岩溶发育区复合地层盾构刀具选型研究与应用

岩溶发育区复合地层地质条件复杂,采用盾构法施工风险高,易出现刀具异常失效等问题。为此,分析该类地层造成刀具异常失效的主要地质风险因素,确定适用于岩溶发育区复合地层的主切削刀具类型。采用模糊理论进行刀具选型,运用刀具综合评判方法得到最终刀具选型方案,形成一套适用于岩溶发育区复合地层盾构刀具选型方法。应用该方法对徐州地铁2号线周庄站-七里沟站区间盾构进行刀具配置,工程应用表明该方法具备可行性。     

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。     

纳米TiN改性金属陶瓷刀具的磨损性能

Ti(C,N)基金属陶瓷由于具有优良的综合性能因而被广泛用作刀具材料。本文探讨了纳米 Ti N对 Ti C基金属陶瓷刀具显微组织的影响 ;还研究了它与 Ti(C,N)基金属陶瓷刀具 (cermetμm,下同 )及 YG8刀具在切削灰铸铁时的磨损曲线及磨损机理。结果表明 ,纳米 Ti N改性 Ti C基金属陶瓷刀具 (cerm etnm,下同 )的效果显著 ;与 cermetμm刀具及 YG8刀具相比 ,cermetnm刀具具有更高的寿命与耐磨性 ;崩刃是 cermetnm刀具主要的失效形式     

新型刀具材料和纳米涂层刀具在干切削中的应用研究

在干切削中,刀具遇到的突出问题是严重的摩擦和高温。本文研究了新型陶瓷刀具材料和纳米涂层刀具,并进行了相应的试验,试验结果表明新型陶瓷刀片具有良好的抗机械冲击和热冲击性能,以及极高的耐磨性和抗破损能力,是用于干切削的理想刀具。随着新型刀具材料的出现,再伴以刀结构的相应改变以及涂层新技术的发展,可以有效提高干切削刀具的耐用度,使干切削像湿切削一样在生产中顺利进行。     

复合地层中不同刃形滚刀与岩石接触行为研究

目的 滚刀截面形状即刃形对滚刀综合性能影响显著,研究不同刃形的滚刀在复合地层中的载荷变化特点,把握各型滚刀应用于复合地层时的优势与劣势,对于减少滚刀失效、降低刀盘偏载具有重要指导意义。方法 通过滚刀破岩试验获取和对比3种刃形的滚刀(平顶、圆顶和螺旋槽滚刀)在软硬复合地层中的切削力、破岩体积等关键指标,同时建立滚刀破岩有限元数值模型,探究滚刀刃形影响其切削岩石性能的机理和规律。结果 在复合地层中工作时,平顶滚刀所需的法向力均值最高,其余滚刀则相近。这是由于圆顶和螺旋槽滚刀破岩时仅有部分表面参与接触,接触面积均小于平顶滚刀,应力集中效应明显,从而降低破岩法向力。螺旋槽滚刀在切削不同强度岩石时的法向力差距最小;圆顶滚刀的法向力标准差的值最小。3种滚刀均形成了粉末状和片状岩石碎片,平顶和圆顶滚刀形成的岩石碎片总体积相近而螺旋槽滚刀略低。结论 复合地层软硬岩强度相差较大时,可选用螺旋槽滚刀以减轻刀盘偏载;硬岩部分强度较高时,推荐选用圆顶滚刀,以减小切削力和载荷冲击。     

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.     

