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PROFESSOR: Now we consider
the process of thermo-forming.

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00:00:54,400 --> 00:00:56,590
In this process, we will
make a simple circuit

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00:00:56,590 --> 00:00:59,590
apart by heating a flat
sheet of polystyrene

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00:00:59,590 --> 00:01:02,140
and then pulling it over
a tool under vacuum.

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00:01:07,660 --> 00:01:09,370
After forming, the
part is usually

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trimmed to a final shape.

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00:01:13,910 --> 00:01:15,770
To begin the process,
the flat sheet

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00:01:15,770 --> 00:01:20,620
is loaded into the machine
and then clamped into place.

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00:01:20,620 --> 00:01:22,670
The sheet is moved
into an oven and heated

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00:01:22,670 --> 00:01:24,380
for a specified amount of time.

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00:01:29,510 --> 00:01:32,060
The oven temperature is
under feedback control

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00:01:32,060 --> 00:01:34,280
and the timing of entering
and exiting the oven

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00:01:34,280 --> 00:01:36,050
is also under program control.

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00:01:40,280 --> 00:01:42,620
After residing in the
oven the desired time,

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00:01:42,620 --> 00:01:45,080
the sheet is moved
over the tool,

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00:01:45,080 --> 00:01:47,270
it comes up to
contact the sheet,

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00:01:47,270 --> 00:01:49,220
and the vacuum is
applied through the tool.

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00:01:55,390 --> 00:01:58,040
This draws the sheet onto
the tool, taking its form

26
00:01:58,040 --> 00:01:59,860
and, at the same
time, cools the sheet.

27
00:02:05,610 --> 00:02:07,470
The part is then
removed from the clamps

28
00:02:07,470 --> 00:02:09,269
and measured using
a vernier caliper.

29
00:02:14,370 --> 00:02:16,320
We will look at two
different thickness sheets

30
00:02:16,320 --> 00:02:18,210
and have two different
resonance times

31
00:02:18,210 --> 00:02:22,320
in the oven for a total of
four different conditions.

32
00:02:22,320 --> 00:02:24,390
Run charts for the
part diameter can then

33
00:02:24,390 --> 00:02:28,634
be plotted noting the effective
thickness and heating time.

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00:02:28,634 --> 00:02:32,078
[MUSIC PLAYING]

35
00:02:45,860 --> 00:02:49,070
Now we consider the process
of sheet metal shearing.

36
00:02:49,070 --> 00:02:51,830
In this process, we
take 5-inch-wide strips

37
00:02:51,830 --> 00:02:54,453
of sheet metal and cut
off 1-inch-wide coupons

38
00:02:54,453 --> 00:02:56,120
to be used in the
brake-forming process.

39
00:03:04,070 --> 00:03:06,650
The key dimensions for the
part are the average width

40
00:03:06,650 --> 00:03:09,380
and the taper along the
length determined by measuring

41
00:03:09,380 --> 00:03:10,490
the width at each end.

42
00:03:13,850 --> 00:03:15,700
The cutting is done
on a simple treadle

43
00:03:15,700 --> 00:03:17,020
shear operated manually.

44
00:03:30,070 --> 00:03:32,160
The cut width is
determined by the location

45
00:03:32,160 --> 00:03:34,200
of the back gauge,
which can be set using

46
00:03:34,200 --> 00:03:36,730
the graduations on the gauge.

47
00:03:36,730 --> 00:03:40,250
Note that these can resolve
to only about 1/16 of an inch.

48
00:03:40,250 --> 00:03:42,280
And citing errors
are likely to happen.

49
00:03:42,280 --> 00:03:43,900
A sheet is inserted
into the shear

50
00:03:43,900 --> 00:03:49,280
as shown and pushed into
contact with the back gauge.

51
00:03:49,280 --> 00:03:51,890
To ensure a square part,
the long edge of the sheet

52
00:03:51,890 --> 00:03:55,170
should be held flush to
the edge fence as shown.

53
00:03:55,170 --> 00:03:57,560
If instead we keep the
cut edge of the sheet

54
00:03:57,560 --> 00:03:59,720
flush to the back
gauge, we could not

55
00:03:59,720 --> 00:04:02,420
eliminate initial tapered
edges on the sheet.

