多齿刀具加工金属长纤维的机理

研究了多齿刀具加工金属纤维的机理．研究发现．多齿刀具各细齿切削属双刃斜角切削．建立了双刃斜角切削模型并用实验验证，从理论上预测各细齿切削时的流屑角．根据流屑角计算各细齿的实际切削前角。结果表明．多齿刀具备细齿切削时具有很大的实际切削前角．这正是多齿刀具能够加工金属长纤维的机理。     

多齿刀具的切削模型及其分屑机理

研制了一种能同时加工出多根微细金属长纤维的新型刀具--多齿刀具。多齿刀具切削时具有分屑作用,将整个切削层切下的同时把切屑分屑形成多根纤维。多齿刀具切削时的分屑作用能高效地制造当量直径在100μm甚至50μm以下的微细金属长纤维。建立了多齿刀具的切削模型,根据切削模型分析了多齿刀具的分屑机理,推导出多齿刀具同时参与切削的齿数及加工出的纤维当量直径计算公式。     

弧齿锥齿轮铣齿加工三维应力仿真及分析

根据弧齿锥齿轮轮坯、刀盘及机床调整参数,建立了弧齿锥齿轮的三维加工模型。研究了金属切削加工有限元分析中所涉及的刀屑界面摩擦模型、刀屑接触定义、切屑分离准则等相关关键技术。建立了弧齿锥齿轮铣齿加工过程的有限元模型,通过ABAQUS软件仿真模拟出了不同工艺参数和刀具参数下的铣齿加工过程,得到了切削层形态及应力分布结果。研究结果表明:刀具前角增大,切削层变形减小,主切削力减小;切削速度增大,主切削力减小;刀具的合理前角应取为20°,切削速度应根据实际情况取较大值。同时也为选取和研究弧齿锥齿轮加工工艺参数提供了一套有效的方法。     

1.4/2.0T型双金属带锯条齿形参数优化设计

优化设计了一种用于锯切模具钢材料的双金属带锯条,通过对不同的齿前角、齿后角和分齿高度模拟研究,分析齿形参数对齿尖切削力和切削温度的影响规律,获得了切削性能最优的刀具前角、后角、齿槽形状等参数组合,并进行了实际锯切试验,得出了切削效率高、使用寿命长的双金属带锯条最优齿形参数。     

带螺旋角双导程蜗轮滚刀齿距测量误差分析

双导程蜗轮滚刀在制造时,其左右侧导程应分别等于原工作蜗杆的左右导程,左右侧切削刃螺纹升角应分别等于原蜗杆的左右侧螺纹升角.由于刀具刃口方向螺旋角与刀具左右侧切削刃实际螺纹升角之间有一定的差别,此时刀具的前刀面与切削刃螺旋平面不垂直,从而引起刀具齿距测量误差.本文在制造带螺旋角双导程蜗轮滚刀时,通过刀具测量对螺旋角与实际...     

螺旋角与螺纹升角不一致情况下滚刀前刃面齿距测量分析

在设计螺旋槽滚刀时会出现螺旋角与螺纹升角不一致的情况,此时由于刀具刃口方向螺旋角与刀具左右侧切削刃实际螺纹升角之间有差别,刀具的前刃面与切削刃螺旋平面不垂直,因此在万工显上测量前刃面齿距时需对齿形进行两次投影换算。如仍按螺纹升角与螺旋角一致情况下进行投影换算测量,会引起刀具齿距测量误差。在制造螺旋角与螺纹升角不一致的滚刀时,对滚刀齿距进行正确投影并精确测量。     

车齿工艺刀具工作角度演变过程建模及分析

车齿工艺是一种高效齿轮切削加工工艺,刀具工作角度是影响切削加工性能的重要参量。车齿工艺由于运动关系和刀具几何形状复杂,导致刀具工作角度在切削过程中不断变化,并受多因素影响。首先基于车齿工艺原理和坐标变换方法建立其运动学模型,并根据车齿刀几何构型建立产形后刀面、前刀面和切削刃的数学模型,结合斜角切削的刀具工作角度定义推导出车齿刀工作前角和后角的计算公式,实现车齿刀工作角度演变过程的解析表示,最后分析了车齿刀设计前角和螺旋角对工作角度的影响。结果表明较大的刀具设计前角主要影响工作前角,而车齿刀螺旋角主要影响工作后角。相关结果可以为刀具结构优化提供理论支撑。     

