基于斜角切削理论的钛合金螺旋铣孔切削力建模

通过分析螺旋铣孔的加工原理和计算加工过程中的运动向量,结合侧刃和底刃对切削力的影响,建立了螺旋铣孔过程的切削力解析模型。提出了基于斜角切削的切削力系数辨识方法,并根据斜角切削过程几何关系推导出摩擦角、剪切角、剪切应力的约束方程。开展切削力系数辨识试验和钛合金螺旋铣孔试验对仿真值进行验证,结果表明,切削力的仿真值与试验值误差较小,平均误差为9.55%,从而验证了斜角切削系数辨识方法的有效性和切削力模型的正确性。     

切削参数对SiCp/Al复合材料切削变形的影响

为研究切削参数对SiC_p/Al复合材料切削变形的影响,通过试验测量的切削力和切屑厚度,计算得到SiC_p/Al复合材料的变形区参数,并分析了切削参数对变形区参数的影响规律,同时拟合得到了切削SiC_p/Al复合材料过程中剪切角与摩擦角的关系。研究结果表明:进给量增大,SiC_p/Al复合材料变形系数和剪应变减小,摩擦角减小,剪切角增大,且SiC_p/Al复合材料的摩擦角大于2024Al,剪切角小于2024Al;切削速度增大,SiC_p/Al复合材料变形系数、剪应变都减小,摩擦角减小但是不显著,剪切角增大; SiC_p/Al复合材料φ=B-C(β-γ)中B值大于2024Al,而斜率C(负值)小于2024Al。     

螺旋铣孔工艺的切削稳定性及工艺参数规划

以螺旋铣孔工艺时域解析切削力建模、时域与频域切削过程动力学建模、切削颤振及切削稳定性建模为基础,研究了螺旋铣孔的切削参数工艺规划模型和方法。切削力模型同时考虑了刀具周向进给和轴向进给,沿刀具螺旋进给方向综合了侧刃和底刃的瞬时受力特性;动力学模型中同时包含了主轴自转和螺旋进给两种周期对系统动力学特性的影响,并分别建立了轴向切削稳定域和径向切削稳定域的预测模型,求解了相关工艺条件下的切削稳定域叶瓣图。在切削力和动力学模型基础之上,研究了包括轴向切削深度、径向切削深度、主轴转速、周向进给率、轴向进给率等切削工艺参数的多目标工艺参数规划方法。最后通过试验对所规划的工艺参数进行了验证,试验过程中未出现颤振现象,表面粗糙度、圆度、圆柱度可以达到镗孔工艺的加工精度。     

无偏心正交车铣理论切削力

为了深入研究无偏心正交车铣加工的切削过程,针对无偏心正交车铣加工变厚度、变深度切削的特点,把切削刃划分为圆周刃和端面刃两部分,分别以其瞬时切削面积为主要研究对象构建了计算各自瞬时切削力的数学模型,并通过数学模型对其瞬时切削力的变化进行了仿真。结果表明,无偏心正交车铣为多参数影响下的变切削力加工,圆周刃、端面刃在切削过程中都发挥重要作用,瞬时切削力的最大值由二者共同决定,但圆周刃上的切削力明显大于端面刃。圆周刃、端面刃几乎同时切入、切出工件,在一次完整的切削过程中圆周刃上的瞬时切削力发生一次突变,端面刃上的瞬时切削力则无突变发生。     

轴向车铣理论切削力的研究

以瞬时切削面积为主要研究对象建立了瞬时切削力的计算模型,并对瞬时切削力的变化进行了仿真。结果表明,轴向车铣为多参数影响下的变切削力加工,单齿瞬时切削力在整个切削过程中都是一个变化量,且圆周刃为主切削刃,其切削力远大于端面刃。在一次完整的切削过程中,整个刀齿的瞬时切削力产生两次突变。     

平头铣刀圆形铣削的切削力预测

针对平头铣刀的圆形铣削,提出一种适用于圆形铣削的切削力预测方法。建立铣刀与工件交点的数学模型,求解工件与铣刀的时变交点进而计算铣削过程中不断变化的切入角与切出角。同时分析了铣刀轨迹曲率效应对瞬时切削厚度的影响。通过槽铣试验来确定切削力系数。基于微分思想,将圆形铣削过程中的瞬时切削厚度运用到切削力模型中计算微元切削力,然后通过积分法获得切削力值。数值仿真与圆形铣削试验结果表明,预测的铣削力和试验结果在幅值和变化趋势上都吻合良好,从而验证了该切削力预测方法的有效性。     

