薄壁件铣削技术研究

在航空航天工业中,薄壁件数控铣削是一种常见的典型加工。本文以薄壁件铣削加工过程为研究对象,完成了对薄板支架零件的数控加工工艺分析,建立了薄壁件加工变形的力学模型,应用有限元分析软件,建立了薄壁件铣削加工变形的模拟环境,总结了薄壁件铣削加工变形的规律,提出了薄壁件加工变形补偿的方法,并在Pro/E软件中生成了走刀路线。本研究成果为解决薄壁件铣削加工问题提供了一定的参考和依据。     

TC4钛合金铣削力及表面粗糙度分析

铣削力和表面粗糙度是评价工件加工工艺质量的重要指标,特别是对于薄壁件的加工,过大切削力会使零件产生弹塑性变形,造成零件过切或欠切,从而严重影响工艺质量.本文通过多因素正交实验,研究了各铣削参数对铣削力及表面粗糙度的影响程度,并建立了铣削力及表面粗糙度的经验预测模型.结果 表明,在铣削力方面,铣削深度和每齿进给量的影响高...     

加工大尺寸零件的表面切削顺序及走刀路径

针对航空发动机大尺寸薄壁件的车削、铣削等机械加工工序,介绍了合理规划这些工序表面加工顺序和走刀路径应遵循的原则,并与传统工艺进行了对比.     

基于UG的航空薄壁件加工工艺研究与实践

针对航空薄壁工件的壁薄以及结构复杂,在加工时会出现刚性低、材料去除率高以及易发生干涉等难点,分析了薄壁件加工变形与残余应力的主要影响因素。为保证在加工过程中薄壁件的刚度,研究制定了薄壁件铣削加工方案,剖析了薄壁件的结构特点,展开了加工工艺研究。根据机床特点利用UG CAM设置参数并进行后置处理,生成了相应的走刀轨迹,并运用VERICUT进行仿真加工,将验证后的加工工艺应用于实际加工中,实现了薄壁件高效率、高精密、高可靠性的数控加工。     

基于有限元分析的走刀策略对铝合金薄壁筋铣削仿真工艺研究

铝合金薄壁筋具有弹载计算机结构件的典型特征,其结构简单但整体刚性差,在加工过程中极易产生加工变形,影响工件的加工精度。为合理选择走刀策略,使用ABAQUS软件对铝合金薄壁筋铣削过程进行有限元仿真建模,分析了不同走刀策略下铣削过程中的铣削力及工件铣削后的变形情况。同时设计对照试验组进行试切验证,通过三坐标测量仪分别测量了薄壁筋在不同走刀策略下的形变,验证了仿真分析结果的正确性。     

虚拟技术在叶轮加工中的应用

叶轮是典型的多轴加工零件,加工中经常出现空刀、过切、欠切、表面质量不高等问题。文中通过应用UG软件的叶轮加工模块完成整体叶轮加工的自动编程,并基于VERICUT软件实现了米克朗UCP710型五轴加工中心铣削整体叶轮的仿真与优化,提高了加工质量和效率。     

航空薄壁件三维铣削过程的有限元仿真

铣削加工中铣削力是导致加工变形的直接原因,而航空薄壁件加工中,加工变形是加工误差产生的主要因素。通过有限元法对航空薄壁件的铣削过程进行三维仿真模拟,揭示了切削深度、切削速度以及摩擦因素对切削力的影响。     

基于MasterCAM二维轮廓铣削的切入/切出方式的比较

轮廓铣削属于工件加工中典型而重要的内容之一。然而,在利用CAD/CAM软件完成二维轮廓自动编程中,由于对切入/切出方式理解不透,常引起在材料上直接下刀、欠切/过切、机床报警及加工效率低等现象。     

薄壁微细铣削参数与工艺试验研究

为了获得高精度的微型薄壁,并揭示铣削参数与走刀次数对薄壁加工质量的影响,文章展开了微细铣削薄壁的参数与工艺试验研究。通过设计并开展单因素对比试验与薄壁制造试验,递进地探究了走刀次数与轴向切深对薄壁尺寸误差的影响。结果显示,多次走刀时,铣削力基本不改变,而薄壁的尺寸精度却能提高;轴向切深越大,增加走刀次数对薄壁尺寸误差的影响越明显;当薄壁高度一定时,存在最佳的走刀次数,使得薄壁尺寸误差最小。这表明,多次走刀所引入的误差影响,可以用来制衡参数等其他因素带来误差影响,从而减小薄壁尺寸误差。因此,实际生产时,通过选择优化参数以及合适的走刀次数,可以有效的提高薄壁尺寸精度。     

