Papers by Keyword: Hard Cutting

Abstract: Vibration of cutting process is an important factor to influence the surface roughness. By Orthogonal design, take hard cutting surface roughness test for bearing steel GCr15 with 62~64HRC, analyzing the law of the variation of cutting parameters effect the amount of vibration and the surface roughness value. And it establishes the formula about vibration and surface roughness. The amount of vibration and the surface roughness increases first and then decreases while the cutting speed increases in a specific area, meanwhile its vibration will reduce and its surface roughness will enlarge while the feed increases. The cutting depth has a little influence to surface roughness and vibration, and the cutting depth is first decreased and then increased accompanied by the tool nose radius increases with the increase of vibration and the surface roughness. The research can provide reference for improving the surface quality.

Abstract: One of the most important issues to be addressed in hard cutting pertains to the evaluation of tool life as it is closely connected to machining quality and overall process cost. The attributes of tool life can be mathematically calculated based on machining conditions and other characteristics of the cutting process. In this paper the formulation developed for CBN tools, applied for the machining of 100Cr6 bearing steel is presented. Experiments were carried out for the validation of the theoretical approach. Additionally, a novel indicator, namely wear intensity, is analyzed and discussed, based on experimental results. Wear intensity is calculated as the ratio of flank wear to cutting length. From the analysis it can be concluded that the prognosis of tool life can be accurate with the proposed method. Furthermore, interesting and useful results are reported in connection to wear intensity and cutting speed in hard cutting.

Abstract: Hard cutting technology is a green cutting technology of broad application prospect, but hard cutting is more likely to produce vibration compared with traditional cutting, and the production efficiency, machining quality, environment, cost and machine tools and tool life will be affected by the precision in the process of hard cutting chatter. Turning hardened steel GCr15 cylindrical bar using PCBN inserts on the lathe CAK6150DI analyzed the cutting vibration signal characteristic in the different state of cutting tool; analyzed the related features of dynamic cutting force and cutting vibration signals; and observed the microstructure on the machined surface. Analysis results show that the vibration of smooth cutting state is given mainly with forced vibration and noise, vibration signals are produced with the typical characteristics of high range frequency in frequency zone, disperse frequency domain energy; When the cutting chatter, strong self-excited vibration appeared and occupied the main position of vibration signal energy, frequency domain energy is concentrated in nearly natural frequency of the main vibration system of the lower cutting. The results of the study can provide theoretical guidance for the control of vibration in hardened cutting process.

Abstract: Hard cutting process is easy to produce serrated chip. Hardened steel GCr15 as the object for the study, chip morphology was studied on hard cutting test and chip cross-sectional microscopic analysis methods. The boundaries of ribbon cuttings to serrated chips cutting was determined, under certain conditions of PCBN cutting tool cutting precision hardened steel GCr15, and form a quantitative description of the chip. With the increase in the amount of cutting, serrated chips have the degree of improved trend, in which the most significant impact of cutting speed, while the hardness increases, the degree of sawtooth also increases. Hard cutting research will enrich the theory provides a theoretical basis for the choice of cutting parameters.

Abstract: The flutter in the hard cutting has a significant impact on the efficiency of production, the quality processed, the environment in processing, the cost, and the life of the machines and tools . However, the application of the method named numerical simulation in MatLab predicted the stability limitation of the hard cutting system, analyzed the influence of cutting system dynamics parameters on the stability limitation of system, at the same time, an experimental verification of hard cutting had been carried out. And the results of analysis showed that improving the system stiffness K and cutting system damping ratio ζ, cutting the stiffness coefficient K_c and the direction coefficient , adjusting the cutting speed to the correct, reducing the amount of turning a_p, decreasing the tip radius of circular arc , increasing the feeding f can be used as the methods of vibration reducing in the system. So the results of the research provide reference for the reasonable choice of cutting parameters.

Abstract: The metal machining 3D finite element model was established on the basis of the thermal-elastic-plastic finite element theory. And the machined surface residual stress simulation in different cutting parameters was obtained through the finite element analysis. It is concluded that the residual stress distribution variation is spoon-shaped curve. When the feed increased, the slope of the curves is smaller, however the speed increased, the slope of the curves is higher and the stress tends to negative values quicker. Finally, the experiments are carried out. The result was basically consistent with the simulation.

Abstract: Based on the application of elliptical vibration cutting method to precision machining of hard and brittle materials and material softening technology through laser heating, a novel composite cutting technique, laser heating and ultrasonic elliptical vibration assisted cutting, is applied to process sintered tungsten carbide. The simulation of the orthogonal cutting process and the effect of frequency and amplitude of vibration and laser heating temperature on cutting force are discussed by using FEA method. Research results have revealed that the main peak of the transient force components increase with the increase of vibration frequency, decrease with the increase of vibration amplitude and laser heating temperature. Moreover, the friction reversal phenomenon is improved with the increase of vibration frequency and amplitude, resulting in the decrease of average cutting force. Compared to common cutting and traditional one-dimensional ultrasonic vibration cutting, the composite cutting technology put forward in this paper has unique cutting force characteristics for such super hard material because of combined action of friction reversal and intermittence cutting for ultrasonic elliptical vibration and material softening for laser heating. The research in the paper has provided a practical reference for the further experiments of laser and ultrasonic assisted cutting.

Abstract: The paper deals with research concerning optimal technological parameters in diamond burnishing after hard turning by standard tool geometry and by wiper geometry. Burnishing is a less known method, by which the surface of workpiece is finished by a harder tool, without chip removal. Experiments focus on the surface roughness of workpiece, at combination of feed (f) and burnishing force (F_p). We measured also machining forces (F_c, F_f, F_p) at hard turning. Workpiece was made of 100Cr6-type bearing steel with hardness of HRC64.

Abstract: The main characteristic of hard turning process is easy to produce serrated chip. The chip deformation will impact greatly turning process. It is very important to analysis the chip formation and morphology during precision turning process of hardened steel. The deformation mechanism of serrated chip formation process and its chip morphology of chips produced during precision turning process of the hardened steel GCr15 is studied in hard cutting experiment by the methods such as numerical simulation of two-dimensional finite element analysis of turning, chip cross-sectional microscopic analysis and other methods .High speed precision turning of hardened steel GCr15 produces morphology of continuous chip and serrated chip; Serrated chip has the typical characteristics of the adiabatic shear slip after section such as apical surface of the serrated chip is composed of multilayer rolling dentate shear plane, a single surface of one tooth is not smooth, but no crack. Extrusion grooves is produced from tooth root to tip; Intensive slip line on serrated chip cross-section can be saw by microscopic observation; Fracture surface of the serrated chip presents small tumor tissues. The results show that the reason of hardened GCr15 steel forming serrated chip is periodic adiabatic shear fracture, and the research provides a theoretical reference application of hard turning technology.

Abstract: The machining of hardened surfaces can be done even fulfilling the ever stricter accuracy and quality prescriptions, besides the economic efficiency. Decisively, hard machining is highlightedly important in finish processes because the components must meet increased functional demands. Therefore the number and/or the hardness of the hard surfaces on the components is continuously increasing. In practice the demand for such components is high since they are more wear resistant and their tool life may be higher. Today there are several possibilities for finish machining of components having hard surfaces. We have done experiments for hard machining of inner cylindrical surfaces. The examined procedures were as follows: grinding, hard turning, combined machining. The first two procedures (hard turning, grinding) have got different procedure-specific advantages and disadvantages. Combining these two procedures, using-up the advantages of them, the efficiency of the production can be increased. This paper outlines these procedures of hard machining, their applicability, the increase of their efficiency, and the possibilities provided by the combination of the procedures.