Search Results (13)

An analysis of the existing methods of sintering diamond-containing composites is presented. On the basis of mathematical modeling and experimental studies, the conditions of the laser liquid-phase sintering of diamond-containing composites under which they retain their strength are determined. The energy and technological parameters of the laser irradiation process are characterized, which determine the range of laser processing modes within which no oxidation and crack formation occur, and a high-quality composite with specified geometrical parameters is formed. It has been proven that composites consisting of synthetic diamond grains and a metal bond do not lose strength under the condition that the temperature during laser heating does not exceed 1600 °C and the exposure time is 0.3 s. Electron microscopy and X-ray diffractometry were used for experimental studies of the microstructure and phase composition of the sintered layers. A new design and manufacturing method for a drum-type abrasive tool with replaceable diamond inserts for grinding large-sized aircraft and shipbuilding products are proposed. Components of a laser technological complex for the implementation of the process of sintering the diamond-containing layer of the abrasive inserts of the drum have been developed. Full article

Nowadays, high requirements imposed by mechanical components make it necessary to develop modern production methods. Additive technologies have been dynamically developing in recent years, showing many advantages associated with the fabrication of elements with complex geometries and structures. One of the areas where the potential of additive technologies is exploited is the rapid tooling sector, which is based on the rapid production of tools and components used in various manufacturing methods. Currently, apart from industrial additive fabrication using metal and plastic powders, desktop and low-cost devices for additive manufacturing are gaining more and more importance in the production of functional elements. This paper presents the experimental results obtained from testing the micro-abrasive acrylonitrile–butadiene–styrene ABS tools fabricated by fused filament fabrication (FFF) technology and reinforced with SD 28/20 diamond grains uniformly distributed on the working surface of the tools after they were made. Precision surface grinding operations of 41Cr4 alloy steel were carried out on a portable five-axis CNC milling machine using wheels with continuous and serrated working surfaces. The tool with a serrated working surface enabled a more efficient material removal and produced a better surface finish. In particular, a low wear rate of both FFF-printed tools was confirmed after all experiments. Promising results were obtained, showing the potential for a wider industrial application of the tested tools. Full article

In recent years, the vitrified bond diamond grinding wheel has been applied widely in automotive, aerospace and machine tools of manufacturing industries. However, the main problems of low intensity and poor wettability between the vitrified bond and diamond abrasive limit its further application. In this study, BaO was added into the basic SiO₂–B₂O₃–Al₂O₃–R₂O vitrified bond system, and the impact of BaO on the wettability, thermal and mechanical behavior of vitrified bond and vitrified bond diamond composites was systematically discussed, respectively. The test indicated that when the vitrified bond containing BaO of 6 wt.% was sintered with diamond abrasive at 750 °C, a continuous barium feldspar phase transition layer between diamond abrasive and the bond was generated, which ameliorated the wet property of the bond–diamond abrasive. The contact angle varied from 59° on the blank sample to 35°, and the expansion coefficient changed from 6.24 × 10⁻⁶/K to 5.30 × 10⁻⁶/K. The Rockwell hardness and flexural strength of the vitrified bond diamond composites achieved the peaks of 117.5 MPa and 113.6 MPa, respectively, which increased by 20.2% and 16.5% compared with that of sample without the addition of BaO. Full article

Machining CMCs under productivity conditions while limiting tool wear and material damage is a challenge for applications such as jet aircraft engines and industrial turbines. This contribution focused on developing a method to characterize the wear of abrasive tools based on fractal dimensions. This solution allows characterization of the state of the tool after each machining and identification of the type of damage to the tool (regular wear of the diamond grains, cleavage, or breakage) and its influence on the cutting forces, in addition to damage to the machined material and the quality of the machined surface. Thus, the chipped area and the maximum chipping are directly associated with the fractal dimension of the tool surface and the metal removal rate of the process. The quality of the surface (Sa, Sz, and Sq) is associated with the fractal dimension of the surface of the tool characterizing the state of the grinding wheel and the radial depth of cut ae characterizing the engagement of the tool in the CMC material. Moreover, the results also demonstrated that the use of an abrasive tool associated with cutting conditions close to milling and not grinding is a viable solution. Full article

