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The Effect of Wheel Wear Rate on the Grinding Performance of Three Wheel Grades
The Effect of Wheel Wear Rate on the Grinding Performance of Three Wheel Grades R. P. Lindsay (1)
Three wheel qrades ( I , K, M ) were used to plunqe qrind 4340 (Rc43) and traverse-qrind 52100 ( R c 6 0 ) Two regions o f cuttina steels. Conditions were varied to produce a ranqe of GRatlos from 355 to 1.64. aehavior (removal rate VS. Dower) existed depending on the wheelwear rate. ContinuoIis relationships between wheelwear rate and power were obtained. The plunge-arindinq wheelwear rates were low (355< G R a t i o c 4 5 ) and the cutting behavlor was influenced by dressinq so that the K qrade produced the best GRatios over the testing range. At high traverse-qrinding metal removal rates, wheelwear rates were high (GRatio
I.
50
Introduction:
Grinding operations qenerally consist of two broad cateqaries: precision grinding, where accuracy of form and finish are prime considerations and stock removal qrinding where hiqh metal removal rates are needed. Most CRN and vitrified-bond wheels are used for precision grinding and some vitrified and all organic-bond wheels are usually used for stock-removal grinding. We performed two tests to see the similarities between the two methods. We plunqeqround 4340 (Rc43) steel and traverse-ground 52100 (Rc60) infeedina. onlv' at one end of the stroke to simulate centerless grindinq. 11.
-
2 10:
s
w
5: .
Metal Removal Rate and Power:
a
.05
.01
Figure 1 shows Power vs. Metal Removal Rate for three wheel qrades. After some threshold power, there was a linear relationship up to about 2 6 of 3.5. This low power-removal rate zone included the plunge grinding data and the first three or five traverse grinding results. Beyond :2 of 3.5, a new
I
Heq Fig. 2
Pi
.5
.I0
. ...I LO
J
2 3
(8-0
Heq with ref. CIRP Data
VS.
erence data for precision plunqe qrindinq. Thus, in most precision grinding operations, lhe region beyond the "knee" will never be seen. Surface finn ishes and GRatios beyond ;r the "knee" are too poor for pre- ucision qrindinq
4r
1
3' 2 . 1.0.
.5.
3
(2).
0
4
2
2; Fiq. 1
6
8
(INCH3/MINUTE,INCH)
Power vs. Zw €or Plunae and T r a v e r s e G r i n d i q
second linear region existed. Using the linear regression program of a calculator we obtained the SlOPeS values for these slopes. The low powei-2: were 7.41, 7.95 and 7.91 horseoower/inch3 per minute 120.2, 21.7 and 21.6 joules/mm3) for I, K and M grades. In the high Power'-Z& regions, the slopes were 0.023, 4.35 and 4.46 horsepower/inch3 per minute (0.063, 11.9 and 12.2 joules/mm3) for I, K and M grades. Figure 2 shows tangential force vs. Heq for the plunge and traverse tests. The tangential force was calculated from the power meter readings o f horsepower. The CIRP data ( 1 ) are from plunge-grinding tests o n lOOCR6 steel done by three universities. While tangential force is more physically meaningful. power is more practical and will be used here. For the width in traverse grinding, w e took the crossfeed width of 0.220 inch (5.6mm). The total measured power and total metal removal rate were divided by the crossfeed to get the horsepower/inch and Zb values shown. Heq calculated from &/Vs went a s high a s 3 . 0 ~ 1 . At the "knee" in Figure 1, heq was about l.Opm, which 1s hiqher than the CIRP ref-
Annals of the CIRP Vol. 32/1/1983
I
10
111. Wheelwear Rates and Power:
z
0.1 :
I
.OS'
3 U
E
J Figure 3 . . shows the Wheel.* . wear Rate vs. .In Power data for these two qrind- N . O l : inq modes. For traverse .005 ' grinding, since we only moved the wheel into the work when the wheel w a s to the right of the workpiece, the .OOl left end o f the wheel had to corner-cut and Mx)5 wore the most. We measured the i wear at three places across the wheel Eace: in the middle .OOo~, S 10 50 and 0.250 inch in from each end POWER' (HP/ INCH) and generally Fig. 3 zs vs: Power qot the wheelwear shape shown ~n Figure 3. We calculated the total wear volume f rom the three measurements, then .
