Industrial Engineering Chapter 9 Fave Ave Mve Since And Calculate The Righthand Side This Equation Tabler

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)3/41460

v

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0.0732A=AD1/4d3/4V

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=AD1/4d3/4V

5000 rpm, or a surface speed of 2080 ft/min,

the temperature rise will be

∆T=AD1/4d3/4V

v1/2

= (18,500)(10)1/4(0.002)3/42080

is

v1/2

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

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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

coco

v1/5=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

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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

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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

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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

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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,

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