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A framework for enhancing the accuracy of ultra precision machining .

机译：一种提高超精密加工精度的框架。

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摘要

This thesis is titled "A Framework for Enhancing the Accuracy of Ultra Precision Machining." In this thesis unwanted relative tool/workpiece vibration is identified as a major contributor to workpiece inaccuracy. The phenomenon is studied via in situ vibrational measurements during cutting and also by the analysis of the workpiece surface metrology of ultra precision diamond face turned aluminum 6061-T6.;By deriving representative equations in the polar coordinate system, it was found that the vibrational pattern repeats itself, leading to what are referred to in this thesis as surface finish lobes. The surface finish lobes describe the waviness or form error associated with a particular frequency of unwanted relative tool/workpiece vibration, given a particular feed rate and spindle speed. With the surface finish lobes, the study of vibrations is both simplified and made more systematic. Knowing a priori the wavelength range caused by relative tool/workpiece vibration also allows one to extract considerable vibration content information from a small white light interferometry field of view. It was demonstrated analytically that the error caused by relative tool/workpiece vibration is always distinct from the surface roughness caused by the feed rate. It was also shown that the relative tool/workpiece vibration-induced wavelength in the feed direction has a limited and repeating range. Additionally, multiple disturbance frequencies can produce the same error wavelength on the workpiece surface. Since the meaningful error wavelength range is finite given the size of the part and repeating, study then focussed on this small and manageable range of wavelengths. This range of wavelengths in turn encompasses a broadband range of possible disturbance frequencies, due to the repetition described by the surface finish lobes.;Over this finite range of wavelengths, for different machining conditions, the magnitude of the waviness error resulting on the cut workpiece surface was compared with the actual relative tool/workpiece vibrational magnitude itself. It was found that several opportunities occur in ultra precision machining to mitigate the vibrational effect on the workpiece surface. The first opportunity depends only on the feed rate and spindle speed. Essentially, it is possible to force the wavelength resulting from an unwanted relative tool/workpiece vibration to a near infinite length, thus eliminating its effect in the workpiece feed direction. Further, for a given disturbance frequency, various speed and feed rate combinations are capable of producing this effect. However, this possibility exists only when a single, dominant and fixed disturbance frequency is present in the process.;By considering the tool nose geometry, depth of cut, and vibrational amplitude over the surface finish lobe finite range, it was found that the cutting parameters exhibit an attenuating or filtering effect on vibrations. Thus, cutting parameters serve to mitigate the vibrational effect on the finished workpiece over certain wavelengths. The filter curves associated with various feed rates were compared. These filter curves describe the magnitude of error on the ultra precision face turned workpiece surface compared with the original unwanted tool/workpiece vibrational magnitude. It was demonstrated with experimental data that these filter curves are physically evident on the ultra precision diamond face turned workpiece surface. It was further shown that the surface roughness on the workpiece surface caused by the feed rate was reduced with relative tool/workpiece vibrations, and in some cases the feed mark wavelength was changed altogether.;The manifestation of vibrations in the feed and in-feed directions of the workpiece was studied over a broadband of disturbance frequencies. It is found that the waviness error measured on the cut workpiece surface was significantly larger than that caused by the feed marks during cutting. Thus it was established that unwanted relative tool/workpiece vibrations are the dominant source of surface finish error in ultra precision machining.;Mean arithmetic surface roughness curves were also constructed, and the filtering phenomenon was demonstrated over a broadband of disturbance frequencies. It is well established that a decrease in the feed rate reduces the surface roughness in machining. However, it was demonstrated that the improved surface finish observed with a slower feed rate in ultra precision diamond face turning was actually because it more effectively mitigated the vibrational effect on the workpiece surface over a broadband of disturbance frequencies. Experimental findings validated this observation. By only considering the effect of vibrations on the surface finish waviness error, it was shown that the workpiece diamond face turned with a feed rate of 2 mum/rev has a mean arithmetic surface roughness, Ra, that was 43 per cent smaller than when a feed rate of 10 mum/rev was used.;
机译：本文的标题为“增强超精密加工精度的框架”。在这篇论文中，不必要的工具/工件相对振动被认为是造成工件误差的主要原因。通过切削过程中的原位振动测量以及通过对超精密金刚石面车削铝6061-T6的工件表面计量学的分析来研究该现象。通过在极坐标系中推导代表性方程，发现了振动模式重复自身，导致在本文中称为表面光洁度裂片。在给定特定的进给速度和主轴转速的情况下，表面光洁度凸角描述了与不想要的相对工具/工件振动的特定频率相关的波纹度或形状误差。使用表面光洁度凸角，可以简化振动研究并使之更加系统化。先验地知道由相对的工具/工件振动引起的波长范围，也允许人们从小的白光干涉测量法的视场中提取可观的振动含量信息。从分析上证明，由相对的工具/工件振动引起的误差总是不同于由进给速度引起的表面粗糙度。还表明，在进给方向上相对的工具/工件振动引起的波长具有有限的重复范围。另外，多个干扰频率会在工件表面产生相同的误差波长。由于有意义的误差波长范围在给定零件尺寸和重复尺寸的情况下是有限的，因此研究将重点放在这个较小且易于管理的波长范围上。由于表面光洁度的重复，该波长范围又包含了可能的干扰频率的宽范围。在此有限的波长范围内，对于不同的加工条件，在切割工件上产生的波纹度误差的大小将表面与实际相对工具/工件的振动幅度进行比较。已经发现，在超精密加工中出现了几种机会，以减轻对工件表面的振动影响。第一个机会仅取决于进给速度和主轴速度。本质上，可以将由于不希望的相对工具/工件振动而产生的波长强制到接近无限的长度，从而消除其在工件进给方向上的影响。此外，对于给定的干扰频率，各种速度和进给速度的组合都可以产生这种效果。但是，只有在该过程中存在一个单一的，占主导地位且固定的干扰频率时，这种可能性才存在。；通过考虑刀尖的几何形状，切削深度以及在表面光洁度有限范围内的振动幅度，我们发现切削参数对振动表现出衰减或滤波作用。因此，切削参数用于减轻某些波长上对成品工件的振动影响。比较了与各种进给速度相关的滤波器曲线。这些过滤器曲线描述了与原始不需要的工具/工件振动幅度相比，超精密端面车削工件表面上的误差幅度。实验数据表明，这些过滤器曲线在超精密金刚石面车削工件表面上是明显可见的。进一步表明，进给速度引起的工件表面粗糙度随刀具/工件的相对振动而减小，并且在某些情况下进给标记的波长会完全改变。;进给和进给中振动的表现在干扰频率的宽带上研究了工件的方向。发现在切割的工件表面上测量的波纹度误差显着大于在切割期间由进给标记引起的波纹度误差。因此，可以确定多余的工具/工件振动是超精密加工中表面精加工误差的主要来源。;还构造了平均算术表面粗糙度曲线，并在宽范围的干扰频率上证明了滤波现象。众所周知，进给速度的降低会降低加工中的表面粗糙度。但是，事实证明，在超精密金刚石端面车削中以较低的进给速度观察到改善的表面光洁度，实际上是因为它可以更有效地减轻在一系列干扰频率下对工件表面的振动影响。实验结果证实了这一观察结果。仅考虑振动对表面粗糙度起伏误差的影响，可以发现以2 mum / rev的进给速度车削的工件金刚石面的平均算术表面粗糙度Ra，比使用10毫米/转的进给速度小43％。

著录项

  • 作者

    Meyer, Paula Alexandra.;

  • 作者单位

    McMaster University (Canada).;

  • 授予单位 McMaster University (Canada).;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 220 p.
  • 总页数 220
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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