【作者】 李增强；

【导师】 董申； 孙涛；

【作者基本信息】 哈尔滨工业大学 ， 机械制造及其自动化， 2008， 博士

【摘要】 超精密切削加工作为超精密加工技术中的代表性技术,现已成为衡量一个国家制造水平高低的重要标志。实现超精密切削加工,不仅需要超精密的切削机床、高精度的检测仪器和超稳定的加工环境,还需要进行切削加工用的高精度圆弧刃金刚石刀具。美日等国高精度圆弧刃金刚石刀具的水平已能达到刃口钝圆半径(锋利度)10nm以内,刀尖圆弧圆度50nm以内。国内高精度刀具的刃口钝圆半径已接近该先进水平,但刀尖圆弧圆度还存在巨大的差距。因此,解决高精度圆弧刃金刚石刀具刀尖圆弧的研磨问题成为当务之急。金刚石晶体具有很强的各向异性,不同的晶面上乃至同一晶面不同方向上的机械性能差异明显。在圆弧刃刀具的刀尖圆弧上,各段圆弧所处的晶面不同,使得各段圆弧存在迥然不同的磨削性能。如果还是使用简单的圆弧研磨方法,研磨的效率必然非常低下。但目前还没有行之有效的模型来描述刀尖圆弧上材料的磨削性能。加之现有研磨设备和研磨工艺存在的诸多缺陷,使得刀尖圆弧的研磨很难达到较高的精度。因此本文从晶体学入手,对圆弧刃金刚石刀具刀尖圆弧的研磨机理、研磨设备及检测技术等展开系统的研究。具体的研究内容包括以下几个方面:首先运用分子动力学模拟的手段,结合周期键链PBC理论解释了金刚石刀具机械研磨过程中材料去除的微观机理。这是首次在原子的尺度上从晶体学的角度对金刚石刀具机械研磨过程做出的微观解释。该微观解释为金刚石刀具刀尖圆弧的机械研磨奠定了理论基础。并依此建立了评价金刚石晶体各晶面中任意方向研磨难易程度的PBC模型。随后进行的材料去除率试验很好得证实了该模型的正确性。其次在PBC模型的基础上,建立了以{100}和{110}晶面为前刀面的金刚石刀具刀尖圆弧上材料去除率比值模型。首次使用数学模型定量地描述了刀尖圆弧上材料的磨削性能。该模型为高效低成本研磨优质圆弧刃金刚石刀具提供了理论依据。并根据该模型得出了不同前刀面刀具刀尖圆弧的优选研磨方向及优选的刀具晶面组合R(110)F(110)。结合材料去除量公式,提出了适于刀尖圆弧研磨的变研磨压力和变研磨时间两种研磨方法。然后在总结现有圆弧刃金刚石刀具研磨机缺点的基础上,使用Pro/Engineering自顶向下设计了一台新型的圆弧刃金刚石刀具研磨机。该研磨机采用T型布局,消除了研磨主轴C轴和往复摆轴X轴重叠布置所带来的相互误差耦合。刀具摆轴使用速度与位置闭环控制,可实现变研磨压力及变研磨时间两种刀尖圆弧的研磨方式。这里还建立了研磨机的空间误差模型,分析了影响刀尖圆弧研磨精度的主要因素。对磨损的金刚石刀具刀尖圆弧的重新修磨,一直以来都是未解决的技术难题。本文分析了刀具重磨的难点问题,详细探讨了刀具重磨中的关键技术及实现手段,制定了一整套圆弧刃金刚石刀具刀尖圆弧的重新修磨工艺流程。目前还没有合适的方法来测量金刚石刀具刀尖圆弧的圆度。最后本文针对金刚石刀具的测量要求,提出了基于AFM的刀尖圆弧检测方法。对现有的AFM系统进行改造,附加一套精密回转气浮轴系,建立了一套新型的金刚石刀具刀尖圆弧圆度的测量系统。并分析了整个系统的误差来源和误差组成,评定了系统的测量精度。针对金刚石刀具测量的特点,提出了一种带有半径约束最小二乘圆拟合的数据处理方法。该方法为工程实际中圆弧刃金刚石刀具刀尖圆弧圆度的检测与评定提供了技术支持。更多还原

