Xipeng Xu

Force ratio in the circular sawing of granites with a diamond segmented blade

Abstract An experimental study was carried out to investigate the characteristics of the force ratio in the circular sawing of several kinds of typical granite with a diamond segmented saw blade over a very wide range of sawing conditions. Measurements were made of the horizontal and vertical force components and the consumed power in order to obtain the tangential and the normal force components. For studying the influence of sawing parameters, experiments were especially designed and conducted in an attempt to keep a constant working state of the segment surface. An additional experiment was also carried out to examine the variation of the force ratio while the working surface of the segments progressively changed. Compared to workpiece velocity, the depth of cut was found to rank first in governing the two force components. In spite of the big difference in sawing difficulty, the force components and their ratios for different granites did not differ as much as was expected. The force ratio increased linearly with increasing wheel speed, whereas the normal force decreased steeply and the tangential force was nearly constant. In a long-time sawing process where the saw blade was not redressed from beginning to end, both the tangential and normal force components increased with the gradual wear of the saw blade while their ratio decreased.

Quantitative analysis of the loads acting on the abrasive grits in the diamond sawing of granites

Abstract An experimental study was carried out to evaluate quantitatively the loads acting on the diamond grits during the circular sawing of two kinds of typical granite with a diamond segmented saw blade. Measurements were made of the horizontal and vertical force components and the consumed power in order to obtain the tangential and the normal force components. The temperatures at the diamond–granite contact zone were measured using a foil thermocouple, the measurements, together with the net sawing power, being used subsequently to estimate the energy partition to the granite by a temperature matching technique. Based on the energy partition values, tip temperatures at individual cutting points were estimated using an analytical model. SEM was used to follow the topographies of worn diamond segments. The average force acting on each diamond grit was found to be only 4% of the diamond compressive strength measured by a static method. The strength disparity of diamond grits and the random protrusion of grits beyond the bond matrix should be significant factors in accounting for the wear of diamond grits. The wear of diamond grits was also found to be closely related to the high temperatures generated at individual cutting points and the pop-out of diamonds from the bond matrix were attributed to the heat conducted to the segments.

Cost-effective machining of granite by reducing tribological interactions

Abstract In order to implement the cost-effective machining of granite materials with diamond impregnated tools, one should realize low tool wear, low energy consumption, and high cutting efficiency, while the accuracy of the workpiece surfaces are maintained to be satisfactory. It is understood that the main factors affecting the tool wear, the energy, and the efficiency during the machining process are related to the tribological interactions that occur at the interface between the diamond tool surface and the workpiece. Based on this consideration, the authors propose a new machining method to machine granite materials to achieve improved cost effectiveness. In the proposed method, the tribological interactions are maintained to a minimum.

Micro-structure detection of a glossy granite surface machined by the grinding process

Abstract In the present paper, an investigation was directed towards the micro-structure detection of a glossy granite surface at each separate stage ranging from sawing to grinding. Scanning electron microscope was employed to study the morphologies of the ground surfaces. A portable roughness instrument and a gloss meter were employed to analyze the roughness and glossiness of the ground surface, respectively. It is shown that the prevailing mechanisms for the grinding of granite vary from brittle-mode removal to ductile-mode removal with the reduction of the diamond grit size. The high glossy surface of granite is a low roughness surface which was formed by diamond grinding in the ductile-mode.

Ceramics Grinding Under the Condition of Constant Pressure

Abstract To meet the increasing demand on the quality and cost of precision components for the semiconductor industries, extensive studies on high efficiency and precision machining of ceramic materials have been conducted over the past few years. It is found that the effects of grinding pressure and the rotational speed of the spindle in the machining of ceramic materials are very significant on the quality of the grinding process. In order to achieve stable grinding conditions for improved performance, a new grinding control scheme in which the grinding pressure is maintained constant throughout the grinding process was explored in the present study. Based on the experimental results, the microanalysis of the ground surfaces, and the comparison of the analytic and measured temperature profiles, the material removal mechanisms for constant pressure grinding were discussed.

