Papers by Keyword: Dressing

Abstract: Dressing of grinding wheel is important value, which can influence final surface. Therefore, it is necessary to address this issue some attention. Dressing is used for sharpening of clogged and blunted grinding wheel and adjustement of their geometric shape. The article deals with one of the experiments that are carried out in this area at FPTM JEPU in Ústí nad Labem. Experiments refer specifically to impact assessment of dressing size on the final selected values of surface integrity. Within the article, the assessment covered the surface roughness Ra, Rz and Rt. At the same time were also scanned using a dynamometer Kistler components of the cutting forces and even here it was possible to observe the influence of the dressing size of the grinding wheel on these values.

Abstract: Structural textural surfaces are those surfaces that have designed feature intended to give specific functional performance. In the last few decades, the understanding of structured surface texture, particularly at a micro and nanometre scale, has played a fundamental role in the development of many advanced applications. After a brief review of current manufacturing methods for textural surface, this paper examines the surface creation during grinding by analysing the kinematics of grinding and associated wheel dressing processes. It has been demonstrated that the features of structural surface can be determined by carefully selected dressing and grinding conditions. The grinding speed ratio between workpiece and wheel is an important factor in determine the layout of the structural pattern generated on the workpiece. The grinding depth not only affects the structural feature depth but also the length and width of the surface structure. The uniformity and repeatability of actual ground feature shape is influenced by the arbitrary nature of distribution of grinding abrasives.

Abstract: The problems of practical application of the combined electric diamond grinding (CEDG) are examined. Experiments were conducted on the grinding tool materials with metal-bonded diamond grinding wheels. In the presented part of the work, the roughness of the machined surface of specimens made of high-speed steel is investigated. It was established that the CEDG makes it possible to decrease the roughness of the machined surface to 30-40 % in comparison with other combined methods and 1.5-2 times in comparison with usual grinding. The application ensures the grinding by diamond wheels in the mode of self-sharpening and guarantees the continuity of its geometric form, which eliminates the defect layer on the machined surface and gives a longer period of wheel stability. The results obtained show that diamond wheels can be successfully used for grinding wide spectrum of tool materials.

Abstract: Diamond grinding wheel is used in high precision grinding process, when work piece has a very high hardness. For a specific grinding interval, the wheel must be properly dressed, in order to remove swarf, sharpen the worn diamond grits, open up new diamond protrusions, and recondition the bond material. Dressing of diamond grinding wheel by alumina dressing tool has been simulated in a pin-on-disk machine in the research. Sharpening of the wheel is indicated by the increase of its roughness value, and surface microstructure with protruding sharp diamond grits. It was found that increasing of sliding distant from 100 to 500 m will increase the roughness of the wheel. The increase of contact load from 10 to 20 N will also increase roughness of the wheel, and the severity of wheel wear, indicated by high values of friction coefficient. A proper dressing of this nickel bonded SD1200 diamond wheel is by sliding against alumina dressing tool for at least 300 m under 10 N load. Sliding velocity has minimal effect to the results. A too large sliding distant and load will cause severe damage to wheel surface, and severe wheel wear, indicated by its large mass loss.

Abstract: A grinding wheel wears rapidly during ultrasonic assisted surface generation of a large aperture aspherical RB-SiC mirror, which leads to an increase of grinding force and profile error. In this paper, different types of resinoid bonded diamond grinding wheel with a same grit size were dressed with high-pressure abrasive water jet. The dressing effects of abrasive water jet were assessed through comparing the 3D roughness of the grinding wheel topographies before and after dressing. The experimental results show that diamond grits of a worn grinding wheel are protruding from bond after dressing. The feed rate of nozzle and the bond materials have significant impact on the 3D surface roughness of the wheel and dressing efficient. The softer binder and the decrease of the feed rates and lead to deeper grooves during dressing of grinding wheel. However, too low feed rate will make a large number of abrasive particles drop from binder, which worsens the wheel topography. Therefore, to dress grinding wheel well and efficiently, optimized feed rate must be chosen.

