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1.
Drilling of carbon composites using a one shot drill bit. Part II: empirical modeling of maximum thrust force 总被引:1,自引:0,他引:1
In order to extend tool life and improve quality of hole drilling in carbon composite materials, a better understanding of ‘one shot’ hole drilling is required. This paper describes the development of an empirical model of the maximum thrust force and torque produced during drilling of carbon fiber with a ‘one shot’ drill bit. Shaw's simplified equations are adapted in order to accommodate for tool wear and used to predict maximum thrust force and torque in the drilling of carbon composite with a ‘one shot’ drill bit. The mathematical model is dependent on the number of holes drilled previously, the geometry of the drill bit, the feed used and the thickness of the workpiece. The model presented here is verified by extensive experimental data. 相似文献
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Chenjun Wei Dejin HuKaizhou Xu Jun Ni 《International Journal of Machine Tools and Manufacture》2011,51(2):165-168
Micromachining using miniature metal bond grinding tools is widely used in microelectromechanical systems. However, dressing of these micro-tools is time-consuming and likely to damage the abrasives. In this paper, a novel dressing technique called electrochemical discharge dressing (ECDD) is presented. A dull micro-end grinding bit and an auxiliary electrode are connected to the cathode and anode of a power supply, respectively. The auxiliary electrode is immersed in an electrolyte, and the grinding face of the tool is in contact with the electrolyte surface. During dressing, metal bond on the tool-electrolyte interface is progressively removed subjected to electrochemical discharge effect, thus creating grain protrusion. Experiments were conducted to evaluate the dressing performance of ECDD in terms of surface morphology of the tool, grinding force and surface roughness of the workpiece. Experimental results show that abrasive grains on the tool protrude without observable damage. The normal grinding force and the surface roughness of the workpiece are reduced by half after dressing. 相似文献
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The thrust force and torque produced during drilling contain important information related to the quality of the hole and the wear of the drill bit [1]. In this paper, the force and torque produced during drilling of carbon fibre using a ‘one shot’ drill bit is investigated. The signals in the time domain were divided into stages and common problems and defects associated with each stage discussed. It is also shown how tool wear and thickness of the workpiece affect the thrust force and torque throughout the drilling process. The findings of this paper are used to develop a mathematical model of the maximum thrust force and torque as described on Part II of this paper and are a valuable reference for future optimisation of drilling carbon composites with a ‘oneshot’ drill bit. 相似文献
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Deep hole drilling processes, which differ significantly from conventional drilling processes, are relevant for a lot of different applications where holes with high length-to-diameter-ratios and very good qualities are necessary. This paper gives an overview of different methods, which are established to produce bore holes with demanding aspects related to diameter, length-to-diameter-ratio, bore hole quality, workpiece materials and complex internal contours. Beside the detailed explanation of the deep hole drilling methods and tools also the fundamentals of the deep hole drilling principle are explained and completely new developed figures and tables summarize the state of the art. In addition for the most important areas the latest results of process and tool development are included. 相似文献
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针对曲轴箱上挺杆孔直径小、位置深、尺寸精度高,各孔加工精度相同等特点,设计了工序比较集中的三工位钻扩铰组合机床,利用三工位转塔头实现钻、扩、铰三工步的转换,节约生产成本,避免定位误差;利用一套夹具装置对工件实行一次快速定位夹紧,避免了工件的重复定位误差;采用悬挂式活动钻模板,解决了细长刀杆刚度不足问题和刀具的定位、导向问题。利用该机床可实现工件快速装卸和可靠定位夹紧,可自动完成三个工位的工作循环,劳动强度低,生产效率高。 相似文献
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《CIRP Annals》1987,36(1):273-276
A new machining process, called mill-drilling has been developed, made up by a combination of deep hole drilling and Milling. The origin, the main characteristica of the process, the tools and the machine tools are being explained. A typical advantage of the mill-drilling process is the constant production of short chips even with tough workpiece materials. A special Problem of the mill-drilling tool is the dynamic behavior of the highly elastic miller drive. Some main points of influence on the dynamic tool load are shown and the results of the mill-drilling tool with and without vibrations. Advantages and disadvantages of the mill-drilling in comparison to conventional drilling processes are discussed. 相似文献
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Yi Li P. D. Funkenbusch S. M. Gracewski J. Ruckman 《International Journal of Machine Tools and Manufacture》2004,44(4):427-438
