Let's take a closer look at the practical side of Optical Tooling. We'll
go over some examples of Optical Tooling principles at work and what
you can do with the instrumentation. As you read on, remember one
thing - Optical Tooling is a very flexible system. The examples listed
below are only a few of the things that are possible using the Optical Tooling
system - you are limited only by your
own imagination. Also, remember that because of this flexibility, you
can often use instruments other than those shown in the illustrations below,
to accomplish the same goals. (For example, a model 76 transit with a
coordinate optical micrometer can often be substituted for a model 2022
alignment telescope.)
Calibration of Laboratory optics
This is a good example of using an alignment telescope to hold an absolute
reference line. Alignment telescopes are used to establish and
maintain principal reference lines of sight (LOS). In addition, they provide the
important functions of autoreflection,
collimation, and
autocollimation. Brunson
alignment telescopes are made of heavy-walled, heat-treated, special alloy steel tubing,
concentrically ground inside and out to extremely close tolerances. The optical
systems are precisely installed to provide accuracy on your projects.
In the illustration below, a model 2062 Alignment Telescope is
autocollimated on the surface of a multi-sided mirror. The mirror is mounted
on a precision angle-turning device, such as an Ultradex™. Since
the 2062 is autocollimated on the mirror, we know that it is looking into the
mirror at exactly a 90 degree angle. Now, the mirror is turned by 90
degrees using the Ultradex mount. The 2062 holds the reference line of sight
(LOS) while this is done. Then, in its new position (known to be exactly
90 degrees from the prior position by virtue of the Ultradex), the
autocollimated image of the alignment telescope's reticle is again
checked. Any deviation from the centerline represents an error in the
mirror. Note that this example only involves holding a reference line of
sight. The 2062 is well-suited to applications that do
not require measurements or micrometer readings.
Holding a reference line of sight for calibration of laboratory equipment
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Generating a perfect right angle
(to make parallel lines)
The sketch below illustrates how a model 2062 can be
used to hold a reference line of sight in a multi-instrument setup. The 2062 in this
instance serves as a reference instrument for positioning a transit using the
principle of collimation. A transit is positioned perpendicular to the
alignment telescope by collimating the transit's cross-axis telescope on the
2062's line of sight. Each time you move the
transit laterally to a new position along the 2062’s line of sight, you can
check the transit against that line of sight. By referring back to this
"absolute" reference line each time you move the transit, you eliminate the
need to "leap frog" from one position to the other (which would tend to
accumulate error each time you move).
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The alignment telescope holds a reference line of sight for a transit
when turning a 90° angle, allowing you to establish a number of parallel lines
which are all perpendicular to the original reference line of sight. |
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Evaluating straightness of bores (Comparing machine components to a centerline)
Optical tooling has some very unique ways to evaluate straightness of components; i.e.,
to determine whether they are all on a common centerline. The model 2022 Alignment
Telescope is similar to the 2062, but has two micrometers which allow it to perform precise
measurements (horizontally and vertically), perpendicular to the line of sight. The telescope
has built-in provisions for keeping the line of sight straight within a focusing range of
2" to infinity, allowing the instrument to be located in the tightest of
setups. The 2022 is also equipped for autocollimation and autoreflection if
required.
The basic idea is to position the instrument so that its line of sight is
collinear with the desired centerline. Sometimes the instrument is positioned
using known master reference targets. Sometimes this is done by autocollimating to
target/mirror combination which gives not only lateral information but
directional information as well (perpendicular to the mirror). Sometimes
this is done by lining up on the center points of the first and last machine
components, or the near and far ends of a bore.
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The line of sight of the telescope is made to pass through targets on
each end of a bore, defining a reference centerline. |
The cool thing about optical tooling is that it is just about foolproof. Let's
say that you look down a
bore to the very end. You can position a target down there (called a
"bore target"). This is a special target that allows you to
center an optical target right in the middle of the bore. Axial legs hold
the target in place and a dial indicator on a sweep arm allows centering of the target in the
bore. This defines the far end of the bore (represented by the disk at
right in the illustration.) You can also position another such target at
the near end (left disk in the illustration). By using any number of
adjustable bases available for our alignment telescopes, you can position the
instrument so that both targets (near and far) appear to be in the center of the
telescope's image. This means that the instrument's line of sight is now
collinear with the targets placed at the centers of the near and far ends of the bore.
Now that you have a reference
centerline defined, it is easy to measure the straightness of the bore by moving
one or both of the bore targets to various positions along the bore. As
long as you don't move the instrument which has been positioned on the
centerline, you can measure the relationship of any other target position to the
reference centerline. Remember that the 2022 has built-in horizontal and
vertical micrometers, which allows a direct reading of any target inside the
bore. If a gravity reference is required, a model 187-S stride vial can be
set on the alignment telescope to establish a level line of sight.
