基于斜角切削的曲线端铣切削力建模

切削力预测是制定与优化加工工艺的重要环节。针对曲线端铣加工过程,提出一种基于斜角切削的切削力建模方法。将刀具沿轴向微分,以曲线微分几何计算微元刃上的工作基面。在微元刃的工作法平面参考系中,应用最小能量原理,构建微元刃中力矢量、速度矢量、流屑角、法向摩擦角、法向剪切角及剪应力等切削参数之间的约束。以单齿直线铣削试验对切削参数进行标定,其中法向摩擦角、法向剪切角及剪应力等可表示为瞬时未变形切屑厚度的函数。选取高强度钢PCrNi3MoVA试件,分别进行圆弧和Bézier曲线端铣加工试验。试验结果表明,曲线端铣时切削力的变化与瞬时进给方向和曲线曲率相关。切削力预测值的幅值大小和变化趋势与试验值一致,验证了该切削力建模方法的有效性。     

复杂几何形状工件的计量解决方案

在计量科学领域,人们根据被测对象几何形状的复杂程度,将工业领域中的测量问题分为箱体类工件测量和具有复杂几何形状工件测量。所谓箱体类工件就是指那些由基本几何元素(点、线、面、圆、圆柱、圆锥、球)组成的几何工件,包括齿轮箱工件,发动机箱体,机床加工部件或者是由简单的自由形状曲面组成的冲压模、铸模、玻壳工件等等。与箱体类工件相对应的是复杂几何形状工件,这类工件主要由具有     

基于机器视觉复杂形状工件的非接触测量方法

介绍一种利用机器视觉技术完成复杂形状工件断面尺寸检测的非接触测量方法,该方法利用数字图像处理算法对高分辨率CCD器件采集的工件断面图像进行处理,可实现多品种工件的多参数自动测量。通过系统结构和工作过程分析了影响测量精度的因素。     

基于遗传算法工具箱的插铣切削力的预测模型

根据插铣核电材料A508-3钢各向最大切削力的正交实验数据,建立插铣过程的切削参数(切削速度、每齿进给量和径向切削宽度)各向最大切削力预测模型。把切削力预测值与实验值的残差平方和为适合度函数,采用谢菲尔大学研究的遗传算法工具箱实现各向最大切削力预测模型的各项参数。结果表明切削力预测模型与实验值吻合较好。本文目的是在特定插铣切削参数条件下预测切削力。     

基于斜角切削理论的立铣切削力预测研究

为了预测立铣加工的切削力,把立铣刀的切削刃离散为一系列无限小的斜角切削单元。对于每个微元斜角切削单元,应用斜角切削理论来建立切屑通过时剪切区的应力、应变、应变率和温度的控制方程。采用数值方法根据控制方程计算出流动应力,并根据斜角切削和铣削之间的力变换关系,把流动应力转化为铣削力。最后,对45钢进行了多组不同切削参数的立铣实验,仿真和实验的对比结果验证了所提出模型的有效性。该方法同样可以用于其他加工方式（如车削和钻削）的建模。     

正交车铣切削层几何形状的仿真与分析

针对现有正交车铣切削层几何形状仿真方法复杂及解析法无法明确其几何形状变化规律的问题,根据正交车铣的运动规律,结合NX 8.5软件提出了正交车铣切削层几何形状的仿真方法,并进行了试验验证和仿真分析。研究结果可为正交车铣切削力和加工振动的分析提供基础,并为正交车铣切削参数的优化提供指导。     

考虑工件变形的五轴侧铣薄壁件铣削力建模

针对铣削加工过程中工件和刀具接触关系的时变性所导致铣削力预测不精准的问题,提出一种综合考虑工件变形作用下的五轴侧铣铣削力建模方法。首先,基于机械Ⅱ型力学模型,综合考虑剪切力和犁切力作用,建立五轴铣削加工微元铣削力模型;其次,利用欧拉-伯努利梁理论计算工件在任意切削深度下的变形量;进而,更新工件变形量引起的切削深度变化,构建考虑工件变形的五轴侧铣薄壁件铣削力模型;最后,通过试验与模型预测结果对比,得出在考虑变形的情况下,X、Y方向上铣削力的平均峰值误差分别减小了4.42%和0.62%,验证了模型的有效性。     