Wear induced changes in grinding tool profile have been studied for a CNC contour grinding process designed for the fabrication of precision optical components. Tool profile was measured experimentally by examining the “footprint” left by the tool when subsequently fed into a prepared surface. A numerical model was developed to predict detailed tool profiles as a function of the process parameters and total removal. Wear caused the development of approximately flat bevels on tools initially trued to a spherical shape, changing both the height and position of the lowest cutting point on the tool, with the potential to produce significant profile errors on the workpiece surface. The observation of approximately flat tool bevels was also used to develop an analytic solution for the tool shape evolution. With this analytic approximation contact height and width can be readily estimated and could be incorporated into an algorithm to adjust the tool path. 相似文献
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This paper presents a study of the effect of process parameters on production accuracy obtained through ultrasonic drilling
of holes in alumina based ceramics using silicon carbide abrasive. Production accuracy in ultrasonic drilling involves both
dimensional accuracy (hole oversize) and form accuracy (out-of-roundness and conicity). The parameters considered are workpiece
material, tool material, grit size of the abrasive, power rating and slurry concentration. Taguchi’s optimization approach
is used to obtain the optimal parameters. The significant parameters are also identified and their effect on oversize, out-of-roundness
and conicity are studied. The results obtained are validated by conducting the confirmation experiments. 相似文献
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为解决电解加工型孔的加工稳定性和形状精度等问题,建立了异形孔电解加工稳定过程中加工间隙数学模型,分析了工具阴极结构对加工区域和非加工区域的电场及其均匀性以及其对电流密度与加工效果的影响,通过优化工件结构改善了加工间隙内的电场分布,使工件形状精度显著提高,并进行相关试验对仿真结果进行验证。得出结论:在相同的电解加工参数下,工具电极的结构对工件的形状精度有着显著的影响,通过优化工具电极结构,改善加工间隙内的电场分布与电流密度,让加工间隙内的流场更为稳定,使工件侧壁垂直度提高,提高了电解加工的形状精度与加工稳定性。 相似文献
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Scott F. Miller Peter J. Blau Albert J. Shih 《International Journal of Machine Tools and Manufacture》2007,47(10):1636-1645
This study investigates the tool wear in friction drilling, a nontraditional hole-making process. In friction drilling, a rotating conical tool uses the heat generated by friction to soften and penetrate a thin workpiece and create a bushing without generating chips. The wear of a conical tungsten carbide tool used for friction drilling a low carbon steel workpiece is studied. Tool wear characteristics are quantified by measuring its weight change, detecting changes in its shape with a coordinate measuring machine, and making observations of wear damage using scanning electron microscopy. Energy dispersive spectrometry is applied to analyze the change in chemical composition of the tool surface due to drilling. In addition, the thrust force and torque during drilling and the hole size are measured periodically to monitor the effects of tool wear. Results indicate that the carbide tool is durable, showing minimal tool wear after drilling 11,000 holes, but observations also indicate the progressively severe abrasive grooving on the tool tip. 相似文献
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《CIRP Annals》2019,68(1):169-172
The effect of pulse current and tool immersion depth on gas film formation and its consequences on machining quality in the pulse electrochemical discharge machining (PECDM) of glass-fiber epoxy reinforced composite are studied. The frequency and duty cycle of the pulse current were controlled for discharging at no more than single spark per cycle. As compared to ECDM with DC current, the PECDM results in smaller hole diameter and smaller heat affected zone (HAZ). Also, lower tool immersion depth results in thinner gas film and smaller HAZ in the workpiece. 相似文献
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Core drilling at small diameters in carbon composite materials is largely carried out using diamond electroplated tools consisting of hollow shafts and simplistic geometries that are likely to work in an abrasional/rubbing mode for material removal. The paper reports a step change in the performance of small diameter core drilling by facilitating a shearing mechanism of the composite workpiece through the utilisation of a novel tool design. This has been achieved by laser producing core drills from solid polycrystalline diamond, incorporating controlled cutting edges where the geometries are defined. To evaluate the efficiency of the shearing vs. abrasion/rubbing cutting mechanisms, a critical comparison between the novel (defined cutting edges) and the conventional electroplated tools (randomly distributed micro-grains) has been made with reference to thrust forces, tool wear mechanisms and their influences on the hole quality (e.g. delamination, fibre pullout). This work has been augmented by studies using high-speed thermal imaging of the two tool types in operation. The examinations have shown that, based on the concept of defined cutting edges in solid diamond, there is the possibility to make significant improvements in core drilling performance, (ca. 26% lower thrust force, minimal tool surface clogging, lower drilling temperatures) resulting in improved cleanliness of fibre fracture and a reduced tendency of material delamination. 相似文献
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对近年来微细电解加工领域的研究现状和发展趋势进行了概述,包括微细电解加工的基础理论、微细电解加工技术和加工装置、影响因素与极间间隙检测控制,以及关键技术和今后的发展方向. 相似文献
17.
