Papers by Keyword: Diamond Tool

Abstract: The purpose of this paper was to investigate the grinding performance of two types of cobalt and vitrified bond diamond tools produced by the hot press for the vertical flat grinding polycrystalline diamond. The worn diamond type and the diamond protrusion observed by the toolmaker or SEM after grinding under two different feed rates of 1 and 5 mm/min and the depth of cut of 2 µm with total depth of 10µm were studied. In addition, the grinding efficiency and the workpiece surface roughness produced were analyzed as well. The experiment results showed that when the feed rate of 1 mm/min during the flat grinding PCD was used, a lower percentage of the good diamond, a higher percentage of flat diamond and pulled-out hole on the worn surface of the cobalt bond diamond tool were obtained. For the vitrified bond diamond tool, the good diamond produced showed a higher percentage and flat grit and pulled-out hole displayed a relatively lower percentage. This may be due to the result of the relatively moderate strength and grit retention of the vitrified bond. Furthermore, the diamond protrusion and the grinding efficiency produced for the vitrified bond diamond tool were better than those for the cobalt bond tool. And the PCD surface roughness obtained was better as well.

Abstract: The demand for high precision optical elements as micro lens arrays for displays increases continually. Economic mass production of such optical elements is done by replication with high precision optical molds. A new approach for manufacturing such molds was realized by diamond machinable and wear resistant sol-gel coatings. Crack free silica based hybrid coatings from base catalyzed sols from tetraethylorthosilicate (TEOS: Si(OC2H5)4) and methyltriethoxysilane (MTES: Si(CH3)(OC2H5)3) precursors were deposited onto pre-machined steel molds by spin coating process followed by a heat treatment at temperatures up to 800°C. Crack-free multilayer coatings with a total thickness of up to 18 µm were achieved. Micro-machining of these coatings was accomplished by high precision fly cutting with diamond tools. Molds with micro-structured coatings were successfully tested for injection molding of PMMA optical components. The wear resistance of the coatings was successfully tested by injection molding of 1000 PMMA lenses. Hardness and elastic modulus of the coatings were measured by nano indentation. The chemical composition was measured by X-ray photo electron spectroscopy (XPS) as a function of the sol-gel processing parameters.

Abstract: Based on orthogonal experiment design, a study on the one-fourth arc special-shaped surface of Lord Red granite was conducted, the relationship between cutting speed, feed rate and cutting depth with tool wear rate and grinding force were analyzed. The research shows that tool wear rate and grinding force are basically reduced with the increase of cutting speed and aggrandized with the increase of feed rate and cutting depth. By regression analysis the empirical formulas of grinding forces are concluded, it is the theoretical foundation for on-line monitoring grinding force to optimize the processing parameters for machining irregular surface of granite.

Abstract: The wear pattern and its mechanisms of Single Crystal Diamond (SCD) tool has been investigated experimentally and theoretically during ultra-precision turning of SiC particle-reinforced aluminum matrix composite. The results showed that micro wear, chipping, peeling, abrasive wear and chemical wear were the dominating wear patterns of SCD tools. Coupled with XRD analysis on the machined surface and Raman studies on the flank wear land of SCD tool, it was pointed that the combined effects of abrasive wear of SiC particles and catalysis of copper in the aluminum matrix have caused the severe graphitization.

Abstract: Tool wear in diamond cutting sinusoidal mircostructured surfaces may be quite different from that in conventional diamond turning as the sharp point tip tool is used and the depth of cut changes cyclically along the profile of the cutting surfaces. In present paper, the diamond tool geometry requirements for cutting sinusoidal microstructured surfaces were analyzed. A series of controlled cutting tests of LY12 were executed on a 2-aixs bench type ultra-precision turning machine which equipped a fast tool servo (FTS). Tool wear patterns were investigated with varied feed speed in diamond cutting sinusoidal microstructured surfaces. The scanning electron microscope (SEM) examination results of tool wear showed that the visible wear was occurred after a short cutting distance. The gradual wear around tool tip and along cutting edges was predominant wear pattern with a low feed speed. The catastrophic fracture wear at tool tip was happened with a high feed speed and the wear of sharp point tip of tool was more serious than that of cutting edges of tool.

