FIELD OF INVENTION
The present invention relates to a system directed to non-contact method of length
measurement in plate mill, where the plate moves on the roll table. The system ensures
that the length of plate cut lies within tolerance limit. More particularly, the invention
relates to the measurement of length of plate under static condition against a fixed scale.
The length measurement system has been developed involving CCTV camera, monitor and
switching modules. The system would thus be simple and accurate and is having the
potential for wide application of accurate measurement of cutting of plates and rolled
sections in the rolling mills of large steel plants.
BACKGROUND ART
It is a common experience to persons working in the plate mills of steel plants that the
conventional length measurement system can be of two types (i) manual method by scale
and (ii) Non Contact method using CCD camera.
In general in a manual method, the front end of the plate, which is irregular in shape, is
first cut by a static shear. The rollers on roll table is rotated by a series of motors. As the
motor rotates, the plate moves on roll table. The scale is calibrated in increasing order-
taking shear as reference zero in the direction of plate movement. When the motor rotated
clockwise, length increases against the static scale.
In conventional method for cutting of plates to desired length in plate mills, first the
irregular shape of the front end of the plate is cut by the shear to bring the front end
perpendicular to length. That point of the plate is taken as reference point as zero. The
marker manually marks the plate of required length to be cut. The operator moves the plate
on roll table and brings the chalk mark exactly below the shear and cuts it. This becomes
the reference point for the next plate length and is taken as zero. The marker again marks
the chalk mark of required length and the operator moves the plate on roll table and brings
the chalk mark exactly below the shear and cuts it. This process continues till the whole
plate is cut in to pieces and generation of some scrap. The marker has to stand for the
whole plate to pass as he marks for each plate. In absence of marker or operator the
operation gets held up and causes delay.
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The Manual method of length measurement of rolled product thus suffers from the
limitations that the chalk mark made manually is not proper, sharp and visible to operator.
Some times the operator while cutting the plate does not know how much tolerance he has
really made. The marker has to stand near the roll table and physically marked each and
every plate to be cut as per order, making such method time consuming and inaccurate and
generating more scrap.
The conventional non contact method of length measurement of rolled products/plates, on
the other hand generally employ one or more Line scan camera or matrix scan camera that
are many times costly than our CCTV based system presently developed for the same
purpose. The repair and maintenance of line scan cameras are also a costly affaire. It also
takes time to procure them. Because of very hot and dusty environment operator marks
very quickly and comes back to cabin causing delay in operation. Moreover, in the existing
system there is no provision for reading the information of number of plates cut and also
accountability of short /cut pieces of the plates.
There has been thus a continuing need to develop a method of measuring the length of
rolled products/plates accurately in a simple and less costly way without the continuous
physical involvement of persons for marking or checking etc., such as to determine the
cutting length of plates within desired tolerances on cut length and control on process
including generation of off-cuts.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to measure the cutting/shearing length of
plates accurately and displaying the same to the operator in cabin without the need for
approaching to the proximity to the plate being rolled and cut to desired length and without
human intervention at site.
A further object of the present invention is directed to a non-contact method of measuring
the length of rolled product also serving as video guidance system to operator to ensure
that the plates are cut as per requirement within the tolerance.
A still further object of the present invention also provide means for very close tolerance on
cutting length to meet customer's requirement/satisfaction.
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Yet another object of the present invention is directed to eliminating manual chalk marking
and single operator instead of two can do entire operation, as conventionally required, while
maintaining the rate of production and productivity.
According to a further object of the present invention is directed to provide low cost, non-
contact method involving devices comprising easily available gadget, to minimize
maintenance time and adopted to use and throw concept, improving productivity and
reducing scrap.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a system for
measuring the length of plate on roll table comprising:
said roll table for plate movement provided with a standard length measuring scale at one
side along the length of the table and plurality of CCTV cameras for each standard length on
the other side facing the standard scale;
switcher/monitor means adapted for selecting the CCTV camera for the corresponding
length and indicate the various length to the operator ;
a CCTV camera means for providing the required output signal to said switcher; and
a display means adapted to display the front end of plate against said standard scale.
A further aspect of the present invention is directed to a system for measuring the length of
plate on roll table wherein the fixed scale zero coincides to shear blade position and the
reading increases in the direction of the plate movement.
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A still further aspect of the present invention is directed to a system for measuring the
length of plate on roll table wherein said monitor is adapted to act as human machine
interface to indicate various lengths to the operator.
A still further aspect of the present invention is directed to a system for measuring the
length of plate on roll table wherein said CCTV camera is adapted to generate analog output
signal and said monitor is adapted to process said analog signals from the CCTV camera.
A still further aspect of the present invention is directed to a system for measuring the
length of plate on roll table comprising VCR means for video recording of the operation
involving said CCTV cameras.
According to another aspect of the present invention directed to a system for measuring the
length of plate on roll table wherein said display /monitor means is in the operator's cabin to
display the length.
A still further aspect of the present invention directed to a method for non-contact length
measurement for application in rolling mill comprising the step of measuring the length of
plate on roll table using the aforesaid system.
A still further aspect of the present invention directed to a method for non-contact length
measurement, comprising:
fixed scale zero reference coinciding with shear blade position and reading increase in the
direction of plate movement;
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scale mark is picked up by said CCTV camera and displayed in a monitor in the operator's
cabin;
movement of the plate is stopped at required length by the operator and the plate is held
and cut into pieces.
According to yet another aspect of the present invention directed to a method for non-
contact length measurement wherein the process is repeated till the full plate is cut into
required pieces.
