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Microdrilling and plastically deformed diameters in brittle CdS crystals
Microdrilling and plastically deformed diameters in brittle CdS crystals F. Goto, S. Kudo and M. Kumagai* A comparison of hole shapes and plastically deformed diameters in brittle CdS crystals using a twist drill and a flat drill with diameters of 50 l~m is described. The results obtained show that when the working depth is more than 30 l~m for a twist drill or more than 40 l~m for a flat drill, the diameter of the holes is nearly constant and the hole shapes are cylindrical or slightly tapered, respectively. Also, the ratio of the diameter of the plastically deformed domain to the diameter of the hole on the surface is about 2 for a twist drill and about 3 for a flat drill.
Keywords: microdrilling, plastic deformation, brittle CdS
The effect of workpiece structure and drill diameter on burr formation in drilling has been investigated by Sugawara and Inagaki 1 for 0.2% C rolled steel, sintered silver sheets, sheets of JIS SUS 321, corresponding to AISI 321, and iron single crystals, using drill diameters of 0.05 to 2.5 mm, rotary speeds of 880 to 6000 rev/min, and feed rates of 0.0386 to 11.58 mm min 1. High-speed micro deep drilling has been studied by Iwata et al 2 for high speed steel JIS SUS 303 Se, corresponding to AISI 303 Se, and brass using vertical and horizontal drilling machines. They used drill diameters of 0.1 to 0.9 mm, spindle speeds of 1500 to 140000 rev/min, nominal feed rates of 30 to 120 mm min 1 and hole depths of 0.4 to 2.5 mm. Both articles deal with metals and alloys. Crystal growth of CdS by the sublimation method has been studied by Maeda et al 3, estimation of the yield point by Goto and Kudo 4 and microhardness and the plastically deformed region in brittle CdS crystals by Goto and Kudo 5. The present article is concerned with the variation in hole shapes and plastically deformed diameters of a microdrilling test using a twist drill and a flat drill with diameters of 50 pm on the (0001) surface of brittle CdS crystals made by the sublimation method. Our purpose was to compare the hole shapes produced by twist drills and flat drills and to examine the ratio of the diameter of the plastically
* Department of MechanicalEngineeringII, Facultyof Engineering, Iwate University, 4-3-5 Ueda, Morioka 020, Japan
PRECISION ENGINEERING
deformed domain to the diameter of the hole on the surface.
Specimens The specimens were made by the sublimation method in a horizontal furnace. Growth conditions were as follows: the maximum temperature was 1100~C, the Ar gas was at atmospheric pressure, and the time was 30 h. We obtained two types of crystal, one a bulk-like hexagonal hollow crystal on sintering at 1070"C with a temperature gradient 10'~C mm -1, and the other a needle-like hollow crystal on reaction at 950°C with a temperature gradient 20~'C mm-1. The flat surfaces of both crystals had (0001), 11010~ and ~1210~ formations. We used the bulk-like hexagonal hollow crystals in the microdrilling test. Because the crystals were as small as a few cubic millimetres, we solidified them in a glass ring with a height of 15 mm and a diameter of 12 mm, with the (0001) surface held on the head of the resin. Experimental
procedures
A vertical precision drilling machine made by Boley Co. and twist drills and flat drills with diameters of 50/~m made by Sphinx Co. were used in the microdrilling test. We used an automatic apparatus with rotary speeds of 1550 and 1950 rev/min, a nominal feed rate of 2/~m s 1, and hole depths of 2 to 100/~m. The apparatus is shown in Fig 1. The specimens were cleaned with CICH-CCI 2, C2H5OH and H20 in turn. After the microdrilling
0141-6359/91/010013-04 © 1991 Butterworth-Heinemann
13
Goto et aI--Microdrilling and plastically deformed diameters in brittle CdS crystals
Results and discussion Influence o f rotary speed on hole shape
Fig 1 Apparatus for the drilling test. The CdS sample is in the centre of the cylindrical resin on the mounting stage
The first microdrilling test was performed using a twist drill with a diameter of 50 #m, rotary speeds of 1950 and 1550 rev/min, a feed rate of 2 #m s -~, at various working depths. The results are shown in Fig 3 and Fig 4. The difference between the nominal drill diameter and the diameter of the hole at the surface depends on the accuracy of the drill chuck and the efficiency of removal of the chips. However, when the working depth is more than about 30 #m, that being the length from the tip to the shoulder of the twist drill, the diameter of the hole on the surface tends to be nearly constant. From Fig 3 and Fig 4 we can see that the diameter of the hole at the surface in Fig 3 is larger than that in Fig 4. So, we think that a rotary speed of 1550 rev/min gives a better result than one of 1950 rev/min.
