径向进给射流电解车削圆柱表面试验

径向进给射流电解车削加工是针对难加工材料回转体零件表面特征,利用电解液从阴极刀具内部喷向工件,刀具沿径向逐渐向工件进给进行电化学溶解的加工方法。通过流场仿真,优选出阴极刀具结构,利用10%的NaNO3溶液对316L不锈钢材料圆柱表面进行试验研究,分析平衡间隙、加工电压、工件转速、电解液压力对材料去除率和工件表面粗糙度的影响。结果表明:利用优选的刀具,对直径20 mm、高度10 mm的316L不锈钢圆柱表面径向单边车削0.5 mm,材料去除率可达0.391 g/min,表面粗糙度Ra<0.2μm。     

低速干车削条件下车刀温度的红外测试研究

利用数控车床和手持式红外测温仪,研究了干车削铝棒过程中车削参数对车刀刀尖温度的影响规律,通过试验得到了不同车削参数下车削温度的时间曲线以及温度均方根值随车削参数的变化曲线。研究结果表明:同一走刀的车削过程中,刀尖温度具有时变特性。随着车削的进行,刀尖温度逐渐升高,至走刀结束时,温度达到最高值;刀具温度与车床主轴转速、进给速度、车削深度成正相关关系,车削参数越大,车削温度越高;刀尖温度均方根值随主轴转速按双线性规律变化,主轴转速超过一定值后,温度均方根值急剧升高;刀尖温度均方根值随进给速度、车削深度近似按线性规律变化,进给速度对刀尖温度的影响较大,车削深度对温度的影响最小。     

细长轴双刀车削加工让刀量误差优化的研究与应用

通过建立细长轴对称式双刀车削模型,推导出刀具加工点理论让刀量公式。对细长轴双刀车削进行静力学仿真分析,得到刀具在加工点让刀量数据。考虑到刀具径向力与背吃刀量的关系,以及引起刀具让刀量误差的其他因素,在刀具加工点理论让刀量公式中引入修正系数k,对仿真曲线和预测理论曲线进行对比分析,确定修正系数k的大小。最后进行数控车削试验,结果表明:将优化后的理论让刀量公式作为补偿函数车削细长轴能显著提高其加工精度。     

铁基粉末冶金零件车削试验研究

采用硬质合金类刀具和陶瓷刀具进行铁基粉末冶金零件的车削对比试验,研究切削速度、切削深度以及进给速度与加工表面粗糙度的关系,得出如下结论:车削铁基粉末冶金零件时,陶瓷刀具的刀具耐用度以及加工表面粗糙度均优于硬质合金类刀具,适合于加工铁基粉末冶金零件。     

车床钻削加工连杆零件小端孔夹具设计及应用

为提高加工效率,采用车床加工连杆零件小端孔,设计夹具实现六点定位,确保定位精度,刀具安装在刀架上,实现刀具轴向进给。该夹具结构简单,使用方便。     

数控车床工件-刀具系统切削动态特性研究

以外圆车削为研究对象,分析车削状态下工件-刀具系统耦合振动动态特性,建立工件-刀具系统非线性动力学模型,得出耦合作用下刀具系统振动微分方程。利用振动测试系统获取刀尖位置在不同进给速度和转速下的振动信号,通过时域和频域分析,探讨刀具振动信号随切削参数的变化规律。研究表明:相同切削条件下,随着进给速度的增加,刀具振动幅值增大,但刀具振动主频变化不大,且振动能量变化不明显。随着主轴转速的增加,刀具振动加速度明显增加。     

薄车削铝合金时已加工表面残留应力的实验研究

为了研究薄切削铝合金时切削用量和刀具材料对已加工表面残留应力的影响,选用两种硬质合金刀具,利用高精度专用车床进行了不同切削速度、进给量、切削深度车削铝合金的实验。实验表明,在切削速度方向,随着切削速度增大,残留应力由残留压应力逐渐渐变为残留拉应力;在进给方向,改变切削速度时,残留应力仍然是残留压应力,不存在残留拉应力;当进给量增大时,进给方向的残留压应力逐渐减小。随切削深度的由小逐渐增大,残留压应力呈现出一种抛物线变化规律,当切削深度为某一数值时,进给方向的残留压应力有一极大值。超细晶粒硬质合金刀具切削后已加工表面残留压应力,小于普通晶粒硬质合金刀具。     

曲轴非圆截面开放式数控车削系统的研究

以车削曲轴非圆截面零件为例,提出一种刀具非圆切削速度模型。基于PC机和PMAC运动控制卡开发非圆截面数控车削系统。在x方向加装直线进给系统,实现刀具的高速往复运动。通过分析截面轮廓信息、x轴进给部件跟随主轴圆光栅反馈角度信号运动,以确定刀具运动轨迹。该车削数控系统在汽车非圆曲轴加工生产线上投入应用,极大地提高了生产效率。     