I
.,..,...,. 247
divided by the cross-reed width and total qrindinq time to get the Z& values for traverse grinding. (The lefl-end WO.IL I S tbe amount that would have to he dressed o f f the wheel radius to obtain P straiqht sheet fare again.) Salcuiated this way, there is a continuous relationship between the plunqe and traverse data for e l l three qrades. Vatice in each mode, the I qrade wore fastest and the Y slowest a t all power values. O b v i o u s l v , then the two cutting iegions of rigure 1 resuit from the wheelwear rate and the strength of the wheel. Uotlce In I'iqure 1 that the "knee" (intersection of the two slooes) occurred at 27. 29 and 34 horsepower/inch for the I , K and M qrades. These are the "breakdown power" levels for these wheels. A t very high 2% values, the grains are fracturing, maybe beinq torn Erom the bond and so they can't dull and the wheel, being very "sharp" s ! cuts with a ?ow Speciflc Power slope. A t lower Z rates, grain dulling can occur and the wheels cut with a higher Soeci- 400 ic Power. The exNCE istence of two slopes is obvious. K-K
Ice/ *\'"
IV. Rating a Wheel using GRatios: Given equivalent surface finish (which is usually dependent on the chip thickness ( 3 ) ) and geometry. the GRatio is a prime factor used to rate the performance of grinding wheels, providinq some wheel doesn't require forces hiqh enough to cause premature machine chatter.
100
FLgure 6 shows the traverse qri nd i ng data: 21.0 Ztr vs. Power' in 'z ' the upDer ' qraph and
- -
76.
n\ z
VS.
Power'in the lower
2
.
'
0.5"
I
I
I
I
....I
5 I0 50 P O W E R ' (HP/INCH)
I
figure 4 shows t.he plunge and t r a j i9. 4 GRatio vs. Power verse grindinq GRatios plotted versus power. In both modes, at any power value. the M gave the highest GRatios and the I the lowest values. hiotice the different levels: 40 to 355 for plunqe (precision) grinding and 1.64 to 22 for traverse (stock-removal) qrinding. In each mode, Lhe X was "best" and the I "poorest" from Figure 4. Figure 5 qives the plunge qrinding tests alone. The upper graph shows the linear relationships of 2; and power and the threshold power values from Figure 1. The threshold power values of 1.79, 2.75 and 4.4 horsepower/inch (52.5. 80.8 and 129.2 watts/mm) increased linearly with the elastic modulii of the three wheels (40.1 50.7 and 58.9KN/mm2).
slopes and the two regions described in Fiqure
1
Fig. 6
e r right, the traverse qrinding data shows the M grade was a l ways best. Figures 1 and 6 showed that
5 10 P O w E R' (HPAN) Zw and 2 s vs. Power
POWER
Zw and 2s
60
( HP/IN) VS.
Power
Figure 7 shows GRatio vs. Zk for plunge and traverse grinding. This i s a "productivity" plot since a user is interested in GRatios at different metal removal rates. A t left the K grade results were highest and the M and I grades gave essentially equivalent GRatios. Thus, for plunge-qrinding, the K would be best on a "GRatio" ranking. Possibly the M would hold corners and form better and the I would use the lowest forces and power so each wheel would have some characteristic making it "best". Notice the two dotted vertical lines at Z& of 0.25 and 0.42
200 100
.
.
,40
20
0
1 are shown in the upper graph, where three dotted horizontal lines are drawn at Zb of 2.1, 5.4 and 7.3 inch3/minute, inch. In the lower graph, as done in Figure 5, three dotted lines connect the power and 25 values at the three constant fw rates. !Cow, however a different pattern emerges: The M grade had the lowest 2's rate and the I had the hiqhest wear rates at all three Zb rates.
