Alumina Wheel Research Articles

EXPERIMENTAL ANALYSIS OF TEMPERATURE IN GRINDING AT THE GLOBAL AND LOCAL SCALES

The purpose of the article is the experimental estimation of the global and local heat fluxes and the corresponding energy partition to the workpiece for regular grinding of 100Cr6 steel with aluminium oxide wheel. By using a grindable thermocouple, the temperature and the real contact length allow determination of the global heat flux and the partition ratio at the wheel scale. The high frequency analysis of the signal has shown maximum flash temperatures of about 1000°C corresponding to the local temperature under the chip-grain unit with very high heating speed of about 100°C/µs. The comparison between theoretical temperature decay and experimental cooling has demonstrated that the time response of the sensor is fast enough for the estimation of the local temperature and power due to the sliding of grain and to the plastic strain of ground materials.

Grindability of Conventionally Produced and Powder-Metallurgy High-Speed Steel

The factors affecting the grindability of high-speed steel (HSS) were investigated by measuring G-ratio and power consumption in surface grinding of 18 grades of HSS of different composition with an aluminium-oxide wheel. The dominant factor affecting grindability was the size of vanadium carbide. The marked difference between HSS produced by the conventional method and the powder-metallurgy method was analyzed. The relationship between power consumption, G-ratio and grindability was investigated.

Power and Wheel Wear for Grinding Nickel Alloy with Plated CBN Wheels

Electroplated CBN grinding wheels are manufactured with a single layer of abrasive grains. The grinding performance of these plated wheels changes significantly as the wheel wears down. The present investigation was undertaken to understand the transient grinding behavior with electroplated CBN wheels in order to provide a logical basis for process control. In this paper, particular attention is directed to the effect of wheel wear and operating parameters on grinding of a nickel alloy. Wheels were worn to various stages and then used to perform grinding tests under various grinding conditions to measure grinding forces and power and to produce ground specimens. Based on models for grinding with conventional aluminum oxide wheels, a power model for grinding of a nickel alloy with plated CBN wheels was established and validated. Microscopic observations of the ground specimens reveal that thermal damage in the form of a White Etch Layer (WEL) appears only when grinding with a worn wheel under conditions that lead to high temperatures.

Grinding force modelling: combining dimensional analysis with response surface methodology

This paper describes a new technique for an empirical modelling of unit grinding force in surface grinding by combining dimensional analysis with Response Surface Methodology (RSM). The grinding experiment on K1045 steel (190 BHN) was carried out using conventional alumina wheels. The predictive grinding force model was developed in terms of spindle speed, work speed, depth of cut, width of cut and the strength of the work material. The adequacy of the model was judged by a variance analysis. Based on the response model, contours in the planes of investigated parameters were generated to predict the grinding conditions for a particular grinding force. The new technique can significantly reduce the number of experiments required for the force modelling and thereby is cost-effective.

Influence of Heat Treatment and Grinding Conditions on Surface Residual Stresses in the Production of Rollers

The aim of this study is to investigate surface residual stresses after heat treatment and grinding processes in the production of rollers. The residual stresses were measured using the X-ray diffraction method utilizing chromium radiation, which has an average penetration depth of 5 μm incident on AISI-E52100 (100Cr6) ball bearing steel. Taguchi design of experiments (DOE) is applied to define the set of experiments for grinding, which facilitates evaluation of the individual influences of process parameters on residual stresses and also eliminates unnecessary experiments. Response of residual stresses to each parameter is evaluated with the help of the results of residual stress measurements by X-ray diffraction. In grinding with aluminum oxide wheels, it was concluded that the lower the cutting speed and the higher the workpiece speed the higher the magnitude of surface compressive residual stresses. Higher compressive stresses were measured in axial direction compared to the circumferential direction after the grinding process.

