硬质合金可转位浅孔钻优化设计及CAD原型系统研究

以提高浅孔钻加工性能、促进浅孔钻批量化生产为目标,对刀体上装有两个等边不等角六边形硬质合金可转位刀片的浅孔钻进行研究。采用向量矩阵法建立切削部分几何模型;采用经典斜角切削理论和经验公式相结合的方法建立浅孔钻的力学模型;基于上述数学模型,以径向合力与扭矩最小为优化目标建立优化程序;在给定已知条件下求出不同切削用量、不同直径条件下的浅孔钻内、外刀片的最优空间位置,并进行分析;最后,基于理论分析与实验数据,建立可转位浅孔钻的参数化CAD原型系统。     

浅孔钻"非稳态"加工应力应变分析

以安装两片硬质合金刀片的可转位浅孔钻为例,在采用有限元方法建立浅孔钻"非稳态"加工时的力学模型的基础上,利用优化后的几何参数用数值仿真技术对各阶段的应力应变进行了研究,得出了最大应变发生的加工阶段、最大应力发生的刀具部位,还得出了加工孔的理论扩大量,为浅孔钻结构设计和使用提供了理论依据.     

可转位浅孔钻的径向力分析及试验研究

为了分析可转位浅孔钻钻孔的径向力,将可转位浅孔钻的切削刃离散为一系列无限小的单刃斜角切削单元。借用单刃斜角切削模型,并根据斜角切削和钻削之间的力变换关系对可转位浅孔钻钻孔的切削力进行分析。通过分析可转位浅孔钻切削刃上各点的几何角度,确定相应斜角切削单元的几何角度。最后对Al7050-T7451进行多组不同切削参数的钻削实验,数值计算和实验结果的比较验证了所提出数学模型的有效性。     

可转位浅孔钻“非稳态”加工时的力学建模

以刀体上装有两个等边不等角六边形硬质合金可转位刀片的浅孔钻为例,用向量矩阵法分析了可转位浅孔钻的几何参数。根据浅孔钻加工特性划分了各个加工阶段,在建立各阶段数学模型的基础上,采用经典斜角切削理论和经验公式相结合的方法进一步分别建立了浅孔钻“钻入”五个阶段和“钻出”三个阶段的力学模型。为进一步研究浅孔钻所受切削力、切削热以及浅孔钻结构的改进、使用等打下了必要的基础。     

可转位浅孔钻的实体建模及网格划分

可转位浅孔钻内外刀片的径向非对称分布,导致钻削时将会产生径向合力,从而影响被加工孔的质量。为最大限度的减小加工时的径向合力,有效研究浅孔钻钻削过程,需借助有限元软件对其进行三维斜角切削分析。由于浅孔钻结构复杂,为创建有限元分析所需要的几何模型,采用Solid-Works软件建立可转位浅孔钻三维模型,并详细介绍了其建模过程;同时在有限元分析软件ANSYS里对其进行网格划分,为后续浅孔钻的应力、应变等分析做好充分准备工作。     

可转位浅孔钻几何角度分析

采用向量矩阵法建立了可转位浅孔钻静态几何角度的数学模型 ,使用该模型可计算出钻头切削刃各点的刃倾角、法前角、法后角及主偏角 ,为进一步研究可转位浅孔钻的钻削力、钻削温度、刀片磨损等提供必要的基础数据。     

可转位浅孔钻非稳态加工的数学模型

以刀体上装有两个等边不等角六边形硬质合金可转位刀片的浅孔钻为例,用向量矩阵法分析了可转位浅孔钻的几何参数.根据浅孔钻的加工特征将其分成稳态和非稳态两个工作状态,将非稳态加工分为钻入五个阶段和钻出三个阶段,并分别对其相应的几何参数的计算建立了数学模型.为对浅孔钻进行进一步力学建模、对其所受切削力、切削热的研究,对浅孔钻结构的改进、使用等打下了必要的基础.     