调直切断机切断系统设计与分析

针对广东省东莞某公司当前生产的高精度线材存在端部切口质量较差的问题,在分析现有锤击式调直切断机的基础上,针对其切断系统进行一种快换刀具切断模及切断液压系统的设计,并利用AMESim液压仿真软件对其切断效果进行仿真分析。结果表明:新的快换刀具切断模机构可有效解决切断时刀具口径与线材直径不一致而导致的线材端口质量问题;采用液压式代替锤击式的切断方式,通过液压夹紧机构使切断模切断线材时能随线材运动,可有效解决线材断面产生毛刺、弯曲变形、倾斜等缺陷问题。     

Mechanics and dynamics of general milling cutters. Part II: inserted cutters

Inserted cutters are widely used in roughing and finishing of parts. The insert geometry and distribution of inserts on the cutter body vary significantly in industry depending on the application. This paper presents a generalized mathematical model of inserted cutters for the purpose of predicting cutting forces, vibrations, dimensional surface finish and stability lobes in milling. In this paper, the edge geometry is defined in the local coordinate system of each insert, and placed and oriented on the cutter body using the cutter's global coordinate system. The cutting edge locations are defined mathematically, and used in predicting the chip thickness distribution along the cutting zone. Each insert may have a different geometry, such as rectangular, convex triangular or a mathematically definable edge. Each insert can be placed on the cutter body mathematically by providing the coordinates of the insert center with respect to the cutter body center. The inserts can be oriented by rotating them around the cutter body, thus each insert may be assigned to have different lead and axial rake angles. By solving the mechanics and dynamics of cutting at each edge point, and integrating them over the contact zone, it is shown that the milling process can be predicted for any inserted cutter. A sample of inserted cutter modeling and analysis examples are provided with experimental verifications.     

立铣刀断屑槽对切削性能影响规律试验研究

采用析因试验法研究断屑槽结构的制备对整体式立铣刀切削性能的影响。选取2把断屑槽分布不同的刀具,以铣刀主轴转速、径向切削深度、每齿进给量为主要因素,建立正交铣削试验。结果表明：断屑槽分布密集的铣刀适合用于加工精度要求不高的零件;断屑槽分布稀释的铣刀,适合用于半精加工要求的工件;对比分析切屑形貌和表面质量,得到用断屑槽分布稀疏的刀具铣削工件时可获得较好的表面质量。     

铣削大理石切削参数对PCD刀具磨损的影响

目的探索PCD刀具磨损机理,以延长刀具使用寿命。方法设计正交试验,研究不同加工参数切削大理石对刀具磨损的影响情况。分析主轴转速、进给速度与切削深度对PCD刀具磨损量的影响规律,以优化切削参数来减小刀具磨损量。根据经验公式,建立单位时间刀具磨损量和固定行程磨损量模型。通过对试验过程刀具振动情况记录,结合刀具实际磨损情况,给出了刀具磨损等级。结果主轴转速的提高可以减少刀具磨损量,进给速度的增大会加剧刀具磨损,而切削深度小于1 mm时,其对刀具磨损量的影响很小,但切削深度大于1 mm时,继续增大切削深度会使刀具快速磨损。利用预测模型能够很好地对刀具磨损情况进行预判,根据磨损等级,得出刀具与机床发生共振时磨损最为严重,在刀具表面产生了明显的犁沟、磨损以及金刚石颗粒脱落。结论在实际加工中,通过提高主轴转速、降低进给速度以及减小切削深度有助于增强刀具的耐用度,避开共振切削参数可以有效降低刀具磨损,主轴转速、进给速度、切削深度分别为12000r/min、500 mm/min、0.5 mm时的切削效果较佳,有最小的刀具磨损量。     

金属陶瓷刀具切削性能的研究

本文研究了纳米TiN改性的TiC基金属陶瓷刀具和超细晶Ti(C,N)基金属陶瓷刀具切削正火态45#钢的切削性能,尝试用SPSS11.5软件对正交试验的数据进行分析。结果表明,这两种刀具的最佳切削条件均为vc=200m/min,ap=0.3mm,f=0.1mm/r。最后分析了它们切削45#钢的磨损机理。     

Numerical simulation and prediction of cutting forces in five-axis milling processes with cutter run-out

