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

00:00:54.400 --> 00:00:56.590
In this process, we will
make a simple circuit

00:00:56.590 --> 00:00:59.590
apart by heating a flat
sheet of polystyrene

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and then pulling it over
a tool under vacuum.

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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To begin the process,
the flat sheet

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is loaded into the machine
and then clamped into place.

00:01:20.620 --> 00:01:22.670
The sheet is moved
into an oven and heated

00:01:22.670 --> 00:01:24.380
for a specified amount of time.

00:01:29.510 --> 00:01:32.060
The oven temperature is
under feedback control

00:01:32.060 --> 00:01:34.280
and the timing of entering
and exiting the oven

00:01:34.280 --> 00:01:36.050
is also under program control.

00:01:40.280 --> 00:01:42.620
After residing in the
oven the desired time,

00:01:42.620 --> 00:01:45.080
the sheet is moved
over the tool,

00:01:45.080 --> 00:01:47.270
it comes up to
contact the sheet,

00:01:47.270 --> 00:01:49.220
and the vacuum is
applied through the tool.

00:01:55.390 --> 00:01:58.040
This draws the sheet onto
the tool, taking its form

00:01:58.040 --> 00:01:59.860
and, at the same
time, cools the sheet.

00:02:05.610 --> 00:02:07.470
The part is then
removed from the clamps

00:02:07.470 --> 00:02:09.269
and measured using
a vernier caliper.

00:02:14.370 --> 00:02:16.320
We will look at two
different thickness sheets

00:02:16.320 --> 00:02:18.210
and have two different
resonance times

00:02:18.210 --> 00:02:22.320
in the oven for a total of
four different conditions.

00:02:22.320 --> 00:02:24.390
Run charts for the
part diameter can then

00:02:24.390 --> 00:02:28.634
be plotted noting the effective
thickness and heating time.

00:02:28.634 --> 00:02:32.078
[MUSIC PLAYING]

00:02:45.860 --> 00:02:49.070
Now we consider the process
of sheet metal shearing.

00:02:49.070 --> 00:02:51.830
In this process, we
take 5-inch-wide strips

00:02:51.830 --> 00:02:54.453
of sheet metal and cut
off 1-inch-wide coupons

00:02:54.453 --> 00:02:56.120
to be used in the
brake-forming process.

00:03:04.070 --> 00:03:06.650
The key dimensions for the
part are the average width

00:03:06.650 --> 00:03:09.380
and the taper along the
length determined by measuring

00:03:09.380 --> 00:03:10.490
the width at each end.

00:03:13.850 --> 00:03:15.700
The cutting is done
on a simple treadle

00:03:15.700 --> 00:03:17.020
shear operated manually.

00:03:30.070 --> 00:03:32.160
The cut width is
determined by the location

00:03:32.160 --> 00:03:34.200
of the back gauge,
which can be set using

00:03:34.200 --> 00:03:36.730
the graduations on the gauge.

00:03:36.730 --> 00:03:40.250
Note that these can resolve
to only about 1/16 of an inch.

00:03:40.250 --> 00:03:42.280
And citing errors
are likely to happen.

00:03:42.280 --> 00:03:43.900
A sheet is inserted
into the shear

00:03:43.900 --> 00:03:49.280
as shown and pushed into
contact with the back gauge.

00:03:49.280 --> 00:03:51.890
To ensure a square part,
the long edge of the sheet

00:03:51.890 --> 00:03:55.170
should be held flush to
the edge fence as shown.

00:03:55.170 --> 00:03:57.560
If instead we keep the
cut edge of the sheet

00:03:57.560 --> 00:03:59.720
flush to the back
gauge, we could not

00:03:59.720 --> 00:04:02.420
eliminate initial tapered
edges on the sheet.

00:04:06.530 --> 00:04:09.560
As the treadle is pushed down,
notice that a clamp comes down

00:04:09.560 --> 00:04:11.570
to hold the sheet just
before the blade moves

00:04:11.570 --> 00:04:12.320
to cut the sheet.

