Today the need for mass produced items is ever growing with the demand for reproducible parts to be of a high precision. The introduction of co-ordinate measuring machines (CMM) has seen the ability to inspect produced 3D parts at faster speeds combined with high precision. The measurements with a CMM are carried out by a touch trigger probe at the interface between the produced part and machine. The probe system includes a stylus tip which makes contact with the workpiece and a probe head where the sensing technology is housed. The probe head and tip are connected by a shaft, typically constructed from steel or graphite fibre. The registration of a touch must be achieved in a minimal time in order to promote sensitivity of the probe.This thesis investigated the current touch trigger technology and found that a piezoelectric sensor may be incorporated into the shaft section. Piezoelectric material is of interest as it is widely used in sensing technology and can be manufactured into small cylindrical structures. This research has investigated the structures required for a sensor that would be applied to a touch trigger probe. An interdigitated electrode or IDE was developed and optimised with the use of computational finite element analysis (FE) and laboratory experiments. From this an understanding of the piezoelectric electromechanical behaviour with respect to the influence of the cylinder and IDE geometry on the electric field distribution and the resulting resonating characteristics was achieved. Optimised IDE electrode, cylinder geometries and piezoelectric materials allowed for the manufacture of prototype piezoelectric touch trigger probes. This was achieved by using a novel laser ablation process to manufacture IDE electrodes on the 3D piezoceramic surface. Analysis of the resonance response of the prototype piezoceramic probes showed good relation to developed FE models. Additionally, the prototype piezoceramic probes gave a good response to a mechanical contact. This thesis presents a working prototype which future work can develop it into a working CMM system.This work describes a novel approach to predict the effects of electric field on piezoelectric materials and the resulting dynamic behaviour in a multi-physics model. This was used to design, manufacture and characterise a working prototype which increases the sensitivity of a touch trigger probe.
|Date of Award
|31 Dec 2012
|Chris Bowen (Supervisor) & Andrew Dent (Supervisor)