Handbook of Advanced Ceramics Machining Episode 3 pps

microholes, which are considered to be pores in HIPSN itself or fracture traces of fragile portions inside HIPSN, becomes very smooth. Thus, a smooth ductile-mode ground surface can also be obtained with plunge grinding of HIPSN ceramic with the coarse #140-mesh wheel. 2.3 Ultra-smoothness Grinding 2.3.1 Ultra-smoothness Grinding Method As stated above, ductile-mode grinding of fine ceramics is possible with plunge grinding with the coarse #140-mesh grain-size diamond wheel. The 3D surface roughness in ductile-mode plunge grinding, however, is limited 10 µm 10 µm 10 µm 10 µm 10 µm 10 µm u w = 5 mm/sec u w = 0.5 mm/sec u w = 0.05 mm/sec (a) SD140Q50M (b) SD800Q50M FIGURE 2.18 Influence of the table speed and wheel grain size on the ground HIPSN surface [V g ¼20 m=sec, t t ¼5 mm, Soluble (1=50)]. Ioan D. Marinescu/Handbook of Advanced Ceramics Machining 3837_C002 Final Proof page 46 2.10.2006 10:34am 46 Handbook of Advanced Ceramics Machining to about 200 nm (R max ) in the above-mentioned experiments because of the formation of grinding grooves. The 3D surface roughness of 200 nm (R max ) is much better than the well-known data obtained in the usual grinding operation. However, the ultrasmooth roughness below 10 nm (R max ), which is almost the same as that after lapping, could not be obtained in plunge grinding. To obtain ultra-smoothness roughness with the coarse-grain-size wheel, it is necessary to diminish and remove the grinding grooves. Now, the ultra-smoothness grinding method has been newly devised [5,6]. The schematic of the new method is shown in Figure 2.21. In the method, the workpiece is fed simultaneously toward the directions normal and parallel to the grinding direction. The method is different from the usual traverse surface grinding in which the crossfeed normal to the grinding direction is RMS: 35.0 nm Surface WVLEN: 646.4 nm Orientation (Front) U: 98 nm L: −91 nm WYKO WYKO 234 176 117 Distance (microns) Distance on surface (microns) Nanometers 59 0 23919214597503 −10.00 −5.00 0 5.00 10.00 98 51 −3 −44 −91 R Crv: −288.9 mm WVLEN: 646.4 nm R Crv: 102.9 m R Cyl: 69.98 mm −0.7Њ Masks: None Profile (124.36) q Њ RA: 45.8 nm P—V: 238 nm RMS: 1.85 nm RA: 1.47 nm P—V: 9.71 nm FIGURE 2.19 A WYKO 3D image and 2D profile of the HIPSN surface ground at n w ¼0.05 mm=sec with the #140-mesh wheel [SD140Q50M, V g ¼20 m=sec, t t ¼5 mm, Soluble (1=50)]. Ioan D. Marinescu/Handbook of Advanced Ceramics Machining 3837_C002 Final Proof page 47 2.10.2006 10:34am Ductile-Mode Ultra-Smoothness Grinding of Fine Ceramics 47 done after grinding the whole width of the workpiece in a pass or stroke of the table. In the method, the crossfeed (v w ) n normal to the grinding direction is faster than the plunge feed (v w ) p parallel to the grinding direction. The experiments are carried out with the NC grinding machine as shown sche- matically and photographically in Figure 2.22 and Figure 2.23, respectively. 400 (nm) 0 0 (µm) (µm) −400 10 Grinding directon 20 20 30 30 40 250 (nm) −250 0 0 1020304050 R z L 49.609 µm 57.403 nm 390.02 nm 220.32 nm RMS R max 40 50 0 10 (µm) FIGURE 2.20 A closeup AFM 3D image and 2D profile of the HIPSN surface ground at y w ¼0.05 mm=sec with the #140-mesh wheel [SD140Q50M, V g ¼20 m=sec, t t ¼5 mm, Soluble (1=50)]. Wheel HPSC B sw (u w ) p (u w ) c (u w ) n Grinding directon FIGURE 2.21 Ultra-smoothness grinding method. Ioan D. Marinescu/Handbook of Advanced Ceramics Machining 3837_C002 Final Proof page 48 2.10.2006 10:34am 48 Handbook of Advanced Ceramics Machining In the experiments, (v w ) n and (v w ) p are set by determining the resultant feed (v w ) c ¼ {(v w ) n þ (v w ) p } 1 2 , crossfeed width B sw and feed width f. The machine is reconstructed with a conventional NC equipment, which has an accuracy of 1 mm for each movement of the X, Y, and Z directions. The experimental conditions are summarized in Table 2.2. 