00:04:29.180 --> 00:04:31.430
The part falls off at
the rear and should

00:04:31.430 --> 00:04:32.900
be collected and numbered.

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The width at each
end is then measured

00:04:42.230 --> 00:04:43.325
using a vernier caliper.

00:04:47.120 --> 00:04:49.910
Both measurements are recorded
so we can get an average width

00:04:49.910 --> 00:04:50.630
and taper.

00:04:57.870 --> 00:05:01.200
For this process, we will share
both aluminum and steel sheets

00:05:01.200 --> 00:05:03.390
and create a run chart for each.

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[MUSIC PLAYING]

00:05:26.850 --> 00:05:29.250
Here, we consider the
process of brake forming.

00:05:39.460 --> 00:05:42.610
The purpose of this process is
to bend flat coupons of sheet

00:05:42.610 --> 00:05:44.400
metal to a finite angle.

00:05:48.090 --> 00:05:50.580
This is accomplished by
applying a three-point load

00:05:50.580 --> 00:05:54.360
using a punch and die, in
this case, mounted in a lathe.

00:05:57.100 --> 00:05:59.500
The lathe provides
a stiff foundation

00:05:59.500 --> 00:06:01.840
and, with the tailstock,
a means of controlling

00:06:01.840 --> 00:06:03.280
the displacement of the punch.

00:06:09.030 --> 00:06:11.160
Here, we see the tooling
mounted in the lathe

00:06:11.160 --> 00:06:13.440
and show the punch moving
as the tailstock lead

00:06:13.440 --> 00:06:16.780
screw is rotated.

00:06:16.780 --> 00:06:18.640
Notice that the
displacement of the punch

00:06:18.640 --> 00:06:21.190
is determined by the
rotations of the hand wheel

00:06:21.190 --> 00:06:22.150
on the tailstock.

00:06:29.640 --> 00:06:32.070
The bend angle is determined
by the displacement

00:06:32.070 --> 00:06:34.800
of the punch relative
to the die but will also

00:06:34.800 --> 00:06:36.780
depend on the thickness
and constitutive

00:06:36.780 --> 00:06:39.720
properties of the sheet.

00:06:39.720 --> 00:06:42.600
The rotational displacement
is measured using the vernier

00:06:42.600 --> 00:06:44.160
on the lead screw.

00:06:44.160 --> 00:06:48.900
In this machine, we can resolve
1 part in 100 per rotation.

00:06:48.900 --> 00:06:52.470
For a lead screw ratio of
1 inch per 10 revolutions,

00:06:52.470 --> 00:06:56.000
this gives a displacement of
1/1,000 of an inch per line

00:06:56.000 --> 00:06:56.625
on the vernier.

00:07:00.010 --> 00:07:02.905
Here, we see the machine being
cycled while forming parts.

00:07:08.610 --> 00:07:10.350
Notice that, when
the load is released,

00:07:10.350 --> 00:07:13.000
the part shows
significant spring back.

00:07:13.000 --> 00:07:14.550
We can show that
this spring back

00:07:14.550 --> 00:07:18.420
is a function of the thickness,
yield stress, elastic modulus,

00:07:18.420 --> 00:07:20.550
and strain-hardening
properties of the sheet

00:07:20.550 --> 00:07:22.080
as well as the
degree of bending.

00:07:26.070 --> 00:07:29.550
The specifications call for a
depth of either 3/10 of an inch

00:07:29.550 --> 00:07:33.360
or 6/10 of an inch or three
or six full revolutions

00:07:33.360 --> 00:07:35.070
of the lead screw.

00:07:35.070 --> 00:07:37.650
The key is determining
the zero angle point where

00:07:37.650 --> 00:07:40.740
the punch just touches the
sheet and then moving three

00:07:40.740 --> 00:07:42.570
or six revolutions further in.

00:07:48.030 --> 00:07:50.940
As each part is formed, we can
measure the resulting angle

00:07:50.940 --> 00:07:53.460
using the machinist's
protractor.

