FIELD OF THE INVENTION
The present invention relates to a system for precise cutting of optimum length of tail end
of hot strip after roughing stand in a hot strip mill in steel plant. More particularly, the
system of the invention involves sensor based detection of tail end of strip, measuring of
speed of strip and cutting of the tail end of strip operatively by a crop shear favoring
optimum cut maintaining perfect rectangularity of the strip end in a simple, reliable and
faster manner and thus improving the yield of the plant. Advantageously also, the system
of the invention is adapted for controlling the crop shear mechanism for tail end cutting
using fiber optic hot metal detector for sensing the tail end and also sensing the speed of
the strip by a pulse tacho means and a programmable controller unit. The system is
directed to ensure significant improvement in quality and productivity/yield, by achieving
desired optimized tail end cutting of hot strip minimizing wastage of processed material,
saving on energy consumption favoring wide industrial application.
BACKGROUND ART
It is well known in the conventional art of hot rolling of slabs into the strips of desired
section, that slabs after passing through the descaler unit are first rolled in the roughing
stands for gradual reduction in thickness and thereafter through the finishing stands,
having a delay table in between roughing and finishing stands. It is also the common
practice in hot strip mills that the coil box and crop shear are located at the end of the
delay table. A crop shear is located after coil box and before the first finishing stand in
conventional hot strip mill layout. The metal coming out from last roughing stand is usually
termed as a transfer bar. The function of the crop shear is to trim off the irregular shaped
portion/length of the transfer bar prior to finish rolling and coiling and thus saving energy
and cost of finishing and also wastage of metal. The tail end portion of the transfer bar
usually stretches over a length in the range of 200-250mm. But if this irregular part of the
transfer bar is allowed to be rolled in the finish stands the corresponding portion will be
drawn to a length of nearly a few meters and coiled. If the tail end of transfer bar is not
cut optimally to exact length and at exact time, there will be incidence of undesirable
waste of time for cutting and removal of the processed materials, because then the rolled
hot strip which is in the form of a coil, has to be uncoiled first for last few turns and

thereafter it is cut by gas cutting operation manually consuming/wasting much of
unproductive man-hours, material and time. It is also an important consideration that in
conventional hot strip mill operation the appropriate length of transfer bar that is
irregularly shaped after passing of slab through the! roughing stands and need to be
cropped prior to its entry into the finishing stand should be precisely determined to save
on cost and improve yield. If too little of the tail end is cropped the last few turns of the
end product will be in a bad shape and it has to be cut by uncoiling and thereby wasting
energy required for rolling. On the other hand, if too much of length is cropped, the good
material is wasted and consequently the yield of the hot strip mill is lowered.
In conventional hot strip mill operation, the tail end detection is performed by Hot Metal
Detector mounted by the side of the roll table and speed of the strip is sensed by tacho
mounted on the first finishing stand. The detection of tail end needed for determining the
exact instant of cut which finally determines the cut length. The cutting speed of the shear
has to match with the strip speed and thus the shear speed has to be synchronized with
the strip speed.
Such conventional system for tail end cutting suffers from the limitations or disadvantages
comprising:
A. Failure of detection/sensing of tail end of strip by hot metal detector causing the
crop shear effecting tail end cutting of the transfer bar. This situation lead to
several transfer bars getting rolled in the finishing stand with out cutting the tail
end, increasing wastage of material or attracting additional subsequent uncoiling,
stretching and manual cutting operation.
B. The sensing and detection of tail end by hot metal detector is not precise, and
thereby causing undesired varied cut length of strip and yield loss.
C. As the actual speed of rolled strip is not sensed, rather it is derived from first
finishing stand speed, the finishing stand speed fluctuates due to looper operation
even though the input bar speed may not fluctuate causing
accumulations/interruptions.
Thus, it is experienced in the related art that there has been a continuing need to
ascertain the optimum length to be cut from tail end of all the transfer bar to save waste
of manpower, time, energy and cost. A fixed cutting length which is just optimum is most