同心不等径非圆截面数控车削系统研究

为了提高同心不等径非圆截面零件加工的质量和效率,对实现该类零件加工的方法进行了研究,提出了一种快速高精度加工同心不等径非圆截面的数控车削方法。设计了数控车削系统的结构,快速刀具进给伺服机构(FTS)采用基于自抗扰控制的直线电机系统。数控系统采用PMAC(Pro-grammable multi-axis controller)多轴运动控制器的时基控制法,实现刀具驱动进给和工件旋转的协调控制,完成该型零件的自动车削。结果表明该型零件的加工精度和加工效率得到了提高。     

基于整体刀具的铣削加工温度有限元分析

在对金属切削的热力学以及热传导过程进行理论分析的基础上,基于整体刀具建立了铝合金薄壁件铣削加工的三维有限元模型。改变切削深度、切削速度以及进给率等工艺参数,分析了铣削工艺参数对温度的影响。仿真结果表明：切削深度对铣削温度影响最大,切削速度和进给率对铣削温度的影响相对较小。将仿真结果与试验测量结果进行对比分析,仿真结果温度值略高于试验结果,但总体变化趋势和规律基本一致。     

钛合金侧铣加工残余应力与变形研究北大核心

为研究加工残余应力对钛合金薄壁结构变形的影响,利用有限元软件建立2D切削模型,分析每齿进给量与刀具刃口半径对加工表面残余应力的影响。利用切削仿真得到的残余应力对薄壁件进行变形仿真分析;分别以每齿进给量0.06、0.08 mm进行闭腔侧铣试验。结果表明:与实测值相比,仿真表面残余应力误差约为20%、最大变形量误差约为12%。所提方法具有一定的可靠性与可行性。     

细长轴车削与磨削参数优化研究

针对细长轴车削和磨削加工参数的选择问题,建立以工件刚度、刀片强度、刀杆刚度、机床进给机构强度、机床功率、机床参数、加工表面粗糙度、加工余量等作为约束条件,以切削速度、进给量、背吃刀量、工件转速、磨削余量、径向进给量等参数为优化变量,以车、磨多工序成本最低为目标的切削参数优化模型。以某型号电机轴为案例,运用MATLAB模式搜索工具箱对其车削和磨削参数进行寻优,与切削参数的传统选择方法比较表明,工序成本可降低35%以上,从而验证了优化模型的有效性。     

基于Filtered-X LMS自适应算法的车削颤振控制系统设计与实验研究

基于Filtered-X LMS自适应滤波算法,设计了一种压电作动器来控制刀具与工件的切削力位移,并进行了数值仿真和实际的切削实验.研究结果表明:在相同的切削条件下,基于Filtered-X LMS自适应滤波算法控制的刀具加工精度明显优于传统刀具的加工精度,能有效的减少车刀的振动量,验证了该控制系统的有效性,对于提高车床的加工精度具有重要的意义.     

基于灰色关联分析的GH2132线材高精度切削参数优化

目的 通过无心车床车削去除GH2132线材的表面缺陷,分析无心车床加工参数对线材表面粗糙度、尺寸误差和表面显微硬度的响应关系,并建立GH2132线材表面灰色关联度多目标优化模型,确定可行工艺参数域。方法 采用响应曲面中心复合设计,测量车削后GH2132线材的表面粗糙度、尺寸误差和表面显微硬度;利用响应曲面法(Response Surface Method,RSM)分别建立表面粗糙度、尺寸误差和表面显微硬度的单目标预测模型,确定单目标优化最优工艺参数组;基于灰色关联分析(Grey Correlation Analysis,GRA)理论,以表面粗糙度、尺寸误差和表面显微硬度为优化指标进行降维处理,构建车削工艺参数与灰色关联度的二阶回归预测模型;绘制车削工艺参数与灰色关联度值的等值线图,确定可行工艺参数域。结果 对建立的表面粗糙度、尺寸误差和表面显微硬度的单目标预测模型进行方差分析,显著度均小于0.000 1。得到了最小表面粗糙度工艺参数组,切削速度n=373.919 r/min,进给速度vf =0.475 m/min。得到了最小尺寸误差工艺参数组,n=375.636 r/min,vf =0.596 m/min。得到了最大表面显微硬度工艺参数组,n=337 r/min,vf = 0.903 m/min。对于灰色关联度多目标预测模型,误差范围为0.13%~9.4%,确定的可行工艺参数域对应的最小灰色关联度值为0.544 37。结论 基于灰色关联分析的多目标预测模型的准确度较高,主轴转速n对多目标的响应程度大于进给速度vf。通过确定可行工艺参数域,为GH2132线材去除表面缺陷提供工程参考。     

Effects of process parameters on workpiece roundness in tangential-feed centerless grinding using a surface grinder