Ute, inch with the K giving the hiqhest GRatios as already described
The cutting behavior was strongly n\ influenced by the effect of dressinq on each grade. Thus the I grade used less (force) power than the K o r M, d u e to its lower threshold power value. Dotted horizontal lines drawn at 0.25 and 0.42 inch3/minute, inch, intersect the lines f o r each grade Fig. 5
248
a t difrerent Dower levels. In the lower graph of riaure 5 , dotted lines connect the Zk values at the m w e r value required by each grade. Thus these dotted lines represent the wheelwear rates f o r each qrade of Z& o f 0.75 and 0.42 inch3/mlnute, inch. lotice that both dotted llnes have a minimum at K grade meaninq i t wore slowest a t both 0.25 and 0.42 metal removal rates. Since alonq each dotted line Zh is constant, t5e wheel having the lowest 2's value will produce the hiahest GRatio since Z'w,'Zk is the GRatio on a "rate" basis. Thus we expect the K arade t q give the best GRatios, at least at z'w o f I 0.25 and 0.42 inch3/ POW E R ' (HPAN) minute, Inch.
T R A V E R S E
0
.
u
'
*
took the highest forces a n d c 3 power however.
I
.
.
*
These data illustrate that GRatios are complex in- a teraction of
0 lo
...
I
I
1 . . ..I
0.5 Fiq. 7
ID
(
.. . I
:
,
I
5 H~/MIN,IN)
CRatio vs. Zw
10
V
.
"
S ce :c I f
I
c - En c ~ q ~ z
ions : ~.
.~ppruac--h we";e use8 i s ? o sh'7w t h a t there hlDs between ~ l :and P o w c r ' (realhas been shown many times ( 4 , s ) . -firma1 forres blit tt.e t e s t . ? we'? an: power :'aiues f s r each i s mere,y z t vs. ~i..he t w o ltsrlv snow the gh.{sical slrenqtr w riieelvear rate c a n a f r e c t cutting sharpness. Another me;h.;.d i s t o divide power'bv the Zk valce used to g e t i number called " s p e c r f ~ c energy." These values (one for each dw value) are ~ s u a i i yplotted v s . Zt?. h e d1d that and Fiqure 8 shows the values f o r a l l rhe grades. "Smooth curves" Specrr ; c energy decreases at rosui t implying : hiqh metal removal rates". In fact, this I S caused en+:rely by the threshold power (force) ralircs and the physical meaning of Figure 1 is completc?y iost in Figure 8 . Moreover, to an ord-nary reader, the "decreasing specific energy" implies "decreaslnq porier" and that's misleading and wronq. :'he
1.
R. snoeys, . J . Peters, "?he Siqnificance of Chrp 'Thickness in Grindinq", 4nnals o f CTRF, V.?: 2 3 7 , 1974.
2.
R . ii ndc a }-, " Fa c t c rs ?, f ie c t L ng Tr 3 ve r s e Ex tern a l Grinding" Society of Yanufacturing Engineers Paper dMSi8-332, SME, Dearborn, Michiqan, 1978.
3.
R. Lindsay. "On the Surface Pin~sh-MetalRemoval Relationship in Precrsion Grinding" Paper ;I72-WA! Prod-13, American Sockety of Yechanical Enqineers Yew York. 1972.
4.
R. S . Hahn, R. Lindsay, "Principles o f Grindlna", Yachinery Maqmzine, Xew York, 1971.
5.
R. S. Hahn, R. P. Lindsay, "On the Dasic Relatiow ships bevween Grindinq Parameters",Annals of CISP VOl . XVIII, 1970.
I"
6 .