desirable. There has thus been a persistent requirement in the hot strip mill process to
develop and provide means for precise sensing of tail end to ensure control on fixed
optimized cutting length of the transfer bar before finish rolling and coiling, crop cut speed
synchronized with the strip feed speed such that the processed material is not wasted and
the yield of the process is enhanced.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide a system for automatic
sensing and determining of the exact precise/optimized length for tail end of transfer bar
for timely cutting by cropping shear after the delay table prior to finish rolling and coiling,
such that the time, energy and cost is saved and yield is improved.
A further object of the present invention is directed to developing a system for exactly
sensing the transfer bar speed so that the shear speed can be synchronized with the
transfer bar speed for proper cutting.
A still further object of the present invention is directed to developing an automatic system
for sensing and detecting the length and speed for ensuring appropriate cutting length of
the transfer bar before it is further finish rolled and coiled in order to save wastage of
material, manpower and energy or processed material and thus a saving on costs of
operation.
A still further object of the present invention is directed to developing an automatic system
for sensing and detecting the length and speed for ensuring appropriate cutting length by
cropping shear, such that the irregular portion of the bar is removed and no defect free
potion of material is removed thereby improving the productivity and yield of the hot strip
mill operation.
A still further object of the present invention is directed to developing an automatic system
for sensing and detecting the length and speed for ensuring appropriate cutting length by
cropping shear, using fiber optic hot metal detector such that the yield loss is minimized.

A still further object of the present invention is directed to developing an automatic system
for sensing and detecting the length and speed for ensuring appropriate cutting length by
cropping shear, such that actual speed of strip is sensed and there is no fluctuation of
speed between finishing stand speed due to looper operation and the input bar speed, thus
ensuring shear speed and strip speed synchronization.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a system for
reliable crop shear tail end cutting in hot strip mill comprising
fiber optic hot metal detectors (HMD), mounted below the roll table, just after coil
box pinch roll and before crop shear adapted for precise detection of tail end
portion of hot strip;
a pulse tacho adapted to measure the pinch roll rotation speed cooperatively with
an encoder means and to thereby generate corresponding signal to determine the
strip speed;
a controller means suitably interfaced and adapted to process the pulse tacho
signal and generate an analog output for the crop shear drive favoring precise
cutting of said detected tail end of transfer bar
Preferably in the above system of the invention there is provided a pair of said fiber optic
hot metal detectors (HMD),
said pulse tacho is mounted on the exit top scale washer pinch roll adapted to measure the
pinch roll rotation speed cooperatively with an encoder means and to thereby generate
said corresponding signal to determine the strip speed based on pinch roll diameter; and
said programmable controller interfaced such as to process the pulse tacho signal and
generate said analog output which is used as the reference for the crop shear drive
favoring precise cutting of said detected tail end of transfer bar by said hot metal detector.

According to another aspect of the system as apove the said fiber optic hot metal
detectors (HMD) are selectively spaced apart and preferably 500mm to 800 mm apart
for said precisely detecting the tail end of the hot strip.
Preferably, fiber optic hot metal detection subsystem comprise Lens assembly, optical
fiber in a flexible stainless steel conduit about 15 meters long, fiber optic cable
terminating accessories and detection electronics including power supply.
Also preferably, the said hot metal detection subsystem comprises air Purge facilities
so as to enable the lens to become free from obstruction using compressed air at 3 - 4
Kg/Cm2 pressures.
The distance from capturing head to target is maintained in the range of 100 mm -
1200 mm, for sensing/detection of tail end of Hot Steel Strip in the temperature range
of 650°C - 1100°C, with response time for Relay Output at 20 msec and Response time
for Transistor output 2 msec.
In accordance with another aspect of the invention, the Fiber Optic Cable from Lens
assembly to Detector is protected by means of staiinless steel pipe adapted to carry the
Fiber optic cable in a flexible stainless steel conduit and lens assembly unit, along with
sockets required for extension of stainless steel pipje to required length.
The said pulse tacho used for transfer bar speed measurement is selected of any make
having pulse per revolution around 600-1200 meet the purpose.
In accordance with a preferred aspect in the above system the said pulse tacho is
adapted to generate Direct Pulse (0°), Quadrature Pulse (90°), Marker Pulse (N) and
Inverted pulses of all.
According to a further aspect the said pulse tacho comprises a metal cast aluminium
encoder, mounted on the top scale washer pinch roll after Crop shear and before first
finishing stand of the Hot Strip Mill, adapted to operate at temperature around 90°C,
Humidity 100%, capable to with stand high shock load.

