Metrology Artifact Design

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Title: Metrology Artifact Design
Author: Folkert, Karalyn Faith
Advisors: Dr. Ronald O. Scattergood, Committee Member
Dr. Jeffrey W. Eischen, Committee Member
Dr. Thomas A. Dow, Committee Chair
Abstract: Part acceptance is based on dimensional inspection by comparison to the tolerance specifications of the part drawing. These measurements are often taken on Coordinate Measuring Machines (CMMs); but the dynamics of the machine will influence the overall measurement. Traditionally, a calibration artifact determines the static influences of the machine such as machine geometry. The goal of this project is to design and fabricate a calibration artifact that will test a CMM both statically and dynamically and determine the effects of those influences. The artifact developed is a ring gauge (6" ID, 8" OD, 1" thickness) that represents the typical size of parts of interest. The ring is 17-4PH stainless steel with a plated layer of electroless nickel (150µm) on the surface. Each face of the ring was diamond turned to a mean surface finish of 37nm RMS due to tool damage and machine error. Sine wave features were machined on the inside and outside diameter (ID and OD) of the ring using a fast tool servo. The wavelength of the sine wave varies continuously along the surface from long wavelength to short wavelength and back to the starting long wavelength over one revolution of the ring. The actual spatial wavelength of the wave sequences from 0.4mm to 6.4mm. The machined peak-to-valley (PV) is within 4% of the desired PV of 10µm. A reference flat surface was also machined on the ID and OD for static measurements. The final artifact is to be measured using a similar measurement strategy as a part to be measured; the same probe diameter is used with various measurement speeds in one orientation. The transfer function of the CMM dynamics is found by comparing the accepted swept sine wave with the measured wave. Each different speed defines a frequency range of the transfer function. By using this artifact to define the magnitude and phase characteristics of the dynamic system, the operator can make decisions referring to the machine's capabilities that exhibits an anticipated error and uncertainty in a measurement.
Date: 2005-11-22
Degree: MS
Discipline: Mechanical Engineering
URI: http://www.lib.ncsu.edu/resolver/1840.16/2212


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