Analysis of Mist Flow in MQL Cutting
Analysis of Mist Flow in MQL Cutting
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DOI：
10.4028/www.scientific.net/kem.257-258.339
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发表时间：
2004-01
期刊：
影响因子：
--
通讯作者：
Y. Kamata;T. Obikawa;J. Shinozuka
中科院分区：
文献类型：
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作者：
Y. Kamata;T. Obikawa;J. Shinozuka
为了保护地球环境，在金属切削中广泛要求不使用含有表面活性氯化合物的切削油。因此，最小量润滑（MQL）引起了人们的关注。在MQL加工中，有必要优化油雾的供应，使油雾集中在刀尖附近，以获得更好的润滑条件。利用通用有限元软件ANSYS/FLOTRAN对MQL切削过程中刀具后刀面与加工表面之间的雾流进行了分析。通过分析，可视化了刀具间隙面与加工表面之间的雾流和压力分布。定量地研究了雾流的速度和方向以及切割速度对供应到切割边缘附近空间的雾量的影响。最后给出了切削过程中最小切削余量的优化条件。切削油广泛用于处理切屑、提高加工精度和表面粗糙度、延长刀具寿命。为了保护地球环境，现在要求在机械加工中使用无氯切削油。废切削油的处理成本日益增加。执行切削油的使用规定。因此，从环境和经济的角度来看，最小量润滑（MQL）引起了人们的关注，并已被大力研究[1，2，3]。在车削[4]、铣削[5]、钻削[6]和攻丝[7]中选择适当的条件时，用压缩空气向刀尖吹少量植物油或可生物降解的合成酯（约10 ml/h）的MQL加工在刀具寿命、润滑效率和表面粗糙度方面与传统的湿式加工几乎相等。在MQL加工中，切削油变成雾状。因此，有必要研究油雾的流动，以有效地将其集中在工具尖端附近。在这项研究中，MQL切断的优化研究的基础上分析的雾流。首先，分析可视化的雾流和压力之间的工具间隙面和完成的表面，并说明了雾吹速度，雾吹角度和切削速度的影响，雾供应到附近的切削刃。其次，通过对排气时后刀面压力分布的测量，证明了在切削刃附近产生的吸力能有效地促使雾流向刀具边缘流动。最后讨论了MQL的最佳切断条件。雾流的三维分析利用有限元软件ANSYS/FLOTRAN，对MQL切削过程中刀具间隙面与加工表面之间的雾流进行了三维分析。分析区域及其有限元网格如图1和2所示。1和2;后角为5 °，切削宽度为5 mm，刀保持器截面为4 mm × 25 mm，槽深为5 mm，无需考虑前角和未变形切屑厚度。由于工具的对称性，只有一半的区域用Key Engineering Materials Online：2004 - 02 - 15 ISSN：1662 - 9795，Vols. 257 - 258，pp 339 - 344 doi：10.4028/www.example.com © 2004 Trans Tech Publications Ltd，Switzerland版权所有。未经Trans Tech Publications Ltd（www.scientific.net）的书面许可，不得以任何形式或任何方式复制或传播本文的任何内容。（Semanticscholar.org-13/03/20，19：19：42）八节点等参六面体。元素和节点的数量分别为1326和1844。由于在通常的MQL切断条件下，喷雾的雷诺数为数万量级，因此假定为稳态可压缩绝热湍流。所用湍流模型为标准k模型。与压缩空气相比，吹到工具尖端的油的量是无限小的。因此，在分析中假设油雾和空气的物理性质相同。图1分析模型（分析区域）图2六面体有限元网格间隙角：° 5控制方程给出了雾流的控制方程，采用i x方向的速度i u和求和约定。(a)连续性方程0）（= i i x u. (1)（B）动量方程
It is widely required not to use cutting oils containing surface reactive chlorine compounds in metal cutting for conservation of the global environment. Therefore, the minimal quantity lubrication (MQL) attracts attentions. In MQL machining, it is necessary to optimize the supply of oil mist so that the mist will concentrate near the tool tip for a better lubrication condition. The mist flow between the tool clearance faces and finished surfaces in MQL cutting was analyzed using a general purpose FEM software ANSYS/FLOTRAN. Through the analysis, the mist flow and pressure between the tool clearance faces and finished surfaces were visualized. Influences of the velocity and direction of the mist flow, and the cutting speed, on the amount of mist supplied to the space near the cutting edge were investigated quantitatively. Finally, optimal conditions of MQL were presented for the cutting process. Introduction Cutting oils are widely used for the disposal of chip, improvement of machining accuracy and surface roughness, and prolongation of tool life. These days, it is required to use chlorine-free cutting oils in machining for the conservation of the global environment. Disposal cost of the waste cutting oils is increasing. Regulations of use of the cutting oils are enforced. Therefore, from the environmental and economical points of view, minimal quantity lubrication (MQL) attracts attentions and has been investigated vigorously [1, 2, 3]. MQL machining that a small amount of vegetable oil or biodegradable synthetic ester (about 10 ml/h) is blown to the tool tip with compressed air is nearly equal to the traditional wet machining in tool life, efficiency of lubrication and surface roughness when appropriate conditions are selected in turning [4], milling [5], drilling [6] and tapping [7]. Cutting oil turns into mist in MQL machining. Therefore, it is necessary to investigate the flow of oil mist to concentrate it near the tool tip effectively. In this study, the optimization of MQL cutting-off was examined based on the analysis of mist flow. First, the analysis visualized the mist flow and pressure between the tool clearance faces and finished surfaces, and illustrated the influences of the mist blowing velocity, mist blowing angle and cutting speed on the amount of mist supplied to near the cutting edge quantitatively. Secondly, measurement of pressure distribution on the flank face when turning air blow off, proved that the suction generated near the cutting edge caused the mist flow to near the tool edge effectively. Finally, better conditions of MQL cutting-off were discussed. Three Dimensional Analysis of Mist Flow The mist flow between the tool clearance faces and finished surfaces in MQL cutting-off was analyzed under three-dimensional conditions using a FEM code ANSYS/FLOTRAN. The region of analysis and its finite element mesh are shown in Figs. 1 and 2, respectively; the clearance angle is 5 degrees, cutting width is 5 mm, the cross section of tool holder is 4 mm×25 mm and the depth of the groove is 5 mm. It is not necessary to take the rake angle and undeformed chip thickness into consideration. Because of the symmetry of the tool, only the half of the region is modeled with Key Engineering Materials Online: 2004-02-15 ISSN: 1662-9795, Vols. 257-258, pp 339-344 doi:10.4028/www.scientific.net/KEM.257-258.339 © 2004 Trans Tech Publications Ltd, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific.net. (Semanticscholar.org-13/03/20,19:19:42) eight-node isoparametric hexahedra. The number of elements and nodes is 1326 and 1844, respectively. A steady-state compressible adiabatic turbulent flow is assumed because Reynolds number of mist blow is of the order of ten thousands under the ordinary MQL cutting-off conditions. The turbulent flow model used is the standard kmodel. The oil blown to the tool tip is infinitesimally small in amount as compared with the compressed air. Hence, it is assumed that the physical properties of oil mist and air are the same in the analysis. Fig. 1 Analysis model (region of analysis) Fig. 2 Hexahedral finite element mesh Clearance angle: ° 5 Governing Equations. Governing equations of the mist flow are written, using the velocity i u in i x direction and the summation convention, are provided. (a) Continuity equation 0 ) ( = i i x u . (1) (b) Momentum equation