R. Lindsay, " 4 Comparlson of Cuttinq and Grindlng Kortti American Metalworking Research Conference (NAMRC1 X . (Society o f Manufacturing Enqineers, Dearborn. Michigan) 1982. Pata",
c c ' .5
.I0
yiq. 8
4,
z$
5
1.0
10
( lN3/MIN,IN)
Power/'Zw v s . Z w
Thf, approach of Figure 1. used many times (2, 3 , 5 ) . was used to relate cuttinq and grinding data.
S i m i l a r "Specific Power" dnd "Yetal Revoval Parame-
ters' (Lambda1 ( 4 . 5 ) exist far cuttinq a s well a s grinding when Z'w was plotted against normal force and poker (cutting force times workspeed). Conclusions:
VI.
These tests support the fol'owing conclusions: Continuous Curves of kheelwcar rate vs. power exist through the precision grindinq and stock r e m o v i l grinding modes. B - Depending on the Wheelwear rate, two reqions of cuttinq behallor (Z;, v s . power or normal forccl exi5L. A -
c
I .
- The transition ~ ~ i nbetween t the precisiongrinding slope and the stock-removal s l o ~ edepends on the strenqth of the wheel.
D - In the precision grinding region, dressinq can affect the cutting action of a wheel so that a
sotter qrade can produce higher GRatios than a harder kheel dependTn9 on tbe interaction of metal rem.;val rite, wheelwear rate and power (force).
E -
Dir~lding power by metal removal rate to a b t a ~ n a serie? of numbers cal-ed "specific energy ard plottinq them against metal removal rate produces a continuods curve which has no phy5:cal significance ind ran be misleading to an ordinary reader.
Operat i ng Condi !.ions Plunae:
Rw = 0 . 7 7 ( I . K ) , 0.53 inch (M):Vw = 130ft/min: Voi;
Traverse:
Bw
= 5.50 inch3/inch. =
2.50 inch (crossfeed:
inch/t 1 : Vw = 130 and 72OLf:mln; (0.0005ca<0.004
vs
= 690rlft:min;
inrb (nrwl, 3 . 0
0.220cSw<1.250
?oI', = 3 1 0 x a
inch1
n
= 20 inch: rIw = 4 . 0
inch (used).
249
Three wheel qrades ( I , K, M ) were used to plunqe qrind 4340 (Rc43) and traverse-qrind 52100 ( R c 6 0 ) Two regions o f cuttina steels. Conditions were varied to produce a ranqe of GRatlos from 355 to 1.64. aehavior (removal rate VS. Dower) existed depending on the wheelwear rate. ContinuoIis relationships between wheelwear rate and power were obtained. The plunge-arindinq wheelwear rates were low (355< G R a t i o c 4 5 ) and the cutting behavlor was influenced by dressinq so that the K qrade produced the best GRatios over the testing range. At high traverse-qrinding metal removal rates, wheelwear rates were high (GRatio
I.
50
Introduction:
Grinding operations qenerally consist of two broad cateqaries: precision grinding, where accuracy of form and finish are prime considerations and stock removal qrinding where hiqh metal removal rates are needed. Most CRN and vitrified-bond wheels are used for precision grinding and some vitrified and all organic-bond wheels are usually used for stock-removal grinding. We performed two tests to see the similarities between the two methods. We plunqeqround 4340 (Rc43) steel and traverse-ground 52100 (Rc60) infeedina. onlv' at one end of the stroke to simulate centerless grindinq. 11.
-
2 10:
s
w
5: .
Metal Removal Rate and Power:
a
.05
.01
Figure 1 shows Power vs. Metal Removal Rate for three wheel qrades. After some threshold power, there was a linear relationship up to about 2 6 of 3.5. This low power-removal rate zone included the plunge grinding data and the first three or five traverse grinding results. Beyond :2 of 3.5, a new
I
Heq Fig. 2
Pi
.5
.I0
. ...I LO
J
2 3
(8-0
Heq with ref. CIRP Data
VS.
erence data for precision plunqe qrindinq. Thus, in most precision grinding operations, lhe region beyond the "knee" will never be seen. Surface finn ishes and GRatios beyond ;r the "knee" are too poor for pre- ucision qrindinq
4r
1
3' 2 . 1.0.
