Dynamics and performance of surface finish measurement styli

The main aim of this project was to characterise measurement stylus dynamic performance prior to manufacture and application. This work investigated each area of stylus production, and its influence of the dynamic performance of the stylus. The literature surrounding stylus dynamics and the wider performance of measurement instrumentation is sparse, with much of the development being undertaken in private. At present, much of stylus design and production is based upon traditional attitudes and practices in; stylus component design, manufacture and stylus assembly, the use and application methods of adhesive, assembly fixturing technique and stylus materials. Investigations were performed into each of these specific areas to understand their impact on overall stylus production. A novel system of stylus fixturing was developed. This adjustable fixturing is significantly more cost effective than current fixture implementations, whilst covering a wider range of applicable styli and allowing the in-process measurement of geometric tolerances. Stylus assembly and measurement methods were developed and implemented using the newly developed fixturing approach. This resulted in an increased assembly consistency, and an improvement in the repeatability and reliability of the dimensional measurement of styli. The observation and characterisation of stylus dynamics has long been a challenging task. A system for the measurement of stylus dynamics was developed, using finite element analysis to inform design decisions, resulting in a realised measurement gantry. The gantry was characterised using accelerometers, allowing the Finite Element Analysis predictions to be tested. A piezoelectric actuator was used as a programmable measurement surface, this allowed automated testing of stylus performance on a range of simulated surface waveforms, with controllable amplitude and frequency. The capabilities afforded by the fixturing system allowed the creation of custom styli, in conventional materials (Carbon Fibre, Aluminium and Ceramics), as well as unconventional materials (Resin, additively manufactured). These styli were tested using the gantry test system and the conventional materials were recommended for stylus applications in the future. The dynamic testing methodology allowed the observation of the primary resonant frequency of the stylus, even in circumstances where the stylus would undergo flight at frequencies below the stylus primary resonant frequency