0 a
I n f l u e n c e o f drill t y p e on h o l e s h a p e To compare the performances of twist drills and flat drills, a third microdrilling test was performed using a flat drill with a diameter of 50 l~m, a rotation speed of 1550 rev/min and a feed rate of 2 #m s -~, at various working depths. The results are shown in Fig 5.
t0o,r._ .......
i
i
o
i J
80J-E :L
Fig 2 Etched figure and typical dimensions of the plastic zone
d o ~4 ¥ db
test, the typical diameters of the holes were measured with the optical microscope of a microvickers indenter MVK-E made by Akashi Co. Then, in order to know the typical dimensions of the plastically deformed domains in the radial directions and how they depend on the working depths, the specimens were etched using a boiling solution of 50 cm 3 HCI (35%) + 27 cm 3 H20 + 70 g CdCI2 ( 5 / 2 ) H20 for 40 to 80 s and washed well with hot water. The etched figures had star-like shapes as shown in Fig 2, and the typical dimensions were measured by the optical microscope to find the diameter of the circle enclosing the etched pit array. 14
o
/
60-
40
i 0
20
1. 40 50 W0rkinq depth, H.rn
1 80
!00
Fig 3 Relation between the diameter of the hole and the working depth using a twist drill at 1950 rev/min and 2 #m s 1. The arrows denote the length from tip to shoulder of the drill JANUARY 1991 VOL 13 NO I
Goto et aI--Microdrifting and plastically deformed diameters in brittle CdS crystals IO0
E ::L
When the working depth is more than about 40/~m, that being the length from the tip to shoulder of the flat drill, the diameter of the hole on the surface tends to be slightly tapered. Moreover in Fig 4 and Fig 5, we can easily see that the diameters of the holes with a flat drill are about 8/~m larger than those with a twist drill because a flat drill does not have a spiral channel and the chip removal efficiency is lower.
8C
Diameter o f the hole a n d plasticafly d e f o r m e d domain
O
E 0
D
A final experiment was performed to compare the plastically deformed domains using a twist drill and a flat drill, and the above-mentioned chemical
0
6C
5.0
40 l 0
I 20
I I 40 60 Working depth, ff.m
I
80
I00
Fig 4 Relation between the diameter of the hole and the working depth using a twist drill at 1550 rev / min and 2 #m s ~. The arrows denote the length from tip to shoulder of the drill
0°
4 o~0
0
O
~ ' o~ c
Flat drill
100
~o3.C
0
o
u
~
E 80 ::L --o "~:
O ~
0
o
oo
0 3
3
OO
"5 $ u_
o
#~~~
E
%DE]
E]
121
D
2.0 Twist drill
60
0 °
4C 0
I
°
I 20
I I 40 60 Working depth, ffm
I 80
ol
].0 100
Fig 5 Relation between the diameter of the hole and the working depth using a flat drift at 1550 rev/min and 2 l~m s I. The arrows denote the length from tip to shoulder of the drill PRECISION ENGINEERING
I
20
I
I
40 60 Working depth, ~Lm
80
I00
Fig 6 Relation between the ratio of the typical diameter of the star pattern to the diameter of the hole on the surface and the working depth, using a twist drift and a flat drift at 1550 rev/min and 2 l~m s 7. The arrows denote the length from tip to shoulder of each drift 15
Goto et a I - - M i c r o d r i l l i n g a n d plastically d e f o r m e d diameters in brittle CdS crystals
etching. The ratio of the typical diameter of the star pattern to the diameter of the hole on the surface is shown in Fig 6. From Fig 6, we can easily see that the result with a twist drill is better than that with a flat drill, because the ratio is about 2 for the t w i s t drill as compared w i t h about 3 for the flat drill. According to a theoretical investigation by Hill 6 the ratio of plastic zone radius c to hole radius a is given by c
__
a where E is Y o u n g ' s modulus, v is Poisson's ratio and Y is yield stress. E and v were approximately estimated from Refs 7 and 8, and Y was estimated from Ref 4. When we use E = 81 GPa, ~,= 0.39 and Y = 350 MPa, c / a is estimated as 11.6. However, this value is larger than our results of 2 to 3, and we think that the reduction of the parameter c / a depends on the chip removal,
Conclusions The conclusions of this study are as follows: • A rotary speed of 1550 r e v / m i n with a feed rate of 2 l~m s 1 is a suitable working condition.
