切削参数对粗精铣合体刀具铣削加工表面质量的影响

采用硬质合金刀具,通过单因素实验对铸铝材料的表面铣削加工过程进行研究,获得最佳的切削参数,提高加工表面质量。实验以粗精铣一次完成工艺代替粗加工—精加工分步完成的加工工艺,研究粗精铣合体刀具加工中最佳的切削参数组合。实验结果表明,对于铸铝零件,切削加工的最佳切削参数组合为:切削速度v=3000r/min、进给量f=1000mm/min、背吃刀量a p=0.3mm。通过比较不同工艺下切削参数与表面质量之间的关系,得出在相同表面质量的要求下,粗精铣合体刀具在铣削过程可简化加工工艺,缩短加工时间。     

切削参数对微细立铣削振动加速度的影响

切削振动是切削加工中的一种伴随现象,由于具有刀具直径小、切削速度高等特性,微细立铣削的切削振动对其加工质量和加工效率有着显著的影响。基于45钢微细立铣削单因素和正交组合试验,分析了直槽铣削时铣削参数对振动加速度影响的基本规律,建立了铣削参数与振动加速度之间的关系模型。研究结果表明:直槽立铣削时,槽宽方向的振动加速度aY总大于进刀方向的振动加速度aX;振动加速度随铣削参数的增加呈上升趋势,其中切削速度是振动加速度的主要影响因素;基于关系模型的振动加速度预测结果与试验结果具有较高的吻合度,可以用来进行振动加速度的预测预报。     

基于切削参数与刀具磨损的铣削振动影响因素研究

为了研究切削加工过程中工艺因素对切削振动的影响,采用正交试验进行不同工艺条件下的铣削试验,采集振动信号并提取信号均方根值,通过方差分析等方法研究铣削参数和刀具磨损对铣削振动的影响规律,结果表明:增大铣削速度和进给量在一定程度上可降低铣削振动,铣削深度和刀具磨损增大会使铣削振动加强;试验因素对铣削振动的影响依次为刀具磨损铣削深度切削速度进给量,其中,刀具磨损与切削深度对铣削振动影响显著。     

切削参数对钛合金叶片铣削力的影响分析

进行钛合金叶片加工时,切削力易导致加工变形,影响加工精度和表面质量。因此利用UG软件建立钛合金叶片和切削刀具的三维模型,采用仿真软件建立铣削仿真模型,研究分析了切削参数的变化对铣削力产生的影响。对仿真所得铣削力进行极差分析,判断切削参数对铣削力的影响情况,并通过实际铣削加工试验对比仿真数据验证其准确性和可行性,基于此仿真模型对切削参数对轴向力的影响程度进行了单因素分析。研究结果表明：铣削钛合金叶片时,切削参数对切削力的影响程度从大到小依次为切削速度、背吃刀量和每齿进给量;切削速度与轴向力成反比,每齿进给量和背吃刀量与轴向力成正比。     

XW-42冷作钢高速加工切削参数优化

在对XW-42冷作钢进行高速切削试验的基础上,建立XW-42冷作钢高速铣削表面粗糙度的经验公式,分析了切削速度、进给率和轴向切削深度对表面粗糙度的影响规律,应用遗传算法得到了最优切削参数,为高速加工切削参数的选择和表面质量的控制提供依据。     

微细立铣削切削振动试验研究

基于45钢微细立铣削试验,分析了微细立铣削切削振动的基本特征,研究了直槽立铣加工时铣削参数对振动加速度和振动位移量影响的基本规律.研究结果表明:在同样的切削工况下,微细立铣削的切削振动远大于大直径立铣刀铣削的情况;铣削参数是振动加速度的主要影响因素,振动加速度随铣削参数的增加都呈上升趋势,但轴向切深H和转速n对振动加速度的影响比进给量f更显著;在一定的参数范围内,减小主轴转速n和增大轴向切深H能够减小振动位移量的大小.     

TC4-DT钛合金铣削表面粗糙度试验研究

针对实际生产中TC4-DT钛合金铣削加工表面质量差问题,以钛合金铣削加工表面粗糙度Ra为研究对象,基于低速干切、高速湿切等条件,设计铣削用量影响表面粗糙度试验方案,分析试验结果,探索工艺参数对钛合金加工表面质量的影响规律,提出了改善TC4-DT钛合金铣削加工表面质量的建议,为进一步研究钛合金加工性能提供了参考和借鉴。     

切削参数对高精度平面加工精度影响研究

为研究钻高速铣削加工过程中不同切削参数对高精度平面表面质量的影响,结合工艺研究优化方案,选用切削速度和进给量两种切削参数类型,运用ABAQUS有限元仿真软件在相同的边界条件及参数下,建立高精度平面的铣削加工模型,并对加工过程进行模拟仿真。得出不同切削参数下表面质量的变化和控制方案。     

