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The following terms are used frequently throughout
this discussion. It might be helpful for you to print this section now
and keep it as a handy reference during your visit.
A | B | C
| D-F | G-H | I-K|
L | M-N | O | P
| Q-R | S | T | U-Z
ARC SECOND - A measure of angle equal to 1/3600th
of a degree or 0.00006"/ft (0.005 mm/M)
AXIAL. Located on, around, or moving along an axis.
AXIS OF ROTATION. A straight line about which
a body or geometric object rotates. The axis of rotation of a spindle
is the line around which the chuck or tool holder rotates.
BCE - BORE CENTER ERROR.
A measure of the offset of a bore's center from a reference bore's center.
BUCK-IN. Adjusting
a laser plane or line to be parallel to the surface being measured (a
table top, a surface plate, or a way surface). Three points are required
to buck-in a laser plane to a reference surface. Two points are needed
to buck-in a straight-line laser to a reference line (i.e., centerline).
BUCKED-IN. See Buck-In.
BUCKING-IN. See Buck-In.
BUTTOCK LINE. An aerospace term used to describe
a reference line that runs along the length or the longitudinal axis of
the aircraft. An aircraft contains several buttock-line sections.
CATENARY SAG.
The curve theoretically formed by a perfectly flexible, uniformly dense
cable that is not capable of being stretched and is suspended from its
endpoints. It is a measure of how much the elevation of a cable drops
between its 2 endpoints.
COLINEAR. Lying on or passing through
a single straight line.
CONCENTRIC. Having a common center.
CONTINUOUSLY ROTATING LASER PLANES.
Laser planes that are generated by an automatically rotating spindle containing
a pentaprism.
DATUM. A reference used as a basis
for calculating or measuring.
FLASHING. A quality
problem in plastic parts that occurs when the molds do not meet exactly
parallel, which cause excess plastic to build up on the part.
FLATNESS.
The state of having a smooth, even, level horizontal surface without
slope, tilt, or curvature.
He-Ne LASER. Helium
Neon laser usually used in interferometry. Usually requires 1 hour warm
up and is not as spatially stable as diode lasers.
INTERFEROMETER.
An instrument that measures changes in the linear position of an machine's
axis. This is accomplished by counting or displaying interference fringes
created by a light source of known wavelength.
LEVEL. Having
a flat, smooth surface as characterized by using gravity as a reference.
Being on a horizontal plane.
LIVE/DYNAMIC DATA. Target readings
displayed on a computer or readout that update automatically as adjustments
are made to the point on a machine that is being measured and aligned.
This allows the user to watch the machine move into alignment.
NORMIN
Method
The NORMIN method was developed by Hamar Laser to compensate for laser
and/or target mounting errors in bore or spindle work. The word is a contraction
of "NORMal and INverted".
To qualify a laser, the NORMIN procedure is used to make the laser parallel
to an axis of rotation in spindle applications or to calculate laser centering
errors in bore applications. For spindle applications, it works like this:
a laser or fixture holding the laser is placed in a spindle in the normal
position (12 o'clock). The laser is turned on and the readings are recorded.
Next, the laser is rotated 180º to the inverted position (6 o'clock),
and a second set of readings is recorded. The 2 sets of readings are averaged
(normal+inverted/2), which calculates the set points. The set points are
the points at which the angular and centering errors have been eliminated
and the laser would then be colinear to the axis of rotation of the spindle.
The laser is adjusted so that the readout shows the set points and thus
it is "qualified" or set up.
For setting up lasers in bore alignment applications, the NORMIN procedure
is used to correct angular mounting errors in exactly the same way as
described above. It can also be used to calculate the laser centering
error. The same procedure is used above, except the average of readings
are not the set points but are "offsets" that are subtracted from the
bore measurements to get an accurate measurement of bore alignment. NORMIN
is also used to calculate the Target Centering Error, which is a measure
of how far off the target's center is to the bore's center.
OFFSET CENTERLINE.
Usually used in roll alignment applications. An offset centerline is a
line established to the side of a process mill that is parallel to the
machine's centerline. It is used as a reference to measure roll parallelism.
ONE ARC SECOND. A measure of angle
equal to 1/3600th of a degree or 0.00006"/ft (0.005 mm/M).
OPTICS. Theodolites, transits,
optical borescopes or any other measuring instrument using optical instruments
to measure levelness and straightness.
PDA -PERSONAL DATA ASSISTANT.
Used as a target readout in the R-1309
PSD -POSITION SENSING DETECTOR.
A piece of silicon that detects the center of energy of the laser beam.
PARALLELISM.
2 or more lines or planes, extending in the same direction and everywhere
equidistant from each other. Planes and lines are said to be parallel
to each other if they never meet when projected out into infinity.
PENTAPRISM.
A 5-sided prism that accepts a laser beam in one side and projects it
at a precise 90º angle out of another side.
POINT-AND-SHOOT LASERS. A type
of laser alignment system that do NOT automatically rotate. To take measurements
the user has to precisely move the laser beam to a target location.
RADIAL. Having
or marked by parts radiating from a common center. Moving or directed
along a radius.
REFERENCE POINTS. Points chosen
on a surface or in a bore that represent the starting point (reference)
for which all other points on the surface or in a bore will be compared.
Also referred to as a datum. For bore, spindle and rotating shaft applications
2 reference points are needed to establish a datum. For surfaces, 3 reference
points are needed to establish a datum.
SELF-CENTERING TARGET.
A 2-axis bore target that automatically centers itself in a bore with
no moving parts.
STATION PLANE. An aerospace term
used to describe a reference plane that runs perpendicular to the buttock
lines of the aircraft. An aircraft contains several station planes. They
are often also referred to as bulkhead-section planes.
STRAIGHTNESS. The state of having
a line that extends continuously in the same direction without curving.
TCE -TARGET CENTERING ERROR.
Calculated by adding the normal and inverted readings and dividing the
result by 2. TCE is a measure of how far from a bore center the target's
center actually is. Can be used to adjust raw readings to find true bore
centering error (BCE).
TOP DEAD CENTER METHOD -
This is used when measuring the parallelism or levelness of rolls. With
the target facing the laser, the roll is rotated slightly back and forth
until the highest point is determined, which is the top dead center of
the roll. This should be used when tight tolerances are needed or when
it is difficult to determine if the target is near top dead center, usually
when measuring vertical rolls.
WATERLINE. An
aerospace term used to describe a horizontal reference plane that runs
throughout the aircraft. Many surfaces and interior features are made
parallel to this reference plane.
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