横刃修磨高长径比微细钻削刀具的钻削性能研究

横刃修磨方法是一种提高钻削刀具加工性能的有效手段.针对横刃修磨高长径比微钻,建立了刀具螺旋槽、非共轴螺旋后刀面和十字型横刃的数学模型,并基于六轴数控工具磨床刃磨制备出直径0.5 mm、长径比为10的横刃修磨高长径比非共轴螺旋后刀面微钻.在304不锈钢材料上开展了普通高长径比微钻和横刃修磨高长径比微钻的对比钻削试验研究,从钻削力、刀具磨损、微小深孔加工质量等方面分析了横刃修磨对高长径比微细钻削刀具钻削性能的影响.结果表明,与普通高长径比微钻相比,横刃修磨高长径比微钻的钻削轴向力和钻尖磨损程度明显降低,在钻削5个微小深孔后,横刃修磨高长径比微钻的后刀面和横刃的最大磨损宽度分别减小了 26％和32％;横刃修磨高长径比微钻所加工的微小深孔具有更规则的入口形状、更低的圆度误差和孔壁粗糙度.研究证实了横刃修磨方法能够显著提高高长径比微钻的钻削性能.     

不同的刃磨方法对钻头性能影响的分析

1引言金属切削刀具的几何形状和角度是影响刀具切削性能和被加工工件质量的主要因素之一。钻头也不例外,合理选择钻尖的几何形状和角度,可以很大程度地改善钻削特性。如苏联查波罗什变压器生产联合公司对麻花钻的切削部分几何形状进行了改进,使主切削刃呈圆弧状。这种钻头的寿命高于标准钻头寿命,在加工碳钢时刀具寿命可提高0.6~5倍;加工铸铁时刀具寿命可提高5倍以上,同时加工表面光洁度可提高1~2级。美国Guhring公司曾做过一系列钻尖几何形状对切削性能影响的试验。试验结果表明:不同的钻尖几何形状(如锥面钻尖、螺旋面钻尖、split钻尖等)在切削时产生的切削扭矩和轴向抗力有很大差异。天津大学科研人员将钻头后刀面刃磨成双曲面后刀面,形成“S”型横刃,这种钻型的轴向力比锥面麻花钻平均下降24%,扭矩平均下降25%,钻孔时的定心和刀具耐用度都得到了改善。由此可见,合理选择钻尖的几何形状和角度在很大程度上可以改善钻削特性。钻尖的几何形状和角度可以通过刃磨获得。2各种刃磨方法分析钻尖刃磨主要是沿主后刀面刃磨,刃磨方法有平面磨法、锥面磨法、圆柱面磨法、螺旋面磨法等。2.1钻尖的平面刃磨法平面刃磨法分为单平面法与双平面法两种,单平面刃磨时...     

微钻头刚度的有限元分析

模拟微钻头螺旋槽和后刀面的刃磨过程,用Unigraphics(简称)软件建立微钻头的三维实体模型。以非共轴螺旋面钻尖为研究对象,分别改变钻芯厚度与钻头直径之比、钻头的螺旋槽长度以及螺旋角,利用有限元软件ANSYS对钻头的扭转刚度、弯曲刚度和受压刚度进行计算分析,为钻头的结构优化设计、提高刀具切削性能和耐用度的研究提供了基础。     

基于钻削刀具后刀面刃磨方程建立的研究

采用锥面磨削法刃磨钻削刀具的后刀面,可显著提高刀具的使用寿命,有利于保证工件加工精度和提高工件表面质量。利用数控加工设备进行锥面磨削或者进行锥面磨削设备的研制中,关键是数学模型（后刀面方程）的建立;据此编制和计算机床坐标值的程序、对刀具刃磨机床进行研制。针对锥面磨削方法中钻削刀具后刀面方程的建立和有关参量的计算作深入的研究。并以该后刀面方程完成刀具刃磨机床的初期开发研制。     