可转位浅孔钻参数优化的数值解法

采用斜角切削理论和试验相结合的方法建立可转位浅孔钻钻削力数值仿真的数学模型。该模型用于研究刀片在刀体上的空间位置参数对钻削力和扭矩的影响,并在给定已知条件下求出经过优化的径向合力为最小的刀片位置参数。     

浅孔钻的径向力平衡及关键参数设计

通过对WCMX型刀片可转位浅孔钻的受力分析,提出应以径向力平衡作为浅孔钻的设计原则;对内刀片的过轴心线值、刀片切削刃的余偏角及内外刀片轴向相对位置、端面相对于圆心位置等重要设计参数进行了分析和阐释,并给出了推荐值;推导出了内刀片偏转角β的计算公式。     

基于径向力的可转位浅孔钻加工孔径误差研究

为研究可转位浅孔钻在切削过程中的钻孔孔径误差,基于可转位浅孔钻的理论几何模型,并利用经典斜切理论得到浅孔钻的径向力、力矩关于刀片几何参数和切削参数的计算公式。选取常用切削参数组合,将计算得的径向合力及力矩作为边界条件,通过ANSYS有限元分析刀体挠度,得出相关钻孔孔径误差的理论值。利用统计学回归方法建立相应数学模型,并通过切削试验验证数学模型的精确性。基于建立的数学模型,通过调节切削参数,可预测并控制孔径误差值,实现浅孔钻在半精加工中对孔径余量的精确控制,有效拓展可转位浅孔钻的应用范围。     

CORRELATION BETWEEN DRILL GEOMETRY AND MECHANICAL FORCES IN MQL CONDITIONS

This article deals about the determination of the suitable cutting tools for the machining of a large welded frame in low carbon steel. Various drill technologies are used in the drilling process such as solid carbide drills, solid carbide modular drills, which consist of coated carbide edges and a sintered steel body or indexable drills. The effects of the drill technologies and the lubricant conditions are compared with taking into account of the cutting conditions and forces. The objective is to link the cutting forces and it distribution along the cutting edges to the cutting parameters the drill geometry and the cooling conditions.     

Cutting characteristics of twist drill having cutting edges for drilling and reaming

In this study, the cutting characteristics of a drill reamer, which has conventional twist drill cutting edges appended for reaming, were investigated. A drill reamer has three types of cutting edges, whose roles are drilling, semi-finishing, and finishing. The cutting characteristics of a conventional twist drill were compared to those of the drill reamer. The cutting characteristics were evaluated using the thrust force, cutting torque, surface roughness, wear behavior of the cutting edges, and cutting edge temperature. The study used a workpiece made of carbon steel. The temperature of the cutting edge for reaming reached a maximum value of approximately 420°C, even though the depth of the cut was very small. The inner surface roughness with the drill reamer was superior to that with the conventional drill, even under dry and low-speed cutting conditions. The abrasive wear observed on the margin face of the cutting edge used for reaming.     

麻花钻磨损特性的研究

通过对调质合金结构钢的大量钻削试验,研究了麻花钻磨损区的图形特征和磨损机理以及钻头失效与磨损图形参数、钻头切削寿命与钻削速度的关系。结果表明,麻花钻的磨损具有非线性特征,钻头转角和主刀刃及横刃区有两个显著不同的磨损区,随钻削速度的提高,这两个磨损区的特征差异及磨损带宽度之比明显增大。在钻削速度较低、钻头失效时,两个磨损区为较均衡的磨粒磨损和粘结磨损;钻削速度较高时,转角区剧烈的粘结磨损和氧化磨损使钻头加快失效,而主刀刃及横刃上的磨损却很小。受此影响,麻花钻的磨钝标准、耐用度问题较为复杂,钻头的寿命（Ｔ）－速度（Ｖ）曲线的泰勒特性范围很窄。     

