Yoshio Ichida

Creep feed profile grinding of Ni-based superalloys with ultrafine-polycrystalline cBN abrasive grits

Abstract This paper presents the grinding characteristics of a newly developed ultrafine-polycrystalline cBN abrasive grit in creep feed profile grinding of Nickel-based superalloys. Experiments for producing a rectangular-shaped groove on a flat surface in one pass by creep feed grinding have been carried out using the new polycrystalline cBN (PcBN-U) grit and a representative conventional monocrystalline cBN (McBN-B1) grit. The grinding forces in grinding with PcBN-U grits are reduced by 20 ∼ 30% compared with McBN-B1 grits. When grinding with PcBN-U grits, both radial wear and profile wear are less, and hence the grinding ratio is around 4 times higher than that with McBN-B1 grits. The size of grit fracture during the grinding process with PcBN-U grits is smaller than that with McBN-B1 grits. It gives lower wheel wear rate and longer wheel life in grinding with PcBN-U than with McBN-B1.

A study on ultra–high-speed cutting of aluminium alloy:: Formation of welded metal on the secondary cutting edge of the tool and its effects on the quality of finished surface

Abstract To investigate the mechanism of ultra–high-speed cutting for aluminium alloy, cutting experiments by using a machine tool equipped with an active magnetic bearing spindle were performed over a range of cutting speeds from 20 to 260 m/s. On the whole, the finished surface tends to improve with an increase in cutting speed. However, the formation of welded metal on the tool edge in the speed range from 100 to 200 m/s promotes the material side flow on the finished surface, which causes the surface roughness to increase.

Nanotopography of ultraprecise ground surface of fine ceramics using atomic force microscope

Summary The nanometer-scale imaging of ultra-precise ground surface of Si 3 N 4 ceramics has been conducted with an atomic force microscope. An ultra-precise surface with a roughness of about 8 nm R max could be generated when fine grain diamond wheel with a grain size of =10.000 was used. The topography of the ultra-precise ground surface is affected by the protrusion of grain boundary phase out of Si 3 N 4 crystal surface as well as by the unevenness of grinding streaks. There is an infinite number of ultrafine projections with a height of less than 1.5 nm on the grinding streak surface. These ultrafine projections have slightly an anisotropic geometry in the shape and in the distribution.

High-efficiency grinding of cold-work die steel with ultrafine-crystalline cBN abrasive grains

This paper presents the grinding characteristics of newly developed ultrafine-crystalline cBN (UcBN) abrasive grains in high-efficiency grinding of cold-work die steel. This new UcBN grain possesses an ultrafine crystal structure composed of sub-micron sized primary crystal grains. The fracture strength of the UcBN grain is about 3.7 times higher than that of conventional monocrystalline cBN grain. The grinding ratio in grinding with the UcBN grain is eight to 11 times higher than those in grinding with conventional typical monocrystalline and polycrystalline cBN grains.

Development of Ultrafine-Crystalline cBN Abrasive Grains for Innovative Grinding Technology

This paper presents some mechanical properties and grinding characteristics of newly developed ultrafine-crystalline cBN (UcBN) abrasive grains. This new UcBN grain possesses an ultrafine crystal structure composed of sub-micron sized primary crystal grains. The fracture strength of the UcBN grain is about 1.5 times higher than that of conventional polycrystalline cBN grain. The grinding ratio in grinding with the UcBN grain is 4–10 times higher than those in grinding with conventional typical monocrystalline and polycrystalline cBN grains. Therefore, the UcBN abrasive grain has an enough ability to innovate the grinding technology.

Polishing Characteristics of CMP for Oxygen Free Copper with Manganese Oxide Abrasives

A series of polishing experiments have been carried out using Mn2O3 as abrasive grains to examine the polishing characteristics of CMP for oxygen-free copper. It has been found that the polishing rate increases as the polishing speed and/or polishing pressure increases, also the role of polishing speed on the polishing rate is more significant than that of the polishing pressure. The effects of the polishing conditions are however small, when polishing a finished surface roughness of about Ra 5 nm. A long polishing time, with an approximately constant polishing rate, can be achieved, without dressing, with a polishing pressure P = 9.4 kPa. It was found that higher polishing pressures could achieve a higher polishing rate, however the polishing pressure would decrease as the polishing time increased.

Evaluation of positioning performance of a fine-coarse mechanism

A new positioning system has been developed to realize both the fine motion and the coarse motion independently and/or simultaneously to reduce the positioning time with guaranteeing positioning accuracy. A conventional speed reducer unit is utilized to cope with this problem in this study. The combination of reducer and overdrive enables to position the end effector with accurate and rapid. This fine-coarse motion of the developed system is realized by only commercial-release parts consisted of two stepping motors and speed reducer aligned in an axis. The main advantage of this mechanism is that there is no stroke limitation in fine and coarse motions compared with the conventional fine-coarse motion stage by usage of PZT device. The basic performances are evaluated by adopting the feedback positioning control in this report. The developed positioning system demonstrates the efficient performance with accurate and rapid positioning.

Fractal Analysis of Self-Sharpening Phenomenon in cBN Grinding

This paper presents a fractal analysis of the self-sharpening phenomenon of the grain cutting edges in cBN grinding. To clarify the self-sharpening mechanism due to the micro fracture of the cutting edges, the changes in three-dimensional profile of the cutting edges in the grinding process have been measured using a scanning electron microscope with four electron probes and evaluated on the basis of the fractal analysis. The fractal dimension for surface profile of the cutting edge formed by the micro fracture is higher than that of the cutting edge formed by the ductile attritious wear. Therefore, the complicated changes in shape of the cutting edge due to the self-sharpening can be evaluated quantitatively using the fractal dimension.

Analysis of Ductile Mode Ground Surface of Optical Glass by Atomic Force Microscopy

The microstructures of ductile mode ground surface of optical glass generated by using fine grained diamond wheels have been investigated with an atomic force microscope. The main results obtained in this paper are summarized as follows: (1) There is an infinite number of ultrafine projections with a height of less than 2.5 nm on the ductile mode ground surface. (2) These fine projections have slightly an anisotropic geometry in the shape. It seems that the anisotropy is closely related to the grinding mechanism. (3) A supersmooth mirror surface with a roughness of 7 ~ 10 nm R m a x can be obtained by using a very fine grain diamond wheel of grain size #10000. The height of ultrafine projections existed on these mirror surface is less than 1.5 nm, which is lower than that on the ductile mode ground surface generated by a diamond wheel with a grain size of #800.

Mirror finish grinding of β-sialon with fine grained diamond wheels

常圧焼結β-サイアロンの微粒ダイヤモンド砥石による平面研削実験を試み, 鏡面研削特性に及ぼす砥石粒度の影響を検討した結果, 粒度6/12μm以下の微粒ダイヤモンド砥石による研削では, 連続流れ型の切屑が生成され, 切屑及び仕上げ面の生成が塑性変形を主体とするメカニズムで行われていることが確かめられた. また粒度6/12μm以下の微粒ダイヤモンド砥石による研削では, 破砕面の非常に少ない平滑な鏡面が得られ, 例えば0.5/3μm砥石による研削では, 仕上げ面粗さ約0.03μm Rmaxの極めて平滑な鏡面が得られた. 研削抵抗二分力, 比研削エネルギーUe及び砥石-工作物接触面最高温度 (砥石研削点最高温度) θmは, 砥粒粒径の減少とともに増大する. また砥粒の平均粒径dが約20μm以下の範囲において, Ue及びθmはともに (-logd) にほぼ比例する.