.5.
3
(2).
0
4
2
2; Fiq. 1
6
8
(INCH3/MINUTE,INCH)
Power vs. Zw €or Plunae and T r a v e r s e G r i n d i q
second linear region existed. Using the linear regression program of a calculator we obtained the SlOPeS values for these slopes. The low powei-2: were 7.41, 7.95 and 7.91 horseoower/inch3 per minute 120.2, 21.7 and 21.6 joules/mm3) for I, K and M grades. In the high Power'-Z& regions, the slopes were 0.023, 4.35 and 4.46 horsepower/inch3 per minute (0.063, 11.9 and 12.2 joules/mm3) for I, K and M grades. Figure 2 shows tangential force vs. Heq for the plunge and traverse tests. The tangential force was calculated from the power meter readings o f horsepower. The CIRP data ( 1 ) are from plunge-grinding tests o n lOOCR6 steel done by three universities. While tangential force is more physically meaningful. power is more practical and will be used here. For the width in traverse grinding, w e took the crossfeed width of 0.220 inch (5.6mm). The total measured power and total metal removal rate were divided by the crossfeed to get the horsepower/inch and Zb values shown. Heq calculated from &/Vs went a s high a s 3 . 0 ~ 1 . At the "knee" in Figure 1, heq was about l.Opm, which 1s hiqher than the CIRP ref-
Annals of the CIRP Vol. 32/1/1983
I
10
111. Wheelwear Rates and Power:
z
0.1 :
I
.OS'
3 U
E
J Figure 3 . . shows the Wheel.* . wear Rate vs. .In Power data for these two qrind- N . O l : inq modes. For traverse .005 ' grinding, since we only moved the wheel into the work when the wheel w a s to the right of the workpiece, the .OOl left end o f the wheel had to corner-cut and Mx)5 wore the most. We measured the i wear at three places across the wheel Eace: in the middle .OOo~, S 10 50 and 0.250 inch in from each end POWER' (HP/ INCH) and generally Fig. 3 zs vs: Power qot the wheelwear shape shown ~n Figure 3. We calculated the total wear volume f rom the three measurements, then .
I
.,..,...,. 247
divided by the cross-reed width and total qrindinq time to get the Z& values for traverse grinding. (The lefl-end WO.IL I S tbe amount that would have to he dressed o f f the wheel radius to obtain P straiqht sheet fare again.) Salcuiated this way, there is a continuous relationship between the plunqe and traverse data for e l l three qrades. Vatice in each mode, the I qrade wore fastest and the Y slowest a t all power values. O b v i o u s l v , then the two cutting iegions of rigure 1 resuit from the wheelwear rate and the strength of the wheel. Uotlce In I'iqure 1 that the "knee" (intersection of the two slooes) occurred at 27. 29 and 34 horsepower/inch for the I , K and M qrades. These are the "breakdown power" levels for these wheels. A t very high 2% values, the grains are fracturing, maybe beinq torn Erom the bond and so they can't dull and the wheel, being very "sharp" s ! cuts with a ?ow Speciflc Power slope. A t lower Z rates, grain dulling can occur and the wheels cut with a higher Soeci- 400 ic Power. The exNCE istence of two slopes is obvious. K-K
Ice/ *\'"
IV. Rating a Wheel using GRatios: Given equivalent surface finish (which is usually dependent on the chip thickness ( 3 ) ) and geometry. the GRatio is a prime factor used to rate the performance of grinding wheels, providinq some wheel doesn't require forces hiqh enough to cause premature machine chatter.
100
FLgure 6 shows the traverse qri nd i ng data: 21.0 Ztr vs. Power' in 'z ' the upDer ' qraph and
- -
76.
n\ z
VS.
Power'in the lower
2
.