2.3.2 Ultra-smoothness Grinding Results Figure 2.24 shows the microscopic photographs of the HPSC surface ground at (v w ) c ¼ 3.33 mm=sec with the #140-mesh wheel. From the figure, it is 1 1 : NC grinding machine : Motor : Spindle : CNC controller : Inverter : Operation board : Coolant supply system : Nozzle 2 2 3 3 4 4 Z X Y 5 5 6 6 7 7 8 8 FIGURE 2.22 Schematic diagram of NC grinding machine. Motor Wheel Nozzle Spindle Inverter Table Coolant supply system CNC controller (YASNAC MX1) Operation board of Electromagnetic chuck FIGURE 2.23 Appearance of NC grinding machine. Ioan D. Marinescu/Handbook of Advanced Ceramics Machining 3837_C002 Final Proof page 49 2.10.2006 10:34am Ductile-Mode Ultra-Smoothness Grinding of Fine Ceramics 49 obvious that no grinding cracks and no grinding grooves are found over the observed workpiece area. Figure 2.25 shows a WYKO 3D image of 256 mm 2 of HPSC surface ground at (v w ) c ¼ 3.33 mm=sec. From the figure, it is found that the workpiece surface is not formed by continuous regular grooves as shown in Figure 2.5 but by some discontinuous short grinding grooves. The 3D surface roughness is about 26 nm (P-V), 3.7 nm (RMS), and 3 nm (R a ), corresponding to near ultra-smoothness surface roughness. The height of the grinding groove is considered to be below about 26 nm (P-V), which is much lower than that in the plunge ductile-mode grinding as shown in Figure 2.5. The pitch of the grinding groove is also not regular as observed Cutting direction 50 µm FIGURE 2.24 Microscopic photograph of the HPSC surface ground at (y w ) c ¼3.33 mm=sec with the #140-mesh wheel by ultra-smoothness grinding method [SD140Q50M, V g ¼20 m=sec, t t ¼5 mm, Soluble (1=50)]. TABLE 2.2 Ultra-smooth Grinding Experimental Conditions Grinding Method Ultra-smoothness Wheel SD140Q50M Workpiece HPSC (HV:3300) Wheel speed V g ¼ 20 m=sec Resultant feed (v w ) c ¼ 3.33 mm=sec Crossfeed width B sw ¼ 18 mm Plunge feed f ¼ 20 mm=stroke Depth of cut t t ¼2 mm Coolant Soluble (1=50) Flow rate: 12 L=min Ioan D. Marinescu/Handbook of Advanced Ceramics Machining 3837_C002 Final Proof page 50 2.10.2006 10:34am 50 Handbook of Advanced Ceramics Machining in plunge grinding. Consequently, the grinding grooves are considered to be removed to some extent. Figure 2.26 shows an AFM 3D image and 2D profiles of 50 mm 2 of HPSC surface ground at (v w ) c ¼ 3.33 mm=sec. The upper and middle 2D profiles parallel to grinding direction are measured at the places excluding and including the microhole, respectively. Obvious microholes can hardly be found on the observed 3D image. From the 2D profiles, the surface roughness values parallel to the grinding direction are about 3 nm (P-V) and 0.8 nm (RMS) excluding microholes and about 9 nm (P-V) and 1 nm (RMS) including microholes, respectively. In addition, the surface roughness normal to the grinding direction is about 8 nm (P-V) and 1.5 nm (RMS). Accordingly, in the measurement of AFM accuracy order, it is reasonable to say that the ground surface with the newly devised method can be ultra- smooth. The entire ground workpiece area of 10 mm 2 , which is further observed widely, however, also consists of the ultrasmooth surface formed by the low height of grooves with no grinding cracks. 