Material automatic control system based on FX1N-40MR PLC

1. Introduction

The continuous batching conveying automatic control system is widely used in cement, coal, metallurgy, chemical industry, feed, food and other industries. It has the characteristics of comprehensive functions, strong flexibility and high cost performance, and is welcomed by continuous batching system integrators and users. The system integrates modern logistics technology, warehousing technology and automation technology, and is an important part of CIMS. It has been widely used abroad, and the technology is also gradually being applied to many industries in my country.

After joining the WTO, my country's commodity distribution and delivery service market will gradually expand the scope and range of opening up. Logistics is a key issue for enterprise development, and logistics will affect the overall survival and development of enterprises. In 2000, logistics costs accounted for 16.7% of the gross domestic product (GDP), while the United States was only less than 10%. In particular, there is a huge gap between the level of logistics equipment of enterprises and developed countries, mainly manifested in low transportation efficiency and amazing waste in the logistics process. We know that the gap is potential and development space. Therefore, improving the level of logistics equipment has become a top priority. The automatic batching vehicle is an important part of transportation distribution in the logistics system. It is a system that can automatically store and take out materials.

2. Material automatic control system process production control

The logistics automatic control system mainly controls the conveying system to complete its material conveying task. There are elevators and conveyor lines at the entrance and exit of the materials. In this way, a closed circulation conveyor line system that can smoothly reach various production locations is formed within the warehouse, production workshop and packaging workshop. All relevant materials and finished products used in the production process must be loaded into boxes with barcodes for transportation and loading. Under the action of the production instructions issued by the