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Measuring a new target
in an intermediate position may show a deviation in the straightness of
the bore, as illustrated above. The micrometers on the alignment
telescope will quantify the error. |
This same alignment principle is used
when positioning new machine components on a line which is defined by existing
components. The targeting may vary slightly, depending upon the
requirements of the job, but the principle is identical to the measurement of a
bore.
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Alignment of bearing journals
Measuring bearing
alignment in an engine block and evaluating for straightness is another easy
task with an instrument like the 2022. Notice that the application is very
similar to a bore alignment (described above). Again, the instrument is
positioned so that the line of sight is coincident with some known or desired
reference. This time, a target placed at various
bearing supports in the engine block and measurements relative to the instrument’s
straight line of sight are made. Horizontal and vertical profiles can be generated for each
bearing housing to determine alignment. We supply a large variety of
targeting to facilitate many different types of alignments. Chances are, we've
seen something like your application before, and have a target that is just right.
Bearing alignment in an engine block
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Extruder alignment
The 2022 Alignment Telescope is also great for measuring the alignment of an extruder tube
relative to a gear box housing. To accomplish this, targets are mounted in the
gear box so that the 2022 can be positioned exactly on the gear box's critical
line. Once the 2022 has been positioned, it optically represents the gear
box's centerline, and measurements can be taken on work targets (or one work
target which is moved to several different positions) in the extruder tube to
determine if the tube is in alignment with the gear box. Deviations from
the centerline can be quantified and technicians can be told exactly how much to
move machine components to bring everything back into alignment. In fact,
an instrument operator can observe the progress while adjustments to the
machinery are being made. Alignments like this are crucial for preventing damage
to a gear box.
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Leveling a machine bed or foundation
The Brunson model 545-190 level, also referred to as a precision sight level, builds upon the
construction and design principles of the alignment telescopes. Precision sight
levels can perform many of the same operations as both the 2062 and 2022 alignment
telescopes. However, they are optimized for leveling operations, having the additional
ability to sweep a horizontal plane and perform precision leveling operations using a
built-in split-bubble vial.
In this example, a precision sight level is mounted on a stable stand, and rough-leveled
using the attached bull's eye vial. Then, the main leveling screw is moved so that
the telescope is brought exactly level. This is determined by watching a magnified
split-bubble image of a very precise vial mounted on the side of the
instrument. This fine-threaded leveling screw makes it very easy to bring
the telescope into a level position within 1 arcsecond.
Leveling a machine bed or foundation
Once the instrument is established as level,
scales are mounted in various positions on the machine bed or foundation.
It is equally easy to use one scale and move it around to the positions of
interest. Readings to the nearest 0.001" inch or 0.03 mm are taken at
each scale position using the precision sight level's micrometer as a
vernier. Scale readings from the different positions are then compared to
determine whether the platform is out of level, in what direction is it out of
level, and by how much. Again, adjustments may be made to the bed while
someone observes the bed's movement by watching the scales through the precision
level's telescope in order to give immediate feedback to the person doing the
adjustment. Once the bed has been nominally leveled, a thorough evaluation
may be made to see if the bed is flat, or whether there is any undesired sag or
curvature.
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Leveling a roll
Precision sight levels may be used to provide horizontal references for
just about anything. Similar to the example
which describes leveling a machine bed, a
precision sight level can be mounted on a stable stand so that it has a
"clear line of sight" at both ends of a roll. This roll might be
in a paper mill, printing press, metals mill, plastic mill, or plastic film
rolling mill.
Sometimes the only way to see both ends of a
roll is to look almost straight down the roll from the end. Even this
situation is easily handled by virtue of the precision horizontal reference
plane created by the level. This illustration shows a plan view of a level
which can be rotated in order to view each end of a roll. A vertical
optical tooling scale is mounted on the roll (either on the bearings, or
preferably, on the surface of the roll itself). Then the level and
associated optical micrometer are used to take readings from scales on each end
of the roll. But how do you know that the scale is actually
vertical? Any of our optical tooling scales can be outfitted with a scale
level, which is a bull's eye vial made with a special mount in order to help
you put your scale in a horizontal or vertical orientation.
Leveling a roll (view from above)
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Making Machine Components Vertical
Making things vertical is almost as easy as
making them horizontal. To do this job, however, you have to use a transit
rather than a level. A procedure called "precision plumbing" can be
performed on any transit which has been mounted on a stable stand or other
foundation. This procedure allows the operator to ensure that the vertical
spindle of the transit is perfectly vertical - as in "exactly parallel to gravity",
not just pointing generally "up and down". After a transit has
been precision-plumbed, we know that the telescope will rotate through a
vertical plane, regardless of what azimuth (horizontal) direction that plane is
oriented.
Plumbing machine tool columns
We then must bring the transit
into a position where it is nominally parallel to the surface that we're trying
to measure. We do this using a simple procedure called "bucking
in". The illustration shows the use of a transit to plumb a machine tool
column (or any vertical surface). In this application, the transit sweeps
a vertical plane through scales that are affixed horizontally to the machine
column. The measurements are relative to this
vertical optical reference plane, and we will quickly know whether the machine is vertical or not,
and how much out of plumb it is. That is, if all of the scales give us
exactly the same reading, we know that the machine surface is parallel to our
vertical plane. But if they're not, we can tell how much the surface is
leaning one way or the other, and in fact whether the surface is flat or curved.
