Papers by Keyword: CBN Wheel

Abstract: Soft magnetic powder cores are made by pressurizing and molding pure iron powder covered with insulation film. The material is used as a component of electro-magnetic converter parts essential for automobiles, home electric appliances and electronic equipment. The material permits downsizing and higher performance of such equipment. The recent severer requirements for performance and dimensional accuracy need a new processing technology that warrants the required level of both magnetic performance and surface quality of the material. However in general, processing - grinding - soft magnetic powder cores can give rise to degradation of magnetic performance and/or chipping or plucking of the ground surface due to the mechanical damage of the insulation film and/or loss of structural particles from the material due to the increase in grinding resistance. The authors performed basic studies for various grinding conditions and wheels that could possibly affect the quality of the material with a view to eliminating these problems. As a result, factors that affect the surface quality were identified, and a method that warrants a higher surface quality was proposed.

Abstract: Rapid Rotation Mirror-like surface Grinding (RRMG), in which combine Rapid Rotation Grinding (RRG) and Truncate Truing with Micro Dressing (TTMD) are combined, is a suitable method for mirror-like surface finishing with high efficiency. The surface roughness of a workpiece decreased with increasing work speed of RRMG, contradicting the conventional grinding principle on grinding geometry and kinematics. Furthermore, it was analyzed that a heat-affected layer and subsurface microstructure of the workpiece having a surface roughness Ra of less than 0.05 μm were obtained by RRMG. As a result, it was clarified that the thickness of the heat-affected layer was decreased and the subsurface microstructure was nanocrystallized, because the grinding temperature was suppressed with increasing peripheral work speed of RRMG.

Abstract: Grinding experiments were conducted using vitrified CBN wheel on particulate reinforced titanium-based matrix composites (PTMCs) and Ti-6Al-4V matrix. The issues discussed are grinding forces, surface roughness, and the formation of surface integrity. The main results are summarized as follows: (1) The grinding forces increase with the increasing workpiece speed and depth of cut during grinding PTMCs and Ti-6Al-4V materials. (2) Decreasing depth of cut properly contribute to obtaining finished surface with good surface during grinding of PTMCs using CBN wheel, but the workpiece speed has little influence on the surface roughness value of PTMCs. (3) The formation of surface integrity of PTMCs is due to the combined removal of the TiC and TiB reinforcements and the Ti-6Al-4V matrix.

Abstract: Particulate reinforced titanium matrix composites (PTMCs) are attracting increasingly attention in various engineering applications. In this paper, comparative grinding experiments of PTMCs were carried out using WA abrasive wheel and CBN abrasive wheel. The morphology of the ground surface was observed by scanning electron microscope. The main results are summarized as follows: (1) The damage of reinforcements in the PTMCs results from the plowing and shearing during grinding in the form of crater, micron gap, broken, coating and micron crack. (2) The formation of grinding chip is a function of the collaborate removal of reinforcements and matrix material. (3) The surface fracture pattern of PTMCs using WA wheel is to form the grinding chip through severe extrusion. While using CBN wheel, the abrasion due to the formation of the wear debris is the main surface fracture pattern of PTMCs.

Abstract: Metal-bonded cBN wheels with regular pores were fabricated using Cu-Sn-Ti alloy, cBN abrasive grains and alumina (Al2O3) bubble particles. Dressing experiments were carried out through rotary dressing method. Subsequently, grinding experiments were conducted on nickel-based superalloy GH4169. Comparative grinding performance was evaluated with vitrified cBN wheels in terms of grinding force and specific grinding energy. The results reveal that the pores in the working layer of the cBN wheels are exposed after rotary dressing. Compared to vitrified cBN wheels, grinding forces and specific grinding energy of the newly developed cBN wheels with regular pores are smaller.

Abstract: Manufacturing of precise couples is the most important key technology for hydraulic products. The hydraulic characteristics are not only strongly correlated with their geometric elements, but also associated with the surface qualities of the couples, including surface roughness and surface texture, and which primarily influence the dead zone, lag rings and friction of the couples. In order to get better surface machining quality of the precise hydraulic couples, the process of surface grinding and polishing was researched. Through process test, the optimum parameters of grinding and polishing processing were found, which made the surface roughness achieved Ra 0.031μm.

Abstract: The experiment of resin-bonded CBN wheel dressing using a diamond dresser assisted with longitudinal ultrasonic vibration along the direction of depth of cut was carried out and the dressing characteristics and grinding performance were discussed in the present paper. The influence of acoustic parameters on the topography of CBN wheel was studied to check the effectiveness of dressing for this method. The experimental results showed that the higher the ultrasonic frequency is, the better the wheel topography. The grinding on K9 optical glass and high speed steel has achieved higher G-ratio than that of traditionally mechanical dressed CBN grinding wheel. The ground surface of high speed steel is better than that of K9 optical glass. According to the interferometer images, it was concluded that the grinding of high speed steel was in ductile cutting regime, while removal of K9 optical glass was in brittle fracture regime.

Abstract: An investigation is reported on the temperature in grinding of titanium alloy (TC4) by using a vitrified CBN wheel at grinding speed up to 120m/s. The temperatures under different grinding parameters were measured by using a sandwiched foil thermocouple. Coupled with the SEM observations on the ground workpiece surfaces, characteristics of temperature in high speed grinding were analyzed and compared with the temperatures in grinding at normal speeds. It is found that grind speed is the most significant factor to determine temperatures, which might be associated with the increase of material removal in the plastic way at higher grinding speed.

Abstract: According to the demand for internal grinding machine in precise machining of air-conditioner compressor piston hole, a kind of high precise CNC internal grinding machine with CBN wheel is developed by adopting self-adaptive control for grinding process. Meanwhile, grinding precision and stability are achieved by overcoming many problems emerging from high-speed grinding process with CBN wheel. More than 100000 times’ grinding experimental results show that the whole performance of grinding machine developed is the same as that of the same kind of international machine. In order to study grinding mechanism with CBN wheels and then improve machine’s capability, grinding data in several machining cycles is analyzed.

Abstract: This study performs an experiment to investigate the effect of process variables such as rotational cutting speeds of the wheel, feed rate of the work-table and grinding depth of cut on surface roughness and the fluctuations of grinding forces for Ti-6Al-4V titanium alloy. STP-1623 ADC surface grinding machine, grinding wheel with CBN material sintering and Ti-6Al-4V titanium alloy workpiece are used in the experiment. The roughness of the grinding surface was measured by the roughness measuring instruments and the fluctuations of grinding forces were measured through dynamometer after each surface layer ground from the workpiece in the experiment. The grinding performance can be ascertained from the signal fluctuations phenomena of the grinding forces both along normal and tangential directions, which may also be utilized as an index for the quality of surface finish judgment. The results show that excellent surface quality being always consistent with the stable grinding force fluctuations and can be obtained under the conditions of slow feed rate of the work-table, high revolutions of the wheel and shallow depth of cut.