Carbon fiber reinforced plastic (CFRP) is used in various industries because of its high specific strength, but it is well known as a difficult material to cut. In this study, we developed a disc-shaped electrodeposited diamond wire mesh grinding wheel as a new method for cutoff and grooving with a large aspect ratio for CFRP. We confirmed that this tool could be used for machining at a feed rate of 1000 mm/min, equivalent to that of an abrasive waterjet. This tool discharges generated chips through the spaces in the wire mesh, preventing clogging and thereby enabling the suppression of machining temperature. No burrs or delamination were observed on the surface machined with the wire mesh grinding wheel, and the surface roughness was Ra = 2.76 µm. However, the groove width was larger than the wheel thickness due to the runout of the wheel. Additionally, the moderate elasticity and durability of the tool suggest that it might extend tool life by avoiding the crushing of abrasive grains. Full article

The application of hard and brittle materials such as single-crystal silicon in small parts has expanded sharply, and the requirements for their dimensional accuracy and processing surface quality have been continuously improved. This paper proposes using mechano-chemical micro-grinding tools to process single-crystal silicon, which can realize the high-quality and efficient processing of such tiny parts through mechano-chemical composite action. The microstructure composition of the mechano-chemical micro-grinding tools was designed, the theoretical analysis model of grinding force was established and verified by experiments, and the temperature field distribution during mechano-chemical micro-grinding of single-crystal silicon was simulated and studied, which provided a theoretical basis for mechano-chemical action. Special micro-grinding tools were developed, and mechano-chemical micro-grinding processing tests were carried out. The results show that the coupling synergy of grinding force and grinding temperature improves the chemical activity of the micro-grinding tools, thereby promoting the solid–solid phase chemical reaction of abrasives and additives at the sharp points of the surface of the micro-grinding tools. And when the content of cerium oxide abrasive is 25%, it is more conducive to the solid–solid phase chemical reaction, and calcium oxide can be used as an additive to promote the active agent of solid–solid phase chemical reaction, improve the degree of chemical reaction, and thus improve the removal rate of materials. Soft reactants that are easy to remove are generated on the surface of monocrystalline silicon and are removed by the mechanical friction between the abrasive grain and the surface of the silicon wafer, and finally achieve low-damage processing with a surface roughness of Ra1.332 nm, which is much better than the surface roughness of Ra96.363 nm after diamond abrasive processing. Full article

The specific features of the destruction of tool ceramics, associated with structural heterogeneity and defects formed during diamond grinding, largely determine their reduced reliability (dispersion of resistance). This is most pronounced at increased heat and power loads on the contact surfaces and limits the industrial application of ceramic cutting tools. The surface layer of industrially produced Al₂O₃+TiC cutting inserts contains numerous defects, such as deep grooves and torn grains. During the milling of hardened steels of the 100CrMn type with increased cutting parameters, the “wear–cutting time” curves have a fan-shaped character with different wear rates. The resistance of the tool that was taken from one batch before reaching the accepted failure criterion has a significant variation in values (VarT is 30%). The study is aimed to evaluate the influence of the condition of the surface layer of Al₂O₃+TiC inserts processed by various types of abrasive treatments, such as diamond grinding, lapping and polishing, on the quality of the (TiAl)N and (TiZr)N coatings and the reliability of prefabricated end mills. The obtained “wear–cutting time” curves are characterized as closely intertwined bundles. The coefficient of resistance variation (the tool’s reliability) decreases by more than two times (14%). This can be used further in coating development to improve the performance of CCT. Full article

With respect to the truing and sharpening of diamond abrasive grinding tools, traditional machining methods are briefly described, and new dressing methods, such as the laser dressing method, are described in detail. It is pointed out that laser dressing of diamond abrasive tools is a green processing method with high efficiency and no environmental pollution. Numerical simulation research on pulse laser dressing of a bronze diamond abrasive grinding wheel was carried out, and a cumulative heat transfer model of laser dressing energy was developed. The temperature evolution law of the bronze bond and diamond abrasive grains dressed by pulsed fiber laser was determined by numerical analysis of the model. An experiment on the laser dressing grinding wheel was carried out; it was found that when the laser power density was 2.52 × 10⁸ W/cm²∼3.36 × 10⁸ W/cm², the bronze bond materials could be properly removed, and the diamond abrasive grains could be better sharpened. The laser dressing method can achieve the combination of diamond abrasive grinding tool sharpening and truing. The experiment not only demonstrated the correctness and feasibility of the theoretical model but also provided process optimization for research into pulse laser dressing of diamond abrasive grinding tools. Full article