Generalized modeling of drilling vibrations. Part I: Time domain model of drilling kinematics, dynamics and hole formation 总被引:1,自引:1,他引:0
Jochem C. Roukema Yusuf Altintas 《International Journal of Machine Tools and Manufacture》2007,47(9):1455-1473
This two part paper presents a comprehensive exercise in modeling dynamics, kinematics and stability in drilling operations. While Part II focuses on the chatter stability of drilling in frequency domain, Part I presents a three-dimensional (3D) dynamic model of drilling which considers rigid body motion, and torsional–axial and lateral vibrations in drilling, and resulting hole formation. The model is used to investigate: (a) the mechanism of whirling vibrations, which occur due to lateral drill deflections; (b) lateral chatter vibrations; and (c) combined lateral and torsional–axial vibrations. Mechanistic cutting force models are used to accurately predict lateral forces, torque and thrust as functions of feedrate, radial depth of cut, drill geometry and vibrations. Grinding errors reflected on the drill geometry are considered in the model. A 3D workpiece, consisting of a cylindrical hole wall and a hole bottom surface, is fed to the rotating drill while the structural vibrations are excited by the cutting forces. The mechanism of whirling vibrations is explained, and the hole wall formation during whirling vibrations is investigated by imposing commonly observed whirling motion on the drill. The time domain model is used to predict the cutting forces and frequency content as well as the shape of the hole wall, and how it depends on the amplitude and frequency of the whirling vibration. The model is also used to predict regenerative, lateral chatter vibrations. The influence of pilot hole size, spindle speed and torsional–axial chatter on lateral vibrations is observed from experimental cutting forces, frequency spectra and shows good similarity with simulation results. The effect of the drill–hole surface contact during drilling is discussed by observing the discrepancies between the numerical model of the drilling process and experimental measurements. 相似文献
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M.B. Cai X.P. Li M. Rahman A.A.O. Tay 《International Journal of Machine Tools and Manufacture》2007,47(3-4):562-569
In cutting of brittle materials, experimentally it was observed that there is a ductile–brittle transition when the undeformed chip thickness is increased from smaller to larger than the tool cutting edge radius of the zero rake angle. However, how the crack is initiated in the ductile–brittle mode transition as the undeformed chip thickness is increased from smaller to larger than the tool cutting edge radius has not been fully understood. In this study, the crack initiation in the ductile–brittle mode transition as the undeformed chip thickness is increased from smaller to larger than the tool cutting edge radius has been simulated using the Molecular Dynamics (MD) method on nanoscale cutting of monocrystalline silicon with a non-zero edge radius tool, from which, for the first time, a peak deformation zone in the chip formation zone has been found in the transition from ductile mode to brittle mode cutting. The results show that as the undeformed chip thickness is larger than the cutting edge radius, in the chip formation zone there is a peak deformation depth in association with the connecting point of tool edge arc and the rake face, and there is a crack initiation zone in the undeformed workpiece next to the peak deformation zone, in which the material is tensile stressed and the tensile stress is perpendicular to the direction from the connecting point to the peak. As the undeformed chip thickness is smaller than the cutting edge radius, there is no deformation peak in the chip formation zone, and thus there is no crack initiation zone formed in the undeformed workpiece. This finding explains well the ductile–brittle transition as the undeformed chip thickness increases from smaller to larger than the tool cutting edge radius. 相似文献