00:07:53.460 --> 00:07:57.390
This is a difficult measurement
and must be made with care.

00:07:57.390 --> 00:08:01.270
In this case, we can resolve to
better than 1/10 of a degree.

00:08:01.270 --> 00:08:02.820
But it is important
to stay tangent

00:08:02.820 --> 00:08:06.020
to the flanks of the part.

00:08:06.020 --> 00:08:08.930
Finally, we record the
angle, the material type,

00:08:08.930 --> 00:08:14.250
and the depth of the
punch on a datasheet.

00:08:14.250 --> 00:08:17.130
A run chart for the
process is then plotted.

00:08:17.130 --> 00:08:20.280
Data is most logically
grouped by material and depth

00:08:20.280 --> 00:08:25.515
since each has a strong
effect on the final angle.

00:08:25.515 --> 00:08:28.952
[MUSIC PLAYING]

00:08:38.309 --> 00:08:40.500
Now we consider the process
of injection molding.

00:08:43.950 --> 00:08:46.950
In this process, we are
manufacturing simple snap rings

00:08:46.950 --> 00:08:49.950
to a specified diameter.

00:08:49.950 --> 00:08:52.620
We start with clear
polypropylene pellets,

00:08:52.620 --> 00:08:56.370
which are melted and injected
into the tool under pressure.

00:08:56.370 --> 00:08:59.940
The injection-molding
machine is rather complex.

00:08:59.940 --> 00:09:03.420
It includes a compounding
and melding screw,

00:09:03.420 --> 00:09:06.630
an injection barrel, as well as
the tooling and tooling clamp.

00:09:09.480 --> 00:09:12.030
The pellets move from a
hopper into a heated barrel

00:09:12.030 --> 00:09:14.820
with a single screw.

00:09:14.820 --> 00:09:17.370
During the melding phase,
the screw rotates and moves

00:09:17.370 --> 00:09:19.410
rearward, storing
the melded plastic

00:09:19.410 --> 00:09:21.330
in the nose of the barrel.

00:09:21.330 --> 00:09:23.910
The melding is affected
mainly by the mechanical shear

00:09:23.910 --> 00:09:29.500
on the pellets and not by
heat transfer from the barrel.

00:09:29.500 --> 00:09:31.960
The barrel is brought into
contact with one tool half

00:09:31.960 --> 00:09:34.195
to create a flow path
into the tool cavity.

00:09:47.540 --> 00:09:49.820
During the injection
cycle, the screw

00:09:49.820 --> 00:09:51.980
first rotates and
then moves backward

00:09:51.980 --> 00:09:55.184
as the plastic is melded.

00:09:55.184 --> 00:09:58.460
It then moves forward
at a specified velocity

00:09:58.460 --> 00:09:59.330
to fill the mold.

00:10:03.330 --> 00:10:05.830
Once the mold is
filled, the screw piston

00:10:05.830 --> 00:10:07.740
switches to pressure control.

00:10:07.740 --> 00:10:10.380
And the additional forward
motion, called packing,

00:10:10.380 --> 00:10:12.900
is caused by the plastic
compressing in the mold

00:10:12.900 --> 00:10:15.522
before it hardens fully.

00:10:15.522 --> 00:10:17.480
The two halves of the
tool are brought together

00:10:17.480 --> 00:10:19.640
under the action of a
large hydraulic clamping

00:10:19.640 --> 00:10:23.600
cylinder, which keeps them
closed during injection.

00:10:23.600 --> 00:10:25.880
The tool itself serves
to cool the part.

00:10:25.880 --> 00:10:28.280
And the temperature of the
part when the tool opens

00:10:28.280 --> 00:10:31.610
depends strongly on the
hold time in the tool.

00:10:31.610 --> 00:10:36.020
This time can also be
programmed into the machine.

00:10:36.020 --> 00:10:38.900
After the hold time,
the tool separates,

00:10:38.900 --> 00:10:41.750
and the part is removed.