The effects of a Ti coating on the performance of metal-bonded diamond composites containing rare earth

The present study was undertaken to examine the effects of a titanium coating on the surfaces of diamond crystals embedded in a metal matrix containing rare earth. Either coated or uncoated diamonds was incorporated into copper, tin, iron, nickel, and rare earth powders. The powders mixed with diamonds were then hot-pressed to form two kinds of specimens. The transverse rupture strength (TRS) of the two specimens was measured and compared. The specimens were also machined by surface grinding using an alumina wheel. The consumed power was monitored in the grinding process. SEM and EDS were used to analyze the fractured and ground surfaces of the specimens. It was found that the TRS of the specimen containing coated diamonds increased by 21% as compared with uncoated diamonds. The consumed grinding power for coated diamonds was found to be lower than uncoated diamonds. Although the weight loss of the specimen with coated diamonds was higher than that of uncoated diamonds at initial grinding stages, it became almost same for both specimens after a period of grinding.

It's a grind [grinding technology

VIPER grinding was developed by Rolls Royce in collaboration with the Grinding Division of Makino-NCMT as a replacement for creep feed grinding of Inconel and other nickel-based alloys using CBN wheels. Using inexpensive vitrified aluminum oxide wheels of small diameter mounted in the spindle of a horizontal machining center (HMC), VIPER grinding has been shown to be 10 times faster at removing metal than milling. To fully understand the potential of the VIPER technology, the paper describes the features of several machining centers including the Makino A55, the Makino A99, and the Makino A100.

Wear of Metal-Bonded Diamond Tools in Different Abrasive Processes

In this present work, an experimental study was carried out to investigate the wear of metal-bonded diamond tools (specimens) in five abrasive processes – stirring diamond specimens in rock slurries and surface grinding the specimens with a vitrified alumina wheel as well as circular sawing of refractory bricks, vitrified silicon carbide wheels and natural granite with segmented diamond blades. Three diamond specimens of different hardness were fabricated by hot pressing. In addition to following the worn morphologies of the diamond tools, forces and power were also monitored in four abrasive processes. During stirring and surface grinding, the wear of the diamond specimens decreased with increasing specimen hardness, whereas the vertical force in surface grinding increased with the specimen hardness. In sawing of granite, however, the wear of the blades was closely related to the vertical force generated in sawing rather than the hardness of the diamond segments. The trends of force changes in sawing of refractory bricks were comparable to those in sawing of granite. But the force ratios in sawing of the SiC wheel were found to be much higher than those in sawing of other two materials.

Performance of Diamond Segments in Different Machining Processes

An investigation is reported of the performance of diamond impregnated segments in three machining processes - circular sawing of granite with diamond segments, dressing of diamond segments with refractory bricks and surface grinding of diamond segments with an alumina wheel. Two kinds of segments were fabricated by incorporating diamonds (either coated or uncoated) into an iron-based bond matrix. Measurements were made of the horizontal and vertical force components in the machining processes. SEM was used to examine the diamond-matrix bonding states and the ground surfaces of the segments. The changes of forces and segment wear (weight loss and wear performance) were found to be basically consistent for the three machining processes.

Evaluation of Grinding Wheel Surface by Means of Grinding Sound Discrimination

In this study, a new technique of in-process evaluation of a grinding wheel surface is proposed. Some specific wheel surfaces are prepared as references by the appropriate truing and/or dressing procedure, and grinding sounds generated by these wheels are discriminated by analyzing the dynamic frequency spectrum by a neural network technique. In the case of a conventional vitrified-bonded alumina wheel, the grinding sound can be identified in the optimum network configuration. Therefore, this system can instantaneously recognize differences in the wheel surface with a good degree of accuracy insofar as the wheel conditions are relatively widely changed. In addition, the network can perceive wheel wear because the grain tips are flattened as grinding proceeds and the grinding sound becomes similar to that of a wheel generated with lower dressing feed. The resinoid-bonded cubic boron nitride (CBN) wheel is also discriminable when a grinding sound in a higher frequency range is analyzed.

ANALYSIS OF WHEEL WEAR USING FORCE DATA IN SURFACE GRINDING

Grinding involves many randomly shaped and distributed abrasive grains removing material from a workpiece. Wheel wear results when these grains dull, fracture or break away. As a result, grinding forces are time-varying. In order to automate and optimize the grinding process an understanding of how forces are generated and change during grinding is critical to avoid workpiece damage, surface finish deterioration, cracking, excessive heat generation, and excessive residue stresses. This paper builds upon the existing grinding literature by studying the relationships between wheel wear and grinding forces for different depths of cut when surface grinding mild steel with an aluminum oxide wheel.