The present authors proposed a new centerless grinding method using a surface grinder in their previous study [Wu, Y., Kondo, T., Kato, M., 2005. A new centerless grinding technique using a surface grinder. J. Mater. Process. Technol. 162–163, 709–717]. In this method, a compact centerless grinding unit composed mainly of an ultrasonic elliptic-vibration shoe is installed onto the worktable of a multipurpose surface grinder to perform tangential-feed centerless grinding operations. However, for the complete establishment of the new method it is crucial to clarify the workpiece rounding process and the effects of process parameters such as the worktable feed rate, the stock removal and the workpiece rotational speed on the machining accuracy, i.e., workpiece roundness, so that the optimum grinding conditions can be determined. In this paper, the effects of the process parameters on workpiece roundness are investigated by simulation and experiments. For the simulation analysis, a grinding model taking into account the elastic deformation of the machine is created. Then, a practical way to determine the machining-elasticity parameter is developed. Further, simulation analysis is carried out to predict the variation of workpiece roundness during grinding and to discover how the process parameters affect the roundness. Finally, actual grinding operations are performed by installing the previously constructed unit onto a CNC surface grinder to confirm the simulation results. The obtained results indicate that: (1) a slower worktable feed rate and higher workpiece rotational speed give better roundness; (2) better roundness can be also obtained when the stock removal is set at a larger value; (3) the workpiece roundness was improved from an initial value of 23.9 μm to a final value of 0.84 μm after grinding.     

Cutting conditions for finish turning process aiming: the use of dry cutting

To avoid the use of cutting fluids in machining operations is one goal that has been searched for by many people in industrial companies, due to ecological and human health problems caused by the cutting fluid. However, cutting fluids still provide a longer tool life for many machining operations. This is the case of the turning operation of steel using coated carbide inserts. Therefore, the objective of this work is to find cutting conditions more suitable for dry cutting, i.e., conditions which make tool life in dry cutting, closer to that obtained with cutting with fluid, without damaging the workpiece surface roughness and without increasing cutting power consumed by the process. To reach these goals several finish turning experiments were carried out, varying cutting speed, feed and tool nose radius, with and without the use of cutting fluid. The main conclusion of this work was that to remove the fluid from a finish turning process, without harming tool life and cutting time and improving surface roughness and power consumed, it is necessary to increase feed and tool nose radius and decrease cutting speed.     

Assessment of some factors influencing tool wear on the machining of glass fibre-reinforced plastics by coated cemented carbide tools

Glass fibre-reinforced plastics (GFRP) composite materials are used in many different engineering fields. The need for machining of GFRP composites has not been eliminated fully. The tool wear reduction is an important aspect during machining. In the present work, an attempt has been made to assess the factors influencing tool wear on the machining of GFRP composites. Experimental design concept has been used for experimentation. The machining experiments are carried out on lathe using two levels of factors. The factors considered are cutting speed, fibre orientation angle, depth of cut and feed rate. A procedure has been developed to assess and optimize the chosen factors to attain minimum tool wear by incorporating (i) response table and effect graph; (ii) normal probability plot; (iii) interaction graphs; (iv) analysis of variance (ANOVA) technique. The results indicated that cutting speed is a factor, which has greater influence on tool flank wear, followed by feed rate. Also the determined optimal conditions really reduce the tool flank wear on the machining of GFRP composites within the ranges of parameters studied.     

Influence from production parameters on the surface roughness of a machined short fibre reinforced thermoplastic

Machining is a relatively new manufacturing method for short fibre reinforced thermoplastics (SFRTP), and the theory and experience from other materials cannot be directly applied. It is therefore necessary to set up new guidelines for how to ensure a satisfactory result from the machining. Experiments were carried out to study how the surface roughness of a SFRTP, machined by turning, was influenced by variations of the feed rate, the cutting speed, the tool radius, the fibre orientation and the interactions between them. The roughness increased for an increasing feed rate and a decreasing tool radius. These parameters interacted, which shows the difficulty of deciding the setting of the production parameters by trial-and-error. Interaction also results in more complicated guidelines for the machining. A slight influence on the roughness was found for low cutting speeds, whereas higher speeds had no significant influence. The roughness was found to be independent of the fibre orientation. The overall conclusion was that it seemed to be possible to set up guidelines for an optimal machining of SFRTP. These recommendations differ from the theoretical ones applicable for the machining of metals.     

五轴联动刀轴矢量插补优化算法

目的研究解决五轴联动机床旋转轴角度采用线性插补方式生成的加工轨迹,导致刀具姿态偏离所设计的理想平面,引发刀具姿态误差的问题,减少非线性误差,提高零件表面质量。方法首先对旋转轴角度线性插补方式引发刀具姿态误差的原理进行了分析,提出了一种刀轴矢量插补优化算法。然后在线性插补的基础上,根据提出的刀轴矢量插补优化算法保证首末点间的刀轴插补矢量始终位于首末刀轴矢量所构成的平面内,实现刀具姿态优化,并在MATLAB中对线性插补和矢量插补优化两种方式进行仿真分析,观测出对应方式下刀轴插补矢量的空间位置。最后利用叶片试件在AB型转台摆头类型机床上进行仿真和加工验证,对比两种刀轴矢量插补方式仿真数据。结果在VERICUT同等条件下仿真,刀轴矢量采用线性插补时,叶片进出汽边误差值分别为-0.218 66 mm和-0.312 58 mm;刀轴矢量插补优化后,叶片进出汽边误差值分别为-0.095 46 mm和-0.099 05 mm。刀具姿态经过插补优化算法后,叶片进出汽边的过切值明显降低。结论刀具姿态经过插补优化算法后,叶片过切值的大小和数目明显减少,使得非线性误差明显降低,从而提高了零件表面质量。