整体叶轮叶片根部特征刀具轨迹规化研究

针对整体叶轮叶片根部特征加工过程中极易产生过切和欠切的问题,提出了适合光滑过渡曲面区域的叶轮叶片根部特征的精加工的刀具轨迹规划优化方法。该方法首先对叶根曲面进行划分,定义加工曲面类型;然后对加工曲面进行刀具轨迹规划,计算出最佳走刀步长和行距;最后在保证刀具不与被加工表面发生过切和欠切的基础上,使得刀具与被加工曲面在刀触点处平面上每个方向的曲率相匹配,并使生成的刀轨光顺简洁,改善曲面加工精度与加工效率。通过对某叶片根部的仿真实例加工验证了该方法的正确性。该方法在多轴数控加工中具有重要的实用价值。     

SIMULATION CONCEPT FOR PREDICTING WORKPIECE VIBRATIONS IN FIVE-AXIS MILLING

The characteristic discontinuous cut of the milling process influences the whole machining process by an increased susceptibility to vibrations of the machine-tool-workpiece system. This can result in undesirable effects on the workpiece surface or in a shorter lifetime of the tool and the spindle. Especially with regard to the machining of thin-walled components, such as turbine blades and thin profiles, the dynamic behavior of the workpiece is of particular interest. In this paper a simulation concept for predicting regenerative workpiece vibrations during the five-axis milling process is presented. This concept combines an accurate and fast simulation of the five-axis machining process including material removal and force calculation with an implemented finite element model for computing workpiece displacements. The simulation results are compared with data from experiments, which were conducted using a milling tool with high stiffness in order to minimize the influence of the milling tool dynamics.     

Development of an automatic arc welding system using SMAW process

In end milling of pockets, variable radial depth of cut is generally encountered as the end mill enters and exits the corner, which has a significant influence on the cutting forces and further affects the contour accuracy of the milled pockets. This paper proposes an approach for predicting the cutting forces in end milling of pockets. A mathematical model is presented to describe the geometric relationship between an end mill and the corner profile. The milling process of corners is discretized into a series of steady-state cutting processes, each with different radial depth of cut determined by the instantaneous position of the end mill relative to the workpiece. For the cutting force prediction, an analytical model of cutting forces for the steady-state machining conditions is introduced for each segmented process with given radial depth of cut. The predicted cutting forces can be calculated in terms of tool/workpiece geometry, cutting parameters and workpiece material properties, as well as the relative position of the tool to workpiece. Experiments of pocket milling are conducted for the verification of the proposed method.     

Three-dimensional process stability prediction of thin-walled workpiece in milling operation

High-speed machining of thin-walled workpiece is widely used in aerospace industry. To optimize the machining parameters in milling operations, the related process stability is required to be predicted. Compared to the existing two-dimensional (2D) milling stability model, a more completed three-dimensional (3D) regenerative process stability prediction model of thin-walled workpiece is presented based on the newly developed dynamic model. The efficiency and accuracy of the regenerative milling stability can be improved in the presented 3D model. The analysis procedure of the stability of flexible dynamic milling is developed in details. The 3D stability lobes are calculated according to the full discretization method and direct integration scheme. To verify the accuracy of presented 3D stability model, the thin-walled workpiece milling sound pressure signal and surface quality are determined in experiments.     

Predictive framework for cutting force induced cylindricity error estimation in end milling of thin-walled components

The static deflections of cutting tool and workpiece are the primary source for the deviation of machined components from the design specifications during end milling of thin-walled geometries. The deviations are expressed as per the Geometric Dimensioning and Tolerancing (GD&T) principles using size, form, and orientation of the features. This paper proposes a computational framework to estimate cutting force induced cylindricity error during end milling of thin-walled circular components. The framework combines computational elements such as Mechanistic force model, Finite Element Analysis (FEA) based workpiece deflection model, Cantilever beam formulation based tool deflection model, and Particle Swarm Optimization (PSO) based cylindricity estimation algorithm. It has been observed that the static deflections of a cutting tool and thin-walled component influence the cylindricity error considerably. The inevitable aspects associated with the end milling of thin-walled circular components such as concave-convex side machining and workpiece rigidity are investigated subsequently. It was observed that the cylindricity error during concave side machining is considerably smaller due to geometric configuration imparting adequate stiffness to thin-walled components. The study also demonstrated that an appropriate combination of productive cutting conditions and the component thickness could reduce cylindricity error considerably. The outcomes of the present study are substantiated by conducting a set of computational simulations and end milling experiments over a wide range of cutting conditions. The computational framework proposed in the present study can assist process planners in selecting appropriate cutting conditions to manufacture thin-walled circular components within tolerance limits specified by the designer.     

