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Title: Instrumentation for measurement of radius and topography of curved surfaces
Author: Siddall, Graham J.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1975
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Effective control of the radius and surface geometry of curved surfaces is of paramount importance in precision engineering, particularly within the bearing industry. Stylus tracer instruments can be designed or adapted to measure such surfaces but are limited in their ability to measure radii of curvature. This thesis is concerned with the design and performance of stylus tracer instrumentation capable of both dimensional and surface measurement. After a review of existing techniques, a simple device is described for establishing the suppressed radius of curvature of a spindle type stylus instrument. An accuracy of determination of 2 m is possible over a wide range of radii, using conventional gauge blocks for setting purposes. An account is given of the design, construction and performance of a comprehensive stylus instrument which features measurement of radii within 2 m over a range of 0.25 to 50 mm. This instrument utilises a low-cost dry bearing spindle with negligible 'stick-slip' and with radial and axial errors of rotation of 0.1 m. Surface texture measurement is possible with a resolution of 5 m and a short term repeatability of 10 nm. Surfaces with are lengths of 2 to 360 can be measured utilising electronic control of the position and velocity of the stylus traverse. The problem of setting up an arcuate component on a stylus instrument is examined and a centring aid is devised in the form of a simple iterative algorithm. The effectiveness of this technique, together with the advantages of an integrated instrument approach, are demonstrated by coupling the instrument on-line to a digital computer. An additional radius measuring device, designed specifically for use with a commercial roundness measuring instrument is described. A unique feature of this system is its capability of measuring the size of the least squares reference circle without the need for precise centring of the component.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available