一种典型数控铣切削参数的优化方法

提出一种典型数控铣加工中切削参数的优化方法。利用测量啮合角来表示切削力的大小,通过大量实验数据建立表示切削力的数学模型。利用模糊逻辑理论拟合切削参数数据集,使拟舍后的切削参数数据集能够在实际加工中具有通用性。根据工件的几何特征来计算啮合角,从而判定切削力以确定各加工区域的进给速度。     

基于刀具进让式进给数控加工技术的研究

通过分析常规数控加工中存在的问题,提出了一种刀具在进给方向上可进让式进给切削工件曲面轮廓的新工艺方法,建立了进让式进给切削数学模型,并从被加工工件的几何形状、切削过程中刀具受力情况及切削区的切削热释放情况等方面,具体分析了采用该方法对加工精度的改善情况,并给出了算法步骤。试验结果表明,新方法有利于减小工艺系统的变形,显著提高了工件的加工精度。     

基于切削力实时测量的弱刚性件加工变形控制

针对整体多框弱刚性件切削易变形之问题,提出了基于切削力实时测量的进给速度实时调整方法。根据铣削变形仿真数据建立了加工过程中进给速度、切削力与工件最大变形之间的非线性数值模型,并通过非线性求根算法求解最大变形和切削力约束下的进给速度最优解,并在开放式数控系统中开发了相应的控制模块。利用所开发的无线轴式测力装置和控制模块开展了铝合金薄壁框切削变形控制实验,结果说明数值模型预测精度在90%以上,实施进给速度优化功能优化后,切削力和工件最大变形分别降低23%和12.3%左右。实验结果表明,经过切削力实时约束和弱刚性件加工进给速度自适应调整,可将薄壁框件侧壁变形控制在规定范围内。     

超声振动铣削陶瓷基复合材料切削力模拟研究

针对陶瓷基复合材料在加工过程中易出现毛刺、分层、崩边等加工问题,提出超声振动切削方法加工陶瓷基复合材料并进行了铣削过程的有限元模拟分析。给出了主轴转速、进给速度对铣削过程中各向切削力的影响,对比分析了超声振动铣削加工与普通铣削加工的切削力波形曲线。结果表明,两种加工方法各向切削力均随主轴转速的增大而减小,进给速度的增大而增大,但当主轴转速达到4000r/min时,超声作用消失,超声振动切削力与普通铣削切削力相当;同时,超声振动铣削加工条件下各向切削力峰值都明显低于普通铣削切削力,平均切削力更是有大幅度降低,超声振动切削方法更适合加工陶瓷基复合材料。     

基于有限元数值模型和进给速度优化的薄壁件侧铣变形在线控制

为实现在加工过程中对薄壁件侧铣产生的较大切削变形进行在线控制,提出基于有限元数值模型和进给速度优化的在线控制策略。根据薄壁件切削过程的有限元仿真结果,建立数控机床进给速度、切削力、工件切削变形间的数值模型,进而确定用于控制变形的最优目标切削力。在具有开放式模块化的数控系统平台上开发了切削力信号实时采集、滤波功能和基于Brent-Dekker算法的进给速度在线优化策略,并根据滤波后的切削力及相应算法在加工过程中实时调整机床进给速度,保证切削力逐渐接近最优控制目标而实现切削变形的在线控制。试验结果表明,经过进给速度在线优化后的切削过程可将薄壁件侧铣变形控制在规定范围内,同时提高了切削效率。     

CVD涂层刀具高速铣削大理石切削力研究

选定切削参数(切削速度、进给速度、切削深度)设计正交试验,进行CVD氮化钛涂层刀具高速铣削大理石切削力试验,利用测力仪测出各组试验的切削力信号图,分析信号图特征得出切削力值,并记录各组切削力试验结果。分析单一切削参数(切削速度、进给速度,切削深度)对切削力变化的影响规律。采用最小二乘法原理对切削力经验公式回归系数进行参数估计,并对经验公式进行相关性检验,检验结果表明显著性很高。最终通过试验结果得出:切削力随着进给速度和切削深度的增加而增大,随着切削速度的增加而减小;并且切削深度对切削力影响最大,切削速度次之,进给速度对切削力的影响最小。     

