圆形刀片铣削P20模具钢的有限元模拟

建立了硬质合金圆形刀片铣削的三维有限元模型,模拟了切削速度和刀片前角变化时的铣削过程,分析了切屑形成过程,研究了切削力、切削温度的变化规律。结果表明:切削速度为400 m/min时切削力及切削温度较小,刀片前角为12°时相对较优。     

A force-model-based approach to estimating cutter axis offset in ball end milling

Cutter runout due to cutter axis offset is quite common in a milling process, yet it is difficult to directly measure the runout geometry of a ball end cutter during the cutting process. This paper presents an analytical method for the estimation of cutter radial offset via forces in ball end milling. Closed form expression for the total milling force in the presence of cutter offset is first obtained. Fourier series coefficients for the offset related force component are shown to be expressed explicitly in terms of the offset geometry and serve as the basis for the identification of the offset geometry from the measured cutting forces. The offset geometry including its magnitude and the phase angle are directly calculated from the measured force component at the spindle frequency through two algebraic expressions. The identification method is finally validated by milling experiments.     

Investigation of surface integrity in end milling of 55NiCrMoV7 die steel under the cryogenic environments

Abstract

Cryogenic assisted machining is experiencing growing popularity and acceptance as a toxic-free, eco-friendly, hazardless process producing improved structural components. This article deals with the analysis of 3D and 2D roughness profiles, surface morphology, residual stress and microhardness of 55NiCrMoV7 die steel after end milling operation under dry, wet, cryogenic CO₂ and LN₂ cooling environments. Among different cooling methods, the cryogenic CO₂ was seen enhancing the surface topography and morphology due to the presence of minimal wear track. The result indicates the production of an insignificant amount of residual stress in the machined surface by the cooling environments at a spindle speed of 1989?rpm and feed rate of 0.02?mm/rev. The surface microhardness values were higher under cryogenic conditions compared to dry and wet conditions. Cryogenic LN₂ provided the highest microhardness value among the four cooling methods.     

基于ANSYS的不同螺旋角立铣刀应力分析

对整体硬质合金立铣刀进行了受力计算,并利用ANSYS软件进行了建模、分析,模拟了刀具真实切削过程中切削力的瞬态变化,得出了在同等切削条件下,不同刀具螺旋角的大小,其动态切削过程中产生的最大应力值将发生较大的变化。     

基于加工仿真的立铣刀三维参数化设计

基于CATIA软件平台进行二次开发,开发出基于加工仿真的高速立铣刀三维参数化设计的CAD软件系统。设计人员输入立铣刀的使用参数和主要结构参数,根据系统的数据库和相关程序自动生成立铣刀的三维CAD模型以及加工立铣刀的砂轮刀位轨迹及NC代码,调用VERICUT软件进行立铣刀磨削加工仿真,从而保证立铣刀参数化设计的三维模型的可加工性,保证刀具设计的质量和缩短刀具设计和制造周期。     

球头铣刀数控加工表面形貌几何仿真的研究

几何仿真是建立铣削力预测模型的基础,而传统的几何仿真只考虑刀具的平动而忽略其转动。本文在同时考虑刀具平动和转动的基础上,利用工件Z-Map表示模型和刀刃离散表示法,提出了一种球头铣刀三轴数控铣削的微观几何仿真算法。该算法鲁棒性好、适用范围广,不仅能高效而准确地仿真铣削表面形貌,而且能准确提供切屑的轮廓,为建立精确的切削力预测模型提供了重要的几何参数。     

A microcontroller-based end milling cutter monitoring and management system

The monitoring of end milling cutting operations for tool breakage is achieved using a low-cost microcontroller-based system. The system is based upon acquiring and analysing machine tool-based signals for characteristic responses to tool breakage. Spindle speed and load signals are shown to be responsive to tool condition and thus capable of supporting the deployed approach. The resulting system operates in real time with tool breakage detection consistently diagnosed within two revolutions. The monitoring function is extended to consider tool wear using analysis methods applied in the time and frequency domains. Decisions about tool condition are made by integrating all relevant information into a rule base. Higher-level tool management functions supported by the deployed system are identified.     

