System for controlling bar cutter in steel bar line

A system for controlling a bar cutter in a steel bar line comprising a rolling length predicting circuit for calculating, on the basis of a scale loss coefficient, a predicted rolling length of a rolling bar material conveyed to the steel bar line, a flying shear cut instructing circuit responsive to the predicted length for determining a cutting length and for operating a flying shear to cut the rolling bar material in accordance therewith, a rolling length measuring circuit for determining an actual rolling length from the cut bar material, and a scale loss coefficient determining circuit for determining the scale loss coefficient based on the actual rolling length so as to correct the predicted rolling length and thereby reduce a cutting error.

BACKGROUND OF THE INVENTION 
A steel bar is generally cut from a bar material in accordance with a 
consumer's purchase order (hereinafter referred to as "a material 
adoption"). Thus, a loss of material is produced in the cutting step. A 
further material loss occurs when material adoption is conducted by 
dividing a bar material into a plurality of bars, aligning the several 
divided bar materials in parallel and then cutting them into the necessary 
length. 
Heretofore, an optimum cutting control of a steel bar has been proposed and 
disclosed, for example, in a thesis by K. Inasaki et al entitled 
"Improvements in Cold Shear Yield of Bar Mill by Computer" Control System, 
pages 207 to 213 of "Tetsu-to-Hagane" Vol. 67, No. 15, in 1981. According 
to this proposal, a rolled material is divided into a plurality of bar 
materials, and the number of times to repeatedly cut the divided bar 
materials into desirable lengths is determined so as to minimize material 
loss and, hence, optimize the overall operation. 
In general, this cutting control relies on the principle of optimization 
which can be described by the equation: 
##EQU1## 
where g.sub.k (x): the loss when the k-th divided bar material is cut x 
times for the material adoption 
f.sub.k (x): the minimum loss expected when k pieces of divided bar 
materials are cut for the material adoption 
f.sub.1 (x)=g.sub.1 (x) 
k=2 to N 
N: The number of divided bar materials 
X: Total number of bars to be cut in parallel 
M.sub.k : The maximum number of cuts possible from the divided bar material 
In other words, since the f.sub.k-1 (X-x) is the minimum loss when (k-1) 
pieces of the divided bar materials are cut for (X-x) times of material 
adoptions, when the x is determined so that the total sum of the f.sub.k-1 
(X-x) and the loss g.sub.k (x) when the k-th divided material is cut x 
times may become minimum, it coincides with f.sub.k (x). If the maximum 
possible number of cutting the k-th divided material is represented by 
M.sub.k, the value of x can take an integer numbers from 0 to M.sub.k. 
Though the conventional cutting control system is executed as described 
above, the prediction of the length of the rolled bar material causes an 
error in the actual rolling length due to a cutting operation based the 
prediction of the length according to the weight of the material. Further, 
since cutting errors also take place at the respective cutting position of 
a flying shear, a considerable difference in length occurs and material 
loss drastically increases. Thus, it is difficult to minimize the loss of 
the bar materials. 
SUMMARY OF THE INVENTION 
This invention has been made in order to eliminate such disadvantages of 
the prior-art system, and has for its object to provide a system for 
controlling a bar cutter in a steel bar line which can eliminate errors in 
the prediction of rolling a bar material and the cutting thereof. 
A system for controlling a bar cutter in a steel bar line according to this 
invention measures the entire rolling length from the cut bar material to 
obtain the actual scale loss coefficient, and determines, based on the 
scale loss coefficient, a correction value for correcting a predicted 
rolling length so as to minimize the material loss. 
Further, this invention obtains a correction amount of a cutting timing in 
the flying shear on the basis of an error between the actual measured 
value of the cut bar material and the corrected rolling length determined 
above so as to accurately control the cutting operation.

