五坐标端铣数控加工计算理论分析

本文介绍了五坐标端铣数控加工中的后跟角计算方法及刀位计算方法,分析了加工误差,包括直线逼近误差和刀轴摆动误差,提出了刀轴摆动误差补偿方法——刀具切触点偏置法,给出了走刀步长、走刀步距及刀具半径计算公式。     

GENERALIZED SIMULATION MODEL FOR MILLED SURFACE TOPOGRAPHY-APPLICATION TO PERIPHERAL MILLING

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MOLECULAR DYNAMICS SIMULATION OF POLISHING PROCESS BASED ON COUPLING VIBRATIONS OF LIQUID

Molecular dynamics method is applied to study the machining mechanisms of polishing based on coupling vibrations of liquid. The physical phenomena of abrasive particles bombarding on silicon monocrystal surface are simulated using Tersoff potentials. The effects of vibration parameters, particle size, incident angle and panicle material are analyzed and discussed. Material removal mechanisms are studied. Deformation and embedment phenomena are found in the simulations. Bombardment will destroy the crystal structures near the impact point, and adhesion effect is responsible for final removal of material.     

铝合金薄壁件高速铣削尺寸精度的试验研究

通过铝合金薄壁件高速铣削的正交试验,对加工尺寸精度的测量结果进行了分析,总结了铣削参数对工件尺寸精度的影响规律,并确定了铣削参数的选用原则.     

MODELING WORKPIECE DYNAMICS USING SETS OF DECOUPLED OSCILLATOR MODELS

During the machining of thin-walled components, the dynamic behavior of the workpiece has a significant influence on the machining process and on the quality of the machined surfaces. In this article, a hybrid simulation concept for modeling regenerative workpiece vibrations is presented, which couples a geometric workpiece model with sets of decoupled harmonic oscillators to take the workpiece dynamics into account.     

薄壁弧形件铣削加工装夹方案的优化

在航空制造业中,为了减轻工件的重量,大量使用薄壁结构零件。对于这类工件,改进工件的夹具布局能够有效地减少工件的变形。本文通过对弧形薄壁件铣削加工夹紧点的位置进行优化来减少工件的变形,并提出了6条启发式规则。这些规则根据各区域内工件的最大变形,依次确定各夹紧点的移动方向,具有较快的优化速度。     

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。     

Position-varying surface roughness prediction method considering compensated acceleration in milling of thin-walled workpiece

Machined surface roughness will affect parts’ service performance. Thus, predicting it in the machining is important to avoid rejects. Surface roughness will be affected by system position dependent vibration even under constant parameter with certain toolpath processing in the finishing. Aiming at surface roughness prediction in the machining process, this paper proposes a position-varying surface roughness prediction method based on compensated acceleration by using regression analysis. To reduce the stochastic error of measuring the machined surface profile height, the surface area is repeatedly measured three times, and Pauta criterion is adopted to eliminate abnormal points. The actual vibration state at any processing position is obtained through the single-point monitoring acceleration compensation model. Seven acceleration features are extracted, and valley, which has the highest R-square proving the effectiveness of the filtering features, is selected as the input of the prediction model by mutual information coefficients. Finally, by comparing the measured and predicted surface roughness curves, they have the same trends, with the average error of 16.28% and the minimum error of 0.16%. Moreover, the prediction curve matches and agrees well with the actual surface state, which verifies the accuracy and reliability of the model.     

A SIMPLIFIED CUTTING FORCE MODEL FOR LIGHT-CUT BALL-END MILLING APPLICATIONS

In light-cut milling operations, specific correlations have been identified empirically between the maximum cutting force on a cutter and its associated cutting parameters, and a series of ball-end milling tests for P20 tool steel has been conducted to establish the nature of these correlations. The experimental results indicate that the maximum cutting force on a cutter can be expressed as a logarithmic function of the associated cutting parameters. This paper describes the structure and testing of a simplified cutting force model for planar milling based on these results.     

基于微型惯性测量组合的大型工件三维位置测量方法

提出了利用微型惯性测量组合进行工件三维位置测量的方法,对这一方法的测量原理进行了详细阐述,对坐标转换、姿态矩阵求解、位置计算等均给出了详细的数学模型及算法。采用普通陀螺及加速度计进行了原理性试验,给出了相应的试验结果。另外,对这一方法进行了误差分析,指出了它不同于一般捷联式系统的特点,分别针对惯性传感器和系统整体给出了相应的误差修正算法,提出了提高测量精度的措施。实际证明,本方法具有实现方便、检测速度快及可实现连续测量等优点,对大型工件及复杂表面的快速测量具有明显得实际意义。     

端铣淬硬钢时新型陶瓷刀具热破损的强激光模拟

利用强激光热模拟实验，模拟好单齿端铣刀在铣削过程中的温度变化规律，并用有限元对刀具的温度场和热应力场进行了分析。从对热冲击后的刀片ＳＥＭ分析发现，在热源附近产生了通过热源以径向为主的网状裂纹。最后对刀具热裂的机理进行了分析。     

GRADE OF STABILITY IN FUZZY CHATTER STABILITY LOBE MODEL IN MILLING

The machining productivity and part quality are typically limited by the regenerative chatter induced by the dynamic interactions of spindle-holder-tool combination system. The conventional chatter stability model predicts the permissible stable axial depth of cut versus spindle speed by plotting the stability lobe diagram which represents two independent regions as absolutely stable zone and instable zone divided by the critical lobe curve. In fact, it is more reasonable to be a transition stage between the stable and instable zone. This paper introduced the grade of stability (GOS) to improve the conventional chatter stability model and study the transition zone in the stability lobe diagram. The variation of transition zone width with the stability sensibilities for different order lobe curve in milling system was analyzed. Sigmoid function was used as the membership function to develop the fuzzy stability lobe model. Then, the fuzzy stability lobe diagram with an adjustable slope coefficient was implemented to improve the mould steel milling process. The improved fuzzy stability model enhances the reliability of stability lobe diagram and guarantees the chatter-free milling process.     