Prediction of simultaneous dynamic stability limit of time�Cvariable parameters system in thin-walled workpiece high-speed milling processes

A method for predicting simultaneous dynamic stability limit of thin-walled workpiece high-speed milling process is described. The proposed approach takes into account the variations of dynamic characteristics of workpiece with the tool position. A dedicated thin-walled workpiece representative of a typical industrial application is designed and modeled by finite element method. The curvilinear equation of modal characteristics changing with tool position is regressed. A specific dynamic stability lobe diagram is then elaborated by scanning the dynamic properties of workpiece along the machined direction throughout the machining process. The results show that, during thin-walled workpiece milling process, material removing plays an important part on the change of dynamic characteristics of system, and the stability limit curves are dynamic curves with time?Cvariable. In practical machining, some suggestion is interpreted in order to avoid the vibrations and increase the chatter free material removal rate and surface finish. Then investigations are compared and verified by high-speed milling experiments with thin-walled workpiece.     

薄壁件变参数铣削系统动态特性的研究

提出一种薄壁件变参数铣削系统动态特性分析方法。考虑铣削过程中的自激振动和强迫振动,建立了薄壁件变参数(模态质量、模态阻尼和模态刚度)铣削系统周期延迟微分方程,借助有限单元法和最小二乘法,获得加工过程中工件系统固有频率和模态质量随刀具位置的连续变化曲线。研究结果显示,薄壁件加工过程中,材料切除对系统动态特性有重要影响。实际加工时,应采取相应措施避免剧烈振动的发生。     

INFLUENCE OF MATERIAL REMOVAL ON THE DYNAMIC BEHAVIOR OF THIN-WALLED STRUCTURES IN PERIPHERAL MILLING

Machining is a material removal process that alters the dynamic properties during machining operations. The peripheral milling of a thin-walled structure generates vibration of the workpiece and this influences the quality of the machined surface. A reduction of tool life and spindle life can also be experienced when machining is subjected to vibration. In this paper, the linearized stability lobes theory allows us to determine critical and optimal cutting conditions for which vibration is not apparent in the milling of thin-walled workpieces. The evolution of the mechanical parameters of the cutting tool, machine tool and workpiece during the milling operation are not taken into account. The critical and optimal cutting conditions depend on dynamic properties of the workpiece. It is illustrated how the stability lobes theory is used to evaluate the variation of the dynamic properties of the thin-walled workpiece. We use both modal measurement and finite element method to establish a 3D representation of stability lobes. The 3D representation allows us to identify spindle speed values at which the variation of spindle speed is initiated to improve the surface finish of the workpiece.     

INFLUENCE OF MATERIAL REMOVAL ON THE DYNAMIC BEHAVIOR OF THIN-WALLED STRUCTURES IN PERIPHERAL MILLING

Machining is a material removal process that alters the dynamic properties during machining operations. The peripheral milling of a thin-walled structure generates vibration of the workpiece and this influences the quality of the machined surface. A reduction of tool life and spindle life can also be experienced when machining is subjected to vibration. In this paper, the linearized stability lobes theory allows us to determine critical and optimal cutting conditions for which vibration is not apparent in the milling of thin-walled workpieces. The evolution of the mechanical parameters of the cutting tool, machine tool and workpiece during the milling operation are not taken into account. The critical and optimal cutting conditions depend on dynamic properties of the workpiece. It is illustrated how the stability lobes theory is used to evaluate the variation of the dynamic properties of the thin-walled workpiece. We use both modal measurement and finite element method to establish a 3D representation of stability lobes. The 3D representation allows us to identify spindle speed values at which the variation of spindle speed is initiated to improve the surface finish of the workpiece.     

Using wire electrical discharge machining for improved corner cutting accuracy of thin parts

The wire electrical discharge machining process (WEDM) allows one to achieved ruled surfaces along intricate contours in hard materials. When one intends to use such a machining process, one has to analyze both the magnitudes of the corners’ radii and the corner’s angles that are formed between adjoining surfaces. Some experimental research work carried out unveiled the systematic occurrence of machining errors when WEDM is used to obtain outside sharp corners, especially in small thickness workpieces. A permanent bending at the crest of sharp corners, which leads to a substantial deviation from the prescribed geometrical shape, was found. The deviation form depends on the magnetic properties of the workpiece material. The research was focused on establishing a means for characterizing this shape error. Moreover, the influence exerted by certain factors, such as the corner angle and the thickness of the workpiece on the above-mentioned machining error was quantified.     

三维有限元分析在高速铣削温度研究中应用

高速切削过程中切削温度对刀具磨损、工件加工表面完整性及加工精度有极大的影响。应用有限元法对高速铣削铝合金薄壁件过程中工件与刀具接触面温度、工件内部的温度分布进行了仿真研究,仿真过程中考虑了切削速度、进给量对切削温度的影响。通过红外热像仪对不同主轴转速下工件表面温度的测量,验证了仿真结果与试验结果比较接近。得出在高速切削铝合金过程中,随着切削速度的增加,刀具与工件接触区的温度变化存在二次效应。该结论对铝合金薄壁件加工具有重要的实用价值。