FIELD OF THE INVENTION
The present invention relates to an automatised cut to length system using Laser Doppler
Velocimeter for state-of-the-art LASER based length measurement and Programmable Logic
Controller (PLC) based control system for ensuring precise cutting length by shearing of
rolled sheets/strips. The system has been developed around laser based sensor and PLC
system and interfaced with existing drive for shear m/c. Installation of sensor involves
erection of major structure for vibration free measurement so as to measure the length
accurately. The new improved cut to length system has ensured reduction in length
variation from 1% to 0.54% of set length, enhancing productivity, saving cost and reducing
downtime of plant.
BACKGROUND OF THE INVENTION
Hot Rolled Coil Finishing (HRCF) Shop of Bokaro Steel Plant is equipped with flying shear
machine providing cut in a length of sizes in the range of 4.5 to 10 meters. The coils
received at HRCF (Hot Rolled Coil Finishing) from Hot Strip Mill is cut in the range of 4.5 to
10 meters at shearing line, packaged and despatched to customer. There are two identical
shearing lines, both equipped with individual flying cut off shear.
The existing shear system consists of traditional servo roll, encoder and logic block to
measure the length and initiate the cut command at appropriate time. The existing system
for length measurement and to initiate the cut command for shear m/c, consists of servo
roll, encoder and control logic blocks fails to predict the correct length due to backlash. The
measurement and control system, being outlived, poses several problems in running and
maintenance of its component.,The related issues are mis-cut, length variation in first cut,
intermediate cuts and last cut. All these abnormalities lead to rejection of sheets and also
sometimes jamming of the sheets in the piler. The yield of shearing line suffers due to
length variation, missing the cut and subsequent rejection of sheets in pilers. At some time
smaller/longer pieces are also cut due to malfunctioning of the system leading to jamming
of sheets and thus reducing production.
Earlier control system of flying shear is based on combination of servo roll and encoder for
cut accuracy. The strip released from uncoiler after processing is fed into two stage leveller

via looper. The output of leveller is pressed by a servo roll and as soon as count equivalent
to set length is completed, the flying shear moves half circle to make a cut on the fly and
returns back to home position. At home position, brakes are applied and the shear is
stopped. The flying shear is rotary type and is driven by ABB make DC drive. A hardware
logic based Russian control system is available.
The above mentioned encoder based cut-to-length system is not able to predict the correct
length of the sheet to be cut. Besides, the control system is behaving erratic and gives false
signal. Further the logic block of the automation system has gone un-repairable as the
system has lived its life (i.e.) >25 yrs and is obsolete. Hence sustenance of the system has
reduced due to repetitive failure, long time taken in trouble shooting and difficulty in
repairing because of non-availability of spare and service support.
In addition to above the earlier system has a problem of mis-cut (mostly in first cut), a
large first cut, length variation in intermediate cuts and large last cut. It is to be noted that
allowed length variation is 0-1% of set length and no tolerance is allowed on the negative
side. Any length variation beyond tolerance amounts to rejection of sheet and business
losses.
There has been thus a need in the art to developing an advanced and accurate cut to length
system for HRCFvshop, for cutting of sheet lengths within the required tolerance limit
avoiding chances of mis-cut, or variation in cutting length leading to rejections or jamming
of sheets in piler leading to production loss.
OBJECTS OF THE INVENTION
The basic object of the present invention is directed to provide an automatised cut to length
system to overcome the disadvantage and drawbacks of earlier servo roll and encoder
based measurement system by involving laser based sensors and PLC based control system
for accurate cutting of rolled sheets by shearing in hot rolled coil finishing shop within
allowable tolerance reducing rejection or loss of production.
A further object of the present invention is directed to provide an improved cut to length
system for accurate cutting of rolled sheets by shearing using non-contact sensor for length.

measurement of running sheet/ coil such as by involving laser Doppler velocimeter for
length measurement to ascertain precise cutting length of rolled sheets.
A still further object of the present invention is directed to an improved cut to length system
for accurate cutting of rolled sheets by shearing wherein an improved control system
involving. PLC (Programmable Logical Controller) is introduced for initiating cut commands
based on measured length by the non-contact laser Doppler velocimeter sensor and
fulfilment of various interlocks to operate the sharing mechanism.
A still further object of the present invention is directed to an improved cut to length system
for accurate cutting of rolled sheets by shearing wherein PC based HMI (Human Machine
Interface) operator desk is provided for setting desired length and displaying the actual cut
length thus making the system more user friendly.
A still further object of the present invention is directed to an improved cut to length system
for accurate cutting of rolled sheets by shearing wherein soft logic is developed and
implemented in place of earlier hardware based logic for length calculation.
A still further object of the present invention is directed to an improved cut to length system
for accurate cutting of rolled sheets by shearing wherein the system ensure easy
maintainability and troubleshooting of control logics/ interlock functions.
A still further object of the present invention is directed to an improved cut to length system
for accurate cutting of rolled sheets by shearing which is adapted to achieve improvement in
cut length accuracy from 1% to 0.65% of set length.
A still further object of the present invention is directed to an improved cut to length system
for accurate cutting of rolled sheets by shearing wherein mechanical set length mechanism
has been replaced by on screen setting facility at operator's disposition.
A still further object of the present invention is directed to an improved cut to length system
for accurate cutting of rolled sheets by shearing which ensure final cut value with zero
negative tolerance and 1% positive tolerance is met 100%.

SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to an automatised cut to length system
for cutting hot rolled sheet/coil to accurate length using flying cut off shear, comprising
non-contact laser based sensors selectively disposed for length measurement of
running sheet/ coil;
a control system involving PLC (Programmable Logical Controller) for initiating cut
commands based on measured length involving the said non-contact laser sensor
and interlocks to operate a shearing mechanism to cut the desired set length;
PC based HMI (Human Machine Interface) for setting desired length, with installed
soft logic for length calculation, and displaying the actual cut length.
A further aspect of the present invention is directed to an automatised cut to length system,
wherein said non contact laser based sensors include high sensitivity Laser Doppler
Velocimeter(LDV) sensors which are speed sensors for accurate speed measurement and
calculation of length by integrating speed over short, fixed interval of time to ensure
extremely accurate length.
A still further aspect of the present invention is directed to an automatised cut to length
system, wherein another sensor for identifying the tail end is installed, said sensor being a
through beam light barrier type;
A still further aspect of the present invention is directed to an automatised cut to length
system, wherein said PLC based controller comprising high speed counter module in PLC for
counting the output of LDV as train of pulses corresponding to speed of sheet and all other
logic and interlocks being interfaced to the PLC including tail end sensor such that the cut
command to flying shear drive and break command to stop the flying shear motor are
generated as programmed in the PLC.
A still further aspect of the present invention is directed to an automatised cut to length
system, wherein said HMI comprises an engineering terminal as and when required for
performance diagnosis of cut to length system and maintenance of it wherein under normal

circumstances it acts as operator terminal and all the operation related to flying shear
accuracy are performed by operator on this terminal.
A still further aspect of the present invention is directed to an automatised cut to length
system, wherein said PC based HMI with installed software is adapted to SET desired length,
enter First cut offset, last cut offset, feed distance between LDV and flying shear and lastly
feed length to be considered equivalent to flying shear response from home position to cut
position.
Yet another aspect of the present invention is directed to an automatised cut to length
system, wherein said LDV sensors are installed involving erection of major structure for
vibration free installation so as to measure the length accurately.
A further aspect of the present invention is directed to an automatised cut to length system,
which enable fine and precise cut to length and improves cut length accuracy from 1% to
0.54% of set length.
A still further aspect of the present invention is directed to an automatised cut to length
system, which would meet 100% process requirement.of final cut value with zero negative
tolerance and 1% positive tolerance.
A still further aspect of the present invention is directed to an automatised cut to length
system, which would avoid rejection of sheets due to large variation in length and jamming
of sheets in piler to thereby facilitate reduction in delay by 75% (i.e.) 10 to 2.5 hrs/month
and thus improving the yield by 0.03%.
The objects and advantages of the present invention are described hereunder in greater
details with reference to the following accompanying non limiting illustrative drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: shows a schematic diagram showing the improved cut to length system according
to the present invention for flying shear Control involving laser Doppler velocimeter and PLC
based control system with HMI interface for precise cutting of sheet length.

Figure 2: shows a photographic image showing the view of mounted LASER Doppler
Velocimeter on structure for vibration free measurement of sheet length to be cut.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING DRAWINGS
The present invention is directed to provide an automatised cut to length system for precise
cutting of length of rolled sheets within acceptable tolerance limit in hot rolled coil finishing
shop by controlled flying shear operation involving an state-of-the-art LASER based length
measurement and Programmable Logic Controller (PLC) based control system which has
been designed and implemented for improved control, technical enhancement and
productivity improvement. Laser Doppler velocimetry (LDV) , is the technique of using
the Doppler shift in a laser beam to measure the velocity in transparent or semi-
transparent fluid flows, or the linear or vibratory motion of opaque, reflecting, surfaces.
The system according to present invention has been developed around laser based sensor
and PLC system and interfaced with existing drive for shear m/c. Installation of sensor
involves erection of major structure for vibration free measurement so as to measure the
length accurately. The new improved cut to length system has ensured reduction in length
variation from 1% to 0.54% of set length.
An improved automation and control system based on length measurement by high
sensitivity laser Doppler sensor along with PLC system has been introduced for shear drive
and fulfilment of various interlocks to operate the shear to cut the desired set length.
Accompanying Figure 1 shows the schematic arrangement of the proposed system
according to the present invention. To overcome the short comings of the previous system,
a new cut to length control system is implemented which is having three main components
as follows:
State-of-the-art sensors:
The control system employs Laser based non contact speed sensors for accurate speed
measurement and calculation of length by integrating speed over short, fixed interval of

