基于静动态力学分析的微细铣刀几何参数优化

在微细铣削过程中,刀具悬伸量、刃口长径比等参数的选择至关重要,适宜的刀具结构参数能有效提高刀具刚度及整体强度,降低刀具折断的概率。针对直径为0.1mm的双刃微细立铣刀展开研究,基于Ansys有限元仿真软件,对具有不同刃口形状、悬伸量、刃口长径比结构的微细铣刀进行应力及模态分析,探讨各参数对微细铣刀刚度的影响,分析刀具折断的主要因素。研究表明:刀具刃口形状以及刃口长径比对微细铣刀模态不造成影响,刀具悬伸量是影响模态的主要因素,在实际加工过程中,应控制刀具悬伸量在15mm～20mm区间内,刃口长径比小于4;针对微细铣刀刀头根部与刀颈的连接处施加圆角进行优化设计,有效改善了应力集中现象。文章的研究成果可以为微细铣削刀具结构优化设计提供理论依据。     

微铣刀制备技术与实验研究

微铣刀制备技术是微细铣削的关键技术之一,对微细铣削加工出的微小零部件的特征尺寸和表面质量有重要影响。从微铣刀具的材料与涂层及其制造工艺两方面,对微铣刀制备技术进行了介绍,并通过线电极电火花磨削方法制备了刀头直径为100μm的微铣刀,初步验证了基于自研μEM-200CDS2微细组合电加工机床开展微铣刀在位制备的能力。     

铣刀悬伸量和主轴转速对切削力的影响

以2A12铝合金铣削过程中的切削力为研究对象。通过两组刀具在不同刀具悬伸量和主轴转速下的铣削试验,测得各向铣削力,利用直接分析法研究了悬伸量和主轴转速对铣削力的交互影响,并使用回归分析法建立了两组刀具各向铣削力经验模型并验证其有效性。分析表明:切削力和刀具悬伸长度没有正比或反比关系,实际上存在着一个不适合加工的悬伸量(临界悬伸量),当超过该悬伸量后切削力反而减小;随着主轴转速的增加,临界悬伸量总体有减小的趋势,这为铣削加工工艺参数的优化选择提供了理论依据。     

影响铣削颤振稳定性的因素与规律分析

应用Altintas切削颤振理论实现了铣削颤振的预测,并对影响铣削稳定性的机床系统因素进行了分析。研究发现,稳定性叶瓣图会受到机床的主轴-刀具系统模态参数影响,尤其是模态刚度、阻尼比和固有频率。另外,通过系统动刚度相同的条件下不同的阻尼比和模态刚度组合对铣削稳定性的影响分析发现,模态刚度对系统稳定性的影响要大于阻尼比的影响程度。分别对影响铣削加工稳定性的刀具参数、工件材料特性以及切削参数等因素及其对铣削稳定性的影响规律进行了分析。结果显示:减小刀具齿数、刀具螺旋角和刀具悬伸量,并增大刀具直径对于改善切削颤振有益;具有较小切向切削力系数和径向切削力系数的材料更容易实现稳定切削;减小铣削宽度,并采用顺铣方式,系统的临界切深更大。     

整体式硬质合金微铣刀的几何结构优化与在位放电制备

基于ANSYS有限元分析软件,对微铣刀进行模态分析和应力变形分析,讨论微铣刀的刀头形状、悬伸量、刀杆直径、刀颈半锥角、刀头长径比等几何结构参数对其动力学性能的影响规律,对比D形、三角形、"一"字形等简单刀头截面形状结构及传统螺旋结构微铣刀的强度和刚度,进而获得微铣刀的几何结构优化参数。采用线电极电火花磨削的方式,在位放电制备出刀头直径约100μm、刃口锋利的D形微铣刀。     

微细铣削加工再生颤振的研究(英文)