'
0.5"
I
I
I
I
....I
5 I0 50 P O W E R ' (HP/INCH)
I
figure 4 shows t.he plunge and t r a j i9. 4 GRatio vs. Power verse grindinq GRatios plotted versus power. In both modes, at any power value. the M gave the highest GRatios and the I the lowest values. hiotice the different levels: 40 to 355 for plunqe (precision) grinding and 1.64 to 22 for traverse (stock-removal) qrinding. In each mode, Lhe X was "best" and the I "poorest" from Figure 4. Figure 5 qives the plunge qrinding tests alone. The upper graph shows the linear relationships of 2; and power and the threshold power values from Figure 1. The threshold power values of 1.79, 2.75 and 4.4 horsepower/inch (52.5. 80.8 and 129.2 watts/mm) increased linearly with the elastic modulii of the three wheels (40.1 50.7 and 58.9KN/mm2).
slopes and the two regions described in Fiqure
1
Fig. 6
e r right, the traverse qrinding data shows the M grade was a l ways best. Figures 1 and 6 showed that
5 10 P O w E R' (HPAN) Zw and 2 s vs. Power
POWER
Zw and 2s
60
( HP/IN) VS.
Power
Figure 7 shows GRatio vs. Zk for plunge and traverse grinding. This i s a "productivity" plot since a user is interested in GRatios at different metal removal rates. A t left the K grade results were highest and the M and I grades gave essentially equivalent GRatios. Thus, for plunge-qrinding, the K would be best on a "GRatio" ranking. Possibly the M would hold corners and form better and the I would use the lowest forces and power so each wheel would have some characteristic making it "best". Notice the two dotted vertical lines at Z& of 0.25 and 0.42
200 100
.
.
,40
20
0
1 are shown in the upper graph, where three dotted horizontal lines are drawn at Zb of 2.1, 5.4 and 7.3 inch3/minute, inch. In the lower graph, as done in Figure 5, three dotted lines connect the power and 25 values at the three constant fw rates. !Cow, however a different pattern emerges: The M grade had the lowest 2's rate and the I had the hiqhest wear rates at all three Zb rates.
Ute, inch with the K giving the hiqhest GRatios as already described
The cutting behavior was strongly n\ influenced by the effect of dressinq on each grade. Thus the I grade used less (force) power than the K o r M, d u e to its lower threshold power value. Dotted horizontal lines drawn at 0.25 and 0.42 inch3/minute, inch, intersect the lines f o r each grade Fig. 5
248
a t difrerent Dower levels. In the lower graph of riaure 5 , dotted lines connect the Zk values at the m w e r value required by each grade. Thus these dotted lines represent the wheelwear rates f o r each qrade of Z& o f 0.75 and 0.42 inch3/mlnute, inch. lotice that both dotted llnes have a minimum at K grade meaninq i t wore slowest a t both 0.25 and 0.42 metal removal rates. Since alonq each dotted line Zh is constant, t5e wheel having the lowest 2's value will produce the hiahest GRatio since Z'w,'Zk is the GRatio on a "rate" basis. Thus we expect the K arade t q give the best GRatios, at least at z'w o f I 0.25 and 0.42 inch3/ POW E R ' (HPAN) minute, Inch.
T R A V E R S E
0
.
u
'
*
took the highest forces a n d c 3 power however.
I
.
.
*
These data illustrate that GRatios are complex in- a teraction of
0 lo
...
I
I
1 . . ..I
0.5 Fiq. 7
ID
(
.. . I
:
,
I
5 H~/MIN,IN)
CRatio vs. Zw
10
V
.
"
S ce :c I f
I
c - En c ~ q ~ z
ions : ~.
