CLIAMS:WE CLAIM:
1. An automated system for closed loop precise length cutting of metal sheets comprising:
a flying cut off shear having a cutter die with operative shear blade to cut metal sheets in the running line;
a flying wheel with clutch and brake operatively connected to said flying cut off shear;
motor drive unit providing for control of the cut motion of the cutter die there between the cutter die stationary position at home and cutting position on command based on means for length calculation with shear blade disposed above the point of cut on the sheet;
said flying cut off shear on receiving signal for cut adapted to engage said clutch of flying wheel and disengage said brake whereby the shear moves downwards to make the cut and thereafter moves up by the flying wheel action when said bakes again engage and clutch disengage to return to the home position and await signals to automatically repeat the next cut motion.

2. The automated system as claimed in claim 1, wherein
said cutter die comprises an upper die and a lower die to cut the metal sheet, said upper die and lower die is adapted to move between said home position and said cutting position;
said motor drive unit comprising a die accelerator motor to move said upper and the lower die form said home position to said cutting position in a speed matched with running speed of the metal sheet in the line to facilitate cutting of the metal sheet in running condition;
said means for length calculation adapted to operate the flying shear upon reaching the cutting position once length criteria and speed matching criteria are fulfilled.

3. The automated system as claimed in claim 2 , wherein the die accelerator motor drives the upper and lower die through a rack-pinion arrangement and a gear assembly to calibrate movement of the die corresponding to one revolution of the motor.

4. The automated system as claimed in anyone of claims 2 or 3, wherein the die accelerator motor includes a low inertia AC Motor with an integrated a resolver to measure the position of the die during movement.

5. The automated system as claimed in anyone of claim 1 to 4 comprising a cut engaging sensor disposed in the lower die to detect reaching of shear blade housed in the die at the cutting position and thereby generate an indicating signal.

6. The automated system as claimed in anyone of claim 1 to 5, wherein said length calculating means includes end of material sensor, line pulse generator, and a reference position sensor.

7. The automated system as claimed in anyone of claim 1 to 6, wherein said length calculating means generates the cutting command once the length criteria and speed matching criteria are fulfilled and control PLC based clutch and brake of the flying shear to execute the cut command.

8. The automated system for precise length cutting of metal sheets as claimed in anyone of claim 1 to 7, comprises AC servo drive to feed current to the low inertia AC motor, said AC servo drive includes an integrated position detection module for single axis motion control.

9. The automated system for as claimed in anyone of claims 1 to 8, comprises
an operator console unit for operating the shear system with a video unit for feeding process parameters including required length, batch details and like;
a programmable HMI Station for parameterization and diagnosis of the AC servo drive generating report related to production of the metal sheet.

10. The automated system as claimed in anyone of claims 1 to 8 wherein said cutter die is configured to cut the corrugate metal sheet in desired length with an error in the length between 0 to +5 mm in the running condition in a galvanized coil corrugating line.

11. A method for cutting the metal sheet in desired length in running condition involving the automated system for closed loop precise length cutting of metal sheets as claimed in anyone of claim 1 to 8, comprising
accelerating the said upper and the lower die to direct them from the home position to the cutting position by involving the die accelerator motor till the upper and the lower die speed matches with speed of the running metal sheet in the line upon receiving command to perform a cutting operation based on length calculation;
locking the speed of the upper and the lower die after matching with the speed of the running metal sheet till the shear blade of the die reaches at the cutting point of the metal sheet;
sending the indicating signal generated by the cut engaging sensor upon detecting the reaching of the shear blade at the cutting position to flying cut off shear housed in the die;
engaging clutch of the flying shear and disengaging brakes to direct the shear blade in downwards direction and cutting the metal sheet;
involving flying wheel action and engaging the brakes and disengaging clutch to move the die with the shear blade at the home position for next cut motion.
,TagSPECI:FIELD OF THE INVENTION:
The present invention relates to precise length cutting of metal sheets in their running condition. In particular, the present invention is directed to develop a system for precise length cutting of metal sheets in their running condition. The present system is adapted to be implemented in a Galvanized Coil Corrugating line to facilitate operation of the Galvanized Coil Corrugating line at its rated capacity to serve productivity aspect simultaneously produce metal sheets with minimum error in the length to serve the qualitative aspect of the Galvanized Coil Corrugating line.