Radial cutter runout is a common issue in milling processes and has a direct effect on milling stability due to variations of resulting chip load and forces. This paper presents a new method to effectively model and predict the instantaneous cutting forces in 5-axis milling processes with radial cutter runout based on tool motion analysis. First, the undeformed chip thickness model taking runout effect into account is established under continuous change of cutter axis orientation by means of the sweep traces of cutter edges. Second, the engaged cutting edge is determined and cutting coefficients are subsequently calibrated. Finally, the method of identifying runout parameters from the measured cutting forces is proposed, and mechanistic method is then applied to predict the cutting force. Since this method is completely based on the relative motion analysis of tool-part, it can reduce the prediction errors of cutting forces effectively and is suitable for generic rotation cutters. Several validation examples are given under different cutting conditions to prove its effectiveness and accuracy. The results reveal that the developed method can predict the cutter forces with a high accuracy and has the ability to be used in simulations and optimizations of five-axis machining.     

An image detection approach to NC rough-cut milling from solid models

This paper presents a method of converting information from a CAD solid model into a form suitable for CAM operation. The rough machining of a cavity into a block is used to illustrate the working of the system. This example was chosen because the machining of cavities presents difficulties as outlined below and rough machining involves the removal of more material than finish machining and therefore is of more economic significance in a production process. A three-axis NC miller is used to cut the cavity which has depth, requiring material to be removed in layers. A computer-based image detection method is used for cutter-path generation and models that contain planar surfaces, general quadratic surfaces, B-spline surfaces and compound surfaces can be treated. The B-rep solid object is transformed into an image as a grid-height model, allowing a three-dimensional object to be approximated by a two-dimensional spatial array. The cutter location (CL) data file is automatically generated from this spatial array. The height change of stock material in each grid is recorded in a two-dimensional array during the machining process and is utilized as an image for further roughing and verification. Efficient machining procedures are obtained by an analysis of cutting simulation, utilizing large cutter sizes for simple shaped portions in the first stage of roughing and then using small cutter sizes for complex portions and to remove uncut material left by the large cutters in a fine roughing operation. This approach allows a three-dimensional cutter path problem to be reduced to one of two dimensions which is solved by image detection of cutting attributes.     

Peripheral milling conditions for improved dimensional accuracy

Peripheral milling with flexible helical cutters is analyzed and modelled. The end mill is modelled as a cantilevered beam clamped to the collet with linear springs. Cutting forces and resulting tool deflection marks on the surface are analytically expressed. It is shown that by proper selection of cutting conditions, the material removal rate can be increased significantly without sacrificing the dimensional accuracy of the finished product. A method of identifying optimal feedrate and width of cut for given cutter dimensions and cutting constants is presented with experimental verification.     

不同斧型钻齿切削刃角下的破岩方式

为进一步理解斧型 PDC钻齿破岩机理,建立PDC钻齿破岩的3D有限元模型,对3种不同切削刃夹角的斧型PDC钻齿破岩方式开展对比研究。结果表明:与150°和165°的钻齿相比,135°的斧型钻齿受到的剪切力和切削力更小,从而具有更高的破岩效率。在相同的后倾角、相同的切削深度和相同的切削力下,165°斧型钻齿切削力波动较小,稳定性更高。与立式车床上的实验数据相比,仿真结果与实验结果总体趋势一致,误差在可接受范围内。      