Thermal aspects in the face grinding of ceramics

Abstract To meet the increasing demand on the quality and cost of precision structural components, extensive studies on high efficiency and precision machining of ceramic materials, including face grinding, have been conducted over the past few years. In the present study, experiments of face grinding two typical ceramics were carried out to study thermal aspects at the wheel–workpiece contact zone. According to the experimental results and the comparison of theoretical and measured temperature profiles, the temperature characteristics and mechanism of energy partition in the face grinding of ceramic materials were discussed. The temperature rise in the workpiece and energy partition during the grinding process were found to be directly related to the machining parameters and the mechanism of material removal.

An experimental study of machining characteristics and tool wear in the diamond wire sawing of granite

A diamond wire sawing process was developed for slicing granite in order to complement the disk sawing. Machining characteristics and tool wear during wire sawing of a granite material that consists of three major minerals, that is, quartz, feldspar and mica, were systematically investigated. The material removal mechanism involved in the sawing was explored. The scanning electron microscope examination of the sawn surfaces of the granite and the analysis of the force and temperature involved in the sawing process indicated that the material removal of the granite was dominated by brittle fracture. The typical cleaving and slipping behaviors of feldspar and mica associated with sawing resulted in unique morphologies on the sawn granite surfaces. The tool wear of the process was characterized by the nonuniform wear of diamond beads impregnated on the wire, with the fore end of the diamond beads experiencing greater wear than the rear part.

Processes for the Generation of Glossiness on Ground Granites and Ceramics

The present investigation was undertaken to explain the mechanisms for the generation of glossiness on diamond ground granites and ceramics by following their t opographic features at each separated stage ranging from rough grinding to fine polishing. The topogr aphic features of the ground granite and ceramic surfaces were quantitatively evaluated in t erms of surface roughness and gloss readings in addition to SEM and AFM observations. Temperature responses at the workpiece-tool contact zone were in-process monitored by using a pair of grindable the rmocouple. It is found that the gloss readings increase with a decreasing surface roughness in an exponential curve, which provides an important basis for more efficiently generating a better gl oss finish on granite surfaces. The surface roughness, and hence glossiness, were found to go through a gradually changing process, during which the material removal mechanism changes gradually from brittle fract ure to ductile flow with a reducing diamond grit size. Temperatures generated during the grinding of granites were found to be not high enough to cause chemical reactions and phase transformation on the granit surfaces. Therefore, the reduction in surface roughness, and hence the increase in surface glossiness, are mainly dependent on the mechanical interactions between the diamond grits and gr anites, rather than thermally induced chemical reactions. Introduction Finely ground granite materials are popularly used as surface dec orative materials in buildings due to their aesthetic color and splendid glossiness, in which case the glos siness is one of the most important quality criterions to evaluate grinding processes. Historically, conventional silicon carbide wheels have been used extens ively for stone polishing. Past studies on the grinding and polishing of stones have mainly focused on tra itional ceramic tools, which have been proven of having such disadvantages as low productivity, short t ool life, high machining costs and an environmental hazard. In response to the growing nee d for more cost-effectively and environmental friendly machining stones, diamond tool s are gradually making inroads into the whole stages in finishing stones from rough grinding to polishing [1-2]. Compared with numerous fundamental investigations on ceramics grinding a nd various unique techniques for the grinding of ceramics [3-4], fewer technical impr ovements have been made in the field of grinding granite with diamonds owing to much fewer fundamental studies. Although some research on diamond grinding of stones have been reported [1-2], they focused mainly on the optimization of operating parameters rather than material removal mechanisms. Therefore, the formation mechanisms for surface glossiness have not yet been underst oo clearly. In order to more cost-effectively grind granite to higher gloss finish, a deeper u nderstanding of the formation mechanisms for surface glossiness is required. The present r s arch was undertaken to explore how surface glossiness and roughness vary at different grinding stages ran ing from rough to fine grinding. It is hoped that new methods for ceramics grinding can be incorporated into granite grinding based on the findings in this study. Key Engineering Materials Online: 2003-04-15 ISSN: 1662-9795, Vols. 238-239, pp 99-104 doi:10.4028/www.scientific.net/KEM.238-239.99