The observed measurements can be used to plumb the machine component.
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Making rolls (or other components) parallel
This is where things get even more interesting. Not as in "difficult",
but actually just more interesting. Let's say that you need to evaluate a
number of machine components to make sure they are all parallel (like rolls in a rolling
mill). One way to approach the job would be like this:
- Establish a reference line running parallel to the entire machine
(so that ideally, all rollers should be perpendicular to this line).
- Set up an instrument to turn a precise right angle from this reference line.
- Measure how parallel each roll is, using the instrument at right
angles to the reference line.
Let's take a close look at each of these steps.
There are several ways to establish the reference line which runs parallel to
the entire machine, but let's use a somewhat typical situation. Suppose
that an "offset centerline" is marked by floor monuments near the
machine. This is a line which is parallel to the machine centerline, which
was established by floor markers at some time in the past. Picture a
vertical plane rising up through these floor markers. We can set up a
model 76-RH transit so that it is directly in line with this vertical plane, and
pointing in the direction established by the floor markers. We'll call
this instrument "A". When this is
done, we have one transit whose line of sight can be used as the reference
because it has been set exactly parallel to the machine centerline. We set
the focus of this instrument at infinity and turn on the reticle illumination
light. Why do we do this? Stay tuned.....
Next, we set up another model 76-RH transit somewhere near
one of the rolls that we want to align. We'll call this one "B".
Remember that the 76-RH has a horizontal cross-axis telescope permanently
focused at infinity, which is mounted exactly perpendicular to the main
telescope. When we point the main telescope of instrument B toward the rolls,
its cross telescope will be pointing back at transit A. Since we focused
A's telescope at infinity and illuminated its reticle, we can collimate B's
cross-telescope on the reticle in A's main telescope. This alignment process
causes the main telescope of B to become exactly perpendicular to the main telescope
of A. Accordingly, the main telescope of instrument B can now sweep a
plane which is perpendicular to the machine centerline.
View from above: A and B work together to determine how far each roll
is from being perfectly perpendicular to the machine's centerline.
We then hold an optical tooling scale on the side of the roll
(near the end), oriented horizontally. Scale
bubble levels help us to know that the scale is actually horizontal and that it is placed properly on
the roll. We take a measurement on this scale using the micrometer on
instrument B. Then we move the scale to the other end of the roll and
repeat the process. Taking measurements on each end of the roll will reveal the
degree to which the roll is not parallel to B's line of sight. We know
that the roll must be parallel to B's line of sight in order to be
perpendicular to the machine centerline.
When we are finished with this roll, we simply move transit B over to the next
roll. Sometimes more than one roll can be measured without moving the
instrument (ex., measuring the right side of one roll and the left side of
another). Since A is still aligned with the offset centerline, all we have to
do is to set up B in another position and re-collimate to A. In this manner
you can check an entire row of rolls or other components for parallelism to any given reference.
(Note: There are other ways to establish the original reference line.
For example, you could perform the measurement process in reverse, setting
transit B parallel to the first roll. Then you could set transit A perpendicular to
B, and use it as the reference for measurement of subsequent rolls. After you
measure all the rolls, you would be able to determine which ones should be adjusted.)
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Checking parallelism of bearings
in a gear box
Checking parallelism of bearings
in a gearbox is also a simple task using optical equipment. In this
example, a 76-RH transit is used to establish the centerline of the first pair of
bearings (at left in illustration). By using "bore targets" or
some other appropriate targeting, the line of sight of this transit's main
telescope is positioned directly on a line between the two bearing centerlines. Then, a
second 76-RH is roughly positioned so that it points down the
centerline of a second pair of bearings. The reticle in the
cross-axis telescope of the first 76-RH is illuminated, and the cross-axis
telescope on the second transit is bought into collimation with the first. This
makes the main telescopes of both instruments precisely parallel, and the second (or
subsequent) pairs of bearings can be evaluated for parallelism to the first.
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Evaluating and aligning machine
tool components
Many of the various capabilities of
Optical Tooling come into play when evaluating machine tool
components. Testing for straightness, level, squareness,
parallelism, colinearity - all can be important depending upon what
machine is being tested. In the illustration, which shows a view
from above, the transit at left establishes a reference line of sight
using scales mounted horizontally on the machine bed ways.
This instrument "bucks in" to the two scales (i.e., is oriented such that
it reads the same position on each scale). This indicates that the
line of sight has been established parallel to the machine ways.
Then, another transit (center of picture) turns a precise right angle
using the first instrument's reference line, and evaluates the orientation
of the ways on the rotary table. Using this basic scheme, a number
of different machine tool parameters may be evaluated (straightness of
ways in two directions, orientation of spindle, travel of spindle, cross
ways on saddle, movement of saddle, etc.)
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