The said Controller means in the system of the invention comprises a programmable
controller comprising of Central Processing Unit, Counter module and Analog output
module, said counter module being bidirectional having provision to connect Direct
Pulse (0°), Quadrature Pulse (90°), Marker Pulse (N) and Inverted pulses of all.
In accordance with a further aspect of the invention there is provide a method for
precise controlled tail end cutting from the transfer bar after roughing stand adapted to
increase yield of hot strip mill using the system as disclosed hereinbefore comprising
the steps of
detecting precisely the tail end portion of the transfer bar of hot strip after
the roughing stands by means of said fiber optic Hot metal detectors located
below the roll table and generating corresponding digital signal to
programmable controller for determining the tail end length to be cut;
measuring precisely the speed of the pinch roll revolution by means of pulse
tacho located on exit top scale washer pinch roll, cooperatively by an
encoder and generating the corresponding output pulse to the
programmable controller to determine the strip speed;
processing said signals by the programmable controller relating to strip
speed and crop shear speed and generating appropriate drive signal for said
crop shear drive to enable determining exact cutting instant of the hot strip
at desired precise optimized length of tail end for all transfer bar.
The details of the invention, its objects and advantages are explained hereunder in greater
detail in relation to non-limiting exemplary illustrations as per the following non-limiting
exemplary illustrations by way of the following accompanying figures.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1: is the schematic illustration of the general layout of Hot strip Mill that shows the
location of crop shear in the delay table where the tail end shall be cut.
Figure 2: is the schematic illustration of an embodiment of the system for tail end cutting
of transfer bar by crop shear according to the present invention, in hot strip mill showing
the preferred location of Hot metal Detectors and Pulse tacho used for transfer bar speed
measurement and programmable controller to process various input signals for analysis
and control of crop shear actuation in synchronization with rolled strip speed.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
The present invention is directed to developing a system for automatic cutting of the hot
rolled strip by crop shear at exact tail end length and cropping time, so as to optimize the
time and cost of operation in a safe, reliable and controlled manner without interruption
and ensuring avoiding rework, wastage of processed material and/or energy consumed in
hot strip mill operations and increasing the yield.
The system according to the invention uses a number of hardware devices and interfacing
software means. The hardware components enabled with software component that counts
the pulses and calculates the linear speed based on the diameter of pinch roll in the
system comprises:
i) Two numbers of fiber optic hot metal detectors mounted below the roll table;
ii) One pulse tacho to sense the linear speed of the transfer bar;
iii) A programmable controller having a central Processing Unit, Counter Module for
processing the Pulse tacho signal, Analog output module for generating 0 to +10 V
DC which corresponds to the strip speed;
Reference is first invited to the accompanying Figure 1, that illustrates the lay out of the
hot strip mill showing the location of the Crop Shear, selectively located after the roughing
mill, followed by delay table and the coil box, but ahead of the first finishing mill stand.

This selective disposition helps cutting off the irregular shaped tail end of desired
controlled length of the hot rolled strip/transfer bar, to avoid subjecting the defective
portion of hot rolled transfer bar, spanning over almost 200-250 mm to finish rolling and
thereby saving material, repair/rework and energy.
Reference is now invited to the accompanying Figure 2 that illustrates an embodiment of
the system according to the present invention comprising the hardware means for
detection of tail end of transfer bars and measurement of the strip speed vis-a-vis the
pinch roll speed to achieve desired speed synchronization to effect exact, precise and
constant tail length cropping shear prior to finish rolling. More importantly, a crop shear
drive unit analyze the signals received from the two numbers of fiber optic hot metal
detectors (HMD) mounted below the roll table for detecting the tail end of the transfer bars
and send the corresponding signals to the programmable controller; and the corresponding
strip speed data received from the pulse tacho which is of type Optical Incremental
Encoder, Redundant system, mounted on the top of scale washer pinch roll before the first
finishing roll stand such that the programmable controller generate a corresponding analog
signal of 0 to +10 V for the crop shear drive as speed reference and achieve desired
automatic end tail cutting operation by cropping shear at a relational synchronized speed
of the strip and the crop with predefined time lag and a tail end length set by the
operator.
The hardware components used in the system of the invention as illustrated in the
accompanying Figure 2 are as follows:
Fiber Optic Hot Metal Detector:
As already described, in the present system for tail end cutting of the hot rolled strip, two
numbers of Fiber Optic Hot Metal Detectors (HMD) are mounted below the roll table, as
compared to conventional disposition at the side of roll table. Out of these two Fiber Optic
Hot Metal Detectors, only one output is taken. However, it is proposed that two numbers
of Fiber Optic Hot Metal Detectors to be mounted at one go during a capital repair of the
mill, to ensure reliable performance. Any one of the two hot metal detector is selected
based on determining based on optimization of length of tail end of the transfer bar. The

