Shandong Aluminum Co., Ltd. electrolytic aluminum plant 20kg continuous casting machine was purchased from Fushun aluminum plant in 1985, mainly used for continuous automatic stacking 20kg aluminum ingots, design capacity of 15t / h. The main work flow is: the high-temperature aluminum water flows from the melting furnace to the mold. When the casting machine moves forward and the natural cooling is performed, the aluminum ingot is ejected from the mold by the impact of the mold and the metal object when reaching the vicinity of the water tank. And fall into the sink.
As the cylinder of the pull-in cylinder moves forward, it is cooled by circulating water; after cooling, it is automatically stacked by the system. During the stacking process, every five aluminum ingots are one layer, and the aluminum ingots in the same layer cross one another in the upward and downward direction, and the orientation of the aluminum ingot is controlled by lifting the cylinder and the ingot cylinder. The direction of stacking between the aluminum ingot layers and the layers alternates. After stacking to a set height, it is transported by a forklift.
The original automatic control system uses F-30 series PLC as the controller, and the limit switches are all impact mechanical limit switches. Due to problems in design and programming, after several years of operation, the system has exposed many problems.
1 limit switch failure rate is high, often crashed; and often send a signal. In the system, the aluminum ingot is released from the mold by the elastic force generated by the metal impact. The vibration generated by the impact of the aluminum ingot is enough to cause the mechanical limit switch contact to malfunction.
2 The system often malfunctions. In severe cases, equipment accidents may occur due to malfunctions. For example, if the lifting limit switch is operated by mistake when the claw is lifted, the trolley will move to the left when the height is not enough, causing the claw to collide with the platform, resulting in both damage.
3 The gripping of the mechanical claws is not reliable, causing chaos in the system and increasing the workload of the operation. The system is heavily worn, especially the limit switches and the mechanical jaws, which need to be checked and repaired almost every week. The amount of maintenance is large, and the equipment operation rate is reduced.
In response to the problems existing in the system, the company improved some of the parts that affect the operation of the system in 2002.
First, the electronic control system to improve the 20kg aluminum ingot continuous casting machine electrical control system and improvement, using the current popular CPMIA programmable controller, select the basic unit CPM1A-40CDR-A as a CPU unit, the I / O points for 24/16, the output is relay output. The CPM1A-20EDR expansion unit is selected to meet the requirements of the system design. The I/O points of this expansion unit are 12/8, and relay outputs are used.
The limit switch adopts non-contact photoelectric switch and proximity switch, and the action is more accurate. Combining the actual conditions of production with programming, various non-normal factors are fully taken into consideration to make the system more stable, reliable and safe.
For safety reasons, the control loop of the mechanical jaw lifting motor adds a rise limit switch. The use of a mechanical switch for the lifting limit is relatively reliable because only the limit switch is actuated in the event of an accident, and the number of operations is small. If an electronic switch is used, there is a problem that the lifetime affects reliability. The selection of other switches can be based on the size of the scene space, 20 ~ 30cm photoelectric switch or TL-N10ME124V2 ~ 3cm proximity switch can be.
The output action of the PLC is isolated by the intermediate relay to prevent external faults (such as stringing into high voltage, etc.) from causing the PLC to be damaged. At the same time, it is convenient for maintenance. The fault point can be judged according to whether the corresponding relay acts to narrow the search range.
In order to facilitate on-site dispatching and emergency handling, a manual/stop/automatic control selection function is also set, and the manual/automatic conversion is realized by a master switch.
Second, the main features of the improvement 1 Although the use of cylinder grabs more reliable movement, but in practice due to a variety of factors, such as the size of the cast aluminum ingot is controlled manually, so the size of each aluminum ingot can not be the same; The reason that the five aluminum ingots are not regularly arranged due to the wear of the mechanical mechanism, etc. Occasionally, the ingot seizure may occur. At this point, the corresponding button can be pressed to input a signal to the control program. The lifting and lowering of the mechanical claw is automatically disconnected by the soft switch in the program, and the operator can manually adjust the button according to the corresponding button.
2 Before the transformation, the mechanical jaws are raised to a sufficient height and the left line is ready for the next cycle. Due to programming and limit switch malfunction, the mechanical jaws do not rise to the set height and the left line Backhaul, collision with the platform. The corresponding protection measures were taken in the control program during the transformation. During the process of left or right of the claws, the system will automatically adjust and raise the height of the claws to avoid colliding with the platform.
3 The input signal of each limit switch is processed to eliminate “jitterâ€. The signal input to the programmable controller for each limit switch is added with a delay time of 0.5 to 1 s depending on the actual situation. The system malfunctioned due to the malfunction of the limit switch. Moreover, the programming adopts the “state†method, in which each step of the mechanical claw is used as a state, and the conversion of each state is controlled only by one input signal, thereby greatly enhancing the reliability of the system control. The power supply of the limit switch does not use the PLC's own DC24 power supply, but uses an external power supply to avoid burning the PLC due to high power consumption.
5 The actions of pushing, pulling, lifting, picking, turning, grasping the spindle, steering and trolley cylinders can be manually, stopped, and automatically controlled, which is convenient and flexible to use. When the master switch is turned to the "middle position", it is in the disconnected state and cannot be controlled manually or automatically.
5 If the claws are turned, they can be adjusted manually at any time.
6 The cooperation of each action sequence is controlled by the program and it is accurate and reliable.
Before the improvement, the operating workers not only had a large workload, but the actual capacity of the equipment was only 1/3 of the design capacity. After the improvement, the number of operating workers was reduced from 3 to 1, and the investment needed for the reconstruction was only 700 yuan. The economic benefits were significant. The improvement is based on the original aluminum ingot production combined with existing equipment, and has implications for the equipment transformation of small and medium-sized electrolytic aluminum plants.