56
00:04:06,530 --> 00:04:09,560
As the treadle is pushed down,
notice that a clamp comes down

57
00:04:09,560 --> 00:04:11,570
to hold the sheet just
before the blade moves

58
00:04:11,570 --> 00:04:12,320
to cut the sheet.

59
00:04:29,180 --> 00:04:31,430
The part falls off at
the rear and should

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00:04:31,430 --> 00:04:32,900
be collected and numbered.

61
00:04:40,250 --> 00:04:42,230
The width at each
end is then measured

62
00:04:42,230 --> 00:04:43,325
using a vernier caliper.

63
00:04:47,120 --> 00:04:49,910
Both measurements are recorded
so we can get an average width

64
00:04:49,910 --> 00:04:50,630
and taper.

65
00:04:57,870 --> 00:05:01,200
For this process, we will share
both aluminum and steel sheets

66
00:05:01,200 --> 00:05:03,390
and create a run chart for each.

67
00:05:09,378 --> 00:05:12,871
[MUSIC PLAYING]

68
00:05:26,850 --> 00:05:29,250
Here, we consider the
process of brake forming.

69
00:05:39,460 --> 00:05:42,610
The purpose of this process is
to bend flat coupons of sheet

70
00:05:42,610 --> 00:05:44,400
metal to a finite angle.

71
00:05:48,090 --> 00:05:50,580
This is accomplished by
applying a three-point load

72
00:05:50,580 --> 00:05:54,360
using a punch and die, in
this case, mounted in a lathe.

73
00:05:57,100 --> 00:05:59,500
The lathe provides
a stiff foundation

74
00:05:59,500 --> 00:06:01,840
and, with the tailstock,
a means of controlling

75
00:06:01,840 --> 00:06:03,280
the displacement of the punch.

76
00:06:09,030 --> 00:06:11,160
Here, we see the tooling
mounted in the lathe

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00:06:11,160 --> 00:06:13,440
and show the punch moving
as the tailstock lead

78
00:06:13,440 --> 00:06:16,780
screw is rotated.

79
00:06:16,780 --> 00:06:18,640
Notice that the
displacement of the punch

80
00:06:18,640 --> 00:06:21,190
is determined by the
rotations of the hand wheel

81
00:06:21,190 --> 00:06:22,150
on the tailstock.

82
00:06:29,640 --> 00:06:32,070
The bend angle is determined
by the displacement

83
00:06:32,070 --> 00:06:34,800
of the punch relative
to the die but will also

84
00:06:34,800 --> 00:06:36,780
depend on the thickness
and constitutive

85
00:06:36,780 --> 00:06:39,720
properties of the sheet.

86
00:06:39,720 --> 00:06:42,600
The rotational displacement
is measured using the vernier

87
00:06:42,600 --> 00:06:44,160
on the lead screw.

88
00:06:44,160 --> 00:06:48,900
In this machine, we can resolve
1 part in 100 per rotation.

89
00:06:48,900 --> 00:06:52,470
For a lead screw ratio of
1 inch per 10 revolutions,

90
00:06:52,470 --> 00:06:56,000
this gives a displacement of
1/1,000 of an inch per line

91
00:06:56,000 --> 00:06:56,625
on the vernier.

92
00:07:00,010 --> 00:07:02,905
Here, we see the machine being
cycled while forming parts.

93
00:07:08,610 --> 00:07:10,350
Notice that, when
the load is released,

94
00:07:10,350 --> 00:07:13,000
the part shows
significant spring back.

95
00:07:13,000 --> 00:07:14,550
We can show that
this spring back

96
00:07:14,550 --> 00:07:18,420
is a function of the thickness,
yield stress, elastic modulus,

97
00:07:18,420 --> 00:07:20,550
and strain-hardening
properties of the sheet

98
00:07:20,550 --> 00:07:22,080
as well as the
degree of bending.

99
00:07:26,070 --> 00:07:29,550
The specifications call for a
depth of either 3/10 of an inch

100
00:07:29,550 --> 00:07:33,360
or 6/10 of an inch or three
or six full revolutions

101
00:07:33,360 --> 00:07:35,070
of the lead screw.

102
00:07:35,070 --> 00:07:37,650
The key is determining
the zero angle point where

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00:07:37,650 --> 00:07:40,740
the punch just touches the
sheet and then moving three

104
00:07:40,740 --> 00:07:42,570
or six revolutions further in.

