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S
traightening &
F
inishing
T
echnology
73
J
uly
/A
ugust
2007
It is important to always keep rolls in sets
with matching diameters. The amount of roll
wear should also be checked on a monthly
basis and logged. A simple procedure is
to measure and monitor the diameter of
the roll at the centre of the profile. When
the difference in the diameter reaches the
OEM’s advised maximum deviation, the
rolls should be reprofiled to bring them
back to standard.
The majority of rolls are manufactured
from high chrome, high carbon tool steel
that is through hardened to values usually
between 58 and 64 Rockwell C. Rolls can
often be reprofiled until the diameter at the
centre is down to about 80 per cent of the
original size.
The 10-roll machine, currently experiencing
increased demand, can reduce tube
ovality to very small tolerances and
straightness of 1:2500. There has been a
quiet revolution taking place in the steadily
increasing demand for tube with very high
straightness requirements. Year upon year,
tubing customers are demanding higher
tolerances of tube straightness and also
tube ovality.
Although the first 10-roll machine was
introduced in the mid 1970s, it was not
until computer machine setting systems
were introduced in around 1989 that such
machines became easier to set up. At that
time, tube makers producing quality tube in
stainless steel and other noble alloys took
up the opportunity to produce straighter
and rounder tube.
Beginning in the late 1980s, carbon steel
tube users also started to install highly
automated tube cutting
machines.
High production quantities
destined for automotive
and domestic product
manufacturers req-uired
the installation of auto
tube loaders and feeding units. This higher
production equipment will not successfully
load or feed anything other than exceedingly
straight tube.
A good example of this change lies within
the tubular steel furniture industry. Lower
grades of welded tube have fed this
industry for countless years. Provided the
tube looked basically straight it met the
purpose and was acceptable to furniture
makers.
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Tapered tubular flagpoles – a
difficult straightening application
Most flagpoles and lamp stands are
made from tubular aluminium or steel,
gradually tapered from base to top, to
reduce weight and lower wind forces.
These tapered tubular products need
to be straight. Normal parallel tubes are
usually rotary straightened by machines
that cannot straighten tapered tubes, as
extremely complex changes in the roll
position settings must take place to rotary
straighten a tapering tubular product.
Turner (see opposite) has launched
a new machine for straightening both
parallel and tapered tubes. The machine
can track tapered tubes at speeds of up
to 150 FPM (45 MPM) using AC vector
drives for roll positioning and laser
gauges to measure tube position.
Enhanced computer software controls
the entire straightening process.
As the tube progresses through
the machine, the roll screws down
positions, straightening offset amount.
All roll angles are automatically and
continuously adjusted to consistantly
track and straighten the tapering tube.
›
Roll configuration: the 10 roll machine
fi
The roll shown below has a worn profile, with
wear having occurred on one side of the profile.
This indicates that the rolls were not correctly
aligned in the machine
fi
Computer setting systems have enabled the
growth of the 10 roll straightening machine
88