大芯厚钻头横刃处参数优化实验

分析大芯厚钻头的结构特点,针对芯厚越大横刃长度越长、必须对横刃进行修磨这一特点,发现钻头的横刃修磨对其使用寿命有着重要的影响。对此进行两种不同的横刃修磨角度和两种不同的槽型的对比试验,在相同的加工参数下加工45钢,发现当钻头具有直线型刃槽型和横刃修磨角度为62°时,其综合性能相对较好。     

加工奥氏体不锈钢用钻头微观几何形状和涂层的优化

钻削奥氏体不锈钢的效果，除了与切削刃几何形状有关外，还与刀具涂层有关。 钻头的微观几何形状显著影响钻削效果 带有各种标准横刃修磨几何形状的麻花钻即将过时，取而代之的将是具有各种不同切削刃微观几何形状的钻头。在本研究中，试验钻头的刃口倒圆半径大致在7～14μm之间，其中有3支钻头在前刀面上增加了0．1mm的倒棱.     

硬质合金钻头刃磨裂纹产生的原因及其预防措施的研究

根据硬质合金材料"三高二低"的特性,可知硬质合金钻头在刃磨过程中极易产生裂纹。简述钻头的刃磨工艺,深入细致地研究了硬质合金钻头刃磨裂纹产生的各种原因,并提出了切实可行的预防措施。采用这些预防措施显著减少了该类钻头刃磨过程中裂纹的产生,对降低企业的生产成本具有重要意义。     

导流片斜锥孔的加工

介绍了导流片斜锥孔的加工方法及钻锥孔的锥形麻花钻头修磨方法     

提高钻头使用寿命探讨

通过对钻头进行修磨,选择适当的切削参数,可以提高钻头的耐用度和工件的表面质量.     

一种新型的钻头刃磨机

本文介绍一种新研制的钻头刃磨机。该机是用圆锥磨法的原理研制而成的,它不仅体积小,重量轻,而且调整方便,可刃磨出加工需要的顶角和后角。它的投入使用,可提高钻头的刃磨质量,从而获得明显的经济效益。     

钻尖结构对碳纤维复合材料制孔质量的影响

碳纤维复合材料在钻削加工中,容易产生毛刺、撕裂等缺陷。本文采用直径为6 mm的硬质合金钻头开展T300及T700碳纤维复合材料的钻削试验,研究钻头螺旋角、刃形和横刃结构对制孔质量的影响。研究结果表明:采用小进给量时,对孔出口质量影响程度最大的是刃型,而螺旋角和横刃的影响很小;采用大进给量时,对孔出口质量影响最大的是螺旋角,其次是刃型,横刃影响最小;直刃口钻头加工的孔出口质量明显优于凸刃口钻头;大螺旋角略优于小螺旋角;有无横刃的孔出口质量对比差异不显著。     

叉型叶根槽铣刀的重磨与检测探讨

大型汽轮机末级长叶根一般为七叉型叶根,为保证其严格的型线与尺寸精度要求,叶根槽铣刀一般要采用8片组合式正前角尖齿成型铣刀,但刀具用钝以后必须使用专用装置或设备修磨后刀面,由此带来了重磨和检测的难度。本文对叉型叶根槽铣刀的重磨与检测装置的原理、刃磨方法、检测手段进行了探讨。     

直纹回转双曲面--电镀CBN珩磨轮的一种新设计

介绍了CBN珩磨轮的一种新的工艺设计，以一般直纹回转面(单叶双曲面)作为砂轮的给定工作面廓形，对径向珩磨轮的修磨问题及设计方法进行了分析和研究。珩磨轮的刀齿面设计按径向珩齿法进行，采用三种方法刃磨(双曲面法，锥面法和近似法)，并对修磨工艺参数进行了优化。根据齿轮参数，用本方法设计的珩磨轮既可选用径向珩齿法加工鼓形齿，也可用纵向珩齿法加工修缘齿。     

加工不同材料时高速钢麻花钻的刃磨

高速钢麻花钻在加工不同材料时，客观上具有不同的加工条件，并且对钻头产生不同的影响，本文对此提出了在加工不同材料时，对钻尖部分要进行不同的刃磨，以提高钻头使用性能及孔加工质量；同时，从实用的角度提出其它一些方法和措施以保证钻头真正发挥其应有的效能。     

Effect of deviation on delamination by saw drill

Various cutting techniques are available to drill holes, but drilling is the most common way in secondary machining of composite materials owing to the need for structure joining. Twist drills are widely used in the industry to produce holes rapidly and economically. Since the twist drill has a chisel edge, increasing the length of a chisel edge will result in an increase in the thrust force generated. Whereas, a saw drill has no chisel edge; it utilizes the peripheral distribution of the thrust force for drilling. As a result, the saw drill can achieve better a machining quality in drilling composite laminates than twist drill. The deviation of cutting edge that occurs in saw drill would result in an increase of thrust force during drilling, causing delamination damage when drilling composite materials in particular. A comprehensive model concerning delamination induced by the thrust force of a deviation saw drill during drilling composite materials has been established in the present study. For a deviation saw drill, the critical thrust force that triggers delamination increases with increasing β. A lower feed rate has to be used with an increasing deviation saw drill in order to prevent delamination damage. The results agree with real industrial experience. A guide for avoiding the drill deviation during drill regrinding or drill wear has been proved analytically by the proposed model, especially when the deviation ratio (β) affects the critical thrust force. This approach can be extended to examine similar deviation effects of various drills.     