MK6335A五轴数控高效钻尖磨床

湖南大学经过20多年的努力,从理论上建立了各种复杂钻型的数学模型,解决了钻尖数学模型及其刃磨参数求解的世界性难题,成功研制了M K6335A五轴数控高效钻尖磨床。该钻尖磨床可以精确刃磨各种倪志福(群钻)钻尖、螺旋面钻尖、双平面钻尖、修磨横刃钻尖、多分屑槽钻尖、阶梯钻等多种先进钻型的高速钢钻头和多种钻型的硬质合金钻头。该机床主要特点:①钻头在刃磨过程中,机床可自动编程、自动加工,磨削效率高,磨削精度好,刃磨后钻尖跳动量不大于0.02m m,几何角度误差不超过1°;②机床采用汉字菜单操作,用户只需在屏幕上选择钻型、设置钻头参数,…     

复杂螺旋面钻尖刃磨原理及实现

研究了平面包络的复杂螺旋面钻头,给出了钻尖结构参数的计算公式,研究了钻尖结构参数与刃磨参数之间的关系,结果表明钻尖的结构圆周后角及尾隙角随着钻头轴向推进速度与自转速度的比值Ｋ２的增大而胡着钻头摆速度与自转速度之比Ｋ１的增大单调减小,随着砂轮与摆动中心的距离Ｈ的则单调减小,随着确定前刀面位置的Ｐ０值的增大而单调减小,随着砂轮平面与钻轴的夹角θ、Ｋ１、Ｋ２、Ｈ的增大先增大后砬小,随着Ｐ０的增大而减小。     

新型非共轴复杂螺旋钻尖的研究与性能测试

麻花钻的钻尖结构对其切削性能影响很大,在加工过程中扭矩和轴向力是反映切削性能的重要指标。本文介绍了一种新型非共轴复杂螺旋钻尖,其后刀面由两个对称于钻头轴线且螺旋回转轴线平行于钻头轴线的复杂螺旋面构成。螺旋面分为切削区域、过渡区域、切屑排出区域三部分,具有钻削力小等优点。对磨削后的该钻头与其他结构钻头进行力学性能测试,分析对比数据可知,得出钻头结构合理结论。     

微细钻头螺旋槽刃磨试验研究

螺旋槽几何结构是影响钻头切削性能和微孔加工质量的重要因素。螺旋槽形状主要取决于刃磨参数、砂轮形状参数以及砂轮位置参数,通过调整砂轮的形状与位置参数即可以获得所需的螺旋槽形状。通过分析砂轮和螺旋槽之间的相对运动关系,建立微细钻头螺旋槽型的刃磨数学模型,并基于Matlab软件对螺旋槽刃磨截形进行了数值仿真,分析了砂轮形状与位置参数对螺旋槽形状、径向前角和螺旋槽宽度的影响规律。研究结果表明砂轮边缘宽度、砂轮锥角、砂轮偏置角度和砂轮偏移距离对螺旋槽截形有明显的影响。随着砂轮边缘宽度和砂轮锥角的增大,径向前角没有变化,但是螺旋槽宽度增大,容屑空间明显增大;随着砂轮偏置角度的增大,螺旋槽径向前角明显增大,螺旋槽宽度减小;随着砂轮偏移距离的增大,径向前角变化较小,而螺旋槽宽度明显增大。基于所建立的刃磨数学模型,刃磨出不同螺旋槽型微细钻头,证实刃磨结果与仿真结果具有较好的一致性。采用所制备的微细钻头进行钻削试验,验证了螺旋槽结构对容屑与排屑能力具有重要影响。     

麻花钻几何参数对钛合金钻削性能的影响

根据麻花钻的实际制造过程,利用UG NX软件在麻花钻螺旋线的法平面内,以实际钻头刃沟铣刀轮廓生成前刀面,并基于锥面刃磨法原理,以两面自然相交的方法生成麻花钻后刀面,完成麻花钻的三维建模。利用DEFORM-3D软件建立了麻花钻钻削钛合金的有限元模型,采用正交试验法分析了麻花钻顶角、螺旋角和横刃斜角对钛合金钻削过程中轴向力的影响规律。结合极差与方差分析,以图表方式直观反映了各因素的影响程度,并获得最佳几何参数组合,为钛合金实际钻削过程中钻头几何参数的选择和优化提供了理论依据。     