BACKGROUND OF THE INVENTION:
Galvanized Coil Corrugating (GC) Line is an integral part of any metal processing plants which are engaged in production of galvanized metal articles. In a typical metal processing plant engaged in the production of galvanized metal sheet, the GC line is used for cutting corrugated metal sheet in a desired length at their running Line.
The process for cutting corrugated metal sheet in a desired length in the GC Line has two important aspects, first being quantitative i.e. productivity and second qualitative i.e. length accuracy, cut edge quality etc.
The productivity aspects of the GC line depends on maximum possible line speed which varies based on cut length under consideration. The shorter the length to be cut, lower the line speed, because in case of producing metal sheet of shorter length, frequency of complete cut sequence is needed to be high. For longer lengths, system may have to wait between two cut sequences, thus the frequency of complete cut sequence will be low. The high speed cutting naturally requires high torque motor with low inertia so that it can be accelerated to a very high speed in short time, say within half a second. For a fixed thickness of sheet, the productivity (Tons/ Hour) depends upon line speed irrespective of cut length.
The second aspect of cutting is qualitative and it depends on the finished product i.e. length of the metal sheet after the cutting operation. In GC line acceptable range for error in the length of the metal sheet lies between 0 to +5 mm. It also means that no negative length is acceptable and positive error beyond 5 mm is also not acceptable as it creates problem during handling and packaging of the metal sheets. The edge quality is also a decisive factor of the qualitative aspect of the GC line and it depends upon speed synchronization between die which carry cutting blades and material speed, sharpness and mechanical adjustment of blade, and precision in flying shear operation. Blunt edges cause quality issues during application at customer site.
In a conventional GC line cut off shear or the cutting blades includes flying cut off shear and it is operated by a flying wheel with clutch and brake. This cut off press finally operates the die which cut the corrugated metal sheet in the running Line. The integrated line operation is controlled by using a control unit.
In the conventional GC line, online close loop shear system involves DC motor and DC drive and the control unit includes microcontroller based field sensors/ interface such as Shaft encoders, operator desk etc.
The electrical system and control unit of such conventional GC line including the flying shear require frequent maintenance including spares. The line speed if the existing GC line is fixed significantly low compare to the driving capacity of the DC motor to motor sparking. E.g. in a typical GC line with DC motor for die acceleration having 91 rpm rated capacity is fixed to less than 30 rpm to avoid motor sparking at higher speed.
Thus there has been a need for developing a new system adapted to be implemented in a GC line to facilitated operation of the GC line at the rated capacity to serve the productivity aspect and simultaneously cut the metal sheets in desired length with an error in the length between 0 to +5 mm to serve the qualitative aspect of the GC line.

OBJECT OF THE INVENTION:
It is thus the basic object of the present invention is to develop an automatic system which would be adapted to cut metal sheet in a desired length in their running condition in a metal processing line.
Another object of the present invention is to develop an automatic system for precise length cutting of metal sheets which would be adapted to be implemented in a GC line to accurately cut corrugated metal sheets in a desired length with an error in the length between 0 to +5 mm.
Yet another object of the present invention is to develop an automatic system for precise length cutting of metal sheets which would be adapted to execute cutting operation in the GC line at the rated capacity of its driving motor to serve the productivity aspect of the GC line

SUMMARY OF THE INVENTION:
Thus according to basic aspect of the present invention there is provided an automated system for closed loop precise length cutting of metal sheets comprising:
a flying cut off shear having a cutter die with operative shear blade to cut metal sheets in the running line;
a flying wheel with clutch and brake operatively connected to said flying cut off shear;
motor drive unit providing for control of the cut motion of the cutter die there between the cutter die stationary position at home and cutting position on command based on means for length calculation with shear blade disposed above the point of cut on the sheet;
said flying cut off shear on receiving signal for cut adapted to engage said clutch of flying wheel and disengage said brake whereby the shear moves downwards to make the cut and thereafter moves up by the flying wheel action when said bakes again engage and clutch disengage to return to the home position and await signals to automatically repeat the next cut motion.