16
• When the working depth is more than 30/~m for a twist drill or more than 40 l~m for a flat drill, the hole shapes are almost cylindrical for a twist drill and slightly tapered for a flat drill, respectively. • The ratio of the typical diameter of the plastically deformed domain to the diameter of the surface hole is about 2 for a twist drill and about 3 for a flat drill= • Results with a t w i s t drill are better than with a flat drill.
References 1 Sugawara, A. and Inagaki, K. Effect of Workpiece Structure on Burr Formation in Micro.drilling, Bud Jap Soc Precision Engng, 4, 1982, 9 2 Iwata, K., Moriwaki, T. and Hoshikawa, M. Fundamemal Study of High Speed Micro Deep Drilling, J Jap Soc Precision Engng, 49, 1983, 240 (m Japanese) 3 Maeda, M., Goto, F. and Miyata, K. Hollow Crystal of Wurzite Type CdS, Jap J App/ Phys, 3, 1964, 426 & P/. 15 4 Goto, F. and Kudo, S. An Estimation of Yield Points in CdS Single Crystal Using Microvickers- and MicrorockwellIndenter, TransJSME, A53, 1987, 2406 (in Japanese) 5 Goto, F. and Kudo, S. Microhardness and Plastically Deformed Regions in CdS Single Crystals,J App/Phys, 6& 7988, 2445 6 Hill, R. The Mathematical Theory, of Plasticity, Clarendon Oxford, 1954 7 Bruce, H. B. American institute o/Physics Handbook, McGraw-HilL New York, 1972 8 Lekhnitskii, S. G. Theory of Elasticity of an Anisotrop/c Body, M/r, Moscow, (1981) (Enq/ish Translation)
J A N U A R Y 1991 VOL 13 NO 1
Keywords: microdrilling, plastic deformation, brittle CdS
The effect of workpiece structure and drill diameter on burr formation in drilling has been investigated by Sugawara and Inagaki 1 for 0.2% C rolled steel, sintered silver sheets, sheets of JIS SUS 321, corresponding to AISI 321, and iron single crystals, using drill diameters of 0.05 to 2.5 mm, rotary speeds of 880 to 6000 rev/min, and feed rates of 0.0386 to 11.58 mm min 1. High-speed micro deep drilling has been studied by Iwata et al 2 for high speed steel JIS SUS 303 Se, corresponding to AISI 303 Se, and brass using vertical and horizontal drilling machines. They used drill diameters of 0.1 to 0.9 mm, spindle speeds of 1500 to 140000 rev/min, nominal feed rates of 30 to 120 mm min 1 and hole depths of 0.4 to 2.5 mm. Both articles deal with metals and alloys. Crystal growth of CdS by the sublimation method has been studied by Maeda et al 3, estimation of the yield point by Goto and Kudo 4 and microhardness and the plastically deformed region in brittle CdS crystals by Goto and Kudo 5. The present article is concerned with the variation in hole shapes and plastically deformed diameters of a microdrilling test using a twist drill and a flat drill with diameters of 50 pm on the (0001) surface of brittle CdS crystals made by the sublimation method. Our purpose was to compare the hole shapes produced by twist drills and flat drills and to examine the ratio of the diameter of the plastically
* Department of MechanicalEngineeringII, Facultyof Engineering, Iwate University, 4-3-5 Ueda, Morioka 020, Japan
PRECISION ENGINEERING
deformed domain to the diameter of the hole on the surface.
