Jian Yun Shen

Surface Characterization of Silicon Wafers Polished by Three Different Methods

The surface roughness and surface morphology of silicon wafers polished by three different polishing methods were analyzed in this paper. A polishing pad was prepared by means of sol-gel technology as semi-fixed abrasive tool. An electroplated polishing pad was chosen as fixed abrasive tool. And a polishing cloth was chosen as free abrasive tool. The results showed that the surface of silicon wafer polished by the sol-gel polishing pad was superior to the other two. It was easy to get mirror effect with few scratches while the free abrasive and fixed abrasive got lots of scratches on 23silicon wafers. The surface roughness of silicon wafer polished by the sol-gel polishing pad reached 1.41nm measured by atomic force microscope (AFM).

Characterization of ELID-Ground Granite Surfaces

In the present study, natural granites were ELID ground with metal-resin bonded diamond wheels on a lap-grinding machine to achieve smooth surface. The surface roughness during the grinding process and final glossiness were examined to describe the formation of finely finished granite surfaces. According to the detailed micro-observation of ground surfaces, it can be concluded that natural granite surface on the main mineral components can be smoothly finished with ELID lap grinding. However, the appearance of natural defects and residual fracture on the ground surface lead to the scattered surface roughness, and restrict the improvement of surface glossiness.

Analysis of Path Distribution in Lapping and Polishing with Single Fixed Abrasive

The path distribution can directly affect the machined workpiece surface quality in lapping and polishing, such as planeness, roughness, etc. In present paper, the influence of rotate speed ratio (RSR) and abrasive position on path distribution was analyzed with a single fixed abrasive. The results show that the RSR and abrasive position has heavy influence on the path distribution. The path distribution with decimal RSR is more intensive and complicate than that with integer RSR, especially complex decimal RSR, and it can be also affected by the abrasive radial and circumferential position, but the shape of path is not changed with different abrasive circumferential position which only affects the initial phase angle of path.

Study on Fixed Abrasive Lapping Hard and Brittle Materials with Brazed Micro Powder Diamond Disk

In this study, two different arrangement lapping disks fixed with brazed diamond pellets were used to lap silicon wafer and alumina ceramic. The effects of the surface morphology, roughness, and removal rate of workpiece caused by lapping pressure, lapping time, workpiece velocity, and disc arrangement were operated with serials experiments. The results of the researches provided guidance for fixed abrasive lapping of hard and brittle materials with the brazed micro powder diamond disk.

Surface Behaviors of ELID Ground Engineering Ceramics

In this study, grinding of Si3N4, SiC, and Al2O3 ceramics under the condition of electrolytic in-process dressing (ELID) system was investigated. The surface appearances of these engineering ceramics during the ELID grinding process were attentively observed to describe the formation of finely finished surfaces. Based on the analysis of material properties and detailed micro-observation of ground surfaces, it can be concluded that the material removal mechanism of engineering ceramic is closely related to its mechanical properties. The silicon nitride ceramic was most easily machined to precision surface among these three engineering ceramics.

Thermal Study in Diamond Grinding of Zirconia

In the present study, zirconia ceramic was ground with a resin-bonded diamond wheel on a precision surface grinding machine. Grinding temperatures generated at the wheel-workpiece contact zone were measured using a sandwiched foil thermocouple, and the net consumed grinding powers were also measured. The energy partition to the diamond abrasives was estimated using measured grinding temperatures and powers. Based on the energy partition values obtained from the analyzed results, the diamond tip temperature was calculated and found to be over 1000°C if the circular grain contact of radius was less than a critical value for ductile field grinding of zirconia ceramic.

Surface Roughness Characteristics of Finely Ground Ceramics

In the present study, surface roughness after grinding with different mesh size diamond wheels were measured to study the surface roughness characteristics of engineering ceramics. According to the surface behaviours and measured surface roughness, the relation between the surface roughness and the properties of these brittle materials was described. Coupled with the micro-observation of ground surfaces, it was concluded that the grinding condition and material properties led to the differences of surface roughness characteristics of brittle materials. The silicon nitride ceramic was the most easily machined to ductile surface among these ceramics.