According to another aspect of the present invention, the present automated system comprises
said cutter die comprises an upper die and a lower die to cut the metal sheet, said upper die and lower die is adapted to move between said home position and said cutting position;
said motor drive unit comprising a die accelerator motor to move said upper and the lower die form said home position to said cutting position in a speed matched with running speed of the metal sheet in the line to facilitate cutting of the metal sheet in running condition;
said means for length calculation adapted to operate the flying shear upon reaching the cutting position once length criteria and speed matching criteria are fulfilled.

According to a further aspect in the present automated system, the die accelerator motor drives the upper and lower die through a rack-pinion arrangement and a gear assembly to calibrate movement of the die corresponding to one revolution of the motor.

According to yet another aspect in the present automated system, the die accelerator motor includes a low inertia AC Motor with an integrated a resolver to measure the position of the die during movement.

According to a further aspect, the present automated system comprises a cut engaging sensor disposed in the lower die to detect reaching of shear blade housed in the die at the cutting position and thereby generate an indicating signal.

According to another aspect in the present automated system, the length calculating means includes end of material sensor, line pulse generator, and a reference position sensor.

According to another aspect in the present automated system, the length calculating means generates the cutting command once the length criteria and speed matching criteria are fulfilled and control PLC based clutch and brake of the flying shear to execute the cut command.

According to yet another aspect, the present automated system for precise length cutting of metal sheets comprises AC servo drive to feed current to the low inertia AC motor, said AC servo drive includes an integrated position detection module for single axis motion control.

According to a further aspect, the present automated system comprises
an operator console unit for operating the shear system with a video unit for feeding process parameters including required length, batch details and like;
a programmable HMI Station for parameterization and diagnosis of the AC servo drive generating report related to production of the metal sheet.

According to yet another aspect in the present automated system, the said cutter die is configured to cut the corrugate metal sheet in desired length with an error in the length between 0 to +5 mm in the running condition in a galvanized coil corrugating line.