The description of the present invention, its objects and advantages are explained in greater
details in relation to the following non-limiting exemplary illustrative figures.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1 is the illustration of the principle of length measurement of plate length on roll
table in conventional method;
Figure 2 is the illustration of the schematic arrangement of CCTV camera for length
measurement of plates on roll table according to the present invention;
Figure 3 is the illustration of actual in-plant trial of CCTV based length measurement system
for measuring cutting/shearing length of plates.
Figure 4 is the illustration of the arrangement of scale in the present CCTV based length
measurement method of the invention.
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DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
Reference is first invited to the accompanying Figure 1 wherein the schematic diagram of
the roll table and static shear arrangement in existing process has been illustrated. Figure
1 explains the basic principle of length measurement. The difference between the initial and
final length reading gives the true length. In this case the initial reading is always Zero and
what ever is the final reading gives the length of plate.
In the existing system, the plate moves from left to right. First the irregular end of the
rolled plate is sheared in a line perpendicular to edge along the length. Fixed scale zero
coincides to shear blade position and reading increases opposite to plate movement. A chalk
marker marks the plate to the required length to be cut. The operator cuts the plate guided
by the chalk mark by operating the shear blade. The marker again marks the required
length to be cut in sequence. This process is repeated till the full length of the plate is cut
into required pieces, leaving some scrap/short piece/s.
Reference is now invited to the accompanying Figure 2 which illustrates the new scheme of
length measurement system according to the invention is implemented for cutting/shearing
plates to desired length with desired degree of accuracy and tolerance, wherein the fixed
scale zero coincides with the shear blade position and reading increases in direction of plate
movement. For each standard length, one camera is installed so that error due to parallax
can be avoided. The cameras are put opposite side of the scale on stand rigidly mounted,
without obstruction of line of sight and on standard length verified. This arrangement leaves
no chance of any error in measurement maintaining desired accuracy.
Figure 3 actually shows the Photograph of CCTV camera installed at work site for trial. The
accompanying Figure 3 also illustrates the actual location of the CCTV cameras along the
roll table in front of the operators cabin for sensing scale markings are picked up by
correspondingly located CCTV camera and displayed in a monitor in operators' cabin. As the
plate is moved by the operator at desired speed by operating the roll table drive motors, he
stops the movement of plate as the required length is displayed on the monitor. The plate is
hold by finger and cut into desired number of pieces. This process is repeated till the full
plate is cut into required pieces. In the present method, neither chalk mark nor the marker
is required. One number of switcher is operatively connected for selecting the CCTV camera
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for the corresponding length and the CCTV camera provides output signal to
switcher/monitor such as to provide the length sensed by the camera in operator's cabin
through a display unit to display the front end of plate against standard scale. Said monitor
is adapted to act as human machine interface to indicate various lengths to the operator
and the system comprising VCR means for video recording of the operation involving said
CCTV cameras.
Reference is next invited to the accompanying Figure 4 that illustrates the arrangement of
scale for CCTV based measurement of plate length. The scale is made of mild steel which is
calibrated and painted for favoring clear detection and capture of reading by the CCTV. The
scale is placed opposite to the camera and the plate whose length is to be measured passes
through in front of the scale under clear unobstructed viewing by the CCTV lens.
Thus according to the present invention, a non-contact method of length measurement of
plate on roll table has been developed using a system of CCTV camera and monitoring unit.
The length is displayed in the operator's cabin. This helps in cutting the rolled products as
per the required dimension. The system does not require any manual intervention in the
rolling line.
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We Claim:
1. A system for measuring the length of plate on roll table comprising:
said roll table for plate movement provided with a standard length measuring scale at one
side along the length of the table and plurality of CCTV cameras for each standard length on
the other side facing the standard scale;
switcher/monitor means adapted for selecting the CCTV camera for the corresponding
length and indicate the various length to the operator ;
a CCTV camera means for providing the required output signal to said switcher; and
a display means adapted to display the front end of plate against said standard scale.
2. A system for measuring the length of plate on roll table as claimed in claim 1 wherein the
fixed scale zero coincides to shear blade position and the reading increases in the direction
of the plate movement.
3. A system for measuring the length of plate on roll table as claimed in anyone of claims 1
or 2 wherein said monitor is adapted to act as human machine interface to indicate various
lengths to the operator.
4. A system for measuring the length of plate on roll table as claimed in anyone of claims 1
to 3 wherein said CCTV camera is adapted to generate analog output signal and said
monitor is adapted to process said analog signals from the CCTV camera.
5. A system for measuring the length of plate on roll table as claimed in anyone of claims 1
to 4 comprising VCR means for video recording of the operation involving said CCTV
cameras.
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6. A system for measuring the length of plate on roll table as claimed in anyone of claims 1
to 5 wherein said display /monitor means is in the operators' cabin to display the length.
7. A method for non-contact length measurement for application in rolling mill comprising
the step of measuring the length of plate on roll table using the system as claimed in
anyone of claims 1 to 6.
8. A method for non-contact length measurement as claimed in claim 7 comprising:
fixed scale zero coinciding to shear blade position and reading increase in the direction of
plate movement;
scale mark is picked up by said CCTV camera and displayed in a monitor in the operator's
cabin;
movement of the plate is stopped at required length by the operator and the plate is held
and cut into pieces.
9. A method for non-contact length measurement as claimed in claim 8 wherein the process
is repeated till the full plate is cut into required pieces.
10. A system for measuring the length of plate on roll table and a method for non-contact
length measurement using such system substantially as hereindescribed and illustrated with
reference to the accompanying figures.
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A non-contact method of length measurement of plate on roll table involving CCTV camera
and monitor unit. The length is displayed in the operator's cabin to operate shearing of plate
to desired length. This method helps in cutting the rolled products according to the required
dimension within desired accuracy and tolerance range. The system does not require any
manual intervention in the rolling line.