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Micromachining Metrology: Measurement and Analysis of Dynamic Tool-tip Trajectory when using Ultra-High-Speed Spindles
Başlık:
Micromachining Metrology: Measurement and Analysis of Dynamic Tool-tip Trajectory when using Ultra-High-Speed Spindles
Yazar:
Nahata, Sudhanshu, author.
ISBN:
9780355981322
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (149 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-10(E), Section: B.
Advisors: O. Burak Ozdoganlar Committee members: Mark D. Bedillion; M. Alkan Donmez; Rahul P. Panat.
Özet:
There is a growing demand for miniature, high-precision components and devices with micro-scale features for applications in biomedical systems, aerospace structures, and energy storage/conversion systems. Mechanical micromachining has become a leading approach to address this demand. In micromachining, a micro-scale cutting tool, such as a micro-endmill with a diameter as small as 10 microns, is rotated by an ultra-high-speed (UHS) spindle to mechanically remove the material from a workpiece. Although micromachining resembles the traditional computer numerically controlled (CNC) machining processes, the micron-scale cutting tools, ultra-high-speed (UHS) spindles, and considerably tighter tolerance requirements bring unique challenges to micromachining.
A specific challenge related to the process accuracy and reproducibility is the characterization of the non-ideal motions of the micro-tool tip when rotated using UHS spindles. The tool tip trajectory dictates both the dimensional accuracy and the surface roughness of micromachined features, and thus, must be well-characterized to satisfy the stringent quality requirements. Although many works in the literature have addressed the aforementioned aspects towards understanding the errors in tool-tip trajectory for macro-scale machining processes, very limited effort has been devoted to addressing those for micromachining with its unique challenges. As such, a comprehensive understanding of tool-tip error motions and their effect on dimensional and surface quality parameters in micromachining is still lacking.
To address this need, the objective of this doctoral research is to develop experimental methods and the associated analysis tools to characterize the non-ideal motions of the tool tip, as well as to evaluate the impact of those motions on dimensional and surface quality of micromachined features. The non-ideal tool tip trajectory is described by the radial throw, which refers to the radial motions of the tool axis as well as those reflected at the individual cutting edges of the tool.
First, a measurement approach to obtain magnitude and orientation of radial throw at the tool-tip is developed. The approach involves measuring the radial throw using laser Doppler vibrometers (LDVs) from two axial locations on the tool shank at a given spindle speed, and then using a vectorial approach to calculate the radial throw at each cutting point along the cutting edges of the micro-tool. To this end, a method to relate the orientation of radial throw with respect to the cutting edges of the microtool is devised. The developed approach is experimentally validated by comparing predicted and measured radial throw at the tip of a custom-fabricated microtool blank. Following the validation, radial throw at tool-tip for a commercial microtool is experimentally studied for a range of operating conditions, viz., varying spindle speeds, tool attachment/detachment cycles, and thermal cycling of the spindle. The uncertainty of the approach is also evaluated through a statistical analysis.
Second, the changes in radial throw arising from static loading of the spindle is studied. It is well known that loads applied on a spindle can alter its motion and error characteristics. Since such loads are present in micromachining processes, understanding the changes in radial throw arising from axial and radial loading of the spindle is important. To this end, we created an experimental facility, where radial and axial loads are applied to the spindle using permanent magnets, which enable providing controlled and repeatable forces to the spindle in a non-contact fashion. To aid in selection of magnet type, dimensions and its placement, a finite-element based model of magnet-to-magnet and magnet-to-artifact interactions is developed in COMSOL Multiphysics and experimentally validated. The effect of external loading on all frequency components of radial throw are studied. The results are presented in both the time and the frequency domain.
Third, a metrology approach to assess the geometric errors of microtools is developed and demonstrated. The geometric errors of microtools, particularly the misalignment between the shank and tool-tip axis and inaccuracies of the positions of cutting edges, directly affect the tool-tip motions. An optical approach including high-magnification objectives and high-resolution rotary states is used for measuring tool geometry in three-dimensions. Novel measurement approaches and post-processing techniques are developed to measure the geometric axis of the tool-shank and the axis-offset between the shank and the fluted region of the microtool.
And fourth, results from different error sources are combined to obtain the total radial throw, and its effects on dimensional and surface quality parameters of the micromachined features are studied through numerical simulations. A three-dimensional tool model is considered, where the radial throw is calculated and added at each axial location to accurately represent the trajectory of the cutting edges. The magnitude and orientation of radial throw is varied to evaluate its effects on peripheral surface roughness, dimensional errors and changes in the uncut chip thickness. (Abstract shortened by ProQuest.).
Notlar:
School code: 0041
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(681764.1) | 681764-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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