微铣刀在位放电制备及微铣削实验

在微细铣削加工中,微铣刀的径向跳动会降低工件的加工精度与表面质量,还会减少刀具使用寿命。为了减少刀具径跳,基于在位制备的思想,介绍了线电极电火花磨削(WEDG)加工微铣刀的原理,搭建了实验平台,设计了在位制备微铣刀的工艺过程和加工参数,提出了放电感知在位检测刀具尺寸的方法,利用WEDG技术制造出刀头直径为76.59μm的微铣刀,并加工出了平均槽宽78.40μm,平均表面粗糙度值Ra 77.50 nm的微结构。     

高速加工铣刀结构参数的分析

高速切削机床激振频率远远超出“机床-刀具-工件”工艺系统的固有低频范围,高速铣削过程中产生的振动,会导致刀具的折断、降低加工精度等。铣削过程中的振动,除了与其加工参数及工件材料性能有关外,还受其自身结构参数的影响。铣刀结构参数对振动的影响体现在影响其结构的振动特性,即其结构的固有频率和振型。因此,研究铣刀结构参数对振动的影响,对降低加工振动、提高高速铣削效率及精度非常必要。     

枞树型核电轮槽叶根铣刀工艺方案设计研究

以核电轮槽2270-091092枞树型叶根精铣刀为例,主要研究了枞树型核电轮槽叶根铣刀刀体建模、刀体制造、夹具设计、刀体加工走刀路线和设计制造子程序树等工艺方案设计.该类刀具从设计到制造完全实现自主开发,拥有自主知识产权.该刀具设计制造完成后,经检测满足设计精度要求,提高了加工效率,降低了加工成本.该刀具对其它核电轮槽...     

基于ABAQUS锯片铣刀的模态分析及优化

针对锯片铣刀在切削加工中易振动导致刀具损坏的问题,以典型的锯片铣刀为例,利用ABAQUS有限元软件对其进行了模态仿真分析,得到了该锯片铣刀前8阶固有频率和基本振型。根据模态分析结果对锯片铣刀的结构进行优化,适当增加轴孔处的厚度和轴孔直径,提高了刀具的固有频率,可有效预防锯片铣刀在工作过程中的振动损坏等不良现象。     

螺纹铣刀牙型轮廓的少干涉优化方法

根据螺纹铣削过程的径向和轴向干涉误差分析,提出了调整铣刀牙型轮廓特征点位置的螺纹铣刀牙型轮廓少干涉优化方法。首先,利用特征点法分别对标准螺纹和螺纹铣刀的牙型轮廓进行参数化表示;然后,建立螺纹轮廓面和螺纹铣刀铣削加工包络面的数学计算模型,以及螺纹铣削加工的干涉误差计算模型;最后,利用干涉模型计算得到的轴向和径向干涉误差,对螺纹铣刀牙型轮廓特征点进行适当调整,优化螺纹铣刀轮廓以减少干涉误差。以?8×1.5螺纹铣刀加工M14×1.5内螺纹的加工仿真与切削实验为例,利用MATLAB计算螺纹铣刀优化后的最大干涉误差为2.6μm,相比于螺纹铣刀优化前(8.1μm)降低了67.9%;内螺纹铣削实验结果表明螺纹铣刀优化后的最大干涉误差仅为15.5μm,相比于普通螺纹铣刀的最大干涉误差值(24.8μm)降低了37.5%。可见,螺纹铣刀牙型轮廓少干涉优化方法能极大减小螺纹铣削加工干涉误差,有效提高螺纹加工精度。     

气浮转台转子结构参数对变形的影响研究及优化设计

为了减小气浮转台在加工尺寸较大的零件时的变形,对转子的各几何参数进行了灵敏度分析.首先了利用Work-bench 中 Static Structural分析出初始设计尺寸下气浮转台的变形量以及应力大小,然后再利用响应曲面优化分析工具(Response Surface)求出所有几何设计尺寸对气浮转台变形量的灵敏度的大小,选出灵敏度较大的尺寸进行优化设计,并最终确定了一组最佳尺寸.对优化后的尺寸进行有限元分析,其变形量得到了明显的减小,最大变形量由13.02μm下降到了 2.98μm,最小变形量由10.39μm下降到了 0.55μm.     

深腔铣削刀具的研制

探讨了在机械加工中,针对深腔类零件的加工,通常采用加长立铣刀,对于径长比较大的加长铣刀径向变形严重的情况,设计制造了专用单齿铣刀,通过使用长径比较大的立铣刀所受应力变形的分析对比,反应了单齿铣刀的可行性及经济性,并对所设计的铣刀进行线性静力学结构分析,针对力体的变形进行了参数优化.以期用该单齿刀具取代传统刀具加工方法,从而提高加工效率和经济效益.     