微细铣削是利用微铣刀在高转速下加工复杂三维结构的制造技术。再生型颤振能引起刀具的严重磨损,降低零件的加工质量,是微细铣削加工面临的主要挑战之一。铣削加工过程中切削系数和系统动态特性的多变影响颤振稳定性。针对该问题,建立了考虑再生效应的微铣削动态铣削力模型和颤振稳定域解析模型,通过模态试验获得机床 - 刀具系统的频响函数,综合使用铣削稳定性判据进行数值分析,获得了颤振稳定域解析解。最后进行了颤振稳定性加工实验,验证了建立的颤振系统动力学模型和颤振解析模型的正确性。     

微细铣刀几何参数对TC4合金加工影响的仿真分析

在微细铣削过程中,刀具前角、刀尖圆弧半径等几何参数的选择与铣削力有着密切的关系,不仅会影响刀具的使用寿命,还会影响铣削过程的稳定性以及工件已加工表面质量。文章针对直径为0.1mm的双刃微细立铣刀展开研究,利用AdvantEdge有限元软件分析不同刀具结构参数铣削钛合金TC4对铣削力、铣削温度的影响规律,并设计正交试验求得三种因素的最优组合,并基于响应曲面法求得微细铣刀几何参数交互影响规律。结果表明:对铣削力造成影响的因素主次顺序为刀尖圆弧半径、径向前角、螺旋角;最小铣削力出现在"小径向前角+小刀尖圆弧半径+大螺旋角"区域。     

刀具变形对螺旋铣削CFRP孔径精度的影响

为了研究刀具变形对螺旋铣削碳纤维复合材料(CFRP)孔径精度的影响,使用硬质合金铣刀对碳纤维复合材料进行螺旋铣削试验,加工后对孔径进行测量,并对铣刀在螺旋铣削过程中受到的径向力而产生的变形进行分析。试验结果表明:螺旋铣削过程中,孔的轮廓线会呈两端粗中间细的形状。铣刀受到的径向力会导致其产生形变,最大变形量出现在刀尖处。在孔的入口处由于铣刀未进入完全切削状态受到的径向力较小,铣刀刀尖处变形量为10.92μm,孔径偏差为56.4μm;在孔径的中间部位,铣刀完全进入铣削状态,其刀尖处变形量为17.92μm,孔径偏差为279.8μm;在孔的出口处铣刀逐渐铣出CFRP,受到的径向力逐渐减小,其刀尖处变形量为9.946μm,孔径偏差为51.5μm。这表明螺旋铣削制孔过程中,刀具变形是影响孔径精度的重要因素。     

微细钻铣刀具表面涂层制备及应用研究进展(Ⅰ)

在微细钻铣刀具上进行涂层制备是有效提高微切削质量与加工效率的方法。金刚石涂层、类金刚石涂层和过渡族金属碳/氮化物涂层在微细钻铣刀具上得到了广泛应用,而应用于传统大直径刀具上的硼化物涂层、氧化物涂层等,在微细钻铣刀具上的应用仍处于开发阶段。刀具表面涂层制备技术主要有物理气相沉积技术、化学气相沉积技术和原子层沉积技术。本文从微细钻铣刀具出发,综述了各种制备方法的特点,介绍了近年来在刀具前处理、涂层晶粒直径、沉积参数控制及刀具夹具设计等关键技术点上的研究进展,对微细钻铣刀具表面涂层的制备具有指导意义。伴随着微细钻铣刀具涂层制备技术的优化更新,涂层材料和涂层结构的不断发展,使得刀具涂层的最高硬度和使用温度不断提高。     

微细铣削中刀具侧刃磨损试验研究

随着科学技术的发展,微小零件广泛应用于各个领域,而微细铣削技术变得越来越重要。在微细铣削中,对刀具磨损的研究占有重要地位。采用直径1 mm的TiAlN涂层平头铣刀,针对微细铣削黄铜H59时的刀具侧刃磨损进行试验研究。发现随着铣削长度的增加,侧刃磨损量呈上升趋势。切削长度为200 m时,两组试验的磨损带宽度变化由快变慢,出现变化临界点。对刀具磨损形式与机制进行分析,发现刀具出现涂层脱落、刀尖钝圆半径变大和微崩刃现象,分析其发生机制为磨粒磨损与粘结磨损。以侧刃后刀面磨损带宽度为试验指标进行正交试验,研究铣削参数对刀具侧刃后刀面磨损的影响主次顺序及最优参数组合。结果表明:每齿进给量、轴向切深、主轴转速和径向切深对刀具磨损的影响依次减少;试验所得最优参数组合为f_z=2μm/齿,a_p=0.3 mm,n=60 000 r/min,a_e=0.15 mm。     

