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comes to a stop. Ignore wheel wear.
By the student. Note that, because of the vari-
negative rake angle and the material properties
abrasive grain, dropped from heights of (a) 1
m, (b) 2 m, and (c) 10 m. Plot the results and
from Eq. (9.11) as
to=5r
=5(0.0005)
to
2.04 ×10−6
or Fave = 77.3 N
being produced by electrochemical machining.
A=πD2
on an electrical-discharge machine, what would
be the estimated machining time?
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9.68 A cutting-off operation is being performed with
a laser beam. The workpiece being cut is 1
4
9.69 Referring to Table 3.3, identify two metals or
metal alloys that, when used as workpiece and
trode): tungsten/lead alloys (R= 0.00266), al-
though the use of lead would be unrealistic for
9.70 It was stated in Section 9.5.2 that, in practice,
where we note that this ratio ranges between 2
and 200, and even higher. Thus, the values are
tain the same grinding temperatures as those
encountered with the existing operating condi-
tions?
or
= 0.0783A
where Ais a constant. The known safe operat-
=A(10)1/4(0.0015)3/41460
v
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0.0732A=AD1/4d3/4V
v
ground. A depth of 0.003 in. is to be removed
from a cylindrical section 8 in. long and with a
3-in. diameter. If each part is to be ground in
not more than one minute, what is the approxi-
mate power requirement for the grinder? What
if the material is changed to a hard titanium
alloy?
or 0.226 in3. Therefore, the minimum metal re-
9.3), the power requirement is
P= (10 hp-min/in3)(0.226 in3/min) = 2.26 hp
9.73 A grinding operation is taking place with a 10-
in. grinding wheel at a spindle rotational speed
of 4000 rpm. The workpiece feed rate is 50
ft/min, and the depth of cut is 0.002 in. Con-
tact thermometers record an approximate max-
imum temperature of 1800◦F. If the workpiece
is steel, what is the temperature if the spindle
speed is increased to 5000 rpm? What if it is
increased to 10,000 rpm?
or
∆T=AD1/4d3/4V
5000 rpm, or a surface speed of 2080 ft/min,
the temperature rise will be
∆T=AD1/4d3/4V
v1/2
= (18,500)(10)1/4(0.002)3/42080
is
v1/2
ing point of steel (see Table 3.3 on p. 106).
Clearly, the temperature cannot increase above
the melting point of the workpiece material.
This indicates that the 10,000 rpm speed, com-
bined with the other process parameters, would
not be a realistic process parameter.
9.74 The regulating wheel of a centerless grinder is
rotating at a surface speed of 25 ft/min and is
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
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9.75 Using some typical values, explain what
changes, if any, take place in the magnitude
of the impact force of a particle in ultrasonic
machining of a hardened-steel workpiece as its
temperature is increased?
Inspecting Eqs. (9.11) and (9.13) we can see
by
Fave =2mv
5r
coco
v1/5=2mv6/5c4/5
o
5r
=2mv6/5E2/5
at room temperature and the other at elevated
temperature, and noting that the density is af-
9.76 Estimate the percent increase in the cost of the
grinding operation if the specification for the
surface finish of a part is changed from 63 to 16
involve an increased cost of about 400%. This
is a very significant increase in cost, and is a
good example of the importance of the state-
ment made throughout the book that, in or-
der to minimize manufacturing costs (see also
Fig. 16.6), dimensional accuracy and surface
9.77 Assume that the energy cost for grinding an
aluminum part is $0.90 per piece. Letting the
specific energy requirement for this material be
8 Ws/mm3, what would be the energy cost if
the workpiece material is changed to T15 tool
steel?