time. These sensors provide extremely accurate length With proper installation. Such a
sensor Lased Doppler Velocity (LDV) is used for the purpose of speed measurement.
Accompanying Figure 2 shows a photographic image showing the view of mounted LASER
Doppler Velocimeter on structure for vibration free measurement of sheet length to be cut.
Another sensor for identifying the tail end is also introduced, the sensor being a through
beam light barrier type.
Controller for fast computation:
The output of LDV is train of pulses corresponding to speed of sheet and these pulses are
counted by high speed counter module in PLC. AM other logic and interlocks are also
interfaced to the PLC including tail end sensor. The cut command to flying shear drive and
break command to stop the flying shear motor are also programmed in the PLC.
Operator Interface with application software:
A HMI has been commissioned which also acts as engineering terminal as and when
required for performance diagnosis of cut to length system and maintenance of it Under
normal circumstances it acts as operator terminal and all the operation related to flying
shear accuracy are performed by operator on this terminal. The software developed has
provision to SET desired length, enter First cut offset, last cut offset, feed distance between
LDV and flying shear and lastly length to be considered equivalent to flying shear response
from home position to cut position.
The integrated system was tested and tuned based on observation for about two months.
After every set of observation, parameters were modified to minimise error.and finally
system has stabilized with almost stable performance. A sample set of data corresponding
to the observed results for trial run has been shown in following Table 1 .for an aimed
cutting length of 6300-6363mm and two different set length 6315mm and 6320mm:


From the above data, it is established that the new improved cut to length system has
ensured reduction in length variation from 1% to 0.54% of set length. Further the system
facilitates reduction in delay by 75% (i.e.) 10 to 2.5 hrs/month and thus improving the yield
by 0.03%.
It can thus be concluded from the above results that:
1. The process requirement of final cut value with zero negative tolerance and 1%
positive tolerance is met 100%.
2. If the set length in HMI is raised by Min. Value, all the cut shall be within 0-20mm
tolerance. The margin shall be more for intermediate cuts and less for first and last
cut to natural speed variation.

The present invention is thus having the following salient advantageous features:
(i) Introduction of non-contact sensor for running length measurement ;
(ii) Implementation of soft logic in place of earlier hardware based logic for length
calculation;
(iij) Easy maintainability & troubleshooting of.control logics/ interlock functions;
(iv) Improvement in cut length accuracy from 1% to 0.54% of set length;
(v) Mechanical set length mechanism has been replaced by on screen setting facility
at operator's disposition.

We Claim:
1. An automatised cut to length system for cutting hot rolled sheet/coil to accurate
length using flying cut off shear, comprising
non-contact laser based sensors selectively disposed for length measurement of
running sheet/ coil;
a control system involving PLC (Programmable Logical Controller) for initiating cut
commands based on measured length involving the said non-contact laser sensor
and interlocks to operate a sharing mechanism to cut the desired set length;
PC based HMI (Human Machine Interface) for setting desired length, with installed
soft logic for length calculation, and displaying the actual cut length.
2. An automatised cut to length system as claimed in claim 1, wherein said non contact
laser based sensors include high sensitivity Laser Doppler Velocimeter(LDV) sensors
which are speed sensors for accurate speed measurement and calculation of length
by integrating speed over short, fixed interval of time to ensure extremely accurate
length.
3. An automatised cut to length system as claimed in anyone of claims 1 or 2, wherein
another sensor for identifying the tail end is installed, said sensor being a through
beam light barrier type.
4. An automatised cut to length system as claimed in anyone of claims 1 to 3, wherein
said PLC based controller comprising high speed counter module in PLC for counting
the output of LDV as train of pulses corresponding to speed of sheet and all other
logic and interlocks being interfaced to the PLC including tail end sensor such that
the cut command to flying shear drive and break command to stop the flying shear
motor are generated as programmed in the PLC.
5. An automatised cut to length system as claimed in anyone of claims 1 to 4, wherein
said HMI comprises an engineering terminal as and when required for performance
diagnosis of cut to length system and maintenance of it wherein under normal

circumstances it acts as operator terminal and all the operation related to flying
shear accuracy are performed by operator on this terminal.
6. An automatised cut to length system as claimed in anyone of claims 1 to 5, wherein
said PC based HMI with installed software is adapted to SET desired length, enter
First cut offset, last cut offset, feed distance between LDV and flying shear and lastly
feed length to be considered equivalent to flying shear response from home position
to cut position.
7. An automatised cut to length system as claimed in anyone of claims 1 to 6, wherein
said LDV sensors are installed involving erection of major structure for vibration free
installation so as to measure the length accurately.
8. An automatised cut to length system as claimed in anyone of claims 1 to 7, which
enable fine and precise cut to length and improves cut length accuracy from 1% to
0.54% of set length.
9. An automatised cut to length system as claimed in anyone of claims 1 to 8, which
would meet 100% process requirement of final cut value with zero negative
tolerance and 1% positive tolerance.
10. An automatised cut to length system as claimed in anyone of claims 1 to 9, which
would avoid rejection of sheets due to large variation in length and jamming of
sheets in piler to thereby facilitate reduction in delay by 75% (i.e.) 10 to 2.5
hrs/month and thus improving the yield by 0.03%.