105
00:07:48,030 --> 00:07:50,940
As each part is formed, we can
measure the resulting angle

106
00:07:50,940 --> 00:07:53,460
using the machinist's
protractor.

107
00:07:53,460 --> 00:07:57,390
This is a difficult measurement
and must be made with care.

108
00:07:57,390 --> 00:08:01,270
In this case, we can resolve to
better than 1/10 of a degree.

109
00:08:01,270 --> 00:08:02,820
But it is important
to stay tangent

110
00:08:02,820 --> 00:08:06,020
to the flanks of the part.

111
00:08:06,020 --> 00:08:08,930
Finally, we record the
angle, the material type,

112
00:08:08,930 --> 00:08:14,250
and the depth of the
punch on a datasheet.

113
00:08:14,250 --> 00:08:17,130
A run chart for the
process is then plotted.

114
00:08:17,130 --> 00:08:20,280
Data is most logically
grouped by material and depth

115
00:08:20,280 --> 00:08:25,515
since each has a strong
effect on the final angle.

116
00:08:25,515 --> 00:08:28,952
[MUSIC PLAYING]

117
00:08:38,309 --> 00:08:40,500
Now we consider the process
of injection molding.

118
00:08:43,950 --> 00:08:46,950
In this process, we are
manufacturing simple snap rings

119
00:08:46,950 --> 00:08:49,950
to a specified diameter.

120
00:08:49,950 --> 00:08:52,620
We start with clear
polypropylene pellets,

121
00:08:52,620 --> 00:08:56,370
which are melted and injected
into the tool under pressure.

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00:08:56,370 --> 00:08:59,940
The injection-molding
machine is rather complex.

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00:08:59,940 --> 00:09:03,420
It includes a compounding
and melding screw,

124
00:09:03,420 --> 00:09:06,630
an injection barrel, as well as
the tooling and tooling clamp.

125
00:09:09,480 --> 00:09:12,030
The pellets move from a
hopper into a heated barrel

126
00:09:12,030 --> 00:09:14,820
with a single screw.

127
00:09:14,820 --> 00:09:17,370
During the melding phase,
the screw rotates and moves

128
00:09:17,370 --> 00:09:19,410
rearward, storing
the melded plastic

129
00:09:19,410 --> 00:09:21,330
in the nose of the barrel.

130
00:09:21,330 --> 00:09:23,910
The melding is affected
mainly by the mechanical shear

131
00:09:23,910 --> 00:09:29,500
on the pellets and not by
heat transfer from the barrel.

132
00:09:29,500 --> 00:09:31,960
The barrel is brought into
contact with one tool half

133
00:09:31,960 --> 00:09:34,195
to create a flow path
into the tool cavity.

134
00:09:47,540 --> 00:09:49,820
During the injection
cycle, the screw

135
00:09:49,820 --> 00:09:51,980
first rotates and
then moves backward

136
00:09:51,980 --> 00:09:55,184
as the plastic is melded.

137
00:09:55,184 --> 00:09:58,460
It then moves forward
at a specified velocity

138
00:09:58,460 --> 00:09:59,330
to fill the mold.

139
00:10:03,330 --> 00:10:05,830
Once the mold is
filled, the screw piston

140
00:10:05,830 --> 00:10:07,740
switches to pressure control.

141
00:10:07,740 --> 00:10:10,380
And the additional forward
motion, called packing,

142
00:10:10,380 --> 00:10:12,900
is caused by the plastic
compressing in the mold

143
00:10:12,900 --> 00:10:15,522
before it hardens fully.

144
00:10:15,522 --> 00:10:17,480
The two halves of the
tool are brought together

145
00:10:17,480 --> 00:10:19,640
under the action of a
large hydraulic clamping

146
00:10:19,640 --> 00:10:23,600
cylinder, which keeps them
closed during injection.

147
00:10:23,600 --> 00:10:25,880
The tool itself serves
to cool the part.

148
00:10:25,880 --> 00:10:28,280
And the temperature of the
part when the tool opens

149
00:10:28,280 --> 00:10:31,610
depends strongly on the
hold time in the tool.

150
00:10:31,610 --> 00:10:36,020
This time can also be
programmed into the machine.