Grinding is one of the effective manufacturing processes with which to produce highly accurate parts with an ultra-fine surface finish. The tool used to remove materials in grinding is called the grinding wheel. Abrasive grains made of extremely hard materials (alumina, silica, cubic boron nitride, and diamond) having a definite grit size but a random shape are bonded on the circumferential surface of the grinding wheel. The fabrication process is controlled so that the wheel exhibits a prescribed structure (in the scale of soft to hard). At the same time, the distribution of grains must follow a prescribed grade (in the scale of dense to open). After the fabrication, the wheel is dressed to make sure of its material removal effectiveness, which itself depends on the surface topography. The topography is quantified by the distribution and density of active abrasive grains located on the circumferential surface, the grains’ protrusion heights, and their pore volume ratio. The prediction of the surface topography mentioned above requires a model that considers the entire manufacturing process and the influences on the grinding wheel properties. This study fills this gap in modelling the grinding wheel by presenting a surface topography model and simulation framework for the effect of the grinding wheel fabrication process on the surface topography. The simulation results have been verified by conducting experiments. This study will thus help grinding wheel manufacturers in developing more effective grinding wheels. Full article

Cutting force is one of the most important factors in the ultrasonically assisted grinding (UAG) of hard and brittle materials. Many theoretical and experimental studies show that UAG can effectively reduce cutting forces. The existing models for UAG mostly assume an ideal grinding wheel with abrasives in both the end and lateral faces to accomplish material removal, whereas the important role of the transition fillet surface is ignored. In this study, a theoretical cutting force model is presented to predict cutting forces with the consideration of the diamond abrasives in the end face, the lateral face, and the transition fillet surface of the grinding tool. This study analyzed and calculated the vibration amplitudes and the cutting forces in both the normal and tangential directions. It discusses the influences of the input parameters (rotation speed, feed rate, amplitude, depth and radius of transition fillet) on cutting forces. The study demonstrates that the fillet radius is an important factor affecting the grinding force. With an increase in fillet radius from 0.2 to 1.2 mm, the grinding force increases by 139.6% in the axial direction and decreases by 70% in the feed direction. The error of the proposed cutting force model is 10.3%, and the experimental results verify the correctness of the force model. Full article

Polycrystalline diamond (PCD) tools are widely used in industry due to their outstanding physical properties. However, the ultra-high hardness of PCD significantly limits the machining efficiency of conventional abrasive grinding processes, which are utilized to manufacture PCD tools. In contrast, electrical discharge grinding (EDG) has significantly higher machining efficiency because of its unique material removal mechanism. In this study, the quality and performance of PCD tools machined by abrasive grinding and EDG were investigated. The performance of cutting tools consisted of different PCD materials was tested by high-speed turning of titanium alloy Ti6Al4V. Flank wear and crater wear were investigated by analyzing the worn profile, micro morphology, chemical decomposition, and cutting forces. The results showed that an adhesive-abrasive process dominated the processes of flank wear and crater wear. Tool material loss in the wear process was caused by the development of thermal cracks. The development of PCD tools’ wear made of small-sized diamond grains was a steady adhesion-abrasion process without any catastrophic damage. In contrast, a large-scale fracture happened in the wear process of PCD tools made of large-sized diamond grains. Adhesive wear was more severe on the PCD tools machined by EDG. Full article

Brushing with bonded abrasives is a finishing process which can be used for the surface improvement of various materials. Since the machining mechanisms of abrasive brushing processes are still largely unknown and little predating research was done on brushing ceramic workpieces, within the scope of this work technological investigations were carried out on planar workpieces of MgO-PSZ (zirconium dioxide, ZrO₂) using brushing tools with bonded grains of polycrystalline diamond. The primary goal was the reduction of grinding-related surface defects under the preservation of surface roughness valleys and workpiece form. Based on microscopy and topography measurements, the grain size s_g and the brushing velocity v_b were found to have a considerable influence on the processing result. Furthermore, excessive tool wear was observed while brushing ceramics. Full article

Rotary ultrasonic machining (RUM) is a nontraditional and cost-effective machining method for hard and brittle materials, such as ceramics, optical glass, composite materials, and so on. RUM is a hybrid process that combines the material removal mechanisms of diamond abrasive grinding and ultrasonic machining. In RUM, a rotating cutting tool with metal-bonded diamond abrasive particles is ultrasonically vibrated in the axial direction while the tool spindle is fed toward the workpiece at a constant feedrate to remove material. It has been reported that continuous rotary ultrasonic machining has been successfully used to drill holes in K9 glass. Intermittent rotary ultrasonic machining is a newly introduced ultrasonic machining process, which uses a slotted cutting tool instead of a common metal bonded diamond cutting tool as used in continuous rotary ultrasonic machining. There has been no reported study to compare the effects of intermittent RUM and continuous RUM when machining K9 glass. This paper, for the first time, presents an experimental investigation to compare intermittent RUM and continuous RUM when machining K9 glass from the perspectives of cutting force, surface roughness, and chipping size. Full article