新型Ta-C涂层铣刀切削性能研究

目的研究Ta-C涂层刀具与普通类金刚石涂层刀具切削2A50铝合金时的性能对比。方法通过实验比较两刃、四刃Ta-C涂层铣刀和两刃、四刃普通类金刚石涂层铣刀,在干式切削条件下切削2A50铝合金的性能。通过相同切削条件下刀具切削距离的长短,比较刀具的使用寿命,并在显微镜下观察切屑的表面形貌,用表面粗糙度仪检测铝合金表面的粗糙度。结果两刃Ta-C涂层铣刀干式切削铝合金时的使用寿命最长,切削距离为116 m。Ta-C涂层铣刀与普通类金刚石涂层铣刀加工工件的表面粗糙度总体呈上升趋势,两刃Ta-C涂层铣刀加工出来的工件表面质量较好,工件表面粗糙度均值为0.692μm。结论相同刀刃数量且结合力良好的涂层铣刀相比较,Ta-C涂层铣刀较普通类金刚石涂层铣刀加工出来的工件表面粗糙度平均值低,同种涂层加工得到的切屑表面微观形貌无明显差别。Ta-C涂层铣刀与普通类金刚石涂层铣刀切削铝合金时,抑制粘刀效果都十分明显,但Ta-C涂层铣刀效果更优。     

刀具前角对聚晶金刚石刀具磨损过程的影响

为了研究刀具前角对聚晶金刚石刀具磨损过程的影响,采用两种不同前角的聚晶金刚石刀具进行各向同性热解石墨切削加工试验,对刀具磨损过程、磨损机理和表面加工质量进行了分析对比研究。通过对试验结果的研究分析表明:两种不同前角的聚晶金刚石刀具磨损都主要发生在后刀面,切削刃都出现了崩刃现象。刀具磨损区域都出现了平行沟槽式的磨损形貌,但是出现的时间存在明显差异。磨粒磨损是这两种不同前角的聚晶金刚石刀具的主要磨损机理,前角为5°的聚晶金刚石的磨损机理还包括冲蚀磨损。与前角为5°的聚晶金刚石刀具相比,前角为-20°的聚晶金刚石刀具具有较好切削加工性能。     

刀具角度的作用

无论用于何种加工,刀具都有三个主要角度：前角、切入角和后角。其作用如下：①前角：影响切削力、切削刃强度和切屑流动杼陛;②切入角（导程角）：控制切削力的方向,有效减薄切屑,保护切削刃最薄弱的部位;③后角：确保刀具切削时不会与工件发生摩擦。     

提高铣刀铣削42CrMo寿命的试验研究

42CrMo为难加工材料,改进铣刀结构参数和材质,提高铣刀加工难加工材料的寿命.通过对加工出现崩刃的铣刀进行分析,提出改进措施.以42CrMo作为被加工工件,通过优化铣刀的后角和前角,分别用X和Y刀具材料,在数控立式铣床上做实验.结果表明:铣刀圆周后角由8°减小到6°,槽前角由12°减小到8°,铣刀寿命相应提高.刀具材料由X换成Y,铣刀寿命大大提高,提高程度比改变刀具角度大.     

铝基碳化硅复合材料刀具精密铣削过程中的磨损性能

选取YG8-1、YG8-2、YT15和YG6X等4种不同材料的三刃硬质合金铣刀及两刃金刚石铣刀,对碳化硅体积分数为50%的铝基碳化硅复合材料进行切削加工,研究不同刀具的磨损性能。结果表明,金刚石刀具的磨损量低于硬质合金的磨损量。硬质合金刀具中,YT15的磨损最为严重,YG6X的磨损量最小。     