Development of micro milling force model and cutting parameter optimization

Taking the minimum chip thickness effect,cutter deflection,and spindle run-out into account,a micro milling force model and a method to determine the optimal micro milling parameters were developed.The micro milling force model was derived as a function of the cutting coefficients and the instantaneous projected cutting area that was determined based on the machining parameters and the rotation trajectory of the cutter edges.When an allowable micro cutter deflection is defined,the maximum allowable cutting force can be determined.The optimal machining parameters can then be computed based on the cutting force model for better machining efficiency and accuracy.To verify the proposed cutting force model and the method to determine the optimal cutting parameters,micro-milling experiments were conducted,and the results show the feasibility and effectiveness of the model and method.     

Milling force prediction using a dynamic shear length model

Modelling of cutting forces in milling is often needed in machining automation. In this paper, a new method for the determination of the cutting forces in face milling is presented, which applies a predictive machining theory originally developed for orthogonal cutting to milling operations, with a dynamic shear length model developed and incorporated. The proposed dynamic shear length model is developed based on the analysis for the true tooth trajectories of a milling cutter, taking into account of the characteristic wavy surface effects in milling. The prediction for the cutting forces is carried out at each step of the angular increment of cutter rotation from input data of fundamental workpiece material properties, tool geometry and cutting conditions. Cutting forces at a cutter tooth can be predicted once the shear angle, shear length, shear plane area, and the shear flow stress along the shear length have been determined. The milling force prediction using the dynamic shear length model is verified through milling experimental tests. The sensitivity of the difference between the static and dynamic shear length models with respect to the feed per tooth and the cutter diameter is discussed.     

Simulation and experimental investigation of the end milling process considering the cutter flexibility

In this paper, a new type of model for the end milling process is presented considering cutter flexibility, which includes not only the static but also the dynamic deflection of the cutter. According to the basic assumption for a linear elastic body, the force acting on the cutter and its deflection in the milling process are both divided into two parts: the static and the dynamic. By considering the regenerative feedback in the practical milling process, the dynamic milling force acting on a unit length of the cutter is derived. Furthermore, a new kind of dynamic deflection model of the cutter is established. Based on this model, a new set of efficient numerical simulation algorithms are presented. In the mean time, the static deflection of the cutter is also formulated. Finally, the simulation and measurement of the milled surface topography for the end milling process show the feasibility of this model.     

行星复合铣削及其刀具研究

行星复合铣削方法是复合加工方法的一种实现形式,该加工方法所产生的切削力较普通端铣加工的切削力有大幅度的降低,从而能有效地降低切削热、减少工件变形、提高刀具寿命。行星复合铣削方法切削力大幅度地降低的主要原因是该方法的切削轨迹使其能将厚切削层分解为细小的切削层,而该方法中的立铣刀的螺旋角和半径对实际切削力的影响很小。行星复合铣削方法在刀盘低速旋转时就能实现高速切削,有效地避开了高速旋转刀盘的动平衡问题,结合其切削力小的优势,通过增大刀盘直径并增加立铣刀数量来提高加工效率。行星铣刀采用行星轮系结构,能够达到行星复合铣削方法切削轨迹要求,具有扭矩大、运转可靠等优势。     

A three-dimensional analytical cutting force model for micro end milling operation

In the present day manufacturing arena one of the most important fields of interest lies in the manufacturing of miniaturized components. End milling with fine-grained carbide micro end mills could be an efficient and economical means for medium and small lot production of micro components. Analysis of the cutting force in micro end milling plays a vital role in characterizing the cutting process, in estimating the tool life and in optimizing the process. A new approach to analytical three-dimensional cutting force modeling has been introduced in this paper. The model determines the theoretical chip area at any specific angular position of the tool cutting edge by considering the geometry of the path of the cutting edge and relates this with tangential cutting force. A greater proportion of the helix face of the cutter participating in the cutting process differs the cutting force profile in micro end milling operations a bit from that in conventional end milling operations. This is because of the reason that the depth-of-cut to tool diameter ratio is much higher in micro end milling than the conventional one. The analytical cutting force expressions developed in this model have been simulated for a set of cutting conditions and are found to be well in harmony with experimental results.     