Theoretical modelling of cutting forces in helical end milling with cutter runout

A theoretical cutting force model for helical end milling with cutter runout is developed using a predictive machining theory, which predicts cutting forces from the input data of workpiece material properties, tool geometry and cutting conditions. In the model, a helical end milling cutter is discretized into a number of slices along the cutter axis to account for the helix angle effect. The cutting action for a tooth segment in the first slice is modelled as oblique cutting with end cutting edge effect and tool nose radius effect, whereas the cutting actions of other slices are modelled as oblique cutting without end cutting edge effect and tool nose radius effect. The influence of cutter runout on chip load is considered based on the true tooth trajectories. The total cutting force is the sum of the forces at all the cutting slices of the cutter. The model is verified with experimental milling tests.     

球头铣刀精铣凸椭球路径分析及程序设计

通过设计精铣加工凸椭球面放射状的走刀路径,推断并验证了该路径所具有的椭圆轨迹特形,建立起编程所需的数学模型,编写精铣凸椭球面的用户宏程序,完成工件的切削加工。     

Multidisciplinary design optimization of a milling cutter for high-speed milling of stainless steel

The milling cutter’s fracture strength is more important than its chemical stability and thermal conductivity in high-speed milling. The multidisciplinary design optimization (MDO) method is employed to optimize the fracture-resistant performance of a milling cutter in this work. An experimental study on high-speed milling of the martensitic stainless steel 0Cr13Ni4Mo is conducted. The cutting forces and cutting temperature in the milling process are measured to provide initial data for the structural optimization of the milling cutter. The mathematical models of cutting force and cutting temperature are studied. Considering that the induced stress in the milling cutter is generated by thermomechanical coupling, the thermoelastic–plastic governing equation in the milling process is introduced in this work. The sensitivity of the structural parameters to the maximum equivalent stress of the milling cutter is calculated, and the structural parameters that have the greatest effects on the maximum equivalent stress are determined as design variables for the cutters’ optimization. The MDO procedure for the cutter’s optimization consists of updating of solid model, finite element analysis of thermomechanical coupling, postprocessing, and optimization algorithm. The MDO results show that the optimized milling cutter has a better fracture-resistant performance than the initial one. The maximum deformation, overall equivalent stress, and deformation are decreased.     

球头立铣刀铣削加工表面粗糙度仿真技术研究

铣削加工表面粗糙度的形成与铣刀和工件振动、主轴偏心、刀具磨损、刀具变形等物理和几何因素有关。多年来中外学者针对各种影响因素建立了“相对单一”的数学模型。这些数学模型只考虑了一种或两种影响因素,还没有建立起描述物理和几何变化过程的综合数学模型,为此对这些相关因素进行了深入研究,建立了基于球头立铣刀的铣削加工表面粗糙度仿真的整体数学模型。从而为虚拟数控加工仿真提供技术支撑。     

轮槽加工中铣削力与铣削温度分布规律研究

轮槽铣刀的改进往往是推动轮槽加工技术进步的最直接动力,而轮槽铣刀不同点的切削用量不同,很难测量出刀具不同点的力和温度。基于微元思想并利用标准盘铣刀和等效方法进行了铣削试验,得到了轮槽铣刀相应型线上铣削力与铣削温度的分布曲线并关注了危险点。     

Space cutter radius compensation method for free form surface end milling

The numerical control (NC) program for multi-axis end milling depends on the parameters of the tool, in particular, the radius of the tool. When there is any tool dimensional change due to various reasons, the user needs to re-generate the NC program, which is a time-consuming procedure. In this article, a cutter radius compensation method for multi-axis end milling is proposed. It takes a general NC program as the input, recovers the normal vectors of the machined surface from the NC program via surface reconstruction, and uses these vectors as compensation vectors to realize space cutter radius compensation. The proposed algorithm of shape reconstruction and normal vector computation has a linear complexity in terms of the number of cutter center location points in the NC program. Thus, real-time computation and compensation is possible. Our method also provides a way to restore the machined surface if the CAD model of the machines surface is not accessible. This has other applications, such as interference detection and manufacturing simulation. The compensation algorithm is shown to be very effective in reducing the number of undercut points through simulation with the software VERICUT and with real milling for real-world NC programs.     

