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by over 50 percent depending on the motor's transient response. In many cases fault
stopping of the motor yields the highest system stresses.
Our computer model is capable of treating stations connected to group by spring,
damper or both. Field measurements indicated that sufficient solution accuracy in
large inertia rolling mill systems can be obtained by neglecting these parameters.
We used a simplified model of the roll bite area because we felt that excessive
massaging of the inputs to effect improved agreement with test results by a few
percentage points was not economically justifiable; in order for the model to
withstand the test of time a fundamental approach to modeling the hot mill drive
system should demonstrate reasonable agreement with test results.
The design theory of a statically determinate rolling mill, including the redesign of
the statically indeterminate characteristic and hyperstatic characteristic, is proposed in
this paper. The statically indeterminate characteristic leading to the nonparallel
running state of rolls is revealed based on analysis of three rolling mills, including a
2200 mm aluminum foil four-high mill, a 1580 mm PC four-high mill, and a 650 mm
bar two-high rolling mill, etc. The hyperstatic characteristic leading to uneven load
performance of four-row roller bearing is caused by redundant constraints in the roll
system based on analysis of 17 two- and four-high rolling mills. In contemporary
four- or six-high plate rolling mills, regular dynamic cross between the rolls is very
common during the whole rolling process. Dynamic cross results in excessive axial
forces causing frequent burning losses of the end-thrust bearings and leads to serious
deviations in the rolling load on both ends of the backup roll. Hence, rolling mills
designed for heavy loads and high speeds have yet to operate at their design load
and speed in a safe and stable way. According to the analysis of the degrees of
freedom of a spatial mechanism, the cause of dynamic cross lies in the statically
indeterminate characteristic of the roll system caused by the small clearance in the
system. In this paper, the theoretical analysis and experi- ments invalidate the
accepted method of the offsetting of the mill. Furthermore, it is shown that
offsetting causes an asymmetrical cross between the rolls. Therefore, it is pro-
posed that offsetting should be eliminated, and additional jack devices should be
intro- duced to maintain the rolls parallel. In addition, bending deflections of the roll
induce hyperstatic characteristics of the roll system due to the existence of redundant
constraints in the system. The hyperstatic characteristic of the roll system results in
uneven load per- formance of the radial roller bearings and shortens bearing life. In
the newly proposed statically determinate four- or six-high plate rolling mill, which
can be operated in a safe and stable way under heavy load and high speed working
conditions, this problem can also be solved.
Rolling mills have a long history of over 500 years and have resumed a rapid
development in the past 30 years. Many multifunctional plate rolling mills designed
for heavy loads, high speed, and accuracy have successively appeared, including the
2050mm continuously variable crown (CVC) four-high mill, 2200mm aluminum foil
four-high mill, 1580mm pair cross (PC) four-high mill, 3500mm mediate and heavy
plate four-high mill, and the 600mm universal crown control (UC) six-high mill [1].
However, in these rolling mills, numerous shortcomings exist, including regular
dynamic cross with a very small angle between the rolls, excessive axial forces