Hot Metal Detectors are mounted below the roll table just after coil box pinch roll and
before crop shear.
The specification of the Fiber Optic Hot Metal Detector (HMD) used in the system is as
follows:
i) Type : Fiber Optic based Hot Metal Detector
ii) Place of installation : Installed below the roller table just after coil box
pinch roll and before hot crop shear of finishing
stands at Hot Strip Mill
iii) Subsystem of each sensor : Lens assembly
15 meter of Optical fiber in a flexible stainless
steel conduit.
Fiber optic cable terminating accessories.
Detection Electronics including power supply.
iv) Air Purging facility : Air Purge facilities to enable the lens become
free from obstruction using compressed air.
Compressed air at 3 - 4 Kg/Cm2 pressures
(contaminated with water, oil and dust) is
available at site.
v) Distance from capturing : 100 mm - 1200 mm
head to target
vi) Material to be sensed : Hot Steel Strip of temperature 650°C - 1100°C
vii) Response time for Relay : 20 msec for relay output
Output
viii) Response time for : 2 msec
Transistor output
ix) Ambient Temperature of : 0°C to + 55°C
Signal Conditioning /
Electronics unit
x) Output : Relay output and Open collector output
xi) Material of Protective Pipe : Stainless Steel pipe of 4 meters length to carry
for Fiber Optic Cable from the Fiber optic cable in a flexible stainless steel
Lens assembly to Detector conduit and lens assembly unit, along with
sockets required for extension of Stainless steel
pipe to required length.
xii) Power Supply : 230 V AC ( + 10% - 15% , 50 HZ ± 3%) / 24 V
DC

Pulse tacho:
The following is the specification of the Pulse tacho used for transfer bar speed
measurement. However, pulse tacho of any make having pulse per revolution around 600-
1200 shall serve the purpose. It is adapted to deliver out put signals comprising Direct
Pulse (0°), Quadrature Pulse (90°), Marker Pulse (N) and Inverted pulses of all. Typical
specification of the pulse tacho used in the system are as illustrated below:
i) Type: Optical Incremental Encoder, Redundant system.
ii) Pulses per revolution :1200
iii)Supply Voltage:12-30 V DC
iv)Outputs : Direct Pulse (0°), Quadrature Pulse (90°), Marker Pulse (N) and Inverted
pulses of all.
v) Number of Electrical outputs : Two Numbers.
vi) Electrical Connection : Screw type terminal box on both side (left and right) for two
sets of electrical outputs.
vii) Terminal box : Integrated cast terminal box with cable gland suitable for cable
diameter up to 15 mm.
viii) Frequency Range :0 to 100 kHz
ix) Load :50 mA per Output
x) Temperature :0 to 100°C
xi) Shaft Diameter :Between 10 to 12 mm
xii) Overall Diameter :Between 120 to 130 mm
xiii) Mounting :Flange mounted and Base mounted
xiv) Protection Class :IP 56
xv) Mounting Location : The encoder has been mounted on the top scale washer pinch
roll after Crop shear and before first finishing stand of the Hot Strip Mill,
xvi) Encoder body :Ail metal cast Aluminum
xvii) Environmental condition : Temperature around 90°C, Humidity 100%, Should
withstand higher shock load;

Programmable Controller means :
Programmable Controller means used in the system basically comprises of Central
Processing Unit, Counter module and Analog output module. Programmable Controller of
any make shall serve the purpose. The counter module should be bidirectional i.e. it
should have provision to connect Direct Pulse (0°), Quadrature Pulse (90°), Marker Pulse
(N) and Inverted pulses of all.
The present system thus provides means for Cutting of tail end of all the transfer bars in a
precise and reliable manner. The length of the end piece is almost constant, thus precise
cutting is possible which increases the yield of the mill. The system thus ensures safe and
reliable operation of hot strip mill by optimizing the cropping shear of tail end length of
strip. The system and the method of detecting the tail and, measuring the strip speed and
programmable controller generated signal controlled operation of the drive of cropping
shear would favour precise and consistent cutting of tail end and thereby eliminating
either carry forward of defective portion of transfer bar in the finish rolling and coiling area
or remove defect portion of transfer bar leading to expensive waste by way of extra
manpower, rework or wasting processed material which is not fit for use or removing good
material as tail end due to lack of proper optimized detection.