不同刃数铣刀螺旋铣孔CFRP/Ti叠层材料研究

为研究不同刃数铣刀螺旋铣孔的情况,分别使用2刃铣刀与4刃铣刀对CFRP/Ti叠层材料进行一体化螺旋铣孔试验。在相同的切削参数条件下,对两种铣刀螺旋铣孔的切削力、刀具后刀面磨损长度、CFRP入口质量及Ti出口质量进行了测量。结果表明:随着叠层材料加工的进行,刀具正常磨损时,刃数越少的铣刀后刀面磨损越快;刀具剧烈磨损后,刃数越多的铣刀,后刀面磨损越迅速。刃数越多的铣刀所产生的轴向推力及径向力越大。在进出口加工质量上,2刃铣刀抑制了Ti出口的飞边现象,4刃铣刀对CFRP的入口毛刺起到抑制作用。     

刀具几何参数对残余应力的影响分析

利用有限元法分析了残余应力与刀具前角和切削刃钝圆半径的关系.结果表明:在前角一定变化范围内,随着前角的增加,工件表面产生的残余拉应力的值先增大后减小,残余拉应力层的厚度与刀具前角关系不明显;残余应力随着切削刃钝圆半径增大而减小,但残余应力层的厚度增大.     

Ti(C,N)基金属陶瓷刀具切削加工有限元模拟

介绍了本课题组研制的一种新的刀具材料--T(iC,N)基金属陶瓷的成分组成及其力学性能;基于大变形-大应变理论、增量理论以及更新拉格朗日算法、采用几何断裂分离准则,建立了二维弹塑性金属正交切削有限元模型,对金属正交切削过程进行了数值模拟;改变刀具前角,得出在不同的刀具前角下T(iC,N)基金属陶瓷刀具在正交切削过程中切削力以及刀具后刀面等效应力变化;分析了切削力、刀具表面等效应力对刀具磨损的影响;模拟结果与相关研究的实验数据吻合。本文的研究为后期研制新的刀具材料提供了理论依据,降低实验成本。     

瓦尔特：刀具切削刃制备的精密测量

德国瓦尔特（Walter）公司开发的HelicheckProandPlus测量机现在已具备了对刀具的切削刃制备（即切削刃圆弧半径）进行精密测量的功能。刀具的切削刃制备作为延长刀具寿命的一种重要方法,已得到日益广泛的应用,但迄今为止,对切削刃制备的精密形貌进行测量还需要使用昂贵的专用测量仪器。为了解决这一问题,瓦尔特的Helicheck测量机在原有测量功能（包括刀具的几乎所有几何形貌特征,如刀尖圆弧半径、前角、螺旋角、径跳、倒棱宽度等）的基础上,又增加了自动测量切削刃圆弧半径的功能。该测量机利用新增的照相机（放大倍数1000倍）和分路LED（发光二极管）光束（安装在专用的、CNC控制的旋转轴上）,能够对最小至5微米的切削刃圆弧半径进行测量。     

考虑多种因素的流屑角求解模型

切削加工中切屑流向的预报是通过流屑角的计算完成的．本文基于Stabler法则和等效刀刃思想，综合考虑了刀具的前角、刃倾角、主偏角、刀片相邻刃设计夹角、刀尖圆弧半径、进给量、切削深度以及被加工材料性质等八个因素建立了计算机求解流屑角的数学模型．并以此分析了以上因素对流屑角的影响规律．     

拐角铣削力建模与MATLAB仿真研究

在模具型腔的加工过程中,拐角铣削加工是不可避免的,其中铣削力是影响工件加工质量和刀具寿命的重要因素。以90°拐角铣削加工为例,利用微元法建立了以刀具参数、进给速度和刀具旋转角度为参变量的铣削力模型,基于MATLAB的GUI模块开发了拐角铣削力仿真软件并进行仿真实验。将仿真结果与采用测力仪测量的结果进行比较,结果显示:仿真结果能有效预测拐角铣削力,为实际切削加工提供参考和理论支撑。     

An improved process simulation system for ball-end milling of sculptured surfaces