铣齿断续切削机理的研究

大模数齿轮铣削具有多刃断续切削和变切屑厚度等特点,属于典型的非自由强力切削.主要从切削力、切屑形态、表面质量等方面对铣齿断续切削的机理进行研究.采用指数经验模型,应用微段切削刃受力积分获得单个刀片瞬时合成转矩,随后考虑刀盘上刀片的分布情况,获得刀盘周期性的载荷,提出铣齿断续切削转矩的计算模型.应用间接测量的试验方法,采集三相异步电动机的主轴输入电流,重构得到切削力,另外通过试验测量出切削变形比,应用理论公式获得切削力.将试验数据和理论计算结果与计算模型进行比较,验证了铣齿加工切削转矩模型的正确性.对切削过程中的残余高度进行几何分析,获得其计算方法.初步完成对铣齿断续切削机理的分析,对铣齿加工精度提供指导作用.     

五轴侧铣加工铣削接触区域建模

五轴侧铣加工时,刀具姿态的时变性使得加工过程中的刀具和工件接触区域复杂多变,提取铣削接触区域对研究多轴铣削中的切削力、加工误差和颤振稳定性至关重要,对此提出一种无需提取待加工表面信息的瞬时接触轮廓解析法。使用一系列离散切削微元表示刀具,根据刀具位置和铣削参数获得各切削微元特征点集,并使用样条曲线对其拟合。综合距离和进给方向条件限制筛选出每段切削微元的切入/切出点,同时表示在工件坐标系中获得瞬时接触轮廓。仿真和试验结果表明,最大切入/切出角误差均在3%以内,且计算效率约为实体建模法的9.5倍,证明了本方法的准确性和高效性。     

基于刀具跳动的环形铣刀切削厚度模型的切削力计算

数控铣削过程中,切削变形引起的瞬时切削厚度是影响铣削加工切削力建模的重要参数之一,针对环形铣刀的切削特点,在考虑刀具跳动的情况下,对真实刀刃轨迹运动进行分析。将微细铣削的加工过程用宏观铣削来表示,从而建立了基于宏观铣削过程中刀具跳动下精密加工的瞬时切削厚度。通过仿真模拟和切削力试验来预测切削力,预测结果和试验结果具有一致性,表明该模型可以更好的预测加工过程中的切削力。     

基于模糊分析方法的钛合金插铣加工切削参数优化

合理的切削参数有利于提高刀具的使用寿命和切削效率,因此,进行切削加工过程中的切削参数优化尤为重要。本文以提高钛合金插铣加工效率,减小加工过程中的切削力为目的,对钛合金TC4进行插铣试验。基于切削试验数据,选择切削速度、切削宽度和每齿进给量作为评价因子,以材料去除率与切削力作为评价指标,运用模糊分析方法对切削参数进行综合评价,得出切削参数对综合指标的影响程度从大到小依次为:切削速度、切削宽度和每齿进给量,并实现切削参数的优化,为实际生产加工提供参考依据。     

A new method for cutting force prediction in peripheral milling of complex curved surface

The instantaneous uncut chip thickness and entry/exit angle of tool/workpiece engagement vary with tool path, workpiece geometry and cutting parameters in peripheral milling of complex curved surface, leading to the strong time-varying characteristic for instantaneous cutting forces. A new method for cutting force prediction in peripheral milling of complex curved surface is proposed in this paper. Considering the tool path, cutter runout, tool type(constant/nonconstant pitch cutter) and tool actual motion, a representation model of instantaneous uncut chip thickness and entry/exit angle of tool/ workpiece engagement is established firstly, which can reach better accuracy than the traditional models. Then, an approach for identifying of cutter runout parameters and calibrating of specific cutting force coefficients is presented. Finally, peripheral milling experiments are carried out with two types of tool, and the results indicate that the predicted cutting forces are highly consistent with the experimental values in the aspect of variation tendency and amplitude.     