9.78 Derive an expression for the angular velocity of
the wafer as a function of the radius and angu-
lar velocity of the pad in chemical mechanical
By the student. Refer to the figure above and
consider the case where a wafer is placed on the
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
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reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
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9.79 A 25-mm-thick copper plate is being machined
by wire EDM. The wire moves at a speed of 1.5
m/min and the kerf width is 1.5 mm. Calculate
9.80 An 8-in. diameter grinding wheel, 1 in. wide,
is used in a surface grinding operation per-
(c) The rate of chip production is given by
n=V wC = (5000)(12)(0.15)(300)
or n= 2.7×106chips/min.
9.81 A 150-mm-diameter tool steel (u= 60 W-
s/mm3) work roll for a metal rolling operation
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
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ple 9.1 on p. 532, except the undeformed chip
l=sDd
1 + (D/Dw)=s(0.25)(0.00004)
1 + (0.25)/(0.15)
be
= (0.00004)(0.075)(4.7)
= 1.41 ×10−5m3/min = 235 mm3/s
P=u(MRR) = (60)(235) = 14.1 kW
23.6= 597 N
steel shot; (b) 0.1-mm-diameter cubic boron
2.1, 3.3 and 8.6.)
The time of contact depends on the elastic
wave velocity in the workpiece; for steel, where
to
13.9×10−6
Steel 2.5 8025113.9 56.7
Tungsten 3 19,29018.32 393.3
1. From Table 2.1.
2. From Table 8.6.
extreme case of a rubber ball, similar to a toy
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9.83 Assume that you are an instructor covering the
and understanding on the part of the students,
and has been found to be a very valuable home-
9.84 Would you consider designing a machine tool
that combines, in one machine, two or more of
the processes described in this chapter? Ex-
machine be useful? Make preliminary sketches
9.85 With appropriate sketches, describe the prin-
By the student. This is an open-ended problem
that would also be suitable for a project. The
9.86 As also described in Section 4.3, surface finish
can be an important consideration in the de-
dressing techniques, and the processing param-
eters such as feed, speed, and depth of cut.
9.4.1. Design a setup and suggest a series of
effective system on a microscale, such as in-
9.88 Describe how the design and geometry of the
workpiece affects the selection of an appropri-
ing surfaces, such as with gear teeth where the
wheel edge radius must be less than the gear
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
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9.90 How would you produce a thin circular disk
with a thickness that decreases linearly from
the center outward?
tion 9.10), and withdraw it slowly while it is
pending on workpiece shape and accuracies re-
quired; note, however, that there has to be a
9.93 Conduct a literature search and explain how
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
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reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
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9.94 Visit a large hardware store and inspect the var-
ious grinding wheels on display. Make a note
increased reluctance on students to gain prac-
tical experience and exposure to machinery by
Fig. 9.2. Those in Fig. 9.3 are less common and
also more expensive. Students may also com-
surfaces using a magnifier or a microscope, and
By the student. This is a good project and can
9.96 In reviewing the abrasive machining processes
in this chapter it will noted that some processes
use bonded abrasives while others involve loose
Honing
Superfinishing
sizes, the material removal
rates, surface finish, and lay
(see Fig. 33.2 on p. 1039).
9.97 Based on the topics covered in Chapters 6
through 9, make a comprehensive table of hole-
students. The statement of the problem implies
(a) piercing, (b) punching, (c) drilling and bor-
9.98 Precision engineering is a term used to describe
Based on their process capabilities, make a list
of advanced machining processes (in decreasing
order of quality of parts produced). Include a
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ther singly or in combination, to produce or
finish tools and dies for metalworking opera-
tions. Prepare a brief technical paper on these
methods, describing their advantages and limi-
tations, and giving typical applications.
would be difficult to apply to a variety of non-
metallic or rubberlike materials. Explain your
9.101 Make a list of the processes described in this
chapter in which the following properties are
relevant or significant: (a) mechanical, (b)
chemical, (c) thermal, and (d) electrical. Are
there processes in which two or more of these
properties are important? Explain.
trochemical machining,
electrochemical grinding,
© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
likewise. For information regarding permission(s), write to:
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© 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.
This material is protected by Copyright and written permission should be obtained from the publisher prior to any prohibited
reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or
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