浅孔钻钻削过程中的有限元动态仿真

基于Deform 3D有限元软件平台,采用数值仿真技术,建立了浅孔钻钻削加工45钢的有限元模型。动态模拟了浅孔钻钻削过程,获得了浅孔钻钻削加工过程中变形工件的等效应力和温度,分析预测了加工过程中硬质合金刀具所受的主切削力、径向力以及两刀片所受的扭矩及评估刀片的磨损情况。     

ENERGETICAL APPROACH FOR SEMI-ANALYTICAL DRILLING MODELLING

Drilling modelling is a complex task and has been extensively studied from an experimental viewpoint. However, only few studies have been done on the analytical modelling of this machining operation. The geometry of a drill and the kinematics of drilling are such that tool angles as well as the cutting conditions undergo great variations along the cutting edges. The calculation of the forces in drilling thus requires a cutting model covering the whole range of these variations. Moreover, on the chisel area, the cutting speed and the angles are such that the phenomena cannot be regarded as cutting. In this case, the material is plastically deformed when passing by tool edge, just as in indentation. In this study, we propose a semi-analytical model that allows determining forces on the tool, as well as heat fluxes and temperatures along the edges of the drill. In this model, the main cutting edge and the chisel edge are considered. It also takes into account the elastic relaxation on the clearance face with edge acuity, as well as a proper modelling of the phenomena occurring at chisel edge in relation with its geometry and the kinetics of a drilling operation.     

Effects of Coating Materials on the Machinability of a Nickel Base,C-263, Alloy

PVD coated (TiN/TiCN/TiN, TiAIN and TiZrN) and uncoated carbide tools were used to machine a nickel base, C-263, alloy at high-speed conditions. The test results show that the multiple TiN/TiCN/TiN coated inserts gave the best overall performance in terms of tool life when machining at cutting speeds up to 68 m min and at depths of cut of 0.635 mm, 1.25 mm and 2.54 mm. All the tool grades tested gave fairly uniform surface roughness (Ra) values, below the rejection criterion, at lower speed conditions. The TiZrN coated inserts gave the lowest component forces when machining at lower cutting speed conditions while the TiA/N coated inserts gave the lowest component forces when machining at a higher speed of 68 m min^?1 and depth of cut of 1.25 mm. This tool performance can generally be attributed to the difference in their ability to provide effective lubrication at the cutting zone, thermal conductivity of the coating materials as well as the cutting conditions employed. The uncoated carbide tools generally encountered more severe crater wear, chipping/fracture of the cutting edges as well as pronounced notching during machining. This is due to their inability to provide effective lubrication at the cutting zone, thus impeding the gliding motion of the chips along the rake and flank faces respectively, thus accelerating flank wear. Analysis of the worn tool edges revealed adhesion of a compact “fin-shaped” structure of hardened burrs with saw-tooth like edges. This generally alters the initial geometry of the cutting edge, consequently resulting to poor surface finish with prolonged machining.     

Mechanistic model for drills with double point-angle edges

This article introduces a mechanistic model for predicting thrust force and torque during the drilling process of aluminium alloy Al 7075-T6. The drill used is specially designed to machine aluminium alloys used in aerospace applications; it is a tool with double-point angle edges, specially designed to avoid part distortion at the drill entrance into material. The mechanistic model requires obtaining specific cutting coefficients; those coefficients are adjusted following two methods. On the one hand, they are adjusted with regard to the geometrical parameter Z coordinate of the discretized points of the drill main edge. On the other, they are adjusted with regard to cutting speed and inclination angle, which vary along the main edge. The specific coefficients are obtained from a series of experimental tests in which the mechanistic model is applied in a reverse way. The model is validated in a wide range of cutting conditions, both within and outside the range of cutting conditions used, to obtain the coefficients. Results show close correlation between the models and the experimental data in the first case (less than 15% errors) and error between 20 and 35% in the second case.