旋转超声钻削的切削力数学模型及试验研究

通过分析硬脆材料脆性断裂去除机理和旋转超声加工特点,确定旋转超声加工时单颗磨粒的切削时间、切削深度、切削速度及切削轨迹长度,建立旋转超声恒进给率钻削硬脆材料的切削力数学预测模型。光学玻璃加工试验研究表明,切削力随进给速度的增大而增大,随主轴转速的提高而减小;在高进给速度条件下,切削力对主轴转速的变化更为敏感,在低主轴转速条件下,切削力对进给速度的变化更为敏感;从而很好地验证了已建立的切削力数学预测模型。旋转超声加工和普通加工的对比试验表明,旋转超声钻削加工可以有效降低切削力,一定程度上减小出孔崩边尺寸,从而提高加工效率、降低加工成本。根据旋转超声加工的表面粗糙度值略高于普通加工,提出硬脆材料脆性断裂去除时磨粒实际切削深度决定加工表面粗糙度的判断。     

基于虚拟加工技术的铣削过程优化研究

提出了利用虚拟加工技术对数控加工过程进行恒切削力优化的方法，在利用虚拟加工单元预测切削力的基础上，根据切削过程优化理论和方法，对数控程序中切削速度和进给速度优化后进行加工，达到对切削过程进行恒切削力控制的目的。实验验证了该方法的可行性。     

基于Abaqus/explicit的钛合金高速切削切削力模拟研究

针对高速切削钛合金时切削力的问题,利用有限元分析软件Abaqus的Johnson Cook材料模型及Johnson Cook断裂准则,对钛合金高速切削切削力进行了仿真研究,分析钛合金高速切削加工过程中各切削参数（包括进给量、切削深度和切削速度）对切削力的影响.结果表明,切削力、进给力、单位面积切削力和单位面积进给力都随速度的增大而减小;但随着进给速度的增大,切削力和进给力都增大,而单位面积的切削力和进给力都减小.     

塑窗型材锯切工影响参数试验研究

针对塑窗型材切削加工工艺特点,优选影响型材加工的主要因素,设计试验方案,使用Kistler9275B测力系统测量并记录在不同参数组合下的切削力,使用正交试验方法分析试验数据,得到进给速度、切削宽度和冷却风强度对型材切削力的影响规律,并找出进给速度、切削宽度和冷却风强度的最佳组合.结果表明,在保证加工质量前提下,切削宽度...     

ENHANCEMENT OF PRODUCTIVITY BY INTELLIGENT PROGRAMMING OF FEED RATE IN 3-AXIS MILLING

An optimized feed scheduling strategy (OFSS) is proposed in this paper to maximize the metal removal rate in 3-axis milling while guaranteeing the machining accuracy. This strategy integrates the feed drive dynamics, described by the acceleration/deceleration (Acc/Dec) profile, with the minimum-time trajectory planning in order to achieve the desired feed rate at the appropriate position. An optimum use of the feed drive capabilities is considered to track the changes in the cutting geometry along the tool path. Therefore, this strategy combines different constraints and various criteria in modifying the feed rate to maintain near-constant cutting force resulting in highly non-linear problem. The constraints include the cutting force, the feed rate boundaries, the contour error and the characteristics of the (Acc/Dec) profile. The criteria are the maximum production rate, the machining accuracy and safety. The performance of the OFSS in terms of these criteria, is compared to two end milling operations where the trajectory planning disregards the feed drive dynamics. The first is based on a feed scheduling strategy using control points (FSCP). The second is a milling operation with nominal feed rate. By increasing the feed rates, the OFSS improves the machining accuracy, reduces the machining time, and allows a better regulation of the cutting force.     