In the drawings, the same symbols indicate the same or corresponding parts. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is a schematic view of the entire steel bar rolling line. In FIG. 1, 
numeral 1 designates a heating furnace for heating a bar material 6. After 
the heated bar material 6 is rolled by a rough rolling mill 2 into an 
adequate thickness and width, it is fed to a crop shear 7. The crop shear 
7 cuts the abnormal shaped portions of the front and tail ends of the 
material 6. The material 6 thus cut (i.e. at the abnormal shaped portions) 
is rolled by a rolling mill 4 into the size of a final product, is 
subjected to a material adoption having a suitable length by a flying 
shear 3, and then fed to a cooling floor 5. 
In order to determine the dividing length and number of the material 6 to 
be cut by the flying shear 3 in this rolling line, the entire rolling 
length of the material 6 is predicted as below. 
The bar material 6 is extracted from the heating furnace 2, then rolled 
through the rough rolling mill 2 and the finishing rolling mill 4, and cut 
by the flying shear 3. At this time, the following relation equation is 
used to predict the entire rolling length. 
EQU L.sub.0 =f(W.sub.0, W.sub.c, kg/m, S.sub.LOSS) (1) 
where 
L.sub.0 : Predicted entire rolling length 
W.sub.0 : Weight of material 
W.sub.c : weight of crop (i.e. weight of cut off and pieces) 
kg/m: Unit weight 
S.sub.LOSS : Scale loss coefficient 
The dividing length and number of the material to be cut are determined 
with respect to the entire predicted rolling length value represented by 
the equation (1), and the material is accordingly cut by the flying shear 
3 as a first stage. 
Therefore, when the entire predicted rolling length value and the cutting 
timing by the shear coincide with desired values, the optimum cutting 
control is conducted. 
It is first necessary to accurately know the scale loss coefficient so as 
to bring the entire predicted rolling length value into coincidence with 
the measured value. After the material is treated in the line, the length 
of the divided materials cut at the cooling floor inlet side are measured, 
the total length of the divided materials is obtained as the measured 
rolled value so as to obtain the actual measured value corresponding to 
one entire rolling length, and the measured value is substituted for the 
above-mentioned prediction equation to determine the scale loss 
coefficient. 
Then, in order to eliminate the cutting error by the flying shear, the 
length of the divided materials cut at the cooling floor inlet side are 
measured, the rate of the displacement with respect to the length of the 
material adoption is examined, and the correction amount is added to the 
cutting timing to regulate it, whereby the cutting error can be 
compensated. However, the finally divided materials are out of proportion 
since they are also affected by the influence of the error of the measured 
rolling length value. 
An embodiment based on the above-mentioned principle is shown in FIG. 2. 
In FIG. 2, numeral 11 designates an entire rolling length predicting 
circuit, numeral 12 designates a dividing length instructing circuit, 
numeral 13 designates a divided material length measuring circuit, numeral 
14 designates an entire rolling length measuring circuit, numeral 15 
designates a scale loss coefficient determining circuit, numeral 16 
designates a flying shear cut instructing circuit, numeral 17 designates a 
bar material measuring sensor, and numeral 18 designates a cutting timing 
regulator. 
The scale loss coefficient deciding circuit 15 calculates S.sub.LOSS from 
the equation (1) on the basis of the actual measured data of the measuring 
circuit 14. 
The crop weight W.sub.c of the equation (1) is the weight of the portion 
cut off at the front and tail ends of the material by the shear 
immediately before the bar material 6 reaches the finishing rolling mill. 
The flying shear cut instructing circuit 16 counts the timing that the 
cutting position arrives at the shear by the detection signal of the 
sensor 17 and outputs a command. The timing is corrected by an error 
signal from the regulator 18. 
In FIG. 2, the rolling length predicted by the abovementioned equation is 
first determined by the entire rolling length predicting circuit 11, and a 
command signal corresponding to the rolling length is fed to the dividing 
length instructing circuit 12. Then, the bar material measuring sensor 17 
detects the end of the bar material, and according to the instructed 
length from the dividing length instructing circuit 12, instructs the 
flying shear cut instructing circuit 16, when the detected value arrives 
at the cutting length, to cut the bar material. When the cut bar material 
is disposed at the cooling floor inlet side, the actual length of the cut 
bar materials are obtained by the divided material measuring circuit 13, 
the actual measured value of the entire rolling length is obtained by the 
entire rolling length measuring circuit 14 to instruct the scale loss 
coefficient deciding circuit 15 accordingly, so that the correction 
coefficient may be determined, which is then associated with the next 
material to be cut. Then, the cutting timing regulator 18 calculates the 
correcting amount of the cutting timing on the basis of the error between 
the actually measured value and the instructed length to instruct the 
flying shear cut instructing circuit 16 accordingly, thereby sequentially 
correcting the timing and cutting of the material. 
The above-mentioned operation is repeated to eliminate the difference 
between the predicted value and the actual measured value, whereby the 
cutting error approaches zero, thereby performing the optimum cutting 
control. 
FIG. 3 shows another embodiment of correcting the cutting timing on the 
basis of an error between the actual measured value of the already cut 
portions of divided materials and the dividing instruction length when the 
bar material is cut by the flying shear. In FIG. 3, the same symbols as 
those in FIG. 2 designate the same or equivalent parts. In FIG. 3, numeral 
11' designates an entire rolling length measuring circuit, numeral 12 
designates a dividing length instructing circuit, numeral 13 designates a 
divided material length measuring circuit, numeral 16 designates a flying 
shear cut instructing circuit, numeral 17 designates a bar material 
measuring sensor, and numeral 18 designates a cutting timing regulator. 
According to this construction, the cutting length is decided on the basis 
of a more significant command by the rolling length measured by the entire 
rolling length measuring circuit 11', and fed to the dividing length 
instructing circuit 12. Then, the bar material measuring sensor 17 detects 
the front end of the bar material, and according to the instructed length 
from the dividing length instructing circuit 12, instructs the flying 
shear cut instructing circuit 16, when the detected value arrives at the 
cutting length to cut the bar material. Further, after this cutting 
operation is executed, the actual length of the cut material is measured 
by the divided material measuring circuit 13, the correcting amount of the 
cutting timing based on the error between the actual measured value and 
the instructed length is calculated by the cutting timing regulator 18 to 
instruct the flying shear cut instructing circuit 16 to correct the timing 
accordingly, thereby sequentially controlling the cutting of the next 
material. 
Accordingly, when this operation is repeated, the cutting length error is 
eliminated to perform the optimum cutting control. 
In the embodiments shown in FIGS. 2 and 3, the on-line function used for 
the present line information has been described. However, the invention is 
not limited to the particular embodiments. For example, the same 
advantages can be also expected even if off-line function for calculating 
in advance is employed.