151
00:10:36,020 --> 00:10:38,900
After the hold time,
the tool separates,

152
00:10:38,900 --> 00:10:41,750
and the part is removed.

153
00:10:41,750 --> 00:10:43,490
In the production
process, the part

154
00:10:43,490 --> 00:10:46,310
would be ejected by a
set of actuated pins.

155
00:10:46,310 --> 00:10:47,960
But here, it is done manually.

156
00:11:03,160 --> 00:11:05,110
After the part is
removed and cooled,

157
00:11:05,110 --> 00:11:07,480
it can be measured
using a vernier caliper

158
00:11:07,480 --> 00:11:08,650
and the diameter recorded.

159
00:11:12,160 --> 00:11:14,710
In this experiment, we will
vary the injection speed

160
00:11:14,710 --> 00:11:17,170
and the hold time to yield
four different production

161
00:11:17,170 --> 00:11:17,860
conditions.

162
00:11:26,620 --> 00:11:29,820
A run chart can then be plotted
for all the data, keeping track

163
00:11:29,820 --> 00:11:30,820
of the machine settings.

164
00:11:40,210 --> 00:11:43,424
Now we consider the
process of CNC turning.

165
00:11:43,424 --> 00:11:46,812
[MUSIC PLAYING]

166
00:11:55,040 --> 00:11:57,950
The part to be manufactured
here is a simple cylinder

167
00:11:57,950 --> 00:12:00,230
of aluminum.

168
00:12:00,230 --> 00:12:05,550
The workpiece is a bar of
0.75-inch-diameter aluminum,

169
00:12:05,550 --> 00:12:10,070
which is to be turned
to 0.675-inch-diameter.

170
00:12:10,070 --> 00:12:13,670
After turning three
parts of 0.75-inch,

171
00:12:13,670 --> 00:12:15,800
length will be cut
off from the bar.

172
00:12:20,970 --> 00:12:22,680
The workpiece is
clamped in the chuck

173
00:12:22,680 --> 00:12:24,300
with a stick out of 3 inches.

174
00:12:27,700 --> 00:12:30,480
The turning and cutoff cycles
are controlled by the NC

175
00:12:30,480 --> 00:12:33,450
controller so the only
operator intervention

176
00:12:33,450 --> 00:12:35,900
is loading of material
and changing of tools.

177
00:12:38,460 --> 00:12:40,620
Note that the machine
frame for this process

178
00:12:40,620 --> 00:12:43,765
is massive so as to minimize
any deflection under machining

179
00:12:43,765 --> 00:12:44,265
loads.

180
00:12:50,300 --> 00:12:51,980
The cycle begins
with a single turning

181
00:12:51,980 --> 00:12:54,707
pass with fixed
spindle speed and feed.

182
00:13:19,600 --> 00:13:21,460
Notice that the
longitudinal motion

183
00:13:21,460 --> 00:13:24,550
is controlled by a servomotor
driving the long-axis lead

184
00:13:24,550 --> 00:13:26,050
screw under program control.

185
00:13:29,580 --> 00:13:31,440
During the experiment,
the operator

186
00:13:31,440 --> 00:13:34,920
will change the spindle speed
once and the feed rate once

187
00:13:34,920 --> 00:13:37,997
for a total of four different
operating conditions.

188
00:14:21,250 --> 00:14:24,010
After turning, we change
to a simple cutoff tool.

189
00:14:24,010 --> 00:14:26,890
And a fast plunge cut
motion separates the parts.

190
00:14:52,430 --> 00:14:54,380
It is important that
each part is captured

191
00:14:54,380 --> 00:14:56,540
as it falls so we can
tell which part of the bar

192
00:14:56,540 --> 00:14:57,740
it was made from--

193
00:14:57,740 --> 00:14:59,840
inner, outer, or middle.

194
00:15:03,720 --> 00:15:06,810
Each part diameter is measured
using a vernier caliper

195
00:15:06,810 --> 00:15:09,535
and recorded in
order of production.

196
00:15:15,240 --> 00:15:17,310
The spindle speed and
feed rate should also

197
00:15:17,310 --> 00:15:18,960
be recorded for each part.

198
00:15:21,600 --> 00:15:24,750
Run charts are then created
for the part in sequence

199
00:15:24,750 --> 00:15:28,100
or by location on the bar.