Abstract: The objective of this work is to develop analysis methods based on 3D-FEM simulations for optimum design of the diamond cutting tools under various loading conditions, considering the sintering process of diamond–metal matrix to originate residual stresses. The work concerns the use of finite element simulation for modelling of thermal residual stresses generated during the sintering process of metal matrix diamond tools normally employed by the industry. Stress distribution fields were determined for the diamond shape using a 4-node, reduced integration ABAQUS solid element type C3D4. The residual stress fields in the nearby region of a diamond particle are examined to study the effects of the sintering temperatures, the stress–strain behaviour of the metal matrix and the compression pressure on the upper surface of the metal matrix. Through the simulations of the cutting forces on the diamond, it is demonstrated that the diamond retention capacity induced by the metal matrix (important for extending the life of a diamond tool) is principally dependent on the sintering process. Optimum design of the diamond cutting tools can be achieved by selecting the appropriate sintering temperatures, the stress–strain behaviour of the metal matrix and the compression pressure on the upper surface of the metal matrix during the sintering process.

Abstract: Silicon–aluminum alloys (Al-Si), with Si contents up to 12% are important materials in automotive and aeronautical industries due to their low density and high wear resistance. The cutting force, surface roughness and tool wear of diamond tools and cemented carbides tool were compared when turning Al-Si alloy. The results indicated that there wasn't remarkable difference between diamond tools and cemented carbides tool in cutting force and surface roughness when rough turning silicon-aluminum alloy. While in finish turning, less cutting force and surface roughness can be obtained when using diamond tools. The flank wears of diamond tools were less than cemented carbides. It was concluded that diamond tools can improve machining characteristics and reduce tool wear.

Abstract: An attempt has been made to investigate the new generational manufacturing technology for multi-layer diamond tools by brazing. A kind of new multi-layer brazed diamond core drills with random grains distribution was made by mixing diamond particles with brazing alloy powders. And a preliminary machining performance experiment was carried out through drilling granite. The testing results show the typical topography of the multi-layer brazed diamond core drills after drilling granite, just like that of multi-layer sintered ones, is that diamond grits drag long tails. Different from multi-layer sintered diamond core drills, no grit pull-outs can be seen during the whole drilling process because of chemical metallurgical effect between diamond grit and brazing alloy, the same as monolayer brazed diamond core drills. The main drawback to this kind of multi-layer brazed diamond tools is each individual particle is not subjected to the same drilling force throughout the drilling operation because of random grain distribution. This leads to premature fracture of the leading particles. Similarly, because large gaps between particles exist, the bond is being exposed to the workpiece, which leads to erosion of the bond. The overall performance is lower tool lives and slower drilling speeds. Therefore, ideally, diamond particles should be evenly distributed throughout the bond, which means they are all subject to the same drilling forces and the multi-layer brazed diamond tool is operated at its optimum efficiency.

Abstract: Effects of some alloying additives such as Cr, Co, Ni, Mn, Al on the microstructures, resulting fracture surfaces of bronze base bonds and diamond composites as well as the bonding between the metal bonds and diamond grits were studied. Experimental results revealed that under the hot pressing conditions sufficient alloying couldn’t develop as it does in the cast bronze. The degree of segregation varied with the melting point of the alloying elements. The metal with higher melting point led to a more serious segregation. Addition of strong carbide formation elements like Cr, Co could improve the bonding between the metal bonds and diamond grits and the retension of metal bond for diamond was enhanced in a way. However the addition of Al, Mn and Ni did not bring much improvement on the bonding between the metal bonds and the diamond grits.

Abstract: While using natural diamond tool to cut stainless steel alloy, the cutting parameters have a great impact on tool life. The impact of cutting parameters on influencing cutting tool life was studied through experiments on using ultrasonic vibration to cut special stainless steel alloy. The experiments were conducted with various cutting speeds, different tool feed rates, altered cutting depths and adapted vibration parameters. Consequently, the relative curve between cutting parameters and tool life was obtained. The experimental results indicated that in the ultrasonic vibration the diamond tool can manufacture stainless steel alloy precisely and made surface quality well. The tool life depended on the spindle speed of machine tool as well as the amplitude and frequency of ultrasonic vibration to a large extent. Among the parameters which affect the processing quality, cutting speed was utmost, followed by feed followed, and the influence of back cutting depth was insignificant.