精密加工变齿厚内齿轮插齿刀设计

针对标准插齿刀通过斜插法或插削角优化法难以实现变齿厚内齿轮高精度加工的问题,提出了一种精密加工变齿厚内齿轮的专用插齿刀设计方法。该插齿刀齿廓方程同时包含刀具几何参数和插削角工艺参数。基于啮合原理推导了刀具齿廓方程,建立了插齿刀切削刃数学模型,给出了插齿刀切削刃参数优化流程。对比分析了不同加工方法的齿形误差,研究了设计参数变化对齿形误差的影响规律。结果表明,所提出的方法在各种设计参数下均能有效减小齿形误差,设计出的刀具按优化倾角做直线插削即可实现变齿厚内齿轮的精密加工,无需对机床进行改造,易于推广。     

小型键槽推刀

苏联哈尔科夫精密仪器制造工厂研制了一种两齿键槽推刀。用一次走刀可加工出装在电机轴上的铝合金叶轮内孔小规格键槽。这种推刀切削部分的宽度与零件键槽等宽,而刀具切削部分的全高应能够进入零件的孔中。这样小型刀具的几何参数难以选定,在计算推刀最佳切削参数时,应注意到在每个刀齿切下的切屑体积,齿背角β、后角α、前角Y、齿槽深度、齿高、齿距等的大小。由这些参数决定了齿槽容积的大小,齿槽的容积必须大于切屑的体积,以免切屑被夹住或贴在齿槽上,已加工表面被刮伤,超负     

CFRP/Al叠层材料二维正交切削过程数值仿真

由于CFRP与Al合金材料之间的差异性,对其构成的叠层材料的加工带来巨大挑战,同时由于实验研究的高成本、时间消耗以及计算机技术的高速发展,数值仿真成为研究切削过程的有力方法。将三维钻削过程简化为由不同的本构模型和损伤准则建立的2D正交切削宏观有限元模型,研究了切削顺序、进给速度、刀具前角对45°纤维角CFRP/Al合金叠层材料切削力和CFRP切削损伤的影响。仿真结果表明:CFRP→Al切削顺序优于Al→CFRP切削顺序。进给速度对切削过程中切削力和切削损伤的影响高于刀具前角。当刀具前角大于5°时,增大刀具前角对45°单向CFRP的切削力和加工后表面损伤影响不显著。     

Characteristics and formation mechanism for stainless steel fiber with periodic micro-fins

Metal fibers have been widely used in many industrial applications due to their unique advantages. In certain applications, such as catalyst supports or orthopedic implants, a rough surface or tiny outshoots on the surface of metal fibers to increase surface area are needed. However, it has not been concerned about the surface morphologies of metal fiber in the current research of metal fiber manufacturing. In this paper, a special multi-tooth tool composed of a row of triangular tiny teeth is designed. The entire cutting layer of multi-tooth tool bifurcates into several thin cutting layers due to tiny teeth involved in cutting. As a result, several stainless steel fibers with periodic micro-fins are produced simultaneously. Morphology of periodic micro-fins is found to be diverse and can be classified into three categories: unilateral plane, unilateral tapering and bilateral. There are two forming mechanisms for the micro-fins. One is that periodic burrs remained on the free side of cutting layer of a tiny tooth create micro-fins of stainless steel fiber produced by the next neighboring tiny tooth; the other is that the connections between two fibers stuck together come to be micro-fins if the two fibers are finally detached. Influence of cutting conditions on formation of micro-fins is investigated. Experimental results show that cutting depth has no significant effect on micro-fin formation, high cutting speed is conducive to micro-fin formation, and feed should be between 0.12 mm/r and 0.2 mm/r to reliably obtain stainless steel fiber with micro-fins. This research presents a new pattern of stainless steel fiber characterized by periodic micro-fins formed on the edge of fiber and its manufacturing method.     