Specimens The specimens were made by the sublimation method in a horizontal furnace. Growth conditions were as follows: the maximum temperature was 1100~C, the Ar gas was at atmospheric pressure, and the time was 30 h. We obtained two types of crystal, one a bulk-like hexagonal hollow crystal on sintering at 1070"C with a temperature gradient 10'~C mm -1, and the other a needle-like hollow crystal on reaction at 950°C with a temperature gradient 20~'C mm-1. The flat surfaces of both crystals had (0001), 11010~ and ~1210~ formations. We used the bulk-like hexagonal hollow crystals in the microdrilling test. Because the crystals were as small as a few cubic millimetres, we solidified them in a glass ring with a height of 15 mm and a diameter of 12 mm, with the (0001) surface held on the head of the resin. Experimental
procedures
A vertical precision drilling machine made by Boley Co. and twist drills and flat drills with diameters of 50/~m made by Sphinx Co. were used in the microdrilling test. We used an automatic apparatus with rotary speeds of 1550 and 1950 rev/min, a nominal feed rate of 2/~m s 1, and hole depths of 2 to 100/~m. The apparatus is shown in Fig 1. The specimens were cleaned with CICH-CCI 2, C2H5OH and H20 in turn. After the microdrilling
0141-6359/91/010013-04 © 1991 Butterworth-Heinemann
13
Goto et aI--Microdrilling and plastically deformed diameters in brittle CdS crystals
Results and discussion Influence o f rotary speed on hole shape
Fig 1 Apparatus for the drilling test. The CdS sample is in the centre of the cylindrical resin on the mounting stage
The first microdrilling test was performed using a twist drill with a diameter of 50 #m, rotary speeds of 1950 and 1550 rev/min, a feed rate of 2 #m s -~, at various working depths. The results are shown in Fig 3 and Fig 4. The difference between the nominal drill diameter and the diameter of the hole at the surface depends on the accuracy of the drill chuck and the efficiency of removal of the chips. However, when the working depth is more than about 30 #m, that being the length from the tip to the shoulder of the twist drill, the diameter of the hole on the surface tends to be nearly constant. From Fig 3 and Fig 4 we can see that the diameter of the hole at the surface in Fig 3 is larger than that in Fig 4. So, we think that a rotary speed of 1550 rev/min gives a better result than one of 1950 rev/min.
0 a
I n f l u e n c e o f drill t y p e on h o l e s h a p e To compare the performances of twist drills and flat drills, a third microdrilling test was performed using a flat drill with a diameter of 50 l~m, a rotation speed of 1550 rev/min and a feed rate of 2 #m s -~, at various working depths. The results are shown in Fig 5.
t0o,r._ .......
i
i
o
i J
80J-E :L
Fig 2 Etched figure and typical dimensions of the plastic zone
d o ~4 ¥ db
test, the typical diameters of the holes were measured with the optical microscope of a microvickers indenter MVK-E made by Akashi Co. Then, in order to know the typical dimensions of the plastically deformed domains in the radial directions and how they depend on the working depths, the specimens were etched using a boiling solution of 50 cm 3 HCI (35%) + 27 cm 3 H20 + 70 g CdCI2 ( 5 / 2 ) H20 for 40 to 80 s and washed well with hot water. The etched figures had star-like shapes as shown in Fig 2, and the typical dimensions were measured by the optical microscope to find the diameter of the circle enclosing the etched pit array. 14
o
/
60-
40
i 0
20
1. 40 50 W0rkinq depth, H.rn
1 80
!00
Fig 3 Relation between the diameter of the hole and the working depth using a twist drill at 1950 rev/min and 2 #m s 1. The arrows denote the length from tip to shoulder of the drill JANUARY 1991 VOL 13 NO I
Goto et aI--Microdrifting and plastically deformed diameters in brittle CdS crystals IO0
E ::L
When the working depth is more than about 40/~m, that being the length from the tip to shoulder of the flat drill, the diameter of the hole on the surface tends to be slightly tapered. Moreover in Fig 4 and Fig 5, we can easily see that the diameters of the holes with a flat drill are about 8/~m larger than those with a twist drill because a flat drill does not have a spiral channel and the chip removal efficiency is lower.