Abstract: Chemical mechanical polishing/ planarization (CMP) is a key technology for fabricating high-efficient semiconductor devices, and the CMP characteristics (removal rate and accuracy, etc.) is depended on the various consumables represented by slurry, polishing pad and dresser used in the CMP process. Currently, in the pad, there are many studies that have pointed the evaluation methodology and the correlation between the pad surface asperity and the CMP characteristics. On the other hand, the dresser is one of the most important consumables because the dresser can control the pad surface asperity, and the diamond grains electrodeposited dresser (diamond dresser) is frequently used. One drawback point of the diamond dresser is that the dressing performance declines owing to the deterioration of the diamond grains. Previously, we have developed a novel flexible fiber dresser that would ensure high performance and longer life of tools, and we have reported the fundamental characteristics by the flexible fiber dresser compared with that of the diamond dresser. In this paper, we will show the results of tool life evaluation of the flexible fiber dresser using a contact image analysis method. As a result, the flexible fiber dresser can be continuously used over 35 hours. Furthermore, the result of having examined the stability of the removal rate of a silicon wafer is reported. Therefore, we found that the flexible fiber dresser is one of the most effective dressing methods for the polishing pad.

Abstract: Chitosan films have been used as dressings for healing burns. The physical and biological properties of these films can be modified by the addition of bioactive substances such as phytotherapics. This work used the casting - solvent evaporation technique for the preparation of chitosan film containing hydrophilic or hydrophobic phytotherapic. The barrier properties, mechanicals properties and microbial penetration were evaluated. The results showed that the films containing the hydrophobic herbal showed lower ability to move fluid and permeability to water vapor compared to the film containing the hydrophilic herbal. For the determination of microbial permeation, film were previously sterilized and were fixed in the mouth of glass vials containing sterile nutrient broth and left on the lab bench for a period of 10 days. Negative and positive controls were also conducted. The chitosan films do not allow the microbial penetration.

Abstract: The manufacturing of molds with diffractive structures requires new approaches in terms of grinding wheel geometry and preparation. To be able to manufacture small geometric features such as widths and depths in the micron range on the mold, ideally sharp edged grinding wheels should be used. This paper will present dressing procedures to create sharp edged grinding wheels by using metal alloy blocks. The results and achieved tip radii of the dressed resin bonded and metal bonded fine grained grinding wheels will be presented. Finally, grinding tests of a tungsten carbide mold with a diffractive structure are conducted and the results of the achieved form accuracy and surface roughness are presented.

Abstract: The effectiveness of gas turbines can be improved significantly by decreasing the friction losses. Compared to smooth surfaces riblet-structures have been proven to reduce skin friction in turbulent flow up to 10 %. For the technical application on compressor blades in turbo machines, micro riblet-structures with a riblet width between 20 μm and 120 μm and a depth of the half width are required. Furthermore, the application on compressor blades needs ideal riblet-geometries with an aspect ratio of 0.5, trapezoid groove geometry and a shape accuracy of the compressor blade about 10 μm. This paper presents the relevant influencing factors on the overall shape accuracy as well as the riblet geometry in five axes grinding of riblet-structures on double curved compressor blades. The results show, that the shape accuracy is affected by the CAD data and the macro-geometry of the grinding wheel. Therefore, specialized requirements on the CAD data were defined in order to increase the shape accuracy. To decrease the influence of the grinding wheel geometry on the overall shape geometry, a method adjusting the grinding wheel geometry on double curved surfaces was developed. Furthermore, the effect of the 5 axes kinematic on the aspect ratio and the profile wear was examined.

Abstract: There are many methods of diamond wheel dressing,broadly divided into mechanical dressing and special processing trimmed two categories.This article describes several different EDM dressing diamond grinding wheel technology and divided into two categories namely:different medium EDM dressing diamond grinding wheel and EDM assisted dressing diamond grinding wheel technology. Summarize recent wheel dressing technology research advances at home and abroad.Elaborated EDM dressing key issues to be addressed, and further research.