Abstract
Polishing of titanium castings was investigated using the newly developed centrifugal barrel polishing apparatus which has two unique characteristics such as a variable rotational speed (100〜1100 rpm) and a specific rotational ratio (N:n=4.5:1) of the turntable (N) and the barrel (n). The polishing efficiency at three kinds of rotational speed (500, 750, 1000 rpm) calculated by the centrifugal force and acceleration theoretically demonstrated the formation of the favorite sliding zone for the polishing at all rotational speed and the higher rotational speed was assumed to be more effective on this apparatus. This assumption was supported by the results where the weight loss (%) of titanium casting plates (15×10×2 mm) by barrel polishing with NR-3 were 0.06, 0.17 and 0.47 at 500, 750 and 1000 rpm, respectively.
Properties of each media for the titanium castings treated by #1500 were evaluated from the barrel polishing without water. NRT-6 and NR-3 were superior to other two media on polishing efficiency, but also found to form dull and irregular surface. On the other hand, although the weight loss of titanium plates by SA and TWG#12 were small, these media were effective to improve surface texture. Especially, the surface gloss polished by TWG#12 was remarkably high. The barrel polishing of titanium plates treated by carborundum was tried using these media in order (from coarse media to fine media) and the excellent surface with 0.63 μm (Rmax) and 441 (Gs20°) was obtained from a series of media (NRT-6, NR-3, SA, TWG#12). These results suggested that the barrel polishing using the newly developed centrifugal barrel polishing apparatus with dry media was effective for the polishing of titanium castings.