.~ppruac--h we";e use8 i s ? o sh'7w t h a t there hlDs between ~ l :and P o w c r ' (realhas been shown many times ( 4 , s ) . -firma1 forres blit tt.e t e s t . ? we'? an: power :'aiues f s r each i s mere,y z t vs. ~i..he t w o ltsrlv snow the gh.{sical slrenqtr w riieelvear rate c a n a f r e c t cutting sharpness. Another me;h.;.d i s t o divide power'bv the Zk valce used to g e t i number called " s p e c r f ~ c energy." These values (one for each dw value) are ~ s u a i i yplotted v s . Zt?. h e d1d that and Fiqure 8 shows the values f o r a l l rhe grades. "Smooth curves" Specrr ; c energy decreases at rosui t implying : hiqh metal removal rates". In fact, this I S caused en+:rely by the threshold power (force) ralircs and the physical meaning of Figure 1 is completc?y iost in Figure 8 . Moreover, to an ord-nary reader, the "decreasing specific energy" implies "decreaslnq porier" and that's misleading and wronq. :'he
1.
R. snoeys, . J . Peters, "?he Siqnificance of Chrp 'Thickness in Grindinq", 4nnals o f CTRF, V.?: 2 3 7 , 1974.
2.
R . ii ndc a }-, " Fa c t c rs ?, f ie c t L ng Tr 3 ve r s e Ex tern a l Grinding" Society of Yanufacturing Engineers Paper dMSi8-332, SME, Dearborn, Michiqan, 1978.
3.
R. Lindsay. "On the Surface Pin~sh-MetalRemoval Relationship in Precrsion Grinding" Paper ;I72-WA! Prod-13, American Sockety of Yechanical Enqineers Yew York. 1972.
4.
R. S . Hahn, R. Lindsay, "Principles o f Grindlna", Yachinery Maqmzine, Xew York, 1971.
5.
R. S. Hahn, R. P. Lindsay, "On the Dasic Relatiow ships bevween Grindinq Parameters",Annals of CISP VOl . XVIII, 1970.
I"
6 .
R. Lindsay, " 4 Comparlson of Cuttinq and Grindlng Kortti American Metalworking Research Conference (NAMRC1 X . (Society o f Manufacturing Enqineers, Dearborn. Michigan) 1982. Pata",
c c ' .5
.I0
yiq. 8
4,
z$
5
1.0
10
( lN3/MIN,IN)
Power/'Zw v s . Z w
Thf, approach of Figure 1. used many times (2, 3 , 5 ) . was used to relate cuttinq and grinding data.
S i m i l a r "Specific Power" dnd "Yetal Revoval Parame-
ters' (Lambda1 ( 4 . 5 ) exist far cuttinq a s well a s grinding when Z'w was plotted against normal force and poker (cutting force times workspeed). Conclusions:
VI.
These tests support the fol'owing conclusions: Continuous Curves of kheelwcar rate vs. power exist through the precision grindinq and stock r e m o v i l grinding modes. B - Depending on the Wheelwear rate, two reqions of cuttinq behallor (Z;, v s . power or normal forccl exi5L. A -
c
I .
- The transition ~ ~ i nbetween t the precisiongrinding slope and the stock-removal s l o ~ edepends on the strenqth of the wheel.
D - In the precision grinding region, dressinq can affect the cutting action of a wheel so that a
sotter qrade can produce higher GRatios than a harder kheel dependTn9 on tbe interaction of metal rem.;val rite, wheelwear rate and power (force).
E -
Dir~lding power by metal removal rate to a b t a ~ n a serie? of numbers cal-ed "specific energy ard plottinq them against metal removal rate produces a continuods curve which has no phy5:cal significance ind ran be misleading to an ordinary reader.
Operat i ng Condi !.ions Plunae:
Rw = 0 . 7 7 ( I . K ) , 0.53 inch (M):Vw = 130ft/min: Voi;
Traverse:
Bw
= 5.50 inch3/inch. =
2.50 inch (crossfeed:
inch/t 1 : Vw = 130 and 72OLf:mln; (0.0005ca<0.004
vs
= 690rlft:min;
inrb (nrwl, 3 . 0
0.220cSw<1.250
?oI', = 3 1 0 x a
inch1
n
= 20 inch: rIw = 4 . 0
inch (used).
249