铝合金铣削力和温度场的试验研究

应用测力仪和红外热像仪对铝合金切削过程中的切削力和温度信号进行了测试,建立了硬质合金立铣刀切削铝合金的铣削力经验模型,可以有效地指导生产,合理选择切削工艺参数。研究发现,铣削温度随切削参数变化趋势与铣削力同步。切屑的长度、圆弧半径、厚度分别受切削深度、切削速度以及每齿进给量影响而使切屑呈现不同形态。立铣刀在切削铝合金时除切削作用外,还伴随较为严重的塑性变形。另外,分析了切削参数对表面质量的影响。     

高速铣削近α钛合金的切削温度研究

切削温度不仅直接影响刀具的磨损和耐用度,而且也影响工件的加工精度和已加工表面质量。由于钛合金导热性差和化学亲和性强等原因,通常在其切削加工时切削温度高、刀具磨损严重,致使切削速度难以进一步提高。本文重点对钛合金高速铣削时的切削温度进行试验研究,阐明夹丝半人工热电偶法测温原理和所测热电势信号的物理意义。试验选用了3种不同类型的硬质合金刀具,系统地研究了切削用量、冷却条件及刀具磨损等因素对近α钛合金高速铣削时切削温度的影响。     

Milling force vibration analysis in high-speed-milling titanium alloy using variable pitch angle mill

Chatter may cause fast wear of tools and poor surface quality of the workpieces at high cutting speed and it will happen on different process parameters; how do we select the suitable cutting speed to suppress the chatter? In this paper, a signal analysis method for milling force and acceleration is adopted to identify chatter, which can obtain the results not only in frequency of chatter but also in the contribution for milling force at different frequencies. Through the milling experiment, the machining vibration behaviors of milling Ti–6Al–4V with variable pitch end mill were investigated. Milling force and acceleration signals obtained from experiment were analyzed and compared at stable and unstable milling processes. The experimental results show that when the chatter occurs, milling forces were found to increase dramatically by 61.9–66.8% compared with that of at stable cutting; machining surface quality became poor and machined surface roughness increases by 34.2–40.5% compared with that of at stable cutting.     

Optimization of machining parameters using genetic algorithm and experimental validation for end-milling operations

Optimization of cutting parameters is valuable in terms of providing high precision and efficient machining. Optimization of machining parameters for milling is an important step to minimize the machining time and cutting force, increase productivity and tool life and obtain better surface finish. In this work a mathematical model has been developed based on both the material behavior and the machine dynamics to determine cutting force for milling operations. The system used for optimization is based on powerful artificial intelligence called genetic algorithms (GA). The machining time is considered as the objective function and constraints are tool life, limits of feed rate, depth of cut, cutting speed, surface roughness, cutting force and amplitude of vibrations while maintaining a constant material removal rate. The result of the work shows how a complex optimization problem is handled by a genetic algorithm and converges very quickly. Experimental end milling tests have been performed on mild steel to measure surface roughness, cutting force using milling tool dynamometer and vibration using a FFT (fast Fourier transform) analyzer for the optimized cutting parameters in a Universal milling machine using an HSS cutter. From the estimated surface roughness value of 0.71 μm, the optimal cutting parameters that have given a maximum material removal rate of 6.0×10³ mm³/min with less amplitude of vibration at the work piece support 1.66 μm maximum displacement. The good agreement between the GA cutting forces and measured cutting forces clearly demonstrates the accuracy and effectiveness of the model presented and program developed. The obtained results indicate that the optimized parameters are capable of machining the work piece more efficiently with better surface finish.     

汽车覆盖件拼接模具硬态铣削过程的动态特性

针对汽车覆盖件拼接模具铣削过程铣削力及振动信号测试失真问题,运用经验模态分解(empirical mode decomposition,简称EMD)结合小波阈值降噪原理,对铣削力及振动信号进行降噪处理。对降噪后的振动信号进行时频域分析,研究了不同切削参数、切削进给方向对铣削拼接模具过程动态特性的影响,得到铣削方向由硬度大材料切向硬度小材料,走刀方向与拼接缝成30°夹角时铣削力突变值较小的结论。发现x,y,z方向的切削分力及振动幅值的突变值与轴向切深及进给速度呈现正相关,与切削速度是非线性关系的特性。该研究结果为汽车覆盖件拼接模具硬态铣削的工艺优化提供了理论支持。     

铣削钛合金加工表面形貌特征参数的预测

钛合金在铣削过程中受迫振动明显,刀—工接触关系不断变化,加工表面形貌特征参数难以预测,已成为制约加工表面质量进一步提高的瓶颈。针对铣削振动与加工表面形貌的非线性随机变化特性进行了切削钛合金试验,采用高斯过程回归法构建铣削振动作用下的加工表面形貌高斯过程模型。分析刀齿误差和铣削振动对加工表面形貌特征参数的影响规律,为以加工表面质量分布一致性为前提的铣削钛合金工艺设计提供参考依据。     

基于BP神经网络的立铣加工振动快速预估

结合研制的立铣加工过程虚拟仿真系统和实验测量铣削力信号,训练并建立BP神经网络模型,快速实现铣削过程刀具-工件系统振动状态的预估.预估的振动结果与实验测量数据较为吻合,表明铣削虚拟仿真系统与神经网络技术的结合能够高效低耗地用于不同铣削加工条件下铣削振动状态的快速预估和加工过程监测.     