MATHEMATICAL MODEL OF MILLING TEMPERATURE AND TEMPERATURE FIELD ANALYSIS FOR THREE-DIMEN-SIONAL COMPLEX GROOVE MILLING INSERT

The mathematical mode1 on the temperature of the waved-edge is constructed accordingto Jaeger's theory of moving solid and based on the used temperature model of the fiat insert. It ispossible to forecast the milling temperature through programming. The comParable experimentshave been done between the two new three-dimension groove inserts (waved-edge insert, great edgeinsert) and flat fake insert. The theoretic forecast is in good agreement with the experimental result.     

CORRELATION-BASED ESTIMATION OF CUTTING FORCE COEFFICIENTS FOR BALL-END MILLING

This article presents a methodology to estimate cutting force coefficients based on the least squares approximation using correlation factor between the estimated and measured cutting forces in order to determine the corresponding tool angular position. This method can be applied on measured cutting force data over any small interval of time that need not contain information of the time instant when the cutting tool enters the workpiece, which has been the main requirement in the conventional method. This allows a quick estimation of the cutting force coefficients regardless of the chosen cutting conditions and tool-workpiece material, which is often the case in industrial machining processes. This proposed method has been validated by comparison of cutting force coefficients obtained using conventional estimation technique for a slot ball-end milling test. Besides being useful for predictive evaluation of forces, such estimation of cutting force coefficients of the cutting force model can be useful for understanding variations in cutting process over the tool life and can assist in online monitoring and process optimization.     

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。     

薄壁零件铣削加工的振动模型

利用Kirchhoff薄板挠度弯曲的规律,分析薄壁结构零件的铣削过程中的振动模型,并结合铣削试验建立薄壁零件立铣加工的振动模型。根据实际加工条件,对振动模型进行数值模拟,分析、验证模型在实际切削加工时的准确性,试验测量结果和数值模拟结果误差很小,说明该假设完全可行,可以用于相关薄壁零件的分析和实际加工,为进一步研究薄壁零件加工振动规律奠定了必要的基础。     

DESIGN AND MANUFACTURE OF STRAIGHT BEVEL GEAR FOR PRECISION FORGING DIE BY DIRECT MILLING

In the manufacture of straight bevel gears, a precision forging method has been mainly used in recent years and the precision forging die has been usually manufactured using electric discharge machining. However, it is difficult to content the high productivity and low manufacturing cost using electric discharge machining because the gears are produced through a process of several steps. In this article, a design and manufacture of a straight bevel gear for a precision forging die by direct milling is developed in order to improve the productivity and manufacturing cost for the gear production. The tooth profile of a straight bevel gear generated by a quasi-complementary crown gear instead of a usual complementary crown gear is introduced. For this study, first the numerical coordinates on the tooth surface of the straight bevel gear were calculated and the tooth profiles were modeled using a 3D-CAD system. Afterward, the direct milling of the precision forging die of the straight bevel gear in the hardened state was carried out using a CNC milling machine based on a CAM process through the calculated numerical coordinates.     

直纹面四坐标侧铣数控加工中的误差分析

将四坐标侧铣加工存在的加工误差分为由四坐标加工自身的局限性引起的误差和法矢异向引起的误差两种 ,分别对这两种误差的产生原因进行了分析并给出了计算公式 ,另外还给出了法矢异向引起的误差沿直母线方向的分布并提出了一种减小法矢异向引起的误差的算法     

虚拟现实环境下载人机动装置仿真系统

系统地介绍了载人机动装置(MMU,Manned maneuvering unit)的虚拟现实仿真环境,建立了MMU动力学／运动学模型、推力系统模型。根据航天员太空行走的特点,建立了航天员多体模型,利用位姿跟踪设备记录操作者的肢体运动信息,并将该信息正确地映射为虚拟环境下航天员的肢体运动。所得到的运动信息实时参与航天员动力学／运动学计算,更加真实地反映出航天员太空行走过程。从虚拟样机控制系统的快速设计和仿真的目的出发, 建立了虚拟现实环境下MMU的分布式仿真系统。控制系统的设计和仿真在MATLAB/Simulink环境下完成,利用网络通信手段实现控制系统与MMU仿真主程序之间的协同仿真。     

PROBABILISTIC PREDICTION OF BURR PATTERNS OF 1045 CARBON STEEL IN FACE MILLING

Face milling burrs in ductile materials such as 1045 carbon steel exhibit three distinct burr patterns: uniform, wavy, and secondary burrs. It is found that the three burr patterns are dependent on the in-plane exit angle, undeformed chip ratio, and undeformed chip area at the exit stage of cut. Empirical equations, representing the burr transition curves from the uniform to wavy burr and wavy to secondary burr, are found. Based on the empirical relationships, a probabilistic model, in which the operational Bayesian modeling approach is adopted to include the empirical equations, is derived for burr prediction.