An empirical survey on the influence of machining parameters on tool wear in diamond turning of large single-crystal silicon optics

We conducted a series of screening experiments to survey the influence of machining parameters on tool wear during ductile regime diamond turning of large single-crystal silicon optics. The machining parameters under investigation were depth-of-cut, feed rate, surface cutting speed, tool radius, tool rake angle and side rake angle, and cutting fluid. Using an experimental design technique, we selected twenty-two screening experiments. For each experiment we measured tool wear by tracing the tool edge with an air bearing linear variable differential transformer before and after cutting and recording the amount of tool edge recession. Using statistical tools, we determined the significance of each cutting parameter within the parameter space investigated. We found that track length, chip size, tool rake angle and surface cutting speed significantly affect tool wear, while cutting fluid and side rake angle do not significantly affect tool wear within the ranges tested. The track length, or machining distance, is the single most influential characteristic that causes tool wear. For a fixed part area, a decrease in track length corresponds to an increase in feed rate. Less tool wear occurred on experiments with negative rake angle tools, larger chip sizes and higher surface velocities. The next step in this research is to perform more experiments in this region to develop a predictive model that can be used to select cutting parameters that minimize tool wear.     

高速车削镍基高温合金GH4169的切削力仿真研究

基于Deform 3D仿真软件建立了GH4169高温合金高速车削的有限元模型,采用四因素三水平正交试验方法研究了切削用量和刀具几何参数对切削力的影响规律,并建立了切削力经验公式。研究结果表明:在高速车削GH4169的过程中,对切削力影响最大的参数是切削深度,其次是进给量和前角,最后是刀尖圆弧半径;切削力随切削深度和进给量的增大而增大,随前角的增大呈现先降低又升高的趋势,而刀尖圆弧半径增大时切削力变化不大;最佳参数组合为:进给量0.2mm/r,切削深度0.4mm,前角10°,刀尖圆弧半径0.2mm。     

MOLECULAR DYNAMICS SIMULATION OF NANOMETRIC CUTTING

Molecular Dynamics (MD) simulations of nanometric cutting of single-crystal copper were conducted to predict cutting forces and investigate the mechanism of chip formation at the nano-level. The MD simulations were conducted at a conventional cutting speed of 5 m/s and different depths of cut (0.724–2.172 nm), and cutting forces and shear angle were predicted. The effect of tool rake angles and depths of cut on the mechanism of chip formation was investigated. Tools with different rake angles, namely 0°, 5°, 10°, 15°, 30°, and 45°, were used. It was found that the cutting force, thrust force, and the ratio of the thrust force to cutting force decrease with increasing rake angle. However, the ratio of the thrust force to the cutting force is found to be independent of the depth of cut. In addition, the chip thickness was found to decrease with an increase in rake angle. As a consequence, the cutting ratio and the shear angle increase as the rake angle increases. The dislocation and subsurface deformation in the workpiece material were observed in the cutting region near the tool rake face. The adhesion of copper atoms to the diamond tool was clearly seen. The same approach can be used to simulate micromachining by significantly increasing the number of atoms in the MD model to represent cutting depths in the order of microns.     

基于黏结-滑移摩擦模型的304不锈钢切削力仿真研究*

通过预测加工304不锈钢时产生的切削力,从而对切削参数和刀具几何参数进行优化,是提高304不锈钢的加工精度、切屑控制及保障刀具寿命的基础。建立304不锈钢切削仿真模型,为提高模型的精确性,选择Johnson-Cook本构方程和黏结-滑移摩擦模型。结果表明：采用黏结-滑移摩擦模型的切削力预测结果更为准确,表明相对于纯剪切摩擦与库仑摩擦模型,黏结-滑移摩擦模型能更准确地描述刀-屑摩擦特性。展开不同参数下的切削力研究,研究发现：切削力随着刀具前角、后角和切削速度的增大而减小,随切削刃钝圆半径和切削厚度、宽度的增大而增大,其中切削宽度、厚度及前角对切削力大小影响较大。研究结果为304不锈钢切削效率的提高和切削机制的研究提供了理论依据。     