2.4 Conclusion Ductile-mode grinding of fine ceramics with the coarse #140-mesh metal- bonded diamond wheel has been shown to be possible in plunge surface grinding. It is estimated that the thermal effect due to the large wear land of the cutting edge on the #140-mesh wheel surface has considerable effect on RMS: 3.66 nm Surface WVLEN: 646.4 nm Orientation (Front) U: 9.6 nm L: −16.5 nm WYKO 234 176 117 Distance (microns) Grinding direction 59 0 9.6 3.1 −3.4 −10.0 −16.5 R Crv: 1.074 mm R Crv: −325.8 mm 81.8Њ masks: A RA: 3.06 nm P—V: 26.1 nm FIGURE 2.25 A WYKO 3D image of the HPSC surface ground at (y w ) c ¼3.33 mm=sec with the #140-mesh wheel by ultra-smoothness grinding method [SD140Q50M, V g ¼20 m=sec, t t ¼5 mm, Soluble (1=50)]. Ioan D. Marinescu/Handbook of Advanced Ceramics Machining 3837_C002 Final Proof page 51 2.10.2006 10:34am Ductile-Mode Ultra-Smoothness Grinding of Fine Ceramics 51 ductile-mode grindability. The various kinds of grinding parameters, that is, table speed, wheel speed, workpiece material property, and so on, influence ductile-mode grindability. As a result, optimum grinding conditions should be selected for ductile-mode grinding. Based on the result obtained in plunge surface grinding, ultra-smoothness grinding method has been newly devised for obtaining the ultra-smoothness roughness below 10 nm (R max ), which is almost the same as that after lapping. According to the experimental inves- tigation using the new ultra-smoothness grinding method, the surface roughness of the ground HPSC ceramic surface of 50 mm 2 measured with A A’ B’ C’ 0 0 10 −10 10 (nm) (nm) −10 −10 10 (nm) 0 0 0 0 1020304050 A A’ B’ C’ B C 0 10 10 (µm) (µm) (µm) 20 20 30 30 40 40 (Invert image) (Normal image) Grinding direction 50 −20 20 (nm) B C R z L : 49.609 µm : 0.830 nm : 2.707 nm : 2.216 nm RMS R max R z L : 49.609 µm : 1.053 nm : 9.103 nm : 3.100 nm RMS R max R z L : 49.609 µm : 1.511 nm : 8.109 nm : 6.374 nm RMS R max FIGURE 2.26 An AFM 3D image and 2D profiles of the HPSC surface ground at (y w ) c ¼3.33 mm=sec with the #140-mesh wheel by ultra-smoothness grinding method [SD140Q50M, V g ¼20 m=sec, t t ¼5 mm, Soluble (1=50)]. Ioan D. Marinescu/Handbook of Advanced Ceramics Machining 3837_C002 Final Proof page 52 2.10.2006 10:34am 52 Handbook of Advanced Ceramics Machining AFM is as smooth as about 9 nm (P-V) and 1.5 nm (RMS). Therefore, in the measurement of AFM accuracy order, it is reasonable to say that the ground surface with the newly devised method can be ultrasmooth. The entire ground workpiece surface of 10 mm 2 , however, is also ultrasmooth. The new method is inadequate for productive ultra-smoothness grinding of fine ceramics. When the method is used after the rough grinding of fine ceramics with the same coarse-grain-size grinding wheel, this may be obtained. Nevertheless, it is considered important that the method is improved toward high productivity due to the investigation of the optimum grinding condition [7–10]. References 1. Yoshioka, J., Hashimoto, F., Miyashita, M., Kanai, A., Abo, A., and Daito, M., Ultraprecision grinding technology for brittle materials. ASME, Shaw, M.C., Grinding Symposium PED, Vol. 16, 1985, 255. 2. Namba, Y., Yamada, Y., Tsuboi, A., Unno, K., and Nakao, H., Surface structure of Mn–Zn ferrite single crystals ground by an ultra-precision surface grinder with various diamond wheels. Annals of the CIRP, Vol. 41, No. 1, 1992, 347. 3. Ichida, Y. et al., Mirror finish grinding of silicon nitride ceramics. Proceedings 1st International Conference on New Manufacturing Technology, 1990, 317. 4. Yasui, H., Arino, Y., and Matsunaga, K., Ductile-mode high smoothness grinding of fine ceramics by diamond wheel of coarse grain size (1st Report), Journal of the Japan Society for Precision Engineering, Vol. 63, No. 9, 1997, 1270. 