【Abstract】 As the representative technology of ultra-precision machining, the ultra-precision cutting becomes an important mark of the manufacturing level of a country. The ultra-precision cutting needs not only cutting machine, high accurate detecting instruments and ultra-stable machining environment, but also high-precision rounded diamond cutting tools. In America and Japan, the cutting edge radius (sharpness) of the tools is minimized less than 10nm and the nose roundness of the tools is improved no more than 50nm. Compared to the cutting edge radius of the tools, domestic has approached the international advanced level, but the nose roundness is left behind a great distance with that. Therefore, it is urgent to solve the high-precision lapping problem of rounded diamond cutting tools’nose arc.The diamond crystal has strongly anisotropy. Mechanical properties in different crystal planes even in different orientations of the same plane are obviously different. Each part of the tool’s nose arc has different lapping performance as they are in different crystal planes. Thus, the simple cylindrical lapping method is not efficient to lap the nose arc of rounded tools. So far there is no effective model for the lapping of the nose arc. And the existing lapping equipments and process has many drawbacks. Therefore, the nose roundness of the lapped nose arc cannot reach the high precision. With the result that, this paper develops the lapping mechanism, equipment and detecting technology of the tool’s nose arc based on crystallology. The research contents are detailed as following:Firstly, the microscopic mechanism of material removal in mechanical lapping of diamond cutting tools is discussed using the period bond chain (PBC) theory and molecular dynamics simulation. It is the first time that this microscopic interpretation for mechanical lapping of diamond cutting tools exposed on atomic scale from the crystallography. And the theoretic basis is established for mechanical lapping of nose arc of the tools by this interpretation. According to this interpretation, a PBC model is built to evaluate the extent of hard lapping in different orientations on different crystal planes in diamond. This model is confirmed by the subsequent experiments of material removal rate in mechanical lapping.Secondly, based on the PBC model, ratio models of material removal rate are proposed for nose arc of tools which use the {100} and {110} crystal plane as the rake faces. The materials lapping performance on nose arc is described by mathematical model for the first time. Further more, these models will give strong support to effective mechanical lapping of the rounded diamond cutting tools’nose arc. And then, the optimization lapping direction is obtained for the nose arc of tools with different rake face. And the optimization composition of the crystal plane is R(110)F(110) for the rounded tools. More over, two lapping methods are proposed for nose arc according to the formula of material removal amount. One is varying lapping pressure; the other is varying lapping time.Thirdly, summarizing of the disadvantages of the existing lapping machine, a new type lapping machine is designed by top-down method of Pro/Engineering for mechanical lapping of rounded diamond cutting tools. This lapping machine uses T-type layout in order to eliminate the coupling error introduced by the overlapping layout of mainshaft (C-axis) and pendulum shaft (X-axis). Oscillating shaft is controlled by the position and speed closed-loop. This ensures the varying lapping pressure and varying lapping time two kinds of lapping methods feasible. In addition, the space error model of the lapping machine is established by means of lower body array to describe the topological structures. And the principal factors are obtained for influencing the lapping quality of rounded diamond cutting tools’nose arc.Re-lapping of the worn diamond cutting tool is an urgent problem to be solved. This paper discussed the key technology and implementation method of tools’re-lapping based on the analysis of key difficulty. Whereafter, a whole process plan is set down for re-lapping of rounded diamond cutting tools’nose arc.The measuring apparatus is necessary to evaluate the lapping quality of the diamond cutting tool. As yet no measuring method is applicable for the nose roundness of the rounded diamond cutting tool. Lastly, this paper put forward a measuring method based on atomic force microscope (AFM) according to the requirements of the diamond cutting tool. A measurement apparatus which composes of a reconstructed AFM and a precision aerostatic bearing is developed. Thereafter the error source and composition of the whole system is analyzed, especially the error caused by alignment. And the measuring accuracy of the measuring system is worked out. Then a new data processing method with radius constraint least-square circle fitting is put forward. This new method will give a strong support to the measurement and evaluation of the nose roundness of rounded diamond cutting tools in engineering practice.更多还原