Experimental Studies on the Grind-Hardening Effect in Cylindrical Grinding

In recent years high-strength and high-temperature alloys are used for structural and other applications. These newer high-performance materials are inherently “more difficult to machine” and also necessitate the need for higher dimensional and geometrical accuracy. Grinding is one of the most familiar and common abrasive machining processes used for the finishing operation. Compared to other machining processes such as turning, milling, etc., the specific energy developed during grinding is very high. At a critical level of specific grinding energy, the temperature rise[1]experienced by the workpiece may be such that thermal damage is induced. Heat damage induced by the grinding process is well documented and may be categorized by temper colors that are at least unsightly and probably indicative of more serious damage, including thermal cracks, tempered zone, etc.,[2]which can lead to catastrophic failure of critical machine parts that shortens the life of products subject to cyclic loading. In this work, a new heat treatment process called “grind hardening” and a mathematical model are introduced, and this work deals with how the in-process energy in grinding can be effectively utilized to improve the surface hardness and surface texture, and also to prevent damages. An experimental study has also been carried out in grinding AISI 6150 and AISI 52100 steels with an alumina wheel, and the results are discussed.

ニューラルネットワークによる砥石作業面状態の識別 砥石作業面性状のインプロセス評価に関する研究

In this study, a new technique of in-process evaluation of the wheel surface is proposed. Five specified wheel surfaces are prepared as the references via the appropriate dressing procedure, and grinding sounds generated by these wheels are discrimi-nated by analyzing the dynamic frequency spectrum with a neural network technique. In the case of conventional vitrified-bonded alumina wheel, grinding sound can be identified under the optimum network configuration in such that learning rate is 0.0029 and number of hidden layer is 420. This system can recognize instantaneously the difference of the wheel surface in a good degree of accuracy insofar as the dressing conditions are relatively widely changed. In addition, the network perceives the wheel wear because the grain tips are flattened as grinding proceeds and the grinding sound resembles to that of the wheel generated with lower dressing feed.

208 Evaluation of Grinding Wheel Surface by Means of Grinding Sound Discrimination

In this study, a new technique of in-process evaluation of the grinding wheel surface is proposed. Some specified wheel surfaces are prepared as the references via the appropriate truing/dressing procedure, and grinding sounds generated by these wheels are discriminated by analyzing the dynamic frequency spectrum of 6-10kHz with a neural network technique. In the case of conventional vitrified-bonded alumina wheel, grinding sound can be identified under the optimum network configuration in such that learning rate is 0.0029 and number of hidden layer is 420. The resinoid-bonded CBN wheel is also discriminable with the grinding sound in higher frequency range. This system can recognize instantaneously the difference of the wheel surface in a good degree of accuracy insofar as the wheel conditions are relatively widely changed. In addition, the network can perceive the unlearned wheel condition as the nearest one.

Studies on the surface quality of the unsteady-state grinding technique

Ultra-precision grinding for advanced ceramics has been achieved by the unsteady-state grinding technique. This paper deals mainly with observing and analyzing the surface quality of silicon nitride ground by a pink fused alumina wheel with different grinding parameters. To optimize the grinding parameters in the process of unsteady-state grinding, experiments of X-ray diffraction, energy spectrum analysis, SEM observation and roughness measurement were performed. The results show that there do exist optimum grinding conditions such as grain size, coolant, and cutting depth, etc. Finally, the surface roughness R a can be as good as 0.01 μm under optimum conditions.

419 ニューラルネットワークによる砥石作業面状態の識別

In this study, a new technique of in-process characterization of the grinding wheel surface is proposed. Some reference topographies of the wheel surface are formed by different dressing conditions. and the condition of the wheel surface is discriminated where the dynamic fre-quency spectrum signals of grinding sound and/or vibration are analyzed by a neural network technique. In the case of conventional vitrified-bonded alumina wheel, both grinding sound and vibration can be identified under the optimum network configuration in such that learning rate is 0.003 and number of hidden layer is 160. Accordingly this system can recognize the differ-ence of the wheel surface in a good degree of accuracy insofar as the micro-topography of abrasive grains are relatively widely changed.

