Optimization of double length cutting program of flying shear and common fault treatment

　　1. Basic functions and composition of flying shear

　　In this rolling line, the flying shear is an important part of the auxiliary transmission equipment in the production line, which has a great impact on the normal production. In this bar rolling line, three start-up and stop flying shears produced by POMINI company are used, which are respectively located at the exit of the last stand of rolling line 1, at the exit of the last stand of rolling line 2, and at the exit of the last stand of finishing rolling line 2. In addition, there is a hot metal detector HMD related to the control function of the flying shear before and after the flying shear. The three flying shears, with the cooperation of the hot metal detector HMD, will complete the functions of head cutting, tail cutting, fixed length cutting and broken cutting. In the design, the flying shear can work in a circuitous or crank type. In addition, in order to change the inertia, the flywheel can be added. When the flying shear works in a circuitous mode, it is used to shear rolled pieces with high speed and small size. When the flying shear works in a crank mode, it is used to shear rolled pieces with low speed and large size. The purpose of adding the flywheel is mainly to increase the shear force.

　　The composition of the flying shear control system is mainly set on the operation station and transmitted to the database unit in ac450 through the communication network for storage, which is used for the application of flying shear control program. Ac450 gives the speed setting and additional torque setting of the flying shear control. The given value drives the motor through DCS600 double closed-loop speed regulation. A position sensor is installed on the shaft of the flying shear to transmit the flying shear position coding signal in 1:1. This feedback signal is transmitted to the flying shear position controller element npct-01 to form the position feedback value.
 

　　2. Working principle of flying shear

　　(1) Basic principle of flying shear

　　The segmented bar shearing process in rolling is to trigger the bar rolling speed calculation, bar length integrator and other functions in the program after a series of detection elements (HMD) before segmented shearing detect signals. The control program takes the speed setting value of the last rack as the speed benchmark to integrate the bar length. When the integral length is equal to the setting value lsetp of the multiple length, it sends a signal to start-h1 to start the multiple length shear for segmented shear; At the same time, the shear signal starts the start2 of the integration element to integrate the length of the next section, and the shear process circulates until the end of bar rolling.

　　In the control of start stop flying shear of this rolling line, the jog mode directly generates speed setting, which belongs to speed control mode, and the rest of the shear working modes belong to position control. In speed control, it is required to set the gain of speed loop and current loop to obtain faster rise time. In the process of position control, it is necessary to adjust the position gain, which will determine the time and accuracy of positioning function. In principle, the position control system is to add a position control outer loop on the basis of double closed-loop speed regulation to form a position control system.

　　Generally, there are the following requirements for position control:

　　① The motor torque shall not exceed the maximum allowable torque of the motor and mechanical system;

　　② It can complete the positioning action in the shortest time, and the positioning meets the specified accuracy requirements;

　　③ There shall be no overshoot in the control process, and the system shall be stable.

　　(2) Action process of flying shear

　　The flying shear cuts the billet while it is moving, so the cutting speed of the flying shear must be synchronized with that of the rolled piece, otherwise it will cause steel stacking. Due to the thickness of the rolled piece, the flying shear has a cutting angle when cutting people, so the speed component of the flying shear in the horizontal direction should be the same as the moving speed of the billet (in practical application, the speed of the cutting edge slightly exceeds the rolling speed when cutting the head).

　　To control the flying shear, it is necessary to understand the movement track of the flying shear and the speed of each point in the track. The rolling speed of the previous stand of the flying shear is directly proportional to the speed of the rolled piece. The flying shear control system obtains the speed of the rolled piece according to the speed of the previous rolling mill provided by the upper computer, and starts the flying shear after comprehensive judgment according to the shear length set on the operating platform and the signal sent by the photocell. The speed of the flying shear is uniformly accelerated between the start of the flying shear and the end of the acceleration of the flying shear. The speed of the flying shear is constant between the end of the acceleration of the flying shear and the coincidence of the cutting edge, which is equal to the set speed at the end of the acceleration of the flying shear. The speed of the flying shear between the coincidence of the cutting edge and the flying shear leaving the rolled piece is constant, which is equal to the actual speed of the flying shear when the cutting edge coincides. Then the flying shear returns to the starting position at a certain speed, The design requires that the flying shear can return to the waiting start position in the shortest time, and a deceleration motion is set in the program.
 

　　3. Remedial procedure for double length cutting of flying shear

　　In the production process, it is easy to be affected by the water vapor of the rolling line and other light sources, resulting in false signals. This will cause inaccurate length calculation, advance or delay of shear action, or even no cutting, and seriously affect the rolling rhythm and yield. This paper mainly aims at the situation that shear16 does not cut, and adds the control program of double length cutting to solve this problem.

　　The basic idea of the program is to use hmddi2.16 after shear16. When HMD detects the head of steel, it starts timing. This time is multiplied by the speed of the last rolling mill to obtain the length L1 passing through the HMD In order to be reliable, the length L2 is obtained by adding 5m to the set length of the double ruler. If the value of L1 is greater than the value of L2, it is considered that shear16 has not been cut to multiple lengths.

　　At this time, CP2 in the operation room sends out an audible and visual alarm to remind the operator, and automatically starts shear16 for double length cutting. The HMD after shear16 is an important detection element. Its sensitivity should be ensured and it should be maintained regularly. Keep in mind that various prerequisites for the start of flying shear, such as the start of hydraulic station and emergency stop interlock, must be linked into the added program. The original ABB program did not design the manual shearing function for shear16. When the flying shear does not act due to various reasons, the blank can only be broken, resulting in waste and hot stop. At the same time of completing the above-mentioned double length shearing remedy procedure, the function of manual shearing is added. The main principle of this function is to directly send the manual signal to the AC80 of the shears, and then start the flying shears.

　　Under the guarantee of the above two measures, the double length cutting of the flying shear can be completed, and a large amount of heat waste and shutdown can be reduced.
 

　　4. Common fault handling of flying shear

　　(1) Fault of excitation module

　　The flying shear uses DCS600 series rectifier module, and its excitation module is external. Based on the summary of previous experience, the rectifier bridge in the excitation module will fail, and the excitation fault is reported in cdp312. At this time, the rectifier bridge can be directly replaced. The cycle is generally 2 years. This fault can be solved by replacing the rectifier bridge regularly.

　　(2) Fan failure

　　Since the fan of rectifier operates for a long time, its bearing is damaged due to long-term wear. We can replace it after about 4 years of service, so as to avoid the failure of the fan due to the bearing.

　　(3) AC80 fault

　　AC80 is a small controller of ABB company. It can connect and expand I / O. The AC80 of share16 is connected to ac450 through af100 bus communication. When ac450 sends the start command, it mainly completes the sequence control and position control in the shear cycle of the flying shear. Its fault phenomenon is that the shear action is irregular, the stop position is not fixed, and the adjustment of the original position and encoder can not be solved. At this time, AC80 shall be replaced in time, and the operation procedure therein shall be guaranteed to be the final version. Since AC80 cannot upload programs, relevant programs should be backed up in time at ordinary times. Its characteristic is that only the backup computer can monitor the operation of the program online.
 

　　5. Conclusion

　　The situation of missing cutting in shear16 times of the length has greatly affected the production. It can cause a lot of hot shutdown time and hot waste. Since the implementation of the above double scale cutting remedial procedures, there has been no case that hear16 does not cut the double scale in the past two years, which has well supported the production.

　　Preventive measures have been taken for some common faults to avoid the occurrence of many problems. And strengthen the daily maintenance of the equipment, so that the operation of the equipment has been greatly improved. The operation is generally stable and can meet the needs of production.