8C
Diameter o f the hole a n d plasticafly d e f o r m e d domain
O
E 0
D
A final experiment was performed to compare the plastically deformed domains using a twist drill and a flat drill, and the above-mentioned chemical
0
6C
5.0
40 l 0
I 20
I I 40 60 Working depth, ff.m
I
80
I00
Fig 4 Relation between the diameter of the hole and the working depth using a twist drill at 1550 rev / min and 2 #m s ~. The arrows denote the length from tip to shoulder of the drill
0°
4 o~0
0
O
~ ' o~ c
Flat drill
100
~o3.C
0
o
u
~
E 80 ::L --o "~:
O ~
0
o
oo
0 3
3
OO
"5 $ u_
o
#~~~
E
%DE]
E]
121
D
2.0 Twist drill
60
0 °
4C 0
I
°
I 20
I I 40 60 Working depth, ffm
I 80
ol
].0 100
Fig 5 Relation between the diameter of the hole and the working depth using a flat drift at 1550 rev/min and 2 l~m s I. The arrows denote the length from tip to shoulder of the drill PRECISION ENGINEERING
I
20
I
I
40 60 Working depth, ~Lm
80
I00
Fig 6 Relation between the ratio of the typical diameter of the star pattern to the diameter of the hole on the surface and the working depth, using a twist drift and a flat drift at 1550 rev/min and 2 l~m s 7. The arrows denote the length from tip to shoulder of each drift 15
Goto et a I - - M i c r o d r i l l i n g a n d plastically d e f o r m e d diameters in brittle CdS crystals
etching. The ratio of the typical diameter of the star pattern to the diameter of the hole on the surface is shown in Fig 6. From Fig 6, we can easily see that the result with a twist drill is better than that with a flat drill, because the ratio is about 2 for the t w i s t drill as compared w i t h about 3 for the flat drill. According to a theoretical investigation by Hill 6 the ratio of plastic zone radius c to hole radius a is given by c
__
a where E is Y o u n g ' s modulus, v is Poisson's ratio and Y is yield stress. E and v were approximately estimated from Refs 7 and 8, and Y was estimated from Ref 4. When we use E = 81 GPa, ~,= 0.39 and Y = 350 MPa, c / a is estimated as 11.6. However, this value is larger than our results of 2 to 3, and we think that the reduction of the parameter c / a depends on the chip removal,
Conclusions The conclusions of this study are as follows: • A rotary speed of 1550 r e v / m i n with a feed rate of 2 l~m s 1 is a suitable working condition.
16
• When the working depth is more than 30/~m for a twist drill or more than 40 l~m for a flat drill, the hole shapes are almost cylindrical for a twist drill and slightly tapered for a flat drill, respectively. • The ratio of the typical diameter of the plastically deformed domain to the diameter of the surface hole is about 2 for a twist drill and about 3 for a flat drill= • Results with a t w i s t drill are better than with a flat drill.
References 1 Sugawara, A. and Inagaki, K. Effect of Workpiece Structure on Burr Formation in Micro.drilling, Bud Jap Soc Precision Engng, 4, 1982, 9 2 Iwata, K., Moriwaki, T. and Hoshikawa, M. Fundamemal Study of High Speed Micro Deep Drilling, J Jap Soc Precision Engng, 49, 1983, 240 (m Japanese) 3 Maeda, M., Goto, F. and Miyata, K. Hollow Crystal of Wurzite Type CdS, Jap J App/ Phys, 3, 1964, 426 & P/. 15 4 Goto, F. and Kudo, S. An Estimation of Yield Points in CdS Single Crystal Using Microvickers- and MicrorockwellIndenter, TransJSME, A53, 1987, 2406 (in Japanese) 5 Goto, F. and Kudo, S. Microhardness and Plastically Deformed Regions in CdS Single Crystals,J App/Phys, 6& 7988, 2445 6 Hill, R. The Mathematical Theory, of Plasticity, Clarendon Oxford, 1954 7 Bruce, H. B. American institute o/Physics Handbook, McGraw-HilL New York, 1972 8 Lekhnitskii, S. G. Theory of Elasticity of an Anisotrop/c Body, M/r, Moscow, (1981) (Enq/ish Translation)
J A N U A R Y 1991 VOL 13 NO 1