Modelling and analysis of micro scale milling considering size effect, micro cutter edge radius and minimum chip thickness

This paper presents mechanisms studies of micro scale milling operation focusing on its characteristics, size effect, micro cutter edge radius and minimum chip thickness. Firstly, a modified Johnson–Cook constitutive equation is formulated to model the material strengthening behaviours at micron level using strain gradient plasticity. A finite element model for micro scale orthogonal machining process is developed considering the material strengthening behaviours, micro cutter edge radius and fracture behaviour of the work material. Then, an analytical micro scale milling force model is developed based on the FE simulations using the cutting principles and the slip-line theory. Extensive experiments of OFHC copper micro scale milling using 0.1 mm diameter micro tool were performed with miniaturized machine tool, and good agreements were achieved between the predicted and the experimental results. Finally, chip formation and size effect of micro scale milling are investigated using the proposed model, and the effects of material strengthening behaviours and minimum chip thickness are discussed as well. Some research findings can be drawn: (1) from the chip formation studies, minimum chip thickness is proposed to be 0.25 times of cutter edge radius for OFHC copper when rake angle is 10° and the cutting edge radius is 2 μm; (2) material strengthening behaviours are found to be the main cause of the size effect of micro scale machining, and the proposed constitutive equation can be used to explain it accurately. (3) That the specific shear energy increases greatly when the uncut chip thickness is smaller than minimum chip thickness is due to the ploughing phenomenon and the accumulation of the actual chip thickness.     

PCBN微型铣刀的制备及应用

聚晶立方氮化硼(PCBN)刀具具有高硬度、高耐磨性、较好的导热性、较低的摩擦系数,同时又具有优良的化学稳定性、热稳定性及加工红硬性,可以以铣磨方式高效加工高硬度、高强度、耐腐蚀性钢材并获得高表面加工质量。在分析PCBN微型铣刀的设计特点与加工难点基础上,成功制备了颈部缩颈3 mm,直径0.2 、0.4 、0.6 以及1.0 mm的PCBN微型球头双螺旋刃铣刀,并使用直径0.4 mm的微型铣刀进行铣削实验。结果表明:制备的PCBN微型铣刀可以高质量、高效率地加工硬度50 HRC的模具钢模具,模具的表面粗糙度R_a值可达0.101 μm,且无阴阳面,满足其表面最终加工要求。      

Feed rate scheduling model considering transverse rupture strength of a tool for 3D ball-end milling

This paper presents an analytical model of off-line feed rate scheduling to determine desired feed rates for 3D ball-end milling. Off-line feed rate scheduling is presented as the advanced technology to regulate cutting forces through change of feed per tooth, which directly affects variation of uncut chip thickness. In this paper, the uncut chip thickness is calculated by following the movement of the position of the cutter center, which is determined by runout and cutter deflection. Also, since the developed cutting force model uses the cutting-condition-independent coefficients, off-line feed rate scheduling can be effectively performed regardless of continuous change of cutting conditions. Transverse rupture strength of the tool is used to determine the reference cutting force at which resultant cutting forces are regulated through feed rate scheduling. Experiments validated that the presented feed rate scheduling model reduced machining time drastically and regulated cutting forces at the reference cutting force.     

立铣刀高速加工铝合金铣削力试验研究

采用多因素正交试验法进行铝合金铣削试验，测得了硬质合金立铣刀的铣削力。使用回归分析法获取了铣削力经验公式并验证其可靠性。与传统经验公式不同，切削速度独立成为一个因素。该公式确定了切削深度，切削宽度，切削速度，进给速度等切削参数对切削力的影响程度，并为设计刀具和选择切削用量提供了依据。