Effects of Cooling Methods on Temperatures in Vertical Grinding Stone

In the present study, natural black granite was ground with a cup-type resin bonded diamond wheel on a vertical spindle grinder. Grinding temperatures under different cooling conditions were measured using a foil thermocouple. Through comparing the measured grinding temperatures, the effects of operating parameter, applied coolant and cooling method on the temperatures were discussed. The results show that the grinding temperature increases with the increasing spindle speed and pressure. The internal application of lubricant oil and coolant may be beneficial to reduce damage to the diamond wheel and workpiece. Introduction Hard and brittle materials, including ceramic, stone and glass, have been widely used in modern industry. It is well known that these materials are difficult to machine, and the cost of machining takes the most fraction of the total cost of component [1-4]. Extensive research on advanced technologies in machining of hard and brittle materials have been conducted over the past several years. Among all the methods for machining of these materials, grinding with diamond wheels is generally, considered as the most cost-effective method. In the present years, vertical grinding has been widely applied to produce components made of hard and brittle materials [3-5]. It is found that the quality of component is greatly dependent on grinding pressure and rotational speed of spindle in the grinding process [6]. For the grinding process requires higher energy input for material removal than other machining methods, grinding temperature plays a very important role relative to surface integrity and wheel life. Post studies have shown that the specific energy of grinding hard and brittle materials is directly relative to the mechanism of material removal and friction between tool and workpiece [7-9]. Consequently, selection of coolants and their applied methods may make great effects on grinding temperature. In this present paper, a series of vertical grinding experiments with different coolants and applied methods were carried out under the different operating conditions to study the temperature characteristics in vertical grinding of black granite. Experimental In this study, vertical grinding tests were conducted on a numerical control (NC) vertical spindle grinding machine. Grinding pressure was controlled by an automatic pneumatic control system, and the spindle rotational speed was adjusted by a converter. The temperature response at the wheel-workpiece contact zone was measured using a foil thermocouple (See Fig.1). The total grinding power at the spindle was measured using a digital power meter (GX3). All the signals of grinding temperature and power recorded by a dynamic signal processing system (Dewe-3010) were transferred to a PC. In the experiments, a range of operating parameters was selected to study the temperature characteristics of vertical grinding. In order to make a deep investigation into the cooling effects of coolants and their applied methods on grinding temperature, water and lubricant oil were selected as coolants and were applied in the methods as shown in Fig.2. The temperature under the condition of drying grinding was also measured to compare the effect of coolant in the grinding. The workpiece used in the experiments was natural black granite. Key Engineering Materials Online: 2004-03-15 ISSN: 1662-9795, Vols. 259-260, pp 383-388 doi:10.4028/www.scientific.net/KEM.259-260.383

Study on Force Characteristics for High Speed Sawing of Quartz Glass with Diamond Blade

High speed sawing is an advanced machining technique for sawing of brittle materials with good component quality and high productivity. In the paper, sawing experiments were carried out to investigate the characteristics of sawing forces by altering many processing parameters in high speed sawing of quartz glass with a diamond blade. The sawing forces and force ratio were analyzed. The conclusions present that in the fixed material removal rate, the increasing of periphery speed can help to lower sawing forces and force ratio; sawing forces increase with material removal rate; in the high speed sawing, the effect of material removal rate on sawing forces is smaller than the one in the low speed.

A Method for Calculating the Maximal Temperature of Single Grain though Analyzing the Grinding Temperature Signal

In the present study, grinding temperature was measured by using a foil thermocouple when granite was ground by SiC wheel. De-noised the temperature signals with soft threshold method base on wavelet transform was conducted to analyze the grinding process. Energy partition to workpiece was estimated to be about 10%~30% by matching the measured temperature to analytically value. The number of active grains was determined by counting the high frequency impulses in the measured temperature signals. The ratio of active grains to total grains was about 4.5%~6.1%. Based on the results, a formula was deduced for calculating the temperature of single grain in the grinding process.