5. Yasui, H., Yamazaki, G., Hiraki, Y., Sakamoto, S., Sakata, M., Saeki, M., and Hosokawa, A., Ultra-smoothness grinding of fine ceramics with #140-mesh grain size diamond wheel, Proceedings of 14th American Society for Precision Engin- eering, Annual Meeting, 1999, 125. 6. Yasui, H. and Yamazaki, G., Possibility of ultra-smoothness grinding of fine ceramics using a coarse grain size diamond wheel, Journal of the Japan Society for Precision Engineering, Vol. 69, No. 1, 2003, 115. 7. Yasui, H., Development of polishingless ultra-smoothness grinding method (1st Report), Journal of the Japan Society for Precision Engineering, Vol. 69, No. 12, 2003, 1713. 8. Yasui, H. and Sawa, T., Effect of grinding fluid supply on ultra-smoothness grinding of fine ceramics, Proceedings of the ASPE 18th Annual Meeting, 2003, 447. 9. Yasui, H. and Sawa, T., Influence of fluid supply on ultra-smoothness grinding of silicon nitride ceramic with #140 metal bond diamond wheel, Proceedings of the ASPE 19th Annual Meeting, 2003, 565. 10. Yasui, H. and Sawa, T., Ultra-smoothness grinding of a glass with #140 metal bond diamond wheel, ICPMT2004, 2004. Ioan D. Marinescu/Handbook of Advanced Ceramics Machining 3837_C002 Final Proof page 53 2.10.2006 10:34am Ductile-Mode Ultra-Smoothness Grinding of Fine Ceramics 53 Ioan D. Marinescu/Handbook of Advanced Ceramics Machining 3837_C002 Final Proof page 54 2.10.2006 10:34am 3 Mechanisms for Grinding of Ceramics S. Malkin and T.W. Hwang CONTENTS 3.1 Introduction 55 3.2 Indentation Fracture Mechanics Approach 56 3.2.1 Median=Radial Cracks: Static Indentor 57 3.2.2 Median=Radial Cracks: Moving Indentor 62 3.2.3 Lateral Cracking and Crushing 65 3.3 Machining Approach 67 3.3.1 Grinding Debris 67 3.3.2 Microscopy of Scratches and Ground Surfaces 67 3.3.3 Grinding Energy and Mechanisms 70 3.3.3.1 Specific Grinding Energy 72 3.3.3.2 Brittle Fracture Energy 74 3.3.3.3 Plowed Surface Area Analysis 78 3.3.3.4 Plowed Surface Energy and Workpiece Properties 79 3.4 Concluding Remarks 81 References 83 3.1 Introduction Despite the development of advanced ceramic materials possessing enhanced properties, the widespread use of these materials for structural applications has been limited mainly because of the high cost of machining by grinding. In the manufacture of ceramic components, grinding can comprise up to 80% of the total cost [1]. Efficient grinding requires selecting Ioan D. Marinescu/Handbook of Advanced Ceramics Machining 3837_C003 Final Proof page 55 6.10.2006 2:06am 55 [...]... (dV)2 =3 ¼ (p=4)2 =3 R2 (a=R)8 =3 , (3: 8) Ioan D Marinescu /Handbook of Advanced Ceramics Machining 38 37_C0 03 Final Proof page 59 6.10.2006 2:06am Mechanisms for Grinding of Ceramics 59 where a is now the indentation radius In this case, the load=crack length relationship becomes P4 =3= c3=2 ¼ (4p=R)2 =3 xÀ1 (Kc EÀ1=2 H5=6 ): (3: 9) Therefore, the load=crack length relations in Equation 3. 1 and Equation 3. 9... would indicate ductile flow 3. 3.2 Microscopy of Scratches and Ground Surfaces A detailed picture of the prevailing mechanisms has been developed from microscopic observations of scratches produced by single-point diamond Ioan D Marinescu /Handbook of Advanced Ceramics Machining 38 37_C0 03 Final Proof 68 page 68 6.10.2006 2:06am Handbook of Advanced Ceramics Machining (a) (b) FIGURE 3. 9 Grinding debris, RBSN... comparable to the 32 5 38 0 32 5 276 410 427 70 HPSN1 Al2O3 HPSN1 HPSN2 SiC1 SiC2 Glass** C ¼ 21 dg ¼ 84 DN400N100B-1=4 DN180N100B-1=4 5.5 27.4 27.0 19.6 13. 3 19.6 18.2 15.0 10.0 H (GPa) 0.75 3. 5 3. 0 5.0 4.5 5.0 5.7 6.6 3. 6 Kc (MPa m1=2) 4.0 14.9 10.5 38 .5 26.6 58.9 38 .5 73. 