Effect of surface grinding on the strength of NiAl and Al 2O 3/NiAl composites

For structural applications, dimensional tolerance has to be controlled tightly. Surface grinding is thus frequently applied to match the requirement. For brittle material, improper surface grinding can degrade their strength considerably. In the present study, an alumina wheel and a diamond wheel were used to grind NiAl and Al 2O 3/NiAl composites. The surface quality, strength and toughness after grinding are investigated. Cracks are formed on the surface of NiAl ground with the alumina wheel. However, there is no crack found on the surface of NiAl ground with the diamond wheel. The strength of the NiAl machined with diamond wheel is three times that of the NiAl machined with alumina wheel. As Al 2O 3 particles are added into NiAl, the presence of weak Al 2O 3/NiAl interfaces limits the formation of large flaws. The strength of the Al 2O 3/NiAl composites is thus less sensitive to the grinding conditions. The present study demonstrates that the Al 2O 3/NiAl composites are tolerant to the surface grinding conditions.

Theoretical Analysis of Heat Partition and Temperatures in Grinding

A theoretical analysis is presented of heat partition and surface temperatures for the grinding of hardened steel with both aluminum oxide and CBN wheels. The numerical predictions of the model are shown to agree with experimental results available in the literature. It is found that heat partition varies over a wide range depending on grinding conditions. Also, heat partition is a strong function of position inside the grinding zone. The presence of the fluid inside the grinding zone can reduce the heat flux into the workpiece and the workpiece temperature significantly. For typical grinding of steel with CBN wheels, or creep feed grinding of steel with aluminum oxide or CBN wheels, it is possible to keep the fluid active and therefore to reduce thermal damage. However, the analysis suggests that the fluid may not be effective inside the grinding zone, in the conventional grinding of steel with aluminum oxide, due to boiling.

The search for an economic domain of operation when grinding below the film boiling limit

An investigation has been conducted to determine whether an economic domain of shallow-cut grinding exists below the film boiling temperature. It identifies the potential benefits of grinding below film boiling and provides preliminary theoretical evidence based on accepted thermal analyses in grinding and the results of previous research. The evidence shows that an economic domain in shallow-cut grinding could exist. The stock removal rate reported by one group of researchers [ Bull Jap. Soc. Precision Engng 17(2), 133 (1983)] [1] was only 1 mm 3 (mm s) −1, whereas 5–6 mm 3 (mm s) −1 is commonly accepted as an economic stock removal rate in shallow-cut grinding. The present thermal analysis indicates that the stock removal rates of 16 mm 3 (mm s) −1 might be possible with alumina wheels operating at conventional wheel speeds with very small depths of cut. Rates higher than 250 mm 3 (mm s) −1 might be possible when using CBN wheels and high wheel speeds.

Comparison of grindability of HIPped austenitic 316L, duplex 2205 and super duplex 2507 and as-cast 304 stainless steels using alumina wheels

The grinding ratios, grinding forces and surface roughnesses of HIPped austenitic (PM 316L), duplex (PM 2205) and super duplex (PM 2507) as well as as-cast (AC 304) stainless steels were measured during grinding using alumina wheels. It was observed that the grinding ratio decreased in the following order: AC 304, PM 316L, PM 2205 and PM 2507 steel, whilst the grinding force increased in the order: AC 304, PM 2205, PM 316L and PM 2507 steel. The surface roughness increased in the order: PM 316L, PM 2205, PM 2507 and AC 304 steel. It was observed also that the ground steel surfaces work-hardened in the following increasing order: AC 304, PM 316L, PM 2205 and PM 2507 steel. Abrasive plowing-wear grooves and adhesive built-up layers of alumina particles were observed on the ground surfaces of the steels, increasing in the following order: AC 304, PM 316L, PM 2205 and PM 2507 steel. Examination of the ground surface profiles of the workpieces showed that there were a considerable number of microcracks and microvoids on the ground surfaces of the steels, increasing in the following order: PM 316L, PM 2205, PM 2507 and AC 304 steel. Finally, the effects of work hardening, chemical interactions between the alumina wheel and the workpiece, as well as microcracks and microvoids, on the grindability of the stainless steels studied were investigated.