PVD涂层刀具高速铣削CoCrMo合金的性能研究

目的为了提高涂层硬质合金刀具的切削性能,研究了物理气相沉积PVD法制备的涂层硬质合金铣刀在高速干式环境下的铣削性能。方法采用阴极电弧技术制备了TiN、TiAlN以及TiAlSiN涂层硬质合金铣刀刀头,通过一同沉积涂层的硬质合金圆片,间接测量得出涂层的显微硬度、厚度和平均摩擦系数,并以CoCrMo合金为切削对象,进行了PVD涂层与无涂层刀具高速铣削下的对比试验。结果TiAlSiN显微硬度最高达3800HV,摩擦系数达0.3,TiAlN涂层平均膜厚为2μm,间接测得TiN、TiAlN以及TiAlSiN涂层的结合力依次为60、58、42N。在三者的切削性能中,TiAlSiN涂层的切削性能比TiAlN和TiN涂层的好,同等切削参数时,TiN刀具的高速铣削时间最短,TiAlSiN涂层的平均磨损值为0.1895,TiN的平均磨损值为0.3047。结论涂层中添加Al、Si,极大地提高了刀具的使用性能,改善了刀具切削过程中的耐磨性、红硬性,极大地延长了刀具的使用寿命。TiAlSiN涂层的硬度高,耐磨损性好,切削性能好,适合高速铣削加工。     

刀片材质对半钢轧辊切削性能的影响

对５种不同刀片材质的刀具进行切削试验,研究了刀片的硬度、抗弯强度和红硬性对半钢轧辊切削工具的切削量及耐用度等性能的影响,得出Ｊ１１材质的刀具综合性能好,适于切削半钢轧辊。     

Static rigid force model for 3-axis ball-end milling of sculptured surfaces

Static rigid force model is used to estimate cutting forces of sculptured surface in a straightforward way, without considering tool deflection, machine tool dynamic behavior and any vibration effects. Two programs were used for calculations, “ACIS” the 3-D geometric modeler and “VISUAL BASIC”. Two programs were edited and used to perform the calculations, the scheme program to model the work piece, tool and cutting edge and to obtain the geometric data and the VISUAL BASIC program design to use ACIS geometric data to calculate the cutting forces. The engaged part of the cutting edge and work piece is divided into small differential oblique cutting edge segments. Friction, shear angles and shear stresses are identified from orthogonal cutting database available in literature. The cutting force components, for each tool rotational position, are calculated by summing up the differential cutting forces. Laboratory tests were conducted to verify the predictions of the model. The work pieces were prepared from CK45 steel using an insert-type ball-end cutter. No coolant was used in any of the experimental works. The cutting forces predicted have shown good agreement with experimental results.     

Machine ensemble approach for simultaneous detection of transient and gradual abnormalities in end milling using multisensor fusion

In a fully automated manufacturing environment, instant detection of the cutting tool condition is essential for the improved productivity and cost effectiveness. This paper studies a tool condition monitoring system (TCM) via machine learning (ML) and machine ensemble (ME) approach to investigate the effectiveness of multisensor fusion technique when machining 4340 steel with multilayer coated and multiflute carbide end mill cutter. In this study, 135 different features are extracted from multiple sensor signals of force, vibration, acoustic emission and spindle power in the time and frequency domain by using data acquisition and signal processing module. Then, a correlation-based feature selection technique (CFS) evaluates the significance of these features along with machining parameters collected from machining experiments. Next, an optimal feature subset is computed for various assorted combinations of sensors. Finally, machine ensemble methods based on majority voting and stacked generalization are studied for the selected features to classify not only flank wear but also breakage and chipping. It has been found in this paper that the stacked generalization ensemble can ensure the highest accuracy in tool condition monitoring. In addition, it has been shown that the support vector machine (SVM) outperforms other ML algorithms in most cases tested.     

YG8硬质合金微织构刀片的切削性能研究

通过摩擦磨损试验初定表面微织构参数,在此基础上制备了沟槽型微织构,并对TC4钛合金进行了正交切削试验,优化了微织构参数,研究了微织构深度、宽度与间距在有切削液润滑下对YG8刀具切削性能的影响。试验结果表明:表面微织构对于切削力影响不大,但可明显减小进给抗力,因而降低摩擦因数,改善刀屑间的摩擦状况,减缓刀片表面磨损。最多可降低19. 20%的摩擦因数并降低31. 8%的后刀面磨损。后刀面加工表面微织构会降低刀刃附近强度,造成更大的磨损。