An experimental investigation on the process parameters influencing machining forces during milling of carbon and glass fiber laminates

Milling is the most feasible machining operation for producing slots and keyways with a well defined and high quality surface. Milling of composite materials is a complex task owing to its heterogeneity and the associated problems such as surface delamination, fiber pullout, burning, fuzzing and surface roughness. The machining process is dependent on the material characteristics and the cutting parameters. An attempt is made in this work to investigate the influencing cutting parameters affecting milling of composite laminates. Carbon and glass fibers were used to fabricate laminates for experimentations. The milling operation was performed with different feed rates, cutting velocity and speed. Numerically controlled vertical machining canter was used to mill slots on the laminates with different cutting speed and feed combinations. A milling tool dynamo meter was used to record the three orthogonal components of the machining force. From the experimental investigations, it was noticed that the machining force increases with increase in speed. For the same feed rate the machining force of GFRP laminates was observed to be very minimal, when compared to machining force of CFRP laminates. It is proposed to perform milling operation with lower feed rate at higher speeds for optimal milling operation.     

Detection process approach of tool wear in high speed milling

The cutting tool wear degrades the quality of the product in the manufacturing process, for this reason an on-line monitoring of the cutting tool wear level is very necessary to prevent any deterioration. Unfortunately there is no direct manner to measure the cutting tool wear on-line. Consequently we must adopt an indirect method where wear will be estimated from the measurement of one or more physical parameters appearing during the machining process such as the cutting force, the vibrations, or the acoustic emission, etc. The main objective of this work is to establish a relationship between the acquired signals variation and the tool wear in high speed milling process; so an experimental setup was carried out using a horizontal high speed milling machine. Thus, the cutting forces were measured by means of a dynamometer whereas; the tool wear was measured in an off-line manner using a binocular microscope. Furthermore, we analysed cutting force signatures during milling operation throughout the tool life. This analysis was based on both temporal and frequential signal processing techniques in order to extract the relevant indicators of cutting tool state. Our results have shown that the variation of the variance and the first harmonic amplitudes were linked to the flank wear evolution. These parameters show the best behavior of the tool wear state while providing relevant information of this later.     

多硬度拼接淬硬钢铣削动力学分析

颤振是金属切削加工过程中由于刀具和工件之间相互作用所产生的一种强烈的自激振动现象,会导致切削力幅值增加且发生剧烈波动,进而降低工件表面质量和刀具使用寿命。针对此问题,基于铣削过程稳定性预测分析方法建立多硬度拼接工件的动态铣削系统,对多硬度拼接模具铣削过程稳定性进行深入研究,实现了对拼接模具铣削加工过程颤振稳定域的仿真,进而研究了模态参数对稳定性叶瓣图形状的影响。最后通过时域分析、表面形貌和刀具磨损的研究,综合验证了稳定性预测曲线的精度。研究结果为多硬度拼接模具铣削加工提供理论基础,并设置合理的加工参数来实现金属最大切除率,为大型汽车覆盖件模具铣削加工提供理论依据及技术指导。     

Envelope dynamic analysis: a new approach for milling process monitoring

Vibration analysis has long been used for the detection and identification of the condition of machine tools. This paper proposes a method for vibration analysis in order to monitor online the milling process quality based on synchronous envelope analysis. Adapting envelope spectral analysis to characterize the milling tool is an important contribution for qualitative and quantitative characterization of milling capacity. It is a stage in modeling the three-dimensional cutting process. To determine different parameters, to understand the phenomenon which takes place during the cutting process, and to validate the monitoring algorithm, it was necessary to build and to use a complex analysis system. An experimental protocol was designed and developed for the acquisition, processing, and analyzing the three-dimensional signal. The vibration envelope analysis is proposed to detect the cutting capacity of the tool with the optimization application of cutting parameters. This purpose is reached by a detailed dynamic study of the manufacturing system divided into two parts. The first one concerns the complete analysis of the machine, of the main spindle. A dynamic analysis method is developed to completely characterize the various components of machine tools. The second is concentrated on the cutting process to condition monitoring and diagnosis. The research is focused on fast Fourier transform optimization of vibration analysis and vibration synchronous envelope to evaluate the dynamic behavior of the machine/tool/workpiece.