TPT May 2012

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May 2012 121
Article
owners of the enterprise are trying to make the roll change and the
adjustment unnecessary. Of course, this can only be a dream as roll
change and adjustment is a must if the tube mill is to produce tubes
of different specifications. The point is, can we get the same result
with automatic roll change and automatic adjustment? The answer
is yes. AUTO-DNSA mill is just such a unit with such capacity. To
understand its functions, we will need to start with the DNSA mill.
DNSA was developed and launched to the market by FD Machinery
in 2009. DNSA stands for Digital Non-strip Set Adjust, which means
all rolls are located digitally and the unit is set and adjusted under
the non-strip status. In other words, the operation no longer relies
on experience, and the commissioning will not have any scrap. So
far two DNSA production lines are in operation and several others
are being manufactured by FD Machinery.
It can be seen from the photos below that the locations of all the
rolls of DNSA mill have been fixed precisely and displayed digitally.
Those figures are not selected by the operation freely. Instead, they
are determined by the mill adjustment cards. What the operator
needs to do is only to adjust the rolls as per the data on the cards to
have the finished products manufactured.
It can also be found from those photos that all
rolls have rapid roll change function so that one
worker can easily replace all the rolls in one
hour without removing even one bolt. For the
needs of digitalisation, the requirements on the
manufacturing precision and equipment rigidity
by DNSA mills are higher than the normal mill in
addition to the special design for some structures.
FD Machinery spent a whole year to complete
the design and manufacture for the first DNSA
mill, and has recieved many invention patents for
the mill.
As mentioned above, easy roll change in short
time, roll change and adjustment in DNSA mill
are all important performance factors of the mill.
The features of various roll change types have
been summarised as follows to facilitate a clear
understanding of roll change.
People have been studying rapid roll change
for a long time. For the horizontal roll, there are
generally five types of rapid roll change mills,
which are respectively side roll change, top roll
change, side shaft change, base plate change,
and base change.
For rapid roll change mills with side roll change,
since drive shafts do not need to be removed,
no standby equipment or spare parts need to
be added, and no secondary roll change is
needed. These kind of rapid roll change mills are
extensively used in the mills of small and medium
size. To change roll for the rapid roll change
mills with side roll change, the mill housing at
the operation side shall be pulled open, then the
sleeves and rolls shall be pulled out from the side. The process
for roll loading shall be in the opposite order. The simple side roll
change unit is a drawing machine driven manually, electrically or
hydraulically, which is used to pull and push the mill housing. The
pulled out mill housing will be lifted by the crane before the rolls are
changed. The vehicular side roll change unit is equipped with a roll
change cart with the drawing machine installed on top. The cart is
installed on the base of the mill via the straight guide rail. The mill
housing is pulled to the roll change cart by the drawing machine and
the cart carrying the mill housing is pushed away manually prior to
roll change. This is a convenient and practical roll change unit. Both
DNSA mill and AUTO-DNSA mill are of the side roll change type.
Rapid roll change mills with top roll change or side shaft change
are common in the early designs. To achieve rapid roll change,
the stand of those two kinds of mills should have one or several
sets of standby shaft units. The rolls shall be installed on the
shaft in advance. When rolls change, one standby shaft unit will
be installed to replace the one set in the mill. The removed shaft
unit will be changed roll in offline. For both top roll change and
side shaft change, the horizontal roll shaft and the drive shaft must
DNSA mill: Squeezing roll