A simulation system is developed in this paper, which deals with the geometry and mechanics of machining with ball-end milling cutters. The geometry of the workpiece, the cutter, and the cutter/workpiece engagement is modeled using a geometric simulation system. This module uses a commercial solid modeler (ACIS) as a geometric engine and automatically extracts the critical geometric information required for the physical simulation system. To calculate the instantaneous cutting forces, a new mechanistic force model is developed. This force model takes into account the variations of the cutting coefficients along the cutting edge, and considers the variations of the rake angle and the chip flow direction on the rake face. The calibration of the developed model is performed for half-immersion ball-end milling operation. The applicability of the developed system is verified experimentally for various up-hill angles. It is shown that as the up-hill angle increases, the ball-nose tip engagement decreases which in turn significantly affects the magnitude of the resultant forces. Also, lower cutting forces and powers are experienced if cutting with the vicinity of the tool tip is avoided.     

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。     

A study of high efficiency face milling tools

A new predictive force model for a single-tooth face milling cutter with a chamfered main cutting edge has been derived. Machining tests has been conducted for fly cutting with a chamfered main cutting edge tools on plane surfaces. An S45C medium carbon plate has been used as the workpiece matrial. Force data from these tests were used to estimate the empirical constants of the mechanical model and to verify its prediction capabilities. The results show a good agreement between the predicted and measured forces.Since tool manufacturers does not provide tools with selected combinations of chamfered main cutting edge, radial angle, axial angle and inclination angles, tool holders manufactured in-house were used in the tests. The tips were prepared to the required geometry using a tool grinder.     

Cutting force prediction of sculptured surface ball-end milling using Z-map

The cutting force in ball-end milling of sculptured surfaces is calculated. In sculptured surface machining, a simple method to determine the cutter contact area is necessary since cutting geometry is complicated and cutter contact area changes continuously. In this study, the cutter contact area is determined from the Z-map of the surface geometry and current cutter location. To determine cutting edge element engagement, the cutting edge elements are projected onto the cutter plane normal to the Z-axis and compared with the cutter contact area obtained from the Z-map. Cutting forces acting on the engaged cutting edge elements are calculated using an empirical method. Empirical cutting mechanism parameters are set as functions of cutting edge element position angle in order to consider the cutting action variation along the cutting edge. The relationship between undeformed chip geometry and the cutter feed inclination angle is also analyzed. The resultant cutting force is calculated by numerical integration of cutting forces acting on the engaged cutting edge elements. A series of experiments were performed to verify the proposed cutting force estimation model. It is shown that the proposed method predicts cutting force effectively for any geometry including sculptured surfaces with cusp marks and a hole.     

Modelling and simulation of chatter in milling using a predictive force model

A predictive time domain chatter model is presented for the simulation and analysis of chatter in milling processes. The model is developed using a predictive milling force model, which represents the action of milling cutter by the simultaneous operations of a number of single-point cutting tools and predicts the milling forces from the fundamental workpiece material properties, tool geometry and cutting conditions. The instantaneous undeformed chip thickness is modelled to include the dynamic modulations caused by the tool vibrations so that the dynamic regeneration effect is taken into account. Runge–Kutta method is employed to solve the differential equations governing the dynamics of the milling system for accurate solutions. A Windows-based simulation system for chatter in milling is developed using the predictive model, which predicts chatter vibrations represented by the tool-work displacements and cutting force variations against cutter revolution in both numerical and graphic formats, from input of tool and workpiece material properties, cutter parameters, machine tool characteristics and cutting conditions. The system is verified with experimental results and good agreement is shown.     

