形切削厚度沿切削刃不断变化,基于刀齿三维摆线轨迹模型,描述相邻刀齿在三维刀工接触区前后表面形成的一对切屑厚度控制点。分析相邻两个刀齿分别经过刀工接触区前后表面控制点的时滞时间,建立变时滞时间的未变形切屑厚度模型。分析工件曲率及加工倾角对铣削时滞及再生作用下的动态切屑厚度的影响规律,建立自由曲面铣削动力学方程。采用全离散和数值解法相结合办法分析小径向切深的球头铣削变时滞动力学特性,预测自由曲面铣削稳定域,分析加工倾角和曲率半径对铣削稳定域的影响规律。自由曲面的加工中通常存在编程误差和加工误差,对球头铣刀铣削淬硬钢模具时的让刀误差、残留高度和插补误差进行分析,揭示自由曲面误差分布特性。通过铣削自由曲面淬硬钢模具让刀误差实验和加工表面形貌实验,分别验证让刀误差及残留高度预测模型。基于不同形面特征误差分布特性,采用过程集成优化方法,对曲面的不同切削区域有针对性的进行补偿。
[Abstract]:With the development of high speed cutting and hard cutting technology, with high hardness, hardened steel mold processing high toughness and high wear resistance is realized by milling instead of grinding, and with high accuracy and high efficiency advantages quickly became the main process of automotive panel die. Because of the large size of the automotive panel die work complex shape, curvature changes frequently, surface quality and machining precision higher characteristic, the mold manufacturing enterprises to control the free surface of mould cutting process and machining accuracy face great challenge. In the free surface hardened steel mold three axis milling process, the cutting force direction changing process system is Department of weak rigidity that is easy to cause the decrease of cutting process stability, decrease the surface quality and machining precision machining, reduce the tool life problem. Thus, the research on the free surface of hardened steel mold ball milling process The cutting force, cutting deformation, milling stability and machining error and compensation, in order to satisfy the free surface, high hardness, high precision and high efficiency of large size mold production needs, to push the car to the hardened mould manufacturing technology progress, promotion has important practical significance to the development and application of high quality free surface mold processing technology. Ball end milling of free form surface hardened steel mold, the curvature of the surface features and machining inclination angle changing makes the transient cutting force in an unstable state, and decrease the load, deformation and stability of cutting tool at the same time, resulting in processing morphology and machining accuracy of free surface is difficult to meet the requirements. The above problems this paper milling for free surface hardened steel die in the study of ball end milling of hardened steel mold milling force and die machining error, the main contents include: according to the anteversion angle of curved surfaces Sideslip angle, spacing, curvature and curvature direction feed direction caused by milling force magnitude and direction of change, the first characterization of free surface curvature features and machining inclination angle, according to ball end milling cutting edge geometry, establish milling cutter tooth actual motion trajectory of the 3D pendulum line model; 3D model based on Cycloidal surface machining, considering the anteversion sideslip angle, spacing, curvature direction and feed direction curvature correction, the undeformed chip thickness model, the influence of workpiece curvature and machining inclination angle of undeformed chip thickness. The establishment of the free surface instantaneous milling force model of machining inclination angle and curvature of the workpiece, analyze the effect of machining inclination angle and workpiece curvature on the transient milling force the proposed free surface transient milling force prediction method, and verified by the experiment, and provides the basis for the tool deflection analysis and dynamic modeling based on the instantaneous free surface. Variation of milling force, using finite element method analysis of ball cutter deflection, partial cutting deformation zone distribution; 3D tooth cycloidal trajectory based on a different cutting edge position deformation of the undeformed chip thickness model considering the influence of undeformed chip thickness deformation of the cutting edge. Analysis of the influencing factors on the deformation of the cutting edge of knife contact area, to establish the prediction model of milling force considering free surface deformation of the cutting area, and through experimental verification, provide a theoretical basis for the machining error. The undeformed chip thickness along the free surface of ball end milling cutting edge changing cutter tooth 3D cycloid trajectory model based on the description of the adjacent knife the tooth in the chip thickness control points before and after 3D tool workpiece contact zone formed on the surface of a delay time. Analysis of two adjacent cutter teeth respectively through the knife contact area before and after surface control points, A variable delay time of the undeformed chip thickness model. Analyze the influence of curvature and inclination of workpiece on dynamic milling time delay and regeneration under the effect of chip thickness, the establishment of a free surface milling dynamics equation. The numerical solution of discrete and combined analysis of the path to the ball end milling cutting depth variable delay dynamic characteristics to predict the milling stability domain of free-form surface, analyze the effect of machining inclination angle and radius of curvature on the milling stability domain. The programming error and machining error are free-form surface machining, the ball end milling of hardened steel mold when the cutter error analysis, residual height and interpolation error, reveal the error distribution characteristics of free surface. Through the milling of free form surface hardened steel mold cutter error test and surface topography experiments were validated and residual error of tool height prediction based on different models. The characteristics of the profile error distribution and the process integration optimization method are used to compensate the different cutting regions of the surface.

【学位授予单位】：哈尔滨理工大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG54

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