PCB常规微钻钻尖平面方程

PCB常规微钻是双刃硬质合金钻头,其钻尖的几何形状会影响微钻钻削性能,因而有必要研究钻尖的几何数学模型。建立了绕任意轴的旋转矩阵的数学形式,推导了常规微钻后刀面的数学模型及相应的横刃斜角和切削刃的数学表达式,从而为微钻的工程设计中选择最佳的结构参数提供参考。     

NC data generation for 6-axis machine tools to produce a helical drill

This study presents a design methodology for grinding a specific helical drill on a CNC 6-axis grinding machine. The proposed methodology comprises three steps: (1) deriving a mathematical model of the helical drill, (2) establishing the ability matrix of the multi-axis grinding machine according to Denavit-Hartenberg (D-H) notation, and (3) constructing configuration matrices to express the required grinding wheel positions and orientations while machining the flute and flank surfaces of the drill. The NC data for the motion values of each axis are obtained by equating the corresponding elements of the CNC ability matrix and the configuration matrices of the grinding wheel. To verify the proposed methodology, a designed helical drill is machined on a 6-axis CNC tool-grinding machine. The methodology presented in this study integrates the drill design and manufacturing activities, thereby making possible the implementation of a more flexible, automatic, cost efficient and controllable design and production process.     

A practical optimization design of helical geometry drill point and its grinding process

Drill with helical geometry drill point was developed to avoid the disadvantages of planar drill. For the visualization design and optimization of helical drill, a numerical modeling and simulation CAD system has been developed based on the mathematical models of helical drill. The characteristics of helical drill, such as lip clearance angle along cutting lip, heel clearance angle along flank surface, cutting edge inclination angle, rake angle, and so on, are described. Therefore, drill geometric parameters are modified reasonably according to different drilling requirements by the aid of the developed CAD simulation system. Besides, grinding parameters are obtained to guide the flank grinding process of helical drill. A case has been given to demonstrate the function of the system. And the calculated grinding parameters in the above case have been applied on a five-axis CNC grinding machine RollomΛtic 620XS with an assistant fixture to accomplish the flank grinding process. Drill geometry of ground drill shows good agreement with the simulative one, which validates the accuracy of proposed model method and relative CAD system.     

平面螺旋运动包络特性的研究

利用解析几何和条件极值理论研究了用平面 (或圆柱面 )砂轮刃磨钻头时形成的钻尖后刀面的包络特性 ,结果表明 ,刃磨形成的钻尖后刀面由平面螺旋运动包络曲面和位于中心区域的非包络曲面组成。非包络区域面积与螺旋运动导程及砂轮平面与旋转轴的夹角有关 ,导程和夹角越大 ,非包络区域也越大     

Modeling,simulation and manufacturing of drill flutes

The designing of twist drill flutes (as well as that of end mills and of some combined tools) cannot be separated from the way they are manufactured. The aim of this paper is to present an intuitive direct method for modelling, simulation and manufacturing of the drill flutes with different shapes using conical grinding wheels with standardized shapes. The mathematical approach is described, which enables us to determine the flute profile in a section perpendicular to its axis as well as the manufacturing parameters. The grinding wheel has an initial position with respect to the cylindrical work piece, which is described using four parameters (Denavit Hartenberg parameters). We have presented algorithms in pseudocode that produce the flute shape and that compute the optimum parameters of the wheel position in the manufacturing process. Subsequently, a software application based on the aforementioned model is able to create visualizations of the flute shape. The analysis of the flute shape has enabled us to understand the influence of the geometrical parameters and the position of the grinding wheel on the resulting product in the grinding process. The order in which these parameters are to be set is also specified. We have built atlases of maps presenting the influence of the geometrical parameters and the position of the grinding wheel in the grinding process upon the shape of the flute. The validity of the method is proven by the agreement of the computed values with the input and output data produced by experiment. The proposed method allows helical flutes to be generated solely by using cylindrical and conical grinding wheels of standard shapes.     

