Effect of cutting parameters on tool wear in diamond turning of new optical aluminium grade
doi: 10.3788/CO.20160905.0579
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摘要: 光学器件和光学测量系统的关键部件主要通过超精密加工制造。铝合金具有很多优势,通常用于光子产业。光学领域对铝合金使用和需求的不断增加,促进了在铸造过程中采用快速凝固技术对铝合金等级重新改良的发展。优异的微观结构和改进的机械和物理性能是新型铝合金等级的特点。目前主要问题在于采用金刚石车削时,由于在切削性方面缺乏对铝合金性能的充分研究,导致机械加工数据库非常有限。本文通过改变金刚石的切削参数,测量切齿安装距超过4 km时金刚石刀具的磨损,研究了快速凝固铝合金RSA 905的切削性能。改变的机械加工参数为切削速度、进给速度和切削深度。结果表明切削速度对金刚石刀具的磨损影响最大。主轴转速为500 rpm、进给速度为25 mm/min、切削深度为15 μm时,刀具磨损达到最大值12.2 μm;主轴转速为1750 rpm、进给速度为5 mm/min、切削深度为5 μm时,刀具磨损达到最小值2.45 μm。通常,较高的切削速度、较低的进给速度和较短的切削深度的组合可以减少金刚石刀具磨损。建立了模型统计以分析金刚石刀具磨损。通过该模型可以生成磨损图,从而确定切削参数产生最小磨损的区域。结果证明,快速凝固铝是更好的选择,为机械工程师使用这种材料提供了参考。Abstract: Critical components in optical devices and optical measuring systems are mainly produced through the ultra-high precision machining. Aluminium alloys have been proven to be advantageous and very commonly used in the photonics industry. This ever-increasing use and demand in optics have led to the development of newly modified grades of aluminium alloys produced by rapid solidification in the foundry process. The newer grades are characterised by the finer microstructures and can improve mechanical and physical properties. Their main inconvenience currently lies in their having a very limited machining database as there is not enough adequate research contributions on their performance in terms of machinability when diamond turned. This paper investigates the machinability of rapidly solidified aluminium RSA 905 by varying diamond cutting parameters and measuring the diamond tool wear over a cutting distance of 4 km. The machining parameters varied were cutting speed, feed rate and depth of cut. The results show that the cutting speed is the most influential parameter on the diamond tool wear. The highest tool wear of 12.2 μm was achieved at the spindle speed of 500 rpm, the feed rate of 25 mm/min and the depth of cut of 15 μm. The lowest tool wear of 2.45 μm was recorded at the spindle of 1750 rpm speed, the feed rate of 5 mm/min and the depth of cut of 5 μm. Generally, a combination of higher cutting speeds, lower feed rates and smaller depths of cut caused less diamond tool wear. Statistical analysis was performed to develop a model for the diamond tool wear. Wear maps were generated from the model to identify zones where the cutting parameters produced the least wear. The results prove the rapidly solidified aluminium is a superior alternative to traditional aluminium alloys and can also provide a reference for machinists using this material.
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Physical mechanical properties AA 6061 AA 6082 RSA 905 Density/(g·cm-3) 2.7 2.7 2.95 Thermal expansion(10-6/K) 23 24 19 Thermal conductivity.(W·m-1·K-1) 166 180 100 Modulus of elasticity/GPa 70 70 91 Ultimate tensile strength/MPa 310 340 600 Yield strength/MPa 270 290 480 Elongation/% 12 6 6 Hardness 100 95 180 Table 2. Wear results
Exp No. Spindle
speed/rpmFeed rate/
(mm·min-1)Feed rate/
(μm·rev-1)Depth of
cut/μmPasses Total
time/sMRR/
(mm3·min-1)Wear/μm 1 1 750 25 14.29 25 20 24 117.81 5.37 2 1 750 25 14.29 5 20 24 23.56 5.07 3 3 000 5 1.67 15 2 14 14.14 2.40 4 1 750 15 8.57 15 12 24 42.41 5.72 5 1 750 15 8.57 15 12 24 42.41 5.72 6 1750 5 2.86 25 4 24 23.56 4.01 7 500 15 30.00 25 42 85 70.69 8.00 8 3 000 25 8.33 15 12 14 70.69 3.36 9 3 000 15 5.00 25 7 14 70.69 3.05 10 500 25 50.00 15 71 85 70.69 12.20 11 3 000 15 5.00 5 7 14 14.14 2.84 12 500 5 10.00 15 14 85 14.14 3.26 13 1 750 5 2.86 5 4 24 4.71 2.45 14 1 750 15 8.57 15 12 24 42.41 5.72 15 500 15 30.00 5 42 85 14.14 3.76 Table 3. Lack of fit tests for tool wear model
Source Sum of squares Mean square P-value Linear 1.840 881 0.204 542 0.002 2 2FI 0.448 910 0.074 818 0.005 9 Quadratic 0.034 532 0.011 510 0.037 4 Cubic 0 Pure Error 0.000 889 0.000 444 Table 4. Analysis of variance for tool wear model
Source Sum of squares Mean square P-value Model 3.439 845 0.491 406 <0.000 1 A-Spindle speed 0.767 201 0.767 201 <0.000 1 B-Feed rate 0.603 784 0.603 784 <0.000 1 C-Depth of cut 0.264 068 0.264 068 0.000 2 AB 1.185 989 1.185989 <0.000 1 AC 0.171 462 0.171 462 0.000 7 BC 0.034 519 0.034519 0.037 8 C^2 0.412 819 0.412 819 <0.000 1 Residual 0.036 980 0.005 282 Lack of fit 0.036 090 0.007 218 0.059 0 Pure error 0.000 889 0.000 444 Cor total 3.476 826 -
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