Force and Energy Characteristics in Grinding of Ceramics

In this study, two typical ceramics were ground with a resin-bonded diamond wheel on a precision surface grinder under different conditions. According to the measured power consumed by the spindle, the normal and tangential force components operating on the grinding wheel, the force ratio, and the specific energy in grinding of ceramics were analyzed. The results show that the ceramic materials are mainly removed in the fracture mode, whi le most of the grinding energy is expended by ductile flow. The friction between the diamond wheel and ceramics should be taken into account in the investigation of the material removal mechanisms for ceramic s grinding. Introduction Special ceramics have been extensively applied in mechanical en gine ring and other industrial engineering for their extraordinary properties. It is required that the components of ceramics should be of high accuracy and good surface quality in the applications. It is well known that ceramics are hard and wear-resistant, which make these materials difficult to machine. Usually, the cost of machining could be 80% total cost of ceramics component [1]. In order to impr ve the machining efficiency and the quality of the product at low cost, a lot of i nvestigations have been carried out to develop advanced technology for high efficiency machining of ceramic s all over the world [1-7]. Meanwhile, the material removal mechanism in grinding of cerami cs has been widely discussed [7-9]. But it is difficult to quantificationally study the machini ng mechanism because of the complexity of the grinding process and removal mode of ceramic materials. In this study, two typical ceramics were ground with a resin-bonde d diamond wheel on a precision surface grinder. The net consumed power, normal and tangential f orce components acted on the diamond wheel were measured under different conditions. According t o the acquired data and machining parameters, the specific energy (which is the energ y expended in removing a unit volume of workpiece material) was calculated. These provided basic d ta and guideline for the quantificational description of the grinding process for ceramics. The analysis by SEM observation of the ground surface of cerami cs was carried out to discover the material removal mechanisms over a range of operating condit ions. Combining with the acquired results from the specific energy and the analysis of ground surface, the material removal mechanisms of ceramics grinding were presented. Moreover, the fri ction effect attributes to a portion of energy consumed for the total specific energy. In this paper , the relation between the friction and the specific energy was discussed. Experimental Tests Grinding experiments were conducted in the up cutting mode on a precisi on surface grinder (MM7120A) as illustrated in Fig.1. In order to make a deep investigation int forces and energy in surface grinding of ceramics, serials of experiments were arrang ed under the operating conditions as listed in Table 1, in which the specifications of diamond wheel are also given. The experiments were specially designed and conducted in an attempt to keep a consta nt working state of the diamond wheel surface, in which case the wheel was dressed by cut ting an oilstone brick before each pass on the grinder. Grinding forces were measured by m eans of a piezoelectric dynamometer Key Engineering Materials Online: 2003-04-15 ISSN: 1662-9795, Vols. 238-239, pp 105-110 doi:10.4028/www.scientific.net/KEM.238-239.105

A curve matching image processing technique for analysis of coolant flow patterns

Abstract A curve matching technique is proposed to process experimentally obtained images to permit analysis of coolant flow patterns, which will be used to determine suitable parameters for an in-process optical measurement method to be used in the machining processes. In the proposed method, an array of ideal images is created based on the theoretical results and the disparities with the actual images are examined through a recursive process. To quantify the assessment of the disparities, an error index is used to determine the most suitable match. The working principle of the proposed technique is presented and the recursive algorithm to examine the image disparities described. To improve the computational efficiency, techniques to offer the necessary enhancement are described. The results of the experimental test demonstrated the effectiveness of the proposed method.