球头铣刀加工倾角对切削力的影响

对球头铣刀刀具轴线和工件加工表面之间的加工倾角进行了理论研究,建立了加工曲面时刀具倾角的数学模型,并通过试验研究了高速铣削铝合金时刀具倾角对切削力的影响规律。随着刀具轴线相对于进给方向倾斜角度β的增大,切削力变化的趋势是减小;编制多轴数控加工程序时可以通过设置合理的刀具倾角来改善切削条件。     

自滚切刀具切削力试验研究

简介了自滚切刀具的基本概念,分析了切削过程中的切削力,对自滚切端铣刀的切削力进行了试验研究,得出了切削力与刀具刃倾角、刀片直径及切削速度之间的关系。试验结果表明,刃倾角对自滚切刀具的合理使用最为重要,各切削分力随刃倾角不同的变化规律源于刀刃工作前后角的变化;较小的刀片直径有利于减小切削力,使切削过程更加平稳;自滚切刀具特别适合于高速切削,较普通刀具切削速度可提高50%以上。     

Cutting Force Model for a Small-diameter Helical Milling Cutter

In the milling process, the major flank wear land area (two-dimensional measurement for the wear) of a small-diameter milling cutter, as wear standard, can reflect actual changes of the wear land of the cutter. By analyzing the wearing characteristics of the cutter, a cutting force model based on the major flank wear land area is established. Characteristic parameters such as pressure parameter and friction parameter are calculated by substituting tested data into their corresponding equations. The cutting force model for the helical milling cutter is validated by experiments. The computational and experimental results show that the cutting force model is almost consistent with the actual cutting conditions. Thus, the cutting force model established in the research can provide a theoretical foundation for monitoring the condition of a milling process that uses a small-diameter helical milling cutter.     

基于切削载荷的余量规划策略

针对高速铣削加工的切削载荷控制问题,提出一种适用于平头立铣刀2.5维铣削加工,考虑切削载荷的余量规划策略——恒力余量。通过加工试验证实了该策略的有效性,并讨论了走刀方向、刀触点轨迹线的连续性、刀具浸入包角和刀具半径对恒力余量规划结果的影响。与传统的几何等距余量规划方法相比,恒力余量策略能够显著改善切削载荷的波动情况,避免切削载荷的突变,为控制铣削载荷提供有效途径。     

An experimental investigation of oblique cutting mechanics

In this study, an experimental investigation of oblique cutting process is presented for titanium alloy Ti-6Al-4V, AISI 4340, and Al 7075. Important process parameters such as shear angle, friction angle, shear stress, and chip flow angle are analyzed. Transformation of the data from the orthogonal cutting test results to oblique cutting process is applied, and the results are compared with actual oblique cutting tests. Effects of hone radius on cutting forces and flank contact length are also investigated. It is observed that the shear angle, friction angle, and shear stress in oblique cutting have the same trend with the ones obtained from the orthogonal cutting tests. The transformed oblique force coefficients from orthogonal tests have about 10% discrepancy in the feed and tangential directions. For the chip flow angle, the predictions based on kinematic and force balance results yield better results than Stabler's chip flow law. Finally, it is shown that the method of oblique transformation applied on the orthogonal cutting data yields more accurate results using the predicted chip flow angles compared to the ones obtained by the Stabler's rule.     

Prediction of cutting force for ball end mill in sculptured surface based on analytic model of CWE and ICCE

Abstract

The force prediction is the precondition of improving equipment utilization ratio and optimizing process for CNC machining. Cutter-workpiece engagement (CWE) and in-cut cutting edge (ICCE) are the keys. In this article, a new analytic method of CWE and ICCE is proposed for ball end milling of sculptured surface and the prediction model of milling force is established. The sculptured surface is discretized into a series of infinitesimal inclined planes corresponding to cutter location points. The geometry relationships of cutter axis, feed direction and inclined plane are defined parametrically. The boundary curves and the boundary inflection points of the CWE are obtained by intersecting spatial standard curved surfaces with rotation transformation of coordinate system. The effective intersection points of the CWE and the cutter edge curve in X_c-Y_ctwo-dimensional plane are the upper and lower boundary points of ICCE. Based on the instantaneous chip thickness considering arbitrary feed direction, the force prediction model for ball end mill of three-axis surface milling is established. Simulation and experiment show that CWE and ICCE calculated by analytic method are well consistent with those of solid method. The predicted cutting forces match well with the measurements both in magnitude and variation trend.     

考虑刀杆柔性的球头铣刀切削力模型的研究

建立了球头铣刀切削力模型，并基于刀具弹性变形模型及刀具避让的切屑厚度数学表达式，建立了切屑厚度与刀具变形量、刀具切削参数之间的数学关系，并提出了切削力收敛算法。最后，通过切削实验对切削力模型进行了验证。