Papers by Author: Alexander Henry Slocum

Abstract: There is a compelling need for development of a surface grinding machine for 450mm diameter silicon-wafers. The authors have developed a new surface grinding machine for the large scale silicon-wafers. The machine has a rotary work table equipped with a constant-flow hydrostatic water bearing. The table system has to attain high static stiffness to achieve higher loop stiffness. This paper investigates static performances of the rotary table by numerical computation. The obtained results are compared with the experimental ones. Accordingly, it is verified that the developed rotary table has sufficient static performances for the large scale silicon-wafer grinding machine.

Abstract: A linear-motor-driven table supported by hydrostatic-water bearings had been developed. The table slider is supported by a single-sided recess type bearing system and preloaded by attractive force using a linear-motor magnet. Since eccentric excitation force is applied to the table slider due to the change of attractive force according to the magnet track position of the linear-motor, pitching motion of the table occurs. This paper investigates the effect of air volume contained in a water-supply tube on the pitching motion. Larger air volume results in lower natural pitching frequency of the table slider, lower logarithmic decrement of the pitching motion and larger pitching angle. When the natural pitching frequency corresponds to the frequency of the eccentric excitation force during table feed, pitching angle grows by resonation.

Abstract: In order to realize environmental-friendly machine tools, a linear-motor-driven table supported by constant-flow hydrostatic water bearings is developed. The table system is free from environmental pollution because the system needs no oil. For simplicity, a single-sided bearing system is chosen for the table-slide. To obtain a high sustaining force, preload is applied to the bearings using the attractive force of an iron core linear-motor’s magnets. The preload is effective in both the vertical and horizontal directions by inclined motor magnets. Miniature gear-pumps supply flow to the bearings without pump pulsation, and the bearings consume very small amounts of water and electric power. The measured table sustaining force was 3.0kN and static stiffness was 0.3kN/m under a flow rate Q=0.92mL/s per bearing and ideal bearing clearance h=16m.