Papers by Author: Song Zhang

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Authors: Song Zhang, Jian Feng Li, Hong Gang Lv, Wei Dong Chen
Abstract: In the present research, an attempt has been made to experimentally investigate the cutting forces in hard milling of H13 steel with coated carbide tools under dry, MQL (minimum quantity lubrication) and MQCL (minimum quantity cooling lubrication) cutting conditions. Based on Taguchis method, four-factor (cutting speed, feed per tooth, radial depth of cut, and axial depth of cut) four-level orthogonal experiments were employed. It is found that the periodical fluctuation of the cutting forces caused by the variation of the undeformed chip thickness with the entry/exit of the cutting edge is an essential feature of the hard milling process. The empirical models for cutting forces are established, and ANOVA (analysis of variance) indicates that the quadratic models can well express the relationship between cutting forces and cutting parameters.
Authors: Song Zhang, Xing Ai, Wei Xiao Tang, J.G. Liu
Abstract: High-speed machining has become mainstream in machining manufacturing industry. In industries such as moldmaking and aerospace, it has become the norm rather the exception. The centrifugal force increases as the square of the speed. At rotational spindle speeds of 6,000 r/min and higher however, centrifugal force from unbalance becomes a damaging factor and it reduces the life of the spindle and the tool, as well as diminishes the quality of the finished product. Under high rotational speed, good balance becomes issue. High-speed machining experimental results shown that a well-balanced tool/toolholder assembly could obviously improve machining quality, extend tool life and shorten downtime for spindle system maintenance etc.
Authors: Lin Tao Zou, Song Zhang, Wei Dong Chen, Guo Qiang Zhao, Bin Zhao
Abstract: In the present research, a model of the cryogenic oil mist flow field of milling cutters with different interior oil channels was conducted to determine the effects of rotational speed, temperature and flow of cold air. For the milling cutters with single direct hole and double direct holes, the increase of the rotational speed has little effect on the velocity and temperature of the measuring points at different distances along the milling cutters. For the milling cutter with double direct holes the separated streamlines of double direct holes are nearer with the rise of the distance because of the viscidity of cutting fluid. When the distance exceeds 5mm, the separated streamlines combine with each other. For the milling cutter with double helical holes the streamlines of cold air present irregularly. At last, some of the simulated results were validated.
Authors: Lin Tao Zou, Song Zhang, Qing Zhang
Abstract: An investigation of the cryogenic oil mist flow field of nozzle was carried out in this study. A domain of the nozzle jet area was modeled with Pro/ENGINEER. CFD (Computational Fluid Dynamics) analysis was used to state the velocity field of different distances from the outlet of nozzle. The simulating velocity field was verified with the experimental results. Experimental results on velocity were measured by SYT-2000 digital multipurpose wind speed gage. The orthogonal experiment was designed to investigate the main effects parameters on velocity and temperature. It indicates that higher flow of cold air and smaller diameter of nozzle’s outlet will generate higher velocity. The temperature of cold air has most influence on the temperature of measuring point. Finally the optimum structure of the spraying nozzle was proposed.
Authors: Song Zhang, Xing Ai, Wei Xiao Tang, Jun Zhao
Authors: Song Zhang, Y.B. Guo
Abstract: High-speed machining thoroughly hardened tool steels has emerged as a competitive finishing technology for making dies and molds. The objective of this paper is to develop an optimization method for the better (i. e., lower value) surface roughness in terms of cutting parameters when high-speed milling hardened H13 steel. The cutting parameters to be considered were cutting speed, feed per tooth, radial depth of cut, and axial depth of cut, respectively. A series of high-speed milling experiments of hardened H13 steel using PVD coated carbide inserts without any cutting fluids were performed to measure the surface roughness data. Taguchi orthogonal arrays, signal-to-noise (S/N) ratio, and analysis of variance (ANOVA) were used to evaluate the effects of cutting parameters on surface roughness and to find the optimal factor/level combination for the better surface roughness. The investigations of this study would be used for design optimization of cutting parameters to obtain the better surface roughness.
Authors: Zhe Li, Song Zhang, Yan Chen, Peng Wang, Ai Rong Zhang
Abstract: Dynamic characteristics of numerical control (NC) machine tools, such as natural frequency and vibration property, directly affect machining efficiency and finished surface quality. In general, low-order natural frequencies of critical components have significant influences on machine tool’s performances. The headstock is the most important component of the machine tool. The reliability, cutting stability, and machining accuracy of a machining center largely depend on the structure and dynamic characteristics of the headstock. First, in order to obtain the natural frequencies and vibration characteristics of the headstock of a vertical machining center, modal test and vibration test in free running and cutting conditions were carried out by means of the dynamic signal collection and analysis system. According to the modal test, the first six natural frequencies of the headstock were obtained, which can not only guide the working speed, but also act as the reference of structural optimization aiming at frequency-shift. Secondly, by means of the vibration test, the vibration characteristics of the headstock were obtained and the main vibration sources were found out. Finally the corresponding vibration reduction plans were proposed in this paper. That provides the reference for improving the performance of the overall unit.
Authors: Qing Zhang, Song Zhang, Jia Man, Bin Zhao
Abstract: Surface roughness has a significant effect on the performance of machined components. In the present study, a total of 49 end milling experiments on AISI H13 steel are conducted. Based on the experimental results, the signal-to-noise (S/N) ratio is employed to study the effects of cutting parameters (axial depth of cut, cutting speed, feed per tooth and radial depth of cut) on surface roughness. An ANN predicting model for surface roughness versus cutting parameters is developed based on the experimental results. The testing results show that the proposed model can be used as a satisfactory prediction for surface roughness.
Authors: Song Zhang, Xing Ai, Jun Zhao, J.G. Liu
Abstract: During high-speed machining, in order to make cutting tools work reliably and obtain ideal machining quality, not only good static characteristics, but also good dynamic characteristics are necessary. In this paper, with the help of the close combination of experimental research and modal parameter identification technique, the dynamic characteristics of the machine tool/cutting tool system were analyzed. Experimental results indicated that studying the effect of the dynamic characteristics on cutting force, machining accuracy and surface roughness could provide theoretical basis for effectively excluding the resonance zone that obviously destroyed machining quality and then optimizing cutting parameters further.
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