等螺旋角锥度铣刀的设计与制造要点

在机械加工中,有些零件的加工常用锥度铣刀。如齿条、V形槽、锥孔等的加工。以前由于受加工条件的限制,我们一般把锥度铣刀设计成直槽形式,这样虽然给制造带来了方便。但直槽锥度铣刀加工出来的产品精度低,表面粗糙度值大,刀具寿命短。随着机床制造业的发展,各种磨削中心相继出现,在这种情况下,等螺旋角锥度铣刀的加工才得以实现。图1是我们为某厂设计制造的一种齿条铣刀,该齿条的模数为m=4mm,压力角α=20°。使用结果表明:刀具寿命是原来直槽高速钢铣刀的10倍,齿条精度提高一级,表面粗糙度值由R_α3.2降至R_α1.6。     

锥球头铣刀铣削力建模及变齿距减振优化设计

在航空发动机叶轮加工过程中,径向铣削力带来的切削振动对加工质量有较大的影响。为了降低切削振动,基于某叶轮的实际加工工况,利用有限元仿真和MATLAB软件计算进行了铣削力建模和分析,以减小切削振动幅值、降低铣刀弯曲变形程度为优化条件进行了铣刀结构的优化设计。     

基于有限元分析的精密铣削装备整机设计优化

在面向高档汽车压缩机涡旋盘零件的加工需求背景下,对其加工装备做了基础设计,并根据课题组基础设定了装备部件的材料。对装备的各运动部件进行了精度分配,得到了课题5μm加工要求需要设计3μm的装备模型,由此设计了装备模型。在装备模型中间加工状态和两端加工状态两种极限状态下分别做了静力学仿真分析,对比了基础设计模型和优化设计模型。在中间加工状态下,基础设计模型加工点位置处和传动部件位置处的变形由0.298μm和0.20μm分别优化到优化设计模型的0.172μm和0.155μm;在两端加工状态下,基础设计模型加工点位置处和传动部件位置处的变形由0.301μm和0.197μm分别优化到优化设计模型的0.197μm和0.201μm。     

薄板类零件加工精度可靠性分析及工艺参数优化

针对薄板类零件加工过程中加工变形导致加工精度低的问题,利用有限元法和高斯过程回归算法建立了加工变形预测模型,综合考虑机床运动误差与工件加工变形,对薄板件加工精度可靠性进行分析,建立了以加工效率和平均加工变形为目标、加工精度可靠度为约束的铣削加工工艺参数优化设计模型,并利用多目标优化算法进行求解,确定了协调加工效率和加工变形最优的工艺参数组合。案例研究结果表明,经优化设计后最低加工精度可靠度达到98.21%,平均加工变形减小21.14%,加工效率提高了4.18%,为薄板类零件铣削加工工艺参数选择提供了一种可行的方法。     

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.     

基于刀具跳动的环形铣刀切削厚度模型的切削力计算

数控铣削过程中,切削变形引起的瞬时切削厚度是影响铣削加工切削力建模的重要参数之一,针对环形铣刀的切削特点,在考虑刀具跳动的情况下,对真实刀刃轨迹运动进行分析。将微细铣削的加工过程用宏观铣削来表示,从而建立了基于宏观铣削过程中刀具跳动下精密加工的瞬时切削厚度。通过仿真模拟和切削力试验来预测切削力,预测结果和试验结果具有一致性,表明该模型可以更好的预测加工过程中的切削力。     

NOMEX蜂窝复合材料超声切削锯齿圆盘铣刀动力学分析

针对圆盘铣刀超声切削过程中出现易碎及抱死等问题展开分析,提出一种用于Nomex蜂窝复合材料超声切削加工的新型锯齿圆盘铣刀。为了保证新型刀具满足生产使用要求,对新型锯齿圆盘铣刀展开分析,推导建立了锯齿圆盘铣刀的动力学模型;应用有限元软件ABAQUS对锯齿圆盘铣刀进行模态分析,验证了锯齿圆盘铣刀结构设计的合理性,为刀具的进一步发展研究提供参数支持。结果表明:锯齿圆盘铣刀第十二阶振型理想,振动稳定,振幅分布有规律,楔角θ=12°为锯齿圆盘铣刀结构的最优选择,符合超声切削加工对刀具的要求。     

面向加工中心的高速铣刀优选系统

针对加工中心高速铣削中刀具及其切削参数选择问题,以已有高速铣削机理研究成果为基础,进行工件高速铣削加工特征研究,并建立高速铣刀优选目标模型和优选规则,完成了基于关系型数据库的高速铣刀优选系统的开发.结果表明,采用该系统优选的铣刀及其切削参数进行高速铣削加工,能有效提高加工品质和加工效率、降低加工成本.     

