The analysis of tool wear mechanisms in dry machining of pre-sintered zirconia dental crowns

Irvine, David

Abstract

The purpose of this thesis was to summarise what knowledge has been gained and what has been learnt through entirety of this doctorate on wear mechanisms in the machining of presintered zirconia used in the dental and medical industries. In the dental industry there has been a shift to using Zirconia for restoration due to its favourable mechanical properties, however machining such a material has ramifications on the tools machining it. Even machining it in a pre-sintered state, which is much softer, has its complication. This work aimed to address the areas of study within the machining of these dental restorations out of pre-sintered zirconia to set forward the rest of research to follow. This research set forth to answer how the carbide ball nose end mills can resist the wear that occurs during the machining of pre-sintered zirconia. Previous work has failed to answer this issues how the carbide is affected specifically. There is little work on the machining conditions of materials similar to presintered zirconia and how the tool affects the material it is cutting This work approached to bridge this gap by discerning an optimal method of machining presintered using existing equipment. In doing so the other minor gaps would be filled on the way to this optimisation. The path to this optimisation was to investigate the tool wear and tool-workpiece interactions during and after the machining process directly. These experiments consisted of machining
pre-sintered zirconia under differing circumstances. This path was chosen as it links any finding directly with the purpose allowing for applicable results and observations. A set of optimal working conditions and a series of specific conditions were determined in chapter 6 along with a framework to aid in machining condition selection. The selection criteria for this optimisation and assistive tools was: time, tool wear and surface finish. Within this work it was also determined how the tool wear affects surface integrity. It was found during this work the wear is in fact third body abrasion and causes trans-granular rupture along the worn surfaces of the carbide end mill. It was also found the workpiece is not subjected to enough heat to harden.

• Thesis Type: Thesis
• Deposit Date: Aug 8, 2022
• Publicly Available Date: Aug 30, 2024
• Public URL: https://uwe-repository.worktribe.com/output/9850991
• Award Date: Aug 30, 2024