The polishing process of advanced ceramic balls using a novel eccentric lapping machine
Abstract The finishing process of advanced ceramic balls can be divided into two steps. The first step is lapping in which most of the stock from the ball is removed at a higher material removal rate. The second step is polishing in which the required ball surface roughness, roundness, and dimensional and geometric accuracy are achieved. In polishing, the abrasive particle size is 1 μm, and the load and speed are lower than lapping. A novel eccentric lapping machine is used for polishing hot isostatically pressed (HIPed) silicon nitride balls. In the initial polishing stage, the polishing load is demonstrated as being most influential in the reduction of surface roughness value Ra. However, in the later polishing stages, the erosive process played a major role in the further reduction of Ra, although the high roughness peaks cannot be removed by erosive process alone. Experimental results also show that, in order to achieve desired surface roughness value, the initial surface quality of the upper plate should be reasonably high, and deep scratches on the ball surface from previous lapping processes should be avoided. The best polishing results achieved were surface roughness values of Ra of 0.003 μm and r.m.s. (Rq) of 0.004 μm, ball roundness of 0.08–0.09 μm. This proves that the novel eccentric lapping machine is also suitable for polishing advanced ceramic balls.
Handbook of ceramics grinding and polishing
Focusing on the machining of ceramic materials such as silicon nitride, silicon carbide, and zirconia, this handbook meets the growing need in industry for a clear understanding of modern improvements in ceramic processing. The presentation is international in scope, with techniques and information represented from the USA, Japan, Germany, and the United Kingdom countries that have made important contributions to the field. The 20 expert chapter authors explore the challenge of reducing the costs of machining operations, a continuing problem in an industry where ceramic parts must be machined into final form to achieve a proper fit. The handbook reveals that the abrasive machining of ceramic materials will always be a requirement because of the difficulty of controlling parts dimensions at the high temperatures required in their creation. The contributors then explain the properties and characteristics of ceramics, the various types of abrasive processes, and typical tests used in the procedures. An entire section of the handbook concerns grinding tools, their conditioning, lubrication, and cooling, checking for wear on the tools, and using them efficiently. The book also examines modern honing and superfinishing tools and machines, and describes advances in the technology, as well as lapping and polishing techniques using chemical compounds and ultrasound. Ceramics is a field where more advanced products are sure to appear. Many of the products will require advanced, better-controlled processing technologies; vastly improved productivity in manufacturing; and increased product reliability. The contributors to this Handbook will assist readers in the attainment of these important goals.
Tribochemically assisted wear of silicon nitride ball
The response of silicon nitride balls to different chemical additives contained in a diamond slurry was studied in a high speed four-ball machine. It was found that there are two effective inorganic chemical additives: acid additive (A) and alkaline additive (B). Use of A or B in the diamond slurry resulted in a high material removal rate and a rough surface. With an increase in the size of the diamond particles contained in the slurry, the material removal rate and the roughness of the surface also increased. Addition of sulfur-containing additives into the diamond slurries produced a decrease in the material removal rate but a smoother surface. The presence of water in the oil-based diamond slurry gave an increase in the material removal rate and a relatively smooth surface. In the ester-containing slurry, there was an increase in the material removal rate and the roughness of the surface.