00:10:41.750 --> 00:10:43.490
In the production
process, the part

00:10:43.490 --> 00:10:46.310
would be ejected by a
set of actuated pins.

00:10:46.310 --> 00:10:47.960
But here, it is done manually.

00:11:03.160 --> 00:11:05.110
After the part is
removed and cooled,

00:11:05.110 --> 00:11:07.480
it can be measured
using a vernier caliper

00:11:07.480 --> 00:11:08.650
and the diameter recorded.

00:11:12.160 --> 00:11:14.710
In this experiment, we will
vary the injection speed

00:11:14.710 --> 00:11:17.170
and the hold time to yield
four different production

00:11:17.170 --> 00:11:17.860
conditions.

00:11:26.620 --> 00:11:29.820
A run chart can then be plotted
for all the data, keeping track

00:11:29.820 --> 00:11:30.820
of the machine settings.

00:11:40.210 --> 00:11:43.424
Now we consider the
process of CNC turning.

00:11:43.424 --> 00:11:46.812
[MUSIC PLAYING]

00:11:55.040 --> 00:11:57.950
The part to be manufactured
here is a simple cylinder

00:11:57.950 --> 00:12:00.230
of aluminum.

00:12:00.230 --> 00:12:05.550
The workpiece is a bar of
0.75-inch-diameter aluminum,

00:12:05.550 --> 00:12:10.070
which is to be turned
to 0.675-inch-diameter.

00:12:10.070 --> 00:12:13.670
After turning three
parts of 0.75-inch,

00:12:13.670 --> 00:12:15.800
length will be cut
off from the bar.

00:12:20.970 --> 00:12:22.680
The workpiece is
clamped in the chuck

00:12:22.680 --> 00:12:24.300
with a stick out of 3 inches.

00:12:27.700 --> 00:12:30.480
The turning and cutoff cycles
are controlled by the NC

00:12:30.480 --> 00:12:33.450
controller so the only
operator intervention

00:12:33.450 --> 00:12:35.900
is loading of material
and changing of tools.

00:12:38.460 --> 00:12:40.620
Note that the machine
frame for this process

00:12:40.620 --> 00:12:43.765
is massive so as to minimize
any deflection under machining

00:12:43.765 --> 00:12:44.265
loads.

00:12:50.300 --> 00:12:51.980
The cycle begins
with a single turning

00:12:51.980 --> 00:12:54.707
pass with fixed
spindle speed and feed.

00:13:19.600 --> 00:13:21.460
Notice that the
longitudinal motion

00:13:21.460 --> 00:13:24.550
is controlled by a servomotor
driving the long-axis lead

00:13:24.550 --> 00:13:26.050
screw under program control.

00:13:29.580 --> 00:13:31.440
During the experiment,
the operator

00:13:31.440 --> 00:13:34.920
will change the spindle speed
once and the feed rate once

00:13:34.920 --> 00:13:37.997
for a total of four different
operating conditions.

00:14:21.250 --> 00:14:24.010
After turning, we change
to a simple cutoff tool.

00:14:24.010 --> 00:14:26.890
And a fast plunge cut
motion separates the parts.

00:14:52.430 --> 00:14:54.380
It is important that
each part is captured

00:14:54.380 --> 00:14:56.540
as it falls so we can
tell which part of the bar

00:14:56.540 --> 00:14:57.740
it was made from--

00:14:57.740 --> 00:14:59.840
inner, outer, or middle.

00:15:03.720 --> 00:15:06.810
Each part diameter is measured
using a vernier caliper

00:15:06.810 --> 00:15:09.535
and recorded in
order of production.

00:15:15.240 --> 00:15:17.310
The spindle speed and
feed rate should also

00:15:17.310 --> 00:15:18.960
be recorded for each part.

00:15:21.600 --> 00:15:24.750
Run charts are then created
for the part in sequence

00:15:24.750 --> 00:15:28.100
or by location on the bar.