ENHANCEMENT OF PRODUCTIVITY BY INTELLIGENT PROGRAMMING OF FEED RATE IN 3-AXIS MILLING

An optimized feed scheduling strategy (OFSS) is proposed in this paper to maximize the metal removal rate in 3-axis milling while guaranteeing the machining accuracy. This strategy integrates the feed drive dynamics, described by the acceleration/deceleration (Acc/Dec) profile, with the minimum-time trajectory planning in order to achieve the desired feed rate at the appropriate position. An optimum use of the feed drive capabilities is considered to track the changes in the cutting geometry along the tool path. Therefore, this strategy combines different constraints and various criteria in modifying the feed rate to maintain near-constant cutting force resulting in highly non-linear problem. The constraints include the cutting force, the feed rate boundaries, the contour error and the characteristics of the (Acc/Dec) profile. The criteria are the maximum production rate, the machining accuracy and safety. The performance of the OFSS in terms of these criteria, is compared to two end milling operations where the trajectory planning disregards the feed drive dynamics. The first is based on a feed scheduling strategy using control points (FSCP). The second is a milling operation with nominal feed rate. By increasing the feed rates, the OFSS improves the machining accuracy, reduces the machining time, and allows a better regulation of the cutting force.     

Machining forces prediction for peripheral milling of low-rigidity component with curved geometry

This study has developed a model in order to predict machining forces for milling low-rigidity component with curved profile. Differing from conventional models used for straight geometries, the new model takes both the deflection of work piece-cutter system and the continuous change of curvature of machined part into account. In the model, a profile with variable curvature is defined and the feed rate per tooth on the profile is derived subsequently. The cutting force is analyzed simulatively by utilizing modified Newton–Raphson iterative algorithm. The simulative results show that the total radial deflection of workpiece–cutter system is the main factor affecting the change of cutting force. Moreover, the feed rate per tooth and its corresponding cutting force changes according to the curvature of the profile. Finally, experiments were carried out to verify the accuracy of the models.     

Modeling and Analytical Solution of Chatter Stability for T-slot Milling

T-slot milling is one of the most common milling processes in industry. Despite recent advances in machining technology, productivity of T-slot milling is usually limited due to the process limitations such as high cutting forces and stability. If cutting conditions are not selected properly the process may result in the poor surface finish of the workpiece and the potential damage to the machine tool. Currently, the predication of chatter stability and determination of optimal cutting conditions based on the modeling of T-slot milling process is an effective way to improve the material removal rate(MRR) of a T-slot milling operation. Based on the geometrical model of the T-slot cutter, the dynamic cutting force model was presented in which the average directional cutting force coefficients were obtained by means of numerical approach, and leads to an analytical determination of stability lobes diagram(SLD) on the axial depth of cut. A new kind of SLD on the radial depth of cut was also created to satisfy the special requirement of T-slot milling. Thereafter, a dynamic simulation model of T-slot milling was implemented using Matlab software. In order to verify the effectiveness of the approach, the transfer functions of a typical cutting system in a vertical CNC machining center were measured in both feed and normal directions by an instrumented hammer and accelerators. Dynamic simulations were conducted to obtain the predicated SLD under specified cutting conditions with both the proposed model and CutPro?. Meanwhile, a set of cutting trials were conducted to reveal whether the cutting process under specified cutting conditions is stable or not. Both the simulation comparison and experimental verification demonstrated that the satisfactory coincidence between the simulated, the predicted and the experimental results. The chatter-free T-slot milling with higher MRR can be achieved under the cutting conditions determined according to the SLD simulation.     

Cutting forces prediction in generalized pocket machining

Cutting force prediction is important for the planning and optimization of machining process. This paper presents an approach to predict the cutting forces for the whole finishing process of generalized pocket machining. The equivalent feedrate is introduced to quantify the actual speed of cutting cross-section in prediction of cutting force for curved surface milling. For convenience, to analyze the process with varying feed direction and cutter engagement, the milling process for generalized pocket is discretized into a series of small processes. Each of the small processes is transformed into a steady-state machining, using a new approximation method. The cutting geometries of each discrete process, i.e., feed direction, equivalent feedrate per tooth, entry angle, and exit angle are calculated based on the information refined from NC code. An improved cutting force model which involves the effect of feed direction on cutting forces prediction is also presented. A machining example of a freeform pocket is performed, and the measured cutting forces are compared with the predictions. The results show that the proposed approach can effectively predict the variation of cutting forces in generalized pocket machining.     

Process modeling and toolpath optimization for five-axis ball-end milling based on tool motion analysis

In free-form surface machining, the prediction of five-axis ball-end milling forces is quite a challenge due to difficulties of determining the underformed chip thickness and engaged cutting edge. Part and tool deflections under high cutting forces may result in poor part quality. To solve these concerns, this paper presents process modeling and optimization method for five-axis milling based on tool motion analysis. The method selected for geometric stock modeling is the dexel approach, and the extracted cutter workpiece engagements are used as input to a force prediction. The cutter entry?Cexit angles and depth of cuts are found and used to calculate the instantaneous cutting forces. The process is optimized by varying the feed as the tool?Cworkpiece engagements vary along the toolpath, and the unified model provides a powerful tool for analyzing five-axis milling. The new feedrate profiles are shown to considerably reduce the machining time while avoiding process faults.     

实体法铣削仿真效率改善及应用算法

轴向切削深度和径向切削宽度是铣削仿真模型求解的几何边界条件,也称为啮合几何参数。根据对啮合参数提取的三类途径的比较,针对直接布尔操作途径仿真效率低的问题,运用集合论描述了实体法铣削仿真中模拟材料去除的布尔运算过程,从时间复杂性角度分析影响实体法铣削仿真效率的因素,提出改善仿真运行效率的4种途径;在此基础上,从几何造型和切削过程两方面给出在仿真计算位置处布尔运算次数由4次减少为1次的可行性分析,提出在简化布尔运算次数情况下的切削几何边界条件的识别和判断算法,对判断算法的有效性和减少布尔运算的时间复杂性进行分析、给出在铣削力仿真中的应用示例,并说明应用范围,从而在保证切削几何边界条件准确提取的同时提高仿真效率,为铣削力等仿真模型的求解奠定基础,推动相关物理仿真研究成果在工程实际中得到切实应用。     

难加工材料型腔圆角数控铣削的切削力预测

在难加工材料型腔的数控铣削过程中,圆角区域的加工阶段,径向切削深度和真实进给量的变化很大程度上影响切削力,造成扎刀、撞刀、振动等很多的问题, 影响工件的加工准确度和刀具的寿命,甚至使得加工无法顺利进行.文中建立端铣刀和圆角轮廓几何关系的数学模型,提出普遍适用于矩形与梯形型腔圆角的切削力预测方法.最后,对型腔圆角切削力的变化规律预测方法进行验证.     

Cutting force prediction in ball-end milling with inclined feed by means of geometrical analysis

A geometrical model for the analysis of cutting forces in ball-end milling has been presented in a previous work (Tsai CL, Liao YS, J Mater Process Technol 205:24–33, 10), which can be used to analyze cutting forces in vertical or horizontal feed. In this paper, the three-dimensional geometrical analysis is depicted with different interacting relations among cutting edge, undeformed chip and shear zone along nonhorizontal cutting direction, and a general geometrical model of inclined feed in ball-end milling is presented. According to the geometrical analysis, the cutting directions of horizontal, vertical, inclined downward, and inclined upward feed are defined with a feed angle. A general force model is derived, and the three-dimensional cutting forces are predicted. Experiments are conducted to verify the geometric force model. The influences of different feed angle and helix angle on cutting forces in inclined downward and inclined upward feed are discussed and simulated.