Download files
Abstract
A comprehensive literature review into the current state of micro-machining and abrasive waterjet (AWJ) machining technologies and the associated sciences has been carried out. It has revealed that a micro-AWJ possesses many traits which are desired by industry, but little research has been devoted to its development and understanding the science behind this machining process.
The AWJ micro-hole machining performance on brittle glasses was first explored through an experimental investigation. It shows that the machined surfaces are smooth with three distinct erosion zones, each exhibiting the characteristics reflecting the behaviour of the fluid flow in that zone. The secondary viscous flow plays a major role in the machining process. It has been found that increasing the water pressure or erosion time increases the hole depth, but has little effect on the hole diameter. Higher abrasive particle concentration can enhance the material removal rate, but reduces the surface quality. Predictive models for the material removal rate and major hole geometrical features have been developed and experimentally verified.
A study of the micro-channeling performance has then been carried out. From an experimental study, it has been found that due to the secondary viscous flow effects, particles impact the target at a shallow angle and ductile mode erosion is predominant. The channel depth is mainly affected by the jet kinetic energy transferred to the target via the abrasive particles. In contrast, the viscous flow plays a main role in the formation of channel width. The formation of channel wall inclination is attributed to the turbulent flow that drives particles to accumulate at the channel bottom. Mathematical models have finally been developed to predict the dimensions of the micro-channels. The predictive models have been experimentally verified and found to be able to give adequate predictions of the major channel geometrical features.
This study has amply demonstrated the machining capability of the micro-AWJ technology. The analysis into the material removal processes has provided an in-depth understanding of the physical science associated with the technology, while the predictive models developed serve as a valuable basis for future process planning to effectively use the technology.