Novel micro-deep-hole drill with variable web thickness and flute width

This study proposes a novel micro-deep-hole drill with variable web thickness and flute width to effectively improve the problem of tool breakage and chip clogging during micro-deep-hole drilling. Firstly, the failure form and failure mechanism of micro-drill are explored by performing drilling experiments, and it is found that the torsion fracture and bending fracture are the main premature failure modes of micro-deep-hole drilling tools. The static simulation analysis of micro-drill is further conducted to investigate the influence of geometric parameters on the stiffness and strength of high-aspect-ratio micro-drill, and the results indicate that the web thickness ratio and flute width have significant effects on drill tip stiffness and spiral groove root strength. To balance the rigidity, strength and chip evacuation capability of micro-deep-hole drilling tools, the new micro-drill with variable web thickness and flute width is developed, supplemented by comparative experiments. The results confirm that the new micro-drill has better chip removal ability, greatly reduces the drilling force, torque, drill tip wear and material peeling phenomenon, and significantly enhances the machining quality of hole wall.     

断屑钻尖后刀面的砂轮磨削位姿算法

定义了断屑钻尖后刀面的结构参数,构建了三个坐标系并分析了对应的转换矩阵;建立了断屑钻尖刃线及后刀面参数化数学模型;采用坐标变换矩阵描述了砂轮的运动方式,借助运动学原理,在数控磨削过程中提出了基于工件坐标系的断屑钻尖后刀面砂轮磨削位姿算法。基于VC++环境,开发了相应的计算程序并进行了一系列的磨削加工和测试来验证所提算法的有效性。测量结果表明：所提算法可保证断屑钻尖后刀面的结构精度,并可灵活调整磨削过程中砂轮姿态。     

Analyses of Drill Flute and Cutting Angles

The analysis of drill cutting angles is important for the design of high-performance drill geometry. The cutting angles along the cutting edge of a drill are determined by the combination of its flute and flank surfaces. This paper examines the analysis of both flute and flank surface models and the evaluation of drill cutting angles. A new mathematical model for an arbitrary drill flute face is developed by sweeping the polynomial representation of the flute cross-sectional curve along the drill axis, with a helical movement. On the basis of the quadratic flank face, a relationship between the grinding and the geometrical design parameters of the flank face is also established. The vector analysis method is employed for the analysis of the cutting angles for various drill geometries. A comparison of the analytical results with the actual measured cutting angles of an example drill has shown that the average error is less than 5%.     

Practical and reliable carbide drill grinding methods based on a five-axis CNC grinder

The carbide drill is an important hole-machining tool. Modern processing solutions set higher requirements for the accuracy and efficiency of carbide drill manufacturing. This paper presents a detailed study of mathematical models of the spiral groove, conical flank, and cutter clearance and proposes three practical and reliable grinding methods using only one standard straight wheel. The spiral groove is ground by controlling three crucial structure parameters: the spiral angle, core diameter, and rake angle. The conical flank is ground by controlling the relief angle, chisel edge angle, and apex angle. The cutter clearance is ground by controlling the ridge width and clearance depth. With these schemes, the wheel position parameters can be computed conveniently and quickly using computer programming, overcoming the low calculation accuracy of empirical formulae and thereby enhancing the efficiency. Using the wheel position parameters, the NC codes applicable to five-axis CNC grinders can be obtained. Furthermore, the reliability of the proposed grinding methods can be verified through CAD simulation and practical manufacture on a five-axis CNC grinder.     

Effects of geometric structure of twist drill bits and cutting condition on tool life in drilling 42CrMo ultrahigh-strength steel

To investigate the influence of the geometric structure of coated cemented carbide twist drills on the drill tool life, drilling experiments of 42CrMo steel were carried out at various cutting parameters. The geometric structure parameters of the specially manufactured drill bits were designed by the multifactor orthogonal experiment method. The effects of cutting edge preparation, drill point geometry, and flute geometry on the tool wear were investigated by the range analysis and variance analysis. And their effects on chip pattern were also studied. Then the influence of cutting parameters on the tool life was investigated. Based on these investigations and extending the tool life, the optimized geometric structure was the honed cutting edge with a radius of 0.06 mm and conventional conical flank, and the corresponding cutting parameters were 80 m/min and 0.18 mm/rev. At last, the tool wear characteristics were discussed and the main wear mechanisms were abrasive wear, adhesive wear, coating exfoliation, and tipping.