We Claim:
1. A system for reliable crop shear tail end cutting in hot strip mill comprising
fiber optic hot metal detectors (HMD) mounted below the roll table, just after coil
box pinch roll and before crop shear adapted for precise detection of tail end
portion of hot strip;
a pulse tacho adapted to measure the pinch roll rotation speed cooperatively with
an encoder means and to thereby generate corresponding signal to determine the
strip speed;
a controller means suitably interfaced and adapted to process the pulse tacho
signal and generate an analog output for the crop shear drive favoring precise
cutting of said detected tail end of transfer bar .
2. A system as claimed in claim 1
wherein there is provided a pair of said fiber optic hot metal detectors (HMD),
said pulse tacho is mounted on the exit top scale washer pinch roll adapted to
measure the pinch roll rotation speed cooperatively with an encoder means and to
thereby generate said corresponding signal to determine the strip speed based on
pinch roll diameter;
said programmable controller interfaced such as to process the pulse tacho signal
and generate said analog output which is used as the reference for the crop shear
drive favoring precise cutting of said detected tail end of transfer bar by said hot
metal detector.
3. A system as claimed in anyone of claims 1 or 2 wherein said fiber optic hot metal
detectors (HMD) are selectively spaced apart and preferably 500mm to 800 mm
apart for said precisely detecting the tail end of the hot strip.
4. A system as claimed in anyone of claims 1 to 3 wherein fibre optic hot metal
detection subsystem comprise Lens assembly, optical fiber in a flexible stainless

steel conduit about 15 meters long, fiber optic cable terminating accessories and
detection electronics including power supply.
5. A system as claimed in anyone of claims 1 to 4, wherein said hot metal detection
subsystem comprises air Purge facilities so as to enable the lens to become free
from obstruction using compressed air at 3 - 4 Kg/Cm2 pressures.
6. A system as claimed in any one of claims 1 to 5, wherein the distance from
capturing head to target is maintained in the range of 100 mm - 1200 mm, for
sensing/detection of tail end of Hot Steel Strip in the temperature range of 650°C -
1100°C, with response time for Relay Output at 20 msec and Response time for
Transistor output 2 msec.
7. A system as claimed in any one of claims 1 to 6, wherein the Fiber Optic Cable from
Lens assembly to Detector is protected by means of stainless steel pipe adapted to
carry the Fiber optic cable in a flexible stainless steel conduit and lens assembly
unit, along with sockets required for extension of stainless steel pipe to required
length.
8. A system as claimed in any one of claims 1 to 7, wherein said pulse tacho used for
transfer bar speed measurement is selected of any make having pulse per
revolution around 600-1200 meet the purpose.
9. A system as claimed in any one of claims 1 to 8, wherein said pulse tacho is
adapted to generate Direct Pulse (0°), Quadrature Pulse (90°), Marker Pulse (N)
and Inverted pulses of all.
10. A system as claimed in any one of claims 1 to 9, wherein said pulse tacho
comprises a metal cast aluminium encoder, mounted on the top scale washer pinch
roll after Crop shear and before first finishing stand of the Hot Strip Mill, adapted to
operate at temperature around 90°C, Humidity 100%, capable to with stand high
shock load.

11. A system as claimed in any one of claims 1 to 10, wherein said Controller means
comprises a programmable controller comprising of Central Processing Unit,
Counter module and Analog output module, said counter module being bidirectional
having provision to connect Direct Pulse (0°), Quadrature Pulse (90°), Marker Pulse
(N) and Inverted pulses of all.
12. A method for precise controlled tail end cutting from the transfer bar after roughing
stand adapted to increase yield of hot strip mill using the system as claimed in any
one of claims 1 to 11, comprising the steps of
detecting precisely the tail end portion of the transfer bar of hot strip after
the roughing stands by means of said fiber optic Hot metal detectors located
below the roll table and generating corresponding digital signal to
programmable controller for determining the tail end length to be cut;
measuring precisely the speed of the pinch roll revolution by means of pulse
tacho located on exit top scale washer pinch roll, cooperatively by an
encoder and generating the corresponding output pulse to the
programmable controller to determine the strip speed;
processing said signals by the programmable controller relating to strip
speed and crop shear speed and generating appropriate drive signal for said
crop shear drive to enable determining exact cutting instant of the hot strip
at desired precise optimized length of tail end for all transfer bar.
13. A system for reliable crop shear tail end cutting in hot strip mill and a method for
such optimized cutting operation using such system substantially as
hereindescribed and illustrated with reference to the non limiting accompanying
illustrative figures.

A system for precise cutting of the tail end of transfer bar at crop shear before finishing
stand in a hot strip mill involving Fiber Optic Hot Metal Detectors (HMD), Pulse tacho and
controller means. In the above system the pulse tacho is adapted to sense the rotational
speed of the pinch roll having constant diameter. The controller means is adapted to
calculate and convert the input data to linear speed of the strip. This linear speed is fed as
0 to +10 V signal to the crop shear drive as reference speed signal. Thus the optimized
tail end cutting of transfer bars are achieved by synchronizing strip and shear speed with
an appropriate time lag. The present system enables detection and cutting of tail end of all
transfer bars as per the desired length precisely and reliably, improving the product
quality, yield and mill productivity and thus ensuring wide industrial application in hot strip
mills of steel plants.