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Must rolls be parallel?
Yes. Rolls should be parallel to ensure that the product
being created is uniform and of good quality. Parallelism
of rolls is even more important when machines are running
at very high speeds and when the rolls are very close to each
other.
How has parallelism traditionally
been measured?
Traditionally, parallelism has been measured by optical means,
using a theodolite and measurement telescopes. This is a time
consuming method that depends on many factors including line of
sight, dependence on an external "centerline" that is separate
from the actual machine, and optical readings.
How does PARALIGN work?
PARALIGN uses three ring laser gyroscopes that can detect
inertial movement. No line of sight is required. This helps us
achieve very reproducible results.
How does a ring laser gyroscope
work?
Two lasers travel in opposite directions on a triangular
route. When the gyroscope is rotated on its axis, one of the
lasers’ rotational paths is shortened while the other beams’
path is lengthened. The difference in time between the two laser
beams is its angular change. PARALIGN consists of three ring
laser gyroscopes, enabling is to take measurements in
three-dimensional space. (Roll, Pitch, and Yaw).
How can PARALIGN be parallel
on the roll without V-Blocks?
Before measurement, PARALIGN is calibrated relatively
parallel to the rolls in the machine. The PARALIGN software has
a filter that ensures that PARALIGN stays within range. It also
has an audible validation clicking sound which is heard when in
range and only values in that range are used in its calculations.
These algorithms allow us to achieve the most reliable results
without additional mechanical support.
Why must PARALIGN re-calibrate
every 20-30 minutes?
Due to the fact that the rolls position is measured in space,
the PARALIGN must factor in the constant rotation of the Earth.
Can I move the roll with
PARALIGN on it?
There is no need. A graphical report is generated that
specifies direction on how to move rolls. Re-measurement after
movement can be done in a matter of minutes. It is beneficial to
have the PARALIGN service team measures the location of each
roll, and then decide which rolls the millwrights should move.
Where on the roll can PARALIGN
take a measurement?
The PARALIGN can be placed anywhere on the rolls’ surface as
long as we have access to 20 degrees (minimum) for the patented
Sweep measurement. This includes top, bottom, or sides.
'Sweep' measurement: To record the measured values
PARALIGN simply slides a short distance along the surface
while the roll is stationary.
How many rolls can be measured
in one day?
Depending on where each roll is located and the accessibility
available, in an 8 hour day, 40 or more rolls can typically be
measured in a paper mill, and 60 or more rolls in other
applications are typical.
Is PARALIGN for sale or
rent?
We offer PARALIGN Service for roll alignment as a service to
our clients. PRUFTECHNIK does not sell PARALIGN at this time.
Why does your service
not also move the rolls?
In most cases it makes more sense for a mill to make
corrections while the PARALIGN service team continues taking
measurements. The graphical report shows the customer the entire
map of their machine and allows them to decide which rolls are
the best choices to move.
Why are there two service
engineers?
There are always two engineers at a site. One Engineer is
used to measure on the surface of the roll, while the other
holds the computer to view and validate all data received.
What can be used as a
reference for parallelism?
The term ‘reference’ refers to any roll that is repeatedly
used as a fixed point. Readings can be plotted out using any
roll as a reference point. This reference point can be changed
later with no effort.
Does accuracy depend on
the location of the roll?
The accuracy of PARALIGN does not depend on the location of
the roll. The roll can be 10 feet high, behind a wall, or in
another building. Line-of-sight or distance do not matter either.
What is the smallest roll
that can be measured?
The smallest roll can be 43cm (17 inches) in length and 8mm
(0.315 inches) in diameter.
Can PARALIGN determine
crowned or bowed rolls?
If the crowned or bowed condition of the roll is known, rolls
of that type can be measured using the Sweep method in three
positions (operator, center, and machine/drive) on the surface
of the roll.
Can the PARALIGN determine
level of a roll?
PARALIGN can determine the level and square (horizontal and
vertical offsets) between any rolls; it cannot determine
absolute elevation in the machine.
What is the calibration
plate?
The calibration plate is the reference point that is used to
re-calibrate every 20-30 minutes for the rotation of the earth.
This plate is set relatively parallel to the rolls in the plant
at the beginning of each measurement job.
The "reference roll" does not have to
be a roll. Ideally, a calibration plate is attached close
to the machine and used by the PARALIGN as a reference. Or
PARALIGN is "zeroed" on the reference roll before
beginning measurement, i.e. the laser gyroscopes are adjusted
for the earth's rotation.
When can we see the report
for the measured machine?
The graphical report can be presented as soon as a set of
measurements are performed. Usually we present different stages
of intermediate reports throughout a day.
Why does PARALIGN not
use a centerline?
PARALIGN measures relative parallelism between rolls and does
not require an external reference such as a centerline. This way
any errors because of a faulty centerline (ground settling, bad
plugs) are avoided.
What if I want to change
the reference roll?
With the click of a button the reference roll can be changed.
More than one reference roll can be given at the customers’
request.
What if my reference
roll is not suitable?
Since the reference roll can be changed very quickly and
easily, a more suitable roll can be chosen at any time. There is
no such thing as a ‘right’ or ‘wrong’ reference roll.
Do you need optics to
set-up your measurements?
The use of optics is not needed to set-up our measurements.
We do not need to use the centerline or have any line-of-sight
in order to find the parallelism between rolls.
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