Dynamic response analysis in end milling using pre-twisted beam finite elements

This paper develops an analytical model for estimating the dynamic responses in end milling, i.e. dynamic milling cutter deflections and cutting forces, by using the finite-element method along with an adequate end milling-cutting force model. The whole cutting system includes the spindle, the bearings and the cutter. The spindle is modelled structurally with the Timoshenko-beam element, the milling cutter with the pre-twisted Timoshenko-beam element due to its special geometry, and the bearings with lumped springs and dampers. Because the damping matrix in the resulting finite-element equation of motion for the whole cutting system is not one of proportional damping due to the presence of bearing damping, the state-vector approach and the convolution integral is used to find the solution of the equation of motion. To assure the accuracy of prediction of the dynamic response, the associated cutting force model should be sufficiently precise. Since the dynamic cutting force is proportional to the chip thickness, a quite accurate alogorithm for the calculation of the variation of the chip thickness due to geometry, run-out and spindle-tool viration is developed. A number of dynamic cutting forces and tool deflections obtained from the present model for various cutting conditions are compared with the experimental and analytical results available in the literature, good agreement being demonstrated for these comparisons. The present model is useful, therefore, for the prediction of end milling instability. Also, the tool deflections obtained using the pre-twisted beam element are found to be smaller than those obtained using the straight beam element without pre-twist angle. Hence neglecting the pre-twist angle in the structural model of the milling cutter may overestimate the tool deflections.     

Cutting force prediction in ball end milling of sculptured surface with Z-level contouring tool path

This paper presents an approach to predict cutting force in 3-axis ball end milling of sculptured surface with Z-level contouring tool path. The variable feed turning angle is proposed to denote the angular position of feed direction within tool axis perpendicular plane. In order to precisely describe the variation of feed turning angle and cutter engagement, the whole process of sculptured surface milling is discretized at intervals of feed per tooth along tool path. Each segmented process is considered as a small steady-state cutting. For each segmented cutting, the feed turning angle is determined according to the position of its start/end points, and the cutter engagement is obtained using a new efficient Z-map method. Both the chip thickness model and cutting force model for steady-state machining are improved for involving the effect of varying feed turning angle and cutter engagement in sculptured surface machining. In validation experiment, a practical 3-axis ball end milling of sculptured surface with Z-level contouring tool path is operated. Comparisons of the predicted cutting forces and the measurements show the reliability of the proposed approach.     

Mechanics and dynamics of general milling cutters.: Part I: helical end mills

A variety of helical end mill geometry is used in the industry. Helical cylindrical, helical ball, taper helical ball, bull nosed and special purpose end mills are widely used in aerospace, automotive and die machining industry. While the geometry of each cutter may be different, the mechanics and dynamics of the milling process at each cutting edge point are common. This paper presents a generalized mathematical model of most helical end mills used in the industry. The end mill geometry is modeled by helical flutes wrapped around a parametric envelope. The coordinates of a cutting edge point along the parametric helical flute are mathematically expressed. The chip thickness at each cutting point is evaluated by using the true kinematics of milling including the structural vibrations of both cutter and workpiece. By integrating the process along each cutting edge, which is in contact with the workpiece, the cutting forces, vibrations, dimensional surface finish and chatter stability lobes for an arbitrary end mill can be predicted. The predicted and measured cutting forces, surface roughness and stability lobes for ball, helical tapered ball, and bull nosed end mills are provided to illustrate the viability of the proposed generalized end mill analysis.     

基于剪切增稠液的高速钢铣刀刃口修整

为研究剪切增稠抛光液对铣刀刃口的影响,以四刃高速钢平头立铣刀为研究对象,对高速钢刀具进行修整,测量铣刀刃口半径,并观测铣刀前刀面、后刀面以及刃口形貌。试验结果表明:修整后,铣刀刃口半径减小,但由于不同切削刃初始状态不同,刃口半径减小的程度不同,最大变化量为7.5 μm,最小变化量为0.4 μm;修整试验只是针对铣刀刃口进行修整,铣刀的前、后刀面无明显变化,磨削痕迹并没有去除;磨料粒度对修整效果有一定影响,a组、b组和c组碳化硅STF试验组修整后,平均刃口半径分别减小4.6、3.6和1.9 μm,磨粒尺寸越大,铣刀刃口半径变化越明显。