The design, development and vibration analysis of a high-speed aerostatic bearing

[摘要] ENGLISH ABSTRACT: This thesis examines the development of a specialized, high-speed bearing in order to reduce vibration levels, reduce cutting times and increase blade stability during diamond sawing.The sawing process is required to be smooth, straight and unhindered – a task which is made difficult by the extreme hardness of the diamond as well as unseen grains which could potentially ruin the cut by deflecting the blade. This has an adverse effect on the quality of the cut and the yield obtained from the stone. The current equipment used for diamond sawing is very basic and a significant improvement can be made in terms of quality and sawing speed with the addition of an improved bearing.An aerostatic bearing was designed in order to achieve lower vibration levels and increased spindle speeds. A speed of 18 500 rpm was achieved with this bearing. A numerical model of the bearing was built with the aim of predicting the bearing's dynamic behaviour. A finite element method (FEM) analysis was done to confirm the rigid body assumption made. Experimental modal analysis (EMA) was done to determine the frequencies and damping ratios of the natural modes of the rotor. The model was seen to predict the frequencies of the modes to within 6%. This model would be used for future design work to ensure that the frequencies of these modes are designed outside of the operating speed range of the aerostatic bearing.Tests were done to compare the vibration levels between the conventional machine and the aerostatic machine during sawing. The overall RMS acceleration was reduced by 70% on the housing of the aerostatic machine and by 50% on the diamond clamp.

[发布机构] Stellenbosch University