3 39 .3 Gc=2 (J=m2) 2.0 6.4 5.5 15.4 9.1 9.1 4.9 11.4 35 .3 As (1 03 J=m2) 1.0 7.4 7.0 28.7 10.5 16.7 16.6 32 .9 0.0 Bs (J=mm3) 1,800 + 85... or small enough to overlap, material removal is Ioan D Marinescu /Handbook of Advanced Ceramics Machining 38 37_C0 03 Final Proof page 70 6.10.2006 2:06am Handbook of Advanced Ceramics Machining 70 4000 Volume removed / length (µm2) Al2O3 (hot-pressed) 30 00 P = 40 N 2000 P = 30 N 1000 0 01 00 200 Distance between scratches (µm) 30 0 FIGURE 3. 11 Material removed per unit length versus distance between scratches... (Kyocera SN220), 180 grit wheel Norton (a ¼ 38 mm, vw ¼ 100 mm=sec, vs ¼ 32 m=sec) (a) as ground; (b) after etching (From Hwang, T.W and Malkin S., ASME J Manuf Sci Eng., 121, 6 23 With permission.) Ioan D Marinescu /Handbook of Advanced Ceramics Machining 38 37_C0 03 Final Proof page 72 6.10.2006 2:06am Handbook of Advanced Ceramics Machining 72 per unit volume of material removal The specific energy is... curves shown in Figure 3. 15 and Ioan D Marinescu /Handbook of Advanced Ceramics Machining 38 37_C0 03 Final Proof page 74 6.10.2006 2:06am Handbook of Advanced Ceramics Machining 74 Wheel a Workpiece vw Ag 2q hm lc FIGURE 3. 14 Illustration of undeformed chip geometry (From Hwang, T.W and Malkin, S., ASME J Manuf Sci Eng., 121, 6 23 With permission.) Figure 3. 16 represent the grinding behavior quite well... -0 .32 400 Grit size 120 200 400 600 200 0.10 Si3N4 (sintered) 5 15 Normal force per grit, fn (N) 10 FIGURE 3. 4 Flexural strength versus normal force per grit (From Ota, M and Miyahara, K., 4th Int Grinding Conf., SME Technical Paper MR90– 537 , 1990 With permission.) Ioan D Marinescu /Handbook of Advanced Ceramics Machining 38 37_C0 03 Final Proof page 62 6.10.2006 2:06am Handbook of Advanced Ceramics Machining. .. Equation 3. 3 and Equation 3. 5 and equating Kr to Kc leads to Kc ¼ x(EH)1=2 (dV)2 =3= c3=2 : (3: 6) For a pyramidal indentor, the indentation volume is dV ¼ (2 =3) a3 cot c, (3: 7) where a is half the diagonal length (Figure 3. 1) Combining Equation 3. 4, Equation 3. 6, and Equation 3. 7 would give the same load=crack length relationship as Equation 3. 1 with j ¼ {(2 =3) 2 =3= a0}x For a spherical indentor of radius... Marinescu /Handbook of Advanced Ceramics Machining 38 37_C0 03 Final Proof page 63 6.10.2006 2:06am Mechanisms for Grinding of Ceramics 63 1200 Longitudinal Strength (MPa) 800 Transverse 400 HPSN 0 0.0 0.1 0.2 Uncut chip thickness (mm) 0 .3 FIGURE 3. 5 Transverse rupture strength versus uncut chip thickness for longitudinal and transverse grinding (From Mayer, J.E., Jr and Fang, G.P., NIST SP 847, 205, 19 93 With... energy dispersive spectroscopy 3. 3 .3 Grinding Energy and Mechanisms A fundamental parameter derived from the grinding forces and machining conditions is the specific grinding energy, which is defined as the energy Ioan D Marinescu /Handbook of Advanced Ceramics Machining 38 37_C0 03 Final Proof Mechanisms for Grinding of Ceramics page 71 6.10.2006 2:06am 71 (a) (b) FIGURE 3. 12 Ground surfaces, HPSN (Kyocera . R, (dV) 2 =3 ¼ (p=4) 2 =3 R 2 (a=R) 8 =3 , (3: 8) Ioan D. Marinescu /Handbook of Advanced Ceramics Machining 38 37_C0 03 Final Proof page 58 6.10.2006 2:06am 58 Handbook of Advanced Ceramics Machining where. Marinescu /Handbook of Advanced Ceramics Machining 38 37_C002 Final Proof page 53 2.10.2006 10 :34 am Ductile-Mode Ultra-Smoothness Grinding of Fine Ceramics 53 Ioan D. Marinescu /Handbook of Advanced Ceramics Machining. Ground Surfaces 67 3. 3 .3 Grinding Energy and Mechanisms 70 3. 3 .3. 1 Specific Grinding Energy 72 3. 3 .3. 2 Brittle Fracture Energy 74 3. 3 .3. 3 Plowed Surface Area Analysis 78 3. 3 .3. 4 Plowed Surface