Mechanistic modeling of bone-drilling process with experimental validation

In this paper, an improved mechanistic model is developed to predict the thrust force and torque for bone-drilling operation. The cutting action at the drill point is divided into three regions: the cutting lips, outer portion of the chisel edge (the secondary cutting edges), and inner portion of the chisel edge (the indentation zone). Models that account for the unique mechanics of the cutting process for each of the three regions are formulated. The models are calibrated to bovine cortical bone material using specific cutting pressure equations with modification to take advantage of the characteristics of the drill point geometry. The models are validated for the cutting lips, the chisel edge, and entire drill point for a wide range of spindle speed and feed rate. The predicted results agree well with experimental results. Only the predictions for the drilling torque on the chisel edge are lower than the experimental results under some drilling conditions. The model can assist in the selection of favorable drilling conditions and drill-bit geometries for bone-drilling operations.     

麻花钻几何参数对不锈钢钻削性能影响的研究

采用ProE和Deform-3D软件分析了影响麻花钻钻411性能关健的几何参数,主要研究麻花钻横刃和顶角对不锈钢钻削过程中切削力、扭矩、刀具磨损的影响.介绍了缩短横刃长度和采用S形横刃螺旋面钻尖对不锈钢钻削力和扭矩的影响.重点分析了顶角影响主切削刃的长度、单位刃长的切削负荷、切削层中切削宽度与切削厚度的比例、切削中轴向力与扭矩、切屑形成与排屑情况.对于在钻削中,如何提高钻头的寿命,提高钻削加工的生产率和孔的加工质量具有重要的指导意义.     

A new mathematical model for multifacet drills derived by using angle-solid model

A new mathematical model for multifacet drills (MFD) is developed using angle-solid-block approach to find the relationship of design parameters. The function of chisel edge angle is defined as ψ=f(ρ′ ,τ ,α_r) in order that the uncertainty of chisel edge geometry determined by existed model can be avoided. The effects of the new mathematical model on the geometry of chisel edge and main cutting edge are shown in this paper. In addition, the new mathematical model has the potential of designing and researching for many tools.     

Conical flank twist drill points

Mathematical models of conical twist drill points usually require that the cutting edge of the drill be straight in three-dimensional space. This requirement restricts the clearance angle to undesirably small values near the chisel edge. By rotating the drill about its axis 5–10° before sharpening, the clearance angle near the chisel edge can be increased at the small penalty of having a slightly curved cutting edge.     

Mathematical model for helical drill point

Helical drill points provide a superior cutting performance in drilling operations, particularly in micro-hole drilling. This paper presents a comprehensive and straightforward method for the design of helical drill points. The proposed method has three particular features. Firstly, a mathematical model of the helicoid grinding surface is developed. This model allows the normal and tangential vectors of the abrasive wheel to be obtained explicitly. Secondly, the mathematical models of the flute and flank surfaces are integrated and therefore the cutting and chisel edges can be obtained by numerical calculation. Finally, the derivation of the model is straightforward and expresses the drill's characteristics (e.g. the semi-point angle, chisel edge, lip clearance angle, heel clearance, angle tool cutting edge inclination, normal rake angle and normal clearance angle) in accordance with all current international standards. The proposed model is capable of describing a wide range of helical drills. The methodology presented in this study facilitates the production of helical drills on a 6-axis CNC grinding machine.     

The effect of chisel length and associated pilot hole on delamination when drilling composite materials

Drilling-induced delamination often occurs both at the entrance and the exit of the workpiece during drilling of composite material. Investigators have studied analytically and experimentally that delamination in drilling can be correlated to the thrust force of the drill. With a pre-drilled pilot hole, the delamination can be reduced significantly. Early reference reported models of drilling-induced delamination, however, the effect of chisel edge length and pilot hole diameter on delamination is rarely discussed. The optimal range of chisel edge length with respect to drill diameter is derived in this paper.     

420B不锈钢牙骨凿表面激光淬火的数值模拟与组织性能

为了提高牙骨凿刃口硬度,延长使用寿命,利用ANSYS参数化设计在420B不锈钢牙骨凿表面进行激光淬火数值模拟,在此基础上进行激光淬火试验,并用光学显微镜、显微硬度计对刃口激光淬火后的显微组织和硬度进行分析。结果表明:在激光功率500 W,扫描速度960 mm/min时,仿真模型模拟得出淬火表面最高温度约1070 ℃。此工艺参数下淬火后刃口截面最高硬度达到57.1 HRC,平均硬度达到51.0 HRC,淬火效果较好。     

Drilling model for cutting lip and chisel edge and comparison of experimental and predicted results. III — drilling model for chisel edge

Observations through a transparent model of the chisel edge drilling into modelling clay indicate that on the region adjacent to the centerline, material is cut in a normal machining process by the rake face, and extruded under the clearance flank when the working clearance angle is positive. As the radius increases, the feed angle decreases and the working clearance angle changes from negative to positive, while the working rake angle changes from a positive (about 30°) to a large negative value (−60°). When the magnitude of the negative rake angle becomes greater than 45°, it is unlikely that machining will occur, and because of this a metal removal process akin to a wear process has been proposed for this region. These processes are considered in the development of a machining model for the chisel edge of a drill.     

The location of the maximum temperature on the cutting edges of a drill

This study analyzes the temperature profile along the cutting edges of a drill and describes how the temperature on the chisel edge can exceed the temperature on the primary cutting edges. A finite element model predicts the temperature distribution in the drill, where the heat flux loads applied to the finite element model are determined from analytical equations. The model for the heat flux loads considers both the heat generated on the shear plane and the heat generated on the rake face of the tool to determine the amount of heat flowing into the tool on each segment of the cutting edges. Contrary to the conventional belief that the maximum temperature occurs near the outer corner of the drill, the model predicts that the maximum temperature occurs on the chisel edge, which is consistent with experimental measurements of the temperature profile.