Thesis (Ph.D.)--Chulalongkorn University, 2010

To find the influential factors in the spherical forming porous polyurethane foam (PPUF). The as received cube specimens having dimensions of 21 mm were ground with the abrasive grit sizes of 20 and 53 μm, the grinding speeds varied from 1.41 to 5.18 m/s, and the cross head speeds controlled at 1, 3, and 5 mm/min. The grinding force signals were recorded using dynamometer. The ground specimens were determined which were shapes, finished diameters, and circularity errors. Tangential and normal grinding forces related with time and frequency domain, material removal rate, and specific grinding energy were analyzed. The effects of grinding factors were assessed via Analysis of Variance (ANOVA) with the significance level (α) of 0.05. The study found that (1) the finished shapes were categorized into four types namely egg, sphere, partial sphere, and squircle (2) the grinding speed significantly influenced on circularity error, finished diameter, tangential force, normal force, and grinding force ratio, while the cross head speed affected on material removal rate and specific grinding energy (3) the finished sphere specimens having diameters between 19.28 and 19.32 mm with circularity errors between 0.57 and 0.61 mm of the 95% confidence interval could be formed at the grinding speed ranged between 2.83 and 3.77 m/s (4) at the grinding conditions where the finished sphere specimens were formed, the tangential and normal forces related with time domain trended to increase with the rates of 0.64x10[superscript -4] N/s and 8.2x10[superscript -4] N/s, respectively, the peak frequencies of tangential force signals were between 5.3 and 7.1 Hz, and the grinding force ratio of tangential and normal force was 1.03±0.15 (5) the grinding speed of 3.30 m/s, cross head speed of 1 mm/min, and abrasive grit size of 53 μm was the best condition of the spherical grinding which provided the minimum circularity error of 0.47 mm.