THE SURFACE INTEGRITY IN MACHINING HARDENED STEEL SKD11 FOR DIE AND MOLD

Milling cutters were evaluated by tool wear, cutting force and vibration. Surface integrity of grinding and milling were investigated by comparing residual stress distributions, metallurgical structure, hardened layer depth and surface roughness. And influence of cutting tool wear on surface integrity was investigated. Experimentations revealed that the preferable surface integrity would be obtained if the proper milling cutter as well as a small wear criterion were adopted to avoid the advent of tempered martensite. The research results pointed out the feasibility of taking milling as the finish machining process instead of grinding in machining hardened steel with high efficiency.     

THE SURFACE INTEGRITY IN MACHINING HARDENED STEEL SKD11 FOR DIE AND MOLD

Milling cutters were evaluated by tool wear, cutting force and vibration. Surface integrity of grinding and milling were investigated by comparing residual stress distributions, metallurgical structure, hardened layer depth and surface roughness. And influence of cutting tool wear on surface integrity was investigated. Experimentations revealed that the preferable surface integrity would be obtained if the proper milling cutter as well as a small wear criterion were adopted to avoid the advent of tempered martensite. The research results pointed out the feasibility of taking milling as the finish machining process instead of grinding in machining hardened steel with high efficiency.     

曲面铣削过程加工路径对切削力和磨损的影响研究

针对不同走刀路径下的复杂曲面加工过程进行球头铣刀铣削Cr12MoV加工复杂曲面研究,分析不同走刀路径下铣削力和刀具磨损的变化趋势。试验结果表明:通过对比分析直线铣削和曲面铣削过程中的最大未变形切屑厚度,可以得出单周期内曲面铣削的力大于直线铣削过程的力,铣削相同铣削层时环形走刀测得的切削力普遍大于往复走刀测得的切削力;以最小刀具磨损为优化目标,运用方差分析法分析得出不同走刀路径的影响刀具磨损的主次因素,同时利用残差分析方法建立球头铣刀加工复杂曲面刀具磨损预测模型,并通过试验进行验证。     

Surface Integrity of Ultrasonically-Assisted Milled Ti6Al4V Alloy Manufactured by Selective Laser Melting

The Ti6Al4V parts produced by the existing selective laser melting (SLM) are mainly confronted with poor surface finish and inevitable interior defects,which substantially deteriorates the mechanical properties and performances of the parts.In this regard,ultrasonically-assisted machining (UAM) technique is commonly introduced to improve the machining quality due to its merits in increasing tool life and reducing cutting force.However,most of the previous studies focus on the performance of UAM with ultrasonic vibrations applied in the tangential and feed directions,whereas few of them on the impact of ultrasonic vibration along the vertical direction.In this study,the effects of feed rate on surface integrity in ultrasonically-assisted vertical milling (UAVM) of the Ti6Al4V alloy manufactured by SLM were systemically investigated compared with the conventional machining (CM) method.The results revealed that the milling forces in UAVM showed a lower amplitude than that in CM due to the intermittent cutting style.The surface roughness values of the parts produced by UAVM were generally greater than that by CM owing to the extra sinusoidal vibration textures induced by the milling cutter.Moreover,the extra vertical ultrasonic vibration in UAVM was beneficial to suppressing machining chatter.As feed rate increased,surface microhardness and thickness of the plastic deformation zone in CM raised due to more intensive plastic deformation,while these two material properties in UAVM were reduced owing to the mitigated impact effect by the high-frequency vibration of the milling cutter.Therefore,the improved surface microhardness and reduced thickness of the subsurface deformation layer in UAVM were ascribed to the vertical high-frequency impact of the milling cutter in UAVM In general,the results of this study provided an in-depth understanding in UAVM of Ti6Al4V parts manufactured by SLM.     

Prediction of vibration amplitude from machining parameters by response surface methodology in end milling

Decreasing vibration amplitude during end milling process reduces tool wear and improves surface finish. Mathematical model has been developed to predict the acceleration amplitude of vibration in terms of machining parameters such as helix angle of cutting tool, spindle speed, feed rate, and axial and radial depth of cut. Central composite rotatable second-order response surface methodology was employed to create a mathematical model, and the adequacy of the model was verified using analysis of variance. The experiments were conducted on aluminum Al 6063 by high-speed steel end mill cutter, and acceleration amplitude was measured using FFT analyzer. The direct and interaction effect of the machining parameter with vibration amplitude were analyzed, which helped to select process parameter in order to reduce vibration, which ensures quality of milling.