3D FE modelling of high-speed ball nose end milling

The paper details research and development of a Lagrangian-based, 3D finite element (FE) model to simulate the high-speed ball nose end milling of Inconel 718 nickel-based superalloy using the commercial FE package ABAQUS Explicit. The workpiece material was modelled as elastic plastic with isotropic hardening and the flow stress defined as a function of strain, strain rate and temperature. Workpiece material data were obtained from uniaxial compression tests at elevated strain rates and temperatures (up to 100/s and 850°C, respectively) on a Gleeble 3500 thermo-mechanical simulator. The data were fitted to an overstress power law constitutive relationship in order to characterise flow behaviour of the material at the level of strain rates found in machining processes (typically up to 10⁵/s). Evolution of the chip was initially seen to progress smoothly, with the predicted machined workpiece contour showing good correlation with an actual chip profile/shape. Cutting force predictions from the FE model were validated against corresponding experimental values measured using a piezoelectric dynamometer, while modelled shear zone/chip temperatures were compared with previously determined experimental data. The model was successful in predicting the forces in the feed and step-over direction to within 10% of corresponding experimental values but showed a very large discrepancy with the thrust force component (～90%). Modelled shear-plane temperatures calculated at the point of maximum cutting force were found to demonstrate very good agreement with measured values, giving a discrepancy of ～5%. The simulation required a computational time of approximately 167 h to complete one full revolution of the ball end mill at 90 m/min cutting speed.     

On the machining characteristics of H13 tool steel in different hardness states in ball end milling

This paper investigates and compares the machining characteristics of AISI H13 tool steel in hardness states of 41 and 20 HRC in the ball end milling process. The machining characteristics are illustrated through three types of process outputs from the milling experiments: the milling force, the chip form, and the surface roughness. Characteristic differences in these process outputs are shown to reflect the hardness effect of the tool steel on the ball end milling process. The mechanistic phenomena of the milling process are revealed by the six shearing and ploughing cutting constants extracted from the milling forces. The experimental results show that all the cutting constants of the softer tool steel are greater than those of the hard steel, indicating that higher cutting and frictional energies are required in the chip shearing as well as in the nose ploughing processes of the softer tool steel. The higher cutting energy is also attested by the more severely deformed, shorter, and thicker chips of the softer steel. Surface roughness of the hard steel is shown to be considerably better than that of the soft steel at all cutting speeds and feed rates and is independent of cutting speed, whereas the surface roughness of the softer steel is significantly improved with increasing cutting speed.     

Chatter and dynamic cutting force prediction in high-speed ball end milling

Machine tool chatter is a serious problem which deteriorates surface quality of machined parts and increases tool wear, noise, and even causes tool failure. In the present paper, machine tool chatter has been studied and a stability lobe diagram (SLD) has been developed for a two degrees of freedom system to identify stable and unstable zones using zeroth order approximation method. A dynamic cutting force model has been modeled in tangential and radial directions using regenerative uncut chip thickness. Uncut chip thickness has been modeled using trochoidal path traced by the cutting edge of the tool. Dynamic cutting force coefficients have been determined based on the average force method. Several experiments have been performed at different feed rates and axial depths of cut to determine the dynamic cutting force coefficients and have been used for predicting SLD. Several other experiments have been performed to validate the feasibility and effectiveness of the developed SLD. It is found that the proposed method is quite efficient in predicting the SLD. The cutting forces in stable and unstable cutting zone are in well agreement with the experimental cutting forces.     

钢渣水洗球磨污水的循环利用

重点介绍了钢渣水洗球污水处理的工艺过程。通过对主要设备选型的分析计算,、得到了选型最优参数、达到了污水处理的最佳效果,杜绝了污水外排、节约水资源。     

高效干式切法盘形齿轮铣刀铣削力的研究

利用干式盘形成形齿轮铣刀在铣齿机上加工齿轮是提高齿轮加工效率有效途径。铣削力是其中的关键因素。研究了齿轮铣削中的顺铣和逆铣两种工艺方法,推导了铣削力计算公式。实验验证,计算的铣削力与实际铣削力基本吻合,该铣削力计算公式可以为铣削工艺选择提供参考。