As the cylinder of the pull-in cylinder moves forward, it is cooled by circulating water; after cooling, it is automatically stacked by the system. During the stacking process, every five aluminum ingots are one layer, and the aluminum ingots in the same layer cross one another in the upward and downward direction, and the orientation of the aluminum ingot is controlled by lifting the cylinder and the ingot cylinder. The direction of stacking between the aluminum ingot layers and the layers alternates. After stacking to a set height, it is transported by a forklift.
The original automatic control system uses F-30 series PLC as the controller, and the limit switches are all impact mechanical limit switches. Due to problems in design and programming, after several years of operation, the system has exposed many problems.
1 limit switch failure rate is high, often crashed; and often send a signal. In the system, the aluminum ingot is released from the mold by the elastic force generated by the metal impact. The vibration generated by the impact of the aluminum ingot is enough to cause the mechanical limit switch contact to malfunction.
2 The system often malfunctions. In severe cases, equipment accidents may occur due to malfunctions. For example, if the lifting limit switch is operated by mistake when the claw is lifted, the trolley will move to the left when the height is not enough, causing the claw to collide with the platform, resulting in both damage.
3 The gripping of the mechanical claws is not reliable, causing chaos in the system and increasing the workload of the operation. The system is heavily worn, especially the limit switches and the mechanical jaws, which need to be checked and repaired almost every week. The amount of maintenance is large, and the equipment operation rate is reduced.
In response to the problems existing in the system, the company improved some of the parts that affect the operation of the system in 2002.
First, the electronic control system to improve the 20kg aluminum ingot continuous casting machine electrical control system and improvement, using the current popular CPMIA programmable controller, select the basic unit CPM1A-40CDR-A as a CPU unit, the I / O points for 24/16, the output is relay output. The CPM1A-20EDR expansion unit is selected to meet the requirements of the system design. The I/O points of this expansion unit are 12/8, and relay outputs are used.
The limit switch adopts non-contact photoelectric switch and proximity switch, and the action is more accurate. Combining the actual conditions of production with programming, various non-normal factors are fully taken into consideration to make the system more stable, reliable and safe.
For safety reasons, the control loop of the mechanical jaw lifting motor adds a rise limit switch. The use of a mechanical switch for the lifting limit is relatively reliable because only the limit switch is actuated in the event of an accident, and the number of operations is small. If an electronic switch is used, there is a problem that the lifetime affects reliability. The selection of other switches can be based on the size of the scene space, 20 ~ 30cm photoelectric switch or TL-N10ME124V2 ~ 3cm proximity switch can be.
The output action of the PLC is isolated by the intermediate relay to prevent external faults (such as stringing into high voltage, etc.) from causing the PLC to be damaged. At the same time, it is convenient for maintenance. The fault point can be judged according to whether the corresponding relay acts to narrow the search range.
In order to facilitate on-site dispatching and emergency handling, a manual/stop/automatic control selection function is also set, and the manual/automatic conversion is realized by a master switch.
Second, the main features of the improvement 1 Although the use of cylinder grabs more reliable movement, but in practice due to a variety of factors, such as the size of the cast aluminum ingot is controlled manually, so the size of each aluminum ingot can not be the same; The reason that the five aluminum ingots are not regularly arranged due to the wear of the mechanical mechanism, etc. Occasionally, the ingot seizure may occur. At this point, the corresponding button can be pressed to input a signal to the control program. The lifting and lowering of the mechanical claw is automatically disconnected by the soft switch in the program, and the operator can manually adjust the button according to the corresponding button.
2 Before the transformation, the mechanical jaws are raised to a sufficient height and the left line is ready for the next cycle. Due to programming and limit switch malfunction, the mechanical jaws do not rise to the set height and the left line Backhaul, collision with the platform. The corresponding protection measures were taken in the control program during the transformation. During the process of left or right of the claws, the system will automatically adjust and raise the height of the claws to avoid colliding with the platform.
3 The input signal of each limit switch is processed to eliminate “jitterâ€. The signal input to the programmable controller for each limit switch is added with a delay time of 0.5 to 1 s depending on the actual situation. The system malfunctioned due to the malfunction of the limit switch. Moreover, the programming adopts the “state†method, in which each step of the mechanical claw is used as a state, and the conversion of each state is controlled only by one input signal, thereby greatly enhancing the reliability of the system control. The power supply of the limit switch does not use the PLC's own DC24 power supply, but uses an external power supply to avoid burning the PLC due to high power consumption.
5 The actions of pushing, pulling, lifting, picking, turning, grasping the spindle, steering and trolley cylinders can be manually, stopped, and automatically controlled, which is convenient and flexible to use. When the master switch is turned to the "middle position", it is in the disconnected state and cannot be controlled manually or automatically.
5 If the claws are turned, they can be adjusted manually at any time.
6 The cooperation of each action sequence is controlled by the program and it is accurate and reliable.
Before the improvement, the operating workers not only had a large workload, but the actual capacity of the equipment was only 1/3 of the design capacity. After the improvement, the number of operating workers was reduced from 3 to 1, and the investment needed for the reconstruction was only 700 yuan. The economic benefits were significant. The improvement is based on the original aluminum ingot production combined with existing equipment, and has implications for the equipment transformation of small and medium-sized electrolytic aluminum plants.
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