According to another aspect of the present invention there is provided a method for cutting the metal sheet in desired length in running condition involving the present automated system for closed loop precise length cutting of metal sheets, the said method comprising
accelerating the said upper and the lower die to direct them from the home position to the cutting position by involving the die accelerator motor till the upper and the lower die speed matches with speed of the running metal sheet in the line upon receiving command to perform a cutting operation based on length calculation;
locking the speed of the upper and the lower die after matching with the speed of the running metal sheet till the shear blade of the die reaches at the cutting point of the metal sheet;
sending the indicating signal generated by the cut engaging sensor upon detecting the reaching of the shear blade at the cutting position to flying cut off shear housed in the die;
engaging clutch of the flying shear and disengaging brakes to direct the shear blade in downwards direction and cutting the metal sheet;
involving flying wheel action and engaging the brakes and disengaging clutch to move the die with the shear blade at the home position for next cut motion.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1 shows a preferred embodiment of the GC line with the system of the present invention.
Figure 2 shows variation of the material velocity and cutter velocity with time in a GC line with the system of the present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES:
As stated herein before, the present invention is directed to develop a new GC line having system which will serve the both qualitative and productivity aspect of the GC line.
The basic requirement for developing a GC line is to drive the die from its standstill home position to cutting position (preferably positioned within 800 mm) in a very high speed preferably 75 meter per minute and then immediately stopping the die and reversed back to the home position for next cut cycle. In normal GC line a typical cut cycle took 2–3 seconds based on length and line speed. This kind of driving can only be fulfilled using low inertia motor.
In the present invention discloses an automatic system for precise length cutting of metal sheets. The system of the present invention is adapted to incorporate in the GC line to serve the basic requirement of the GC line.
The system of the present invention basically includes a flying cut off shear having a cutter die with operative shear blade to cut metal sheets in the running line, a flying wheel with clutch and brake operatively connected to said flying cut off shear and motor drive unit providing for control of the cut motion of the cutter die there between the cutter die stationary position at home and cutting position on command based on means for length calculation with shear blade disposed above the point of cut on the sheet. The flying cut off shear on receiving signal for cut engage said clutch of flying wheel and disengage said brake whereby the shear moves downwards to make the cut and thereafter moves up by the flying wheel action when said bakes again engage and clutch disengage to return to the home position and await signals to automatically repeat the next cut motion. The present system includes a novel AC motor drive technology in the motor in the motor drive unit with a single axis motion control module.
Reference is first invited from the accompanying figure 1, which shows a preferred embodiment of the GC line with the system of the present invention. As shown in the said figure, the system of the present invention for precise length cutting of metal sheets in the GC line includes upper die (1) and lower die (2) moveable between the home position and cutting position to facilitate the cutting of the corrugated metal sheet (3) in their running Line (4). The cut off press operates the upper die (1) and the lower die (2).
The motor drive init includes a die accelerator motor (5) to move the upper and lower die (1, 2) form their home position to their cutting position. The die accelerator motor (5) drives the upper and lower die (1, 2) through a Rack and Pinion arrangement (6) and a gear (8) assembly. The Rack and Pinion arrangement (6) and a gear (8) assembly facilitate to calibrate movement of the die corresponding to one revolution of the motor.
In the present system, the die accelerator motor (5) is preferably a low inertia AC Motor with an integrated a resolver to measure the position of the die during movement.
During the operation of the present system, the upper and the lower die (1,2) remain in waiting mode at the home position and as soon as it receives command to perform a cutting operation based on length calculation, the die accelerator motor (5) quickly accelerate the upper and lower die (1, 2) to match with the speed of metal sheet running in the line and locks to the matched speed i.e. die and the metal sheet moves at same speed and the shear blade of the die reaches at the cutting point of the sheet.
A cut engaging sensor (7) is disposed in the lower die to detect the reaching of the shear blade at the cutting point and thereby generate an indicating signal. The signal is sent to flying cut off shear housed in the die and then clutch of flying shear gets engaged and brakes disengaged. The shear comes down and cuts the metal sheet. After the cutting operation the shears goes up due to flying wheel action and Brakes engage & clutch disengages once again to move the die in their home position for next command. This is entire one cut cycle.
In the present system line an AC servo drive (11) is used to feed current to the low inertia AC motor. A position detection module is also integrated with the AC servo drive for single axis motion control.
The length calculation is done by using a sensor assembly which includes end of Material sensor (14), line Pulse Generator (15), and a reference position sensor (13). Also a shaft encoder can be used to measure line speed and cut length of metal sheet. In a preferred embodiment of the present system a reverse over travel Limit switch (12) is used.
The present system also includes an Operator Console unit (9). The Operator Console unit is used for operating the Shear system. A Video unit (VDU) has also been installed in this unit for feeding process parameters such as required length, batch details etc. The console has several push buttons and selector switches to control the shear system and related auxiliaries. Main functions are Auto/ Manual, RUN, Emergency stop, Crop CUT etc.
A Programming cum HMI Station (10) is also installed for parameterization and diagnosis of the AC servo drive (11). The HMI station generates report related to production of the metal sheet.
In the present system line length calculating sensor assembly issued the cutting command once the length criteria and speed matching criteria are fulfilled and to execute the cut command a PLC is employed which controlled Clutch and Brake of flying shear.

RESULTS:
A GC line with the present system has been implemented in metal processing plant and the variation of the material velocity and cutter velocity time is plotted. The variation plot is shown in the accompanying figure 2. It is found that the in the GC line, the galvanized metal coil after in-line processing through forming stands for corrugation, is accurately cut within accuracy of 0 to +5 mm. The flying shear system runs reliable and on regular basis at speed of 40 meter per minute, and has been tested upto 60 rpm for 3 meter sheet length on trial basis.