IMPROVED MEASUREMENT METHODS FOR IN-PROCESS METROLOGY ON LARGE-SCALE COMPONENTS
1 online resource (189 pages) : PDF
University of North Carolina at Charlotte
Manufacturing processes have inherent errors during machining and in-process metrology is used to determine and correct for these manufacturing errors. In this research, the determination of size (diameter) and form error (surface profile) of large-scale circular features are considered. The objective of the research is to measure, simultaneously, the size and form error of a large-scale circular component through mathematically sound methods with the aid of a novel measuring instrument.This research is motivated by the influence of current manufacturing processes and their in-process metrology methods. The current methods for the determination of component size is accomplished using mechanical instruments, such as calipers and micrometers. These mechanical indicators have the potential to produce unreliable results because the measuring methodology is tied to a two-point measuring method and is dependent upon the skill of the human operator. The method used in this research to measure the size of the component uses three measurement points and reconstructs the diameter of the component using a geometrical model. Every machine with a spindle will experience spindle error motions, which describe the variable position and orientation of the spindle axis as a function of the rotating angle. However, with the spindle having off-axis error motions and the component not having a perfect geometry, measurement of the component form error using a single indicator will be a combination of both the components surface non-uniformity and the spindles axis error motions. In this research a multi-probe error separation method is used to accurately isolate the component form error from the spindle error motions. This research developed a novel measuring instrument able to simultaneously measure both diameter and form error of circular features. The measuring instrument uses three pivoting arms attached to a body, in which is adaptable to a lathe’s turret. The three arms are accompanied by three high-resolution angular encoder modules that produce the angular displacement of the arms, coupled with a kinematic model of the system, are used to reconstruct the diameter and form error of the large-scale circular component. In this research, the results from the measuring instrument, show that it is capable of measuring both diameter and the form error simultaneously. The form error values produce a maximum error of 0.004 mm (0.00016") and the diameter values produce a maximum error of 0.022 mm (0.00087"). These error values are determined with a comparison to a Coordinate Measuring Machine (CMM) value of form error and diameter.Finally, an expanded uncertainty of 0.024 mm (0.00094") is determined for the diameter measurement process of the measuring instrument and an expanded uncertainty of 0.004 mm (0.00016") is determined for the form error measurement process of the measuring instrument.
WIlliams, WeseleyGoch, GertMiller, JimmieFarahi, Faramarz
Thesis (Ph.D.)--University of North Carolina at Charlotte, 2015.
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