AN EXPERIMENTAL EVALUATION OF CUTTING TEMPERATURES DURING HIGH SPEED MACHINING OF HARDENED D2 TOOL STEEL

This paper investigates experimentally the effects of different process parameters on the cutting edge temperature during high speed machining of D2 tool steel using polycrystalline cubic boron nitride (PCBN) tools. The cutting edge temperature is measured using thermocouples. The process parameters considered are cutting speed, feed rate, nose radius, rake angle, and tool wear. The effects of different edge preparations including sharp, honed and chamfered are also investigated. The results show that increasing cutting speed and feed rate increases the cutting temperature while increasing nose radius reduces the cutting edge temperature. In addition, there is an optimum rake angle value at which minimum cutting temperature is generated.     

A SLIPLINE FIELD ANALYSIS OF FREE-CHIP ORTHOGONAL MACHINING WITH ADHESION FRICTION AT RAKE FACE

The paper presents slipline field solutions for metal machining assuming adhesion friction at the chip-tool interface. The field is of “indirect” type and is analyzed by the matrix method suggested by Dewhurst, Dewhurst and Collins. The range of validity of the proposed solutions is examined from the consideration of overstressing of rigid vertices in the assumed rigid regions. Rake angle and rake friction are found to be the most important variables that influence the deformation process in machining. Variation of cutting forces, chip thickness ratio, chip curvature and contact length with rake angle and friction parameters is investigated. It is observed that cutting and thrust forces and cutting ratio decrease as rake angle increases but increase as coefficient of friction increases. However, tool-chip contact length decreases as rake angle increases. As a result the average normal and shear stresses on the tool face increases as rake angle increases though, the cutting and thrust forces decrease. Results indicate that friction coefficient cannot be uniquely determined by the rake angle alone, but may have a range of allowable values for a particular value of rake angle. The theoretical results are compared with experimental data available in literature and also with those obtained by the authors from orthogonal cutting tests.     

带卷屑槽刀具最大前角的数学模型与求解

由于现代数控刀具都设计有卷屑槽,从而使其前刀面不是平面,而是曲面。本文针对前刀面为圆柱面的一部分时,采用向量矩阵法建立最大前角计算的数学模型,应用该模型可以在给定条件下,计算曲面型前刀面车刀的最大前角和其它重要的几何参数。最后,给出了计算实例。     

Blend of sharpness and strength on a ball nose endmill geometry for high speed machining of Ti6Al4V

The applications of titanium alloys are increasingly common at marine, aerospace, bio-medical and precision engineering due to its high strength to weight ratio and high temperature-withstanding properties. However, whilst machining the titanium alloys using the solid carbide tools, even with application of high pressure coolant, reduced tool life was widely reported. The generation of high temperatures at the tool–work interface causes adhesion of work material on the cutting edges, and hence, shorter tool life was reported. In order to reduce the high tool–work interface temperature-positive rake angle, higher primary relief and higher secondary relief were configured on the ball nose endmill cutting edges. Despite of careful consideration of tool geometry, after an initial working period, the growth of flank wear accelerates the high cutting forces followed by work material adhesion on the cutting edges. Hence, it is important to blend the strength, sharpness, geometry and surface integrity on the cutting edges so that the ball nose endmill would exhibit an extended tool life. This paper illustrates the effect of ball nose endmill geometry on high speed machining of Ti6Al4V. Three different ball nose endmill geometries were configured, and high speed machining experiments were conducted to study the influence of cutting tool geometry on the metal cutting mechanism of Ti-6Al-4V alloy. The high speed machining results predominantly emphasize the significance of cutting edge features such as K-land, rake angle and cutting edge radius. The ball nose endmills featured with a short negative rake angle of value ?5° for 0.05～0.06 mm, i.e. K-land followed by positive rake angle of value 8°, has produced lower cutting forces signatures for Ti-6Al-4V alloy.