基于优化子波-神经网络图像识别的工件形状监控

介绍了一种用普通CCD摄像机和激光对旋转工件的形态进行图像采集和状态监控的系统，提出了用于图像处理与识别的子波—神经网络结构，并设计了相应的优化学习算法，可以简化网络并加速收敛。该系统可用于实现自动化精密加工过程中的工件形状监控和刀具诊断，仿真证明了理论算法的有效性。     

接触问题形状优化模型的研究

探讨了以边界元法作为应力分析工具,对弹性接触进行形状优化时优化模型建立的问题。     

高速干式飞刀铣齿切削力模型

利用金属切削理论,采用高速干式飞刀铣齿模拟滚齿切削过程,建立飞刀铣齿切削力模型,推导出飞刀铣削力的计算公式。该模型的建立对进一步分析高速干式滚齿过程中的特征参数、进行切削机理的研究具有重要意义。     

Improved dynamic cutting force model in ball-end milling. Part I: theoretical modelling and experimental calibration

An accurate cutting force model of ball-end milling is essential for precision prediction and compensation of tool deflection that dominantly determines the dimensional accuracy of the machined surface. This paper presents an improved theoretical dynamic cutting force model for ball-end milling. The three-dimensional instantaneous cutting forces acting on a single flute of a helical ball-end mill are integrated from the differential cutting force components on sliced elements of the flute along the cutter-axis direction. The size effect of undeformed chip thickness and the influence of the effective rake angle are considered in the formulation of the differential cutting forces based on the theory of oblique cutting. A set of half immersion slot milling tests is performed with a one-tooth solid carbide helical ball-end mill for the calibration of the cutting force coefficients. The recorded dynamic cutting forces are averaged to fit the theoretical model and yield the cutting force coefficients. The measured and simulated dynamic cutting forces are compared using the experimental calibrated cutting force coefficients, and there is a reasonable agreement. A further experimental verification of the dynamic cutting force model will be presented in a follow-up paper.     

Cutting force model considering tool edge geometry for micro end milling process

The analysis of the cutting force in micro end milling plays an important role in characterizing the cutting process, as the tool wear and surface texture depend on the cutting forces. Because the depth of cut is larger than the tool edge radius in conventional cutting, the effect of the tool edge radius can be ignored. However, in micro cutting, this radius has an influence on the cutting mechanism. In this study, an analytical cutting force model for micro end milling is proposed for predicting the cutting forces. The cutting force model, which considers the edge radius of the micro end mill, is simulated. The validity is investigated through the newly developed tool dynamometer for the micro end milling process. The predicted cutting forces were consistent with the experimental results.     

In-process estimation of radial immersion angle using cutting force in face milling

In this paper, a on-line estimation method of the radial immersion angle using cutting force is presented. The ratio of cutting forces in feed and cross-feed directions acting on the single tooth at the immersion angle is a function of the immersion angle and the ratio of radial to tangential cutting force. It is found that the ratio of radial to tangential cutting force is not affected by cutting conditions and axial rake angle, which implies that the ratio determined by one preliminary experiment can be used regardless of the cutting conditions for a given tool and workpiece material. Using the measured cutting force during machining and predetermined ratio, the radial immersion ratio is estimated in process. Various experimental results show that the proposed method works within5% error range.     

In-process estimation of radial immersion ratio in face milling using cutting force

In order to prevent tool breakage in milling, maximum total cutting force is regulated at a specific constant level, or threshold, through feed rate control. Since the threshold is a function of the immersion ratio, an estimation of the immersion ratio is necessary to flexibly determine the threshold. In this paper, a method of in-process estimation of the radial immersion ratio in face milling is presented. When an insert finishes sweeping, a sudden drop in cutting forces occurs. These force drops are equal to the cutting forces that act upon a single insert at the swept cutting angle and they can be acquired from cutting force signals in the feed and cross-feed directions. Average cutting forces per tooth period can also be calculated from the cutting force signals in two directions. The ratio of cutting forces acting upon a single insert at the swept angle of cut and the ratio of average cutting forces per tooth period are functions of the swept angle of cut and the ratio of radial to tangential cutting force. Using these parameters, the radial immersion ratio is estimated. Various experiments are performed to verify the proposed method. The results show that the radial immersion ratio can be estimated by this method regardless of other cutting conditions.Nomenclature F_T, F_R tangential and radial forces - F_X, F_Y cutting forces in feed direction and cross feed direction - dF_X, dF_Y cutting force differences before and after the immersion angle in X and Y direction - K_s specific cutting pressure - a depth of cut - r ratio between tangential force and radial force - s_t feed per tooth - instantaneous angle of cut - _s swept angle of cut - _T tooth spacing angle - w radial width of cut - R cutter radius - z number of inserts     

A geometrical model of the cut in five-axis milling accounting for the influence of tool orientation

This paper presents a model of the cut geometry in five-axis milling. This allows the establishment of a better model of cutting force to account for the influence of the tool orientation. The formulation of the width and the thickness of the cut were derived and implemented in a computer simulation. The results of simulations were verified experimentally and a good agreement was obtained. The result shows the importance of including the influence of the tool orientation in the cut cross-section calculation.     

3-Dimensional kinematics simulation of face milling

Face milling is currently the most effective and productive manufacturing method for roughing and finishing large surfaces of metallic parts. Milling data, such as surface topomorphy, surface roughness, non-deformed chip dimensions, cutting force components and dynamic cutting behavior, are very helpful, especially if they can be accurately produced by means of a simulation program. This paper presents a novel simulation model which has been developed and embedded in a commercial CAD environment. The model simulates the true tool kinematics using the exact geometry of the cutting tool thus accurately forecasting the resulting roughness. The accuracy of the simulation model has been thoroughly verified, with the aid of a wide variety of cutting experiments. The proposed model has proved to be suitable for determining optimal cutting conditions for face milling. The software can be easily integrated into various CAD–CAM systems.     

Mechanistic modelling of the milling process using complex tool geometry

Mechanistic models of the milling process must calculate the chip geometry and the cutter edge contact length in order to predict milling forces accurately. This task becomes increasingly difficult for the machining of three dimensional parts using complex tool geometry, such as bull nose cutters. In this paper, a mechanistic model of the milling process based on an adaptive and local depth buffer of the computer graphics card is compared to a traditional simulation method. Results are compared using a 3-axis wedge shaped cut – a tool path with a known chip geometry – in order to accommodate the traditional method. Effects of cutter nose radius on the cutting and edge forces are considered. It is verified that there is little difference (1.4% at most) in the predicted force values of the two methods, thereby validating the adaptive depth buffer approach. The numerical simulations are also verified using experimental cutting tests of aluminium, and found to agree closely (within 12%).     

A study on calibration of coefficients in end milling forces model

This paper presents an improved approach to calibrate the cutting coefficients in an end-milling model. In order to predict end-milling forces, lots of simulative models are established. In order to use them, coefficients in the models, for example, cutting pressure constants etc., must firstly be calibrated experimentally, and simulative precision and applicability of the models are influenced by them. For simplicity, using average forces to calibrate cutting parameters are widely adopted by lots of researchers. However, the existence of an instruments zero-drift, noise, etc., will have effect on the precision of experimental data, so, it is difficult to directly obtain exact average-cutting forces through experimental data. Aiming at the above problem, the paper investigates milling forces in the frequency domain, discusses the impact of experimental data at different frequencies on cutting force coefficients and the influence of sensitivity of error on experimental data at different frequencies on coefficients is studied. Based on the research, an improved method to calibrate the cutting coefficients is provided. Based on a series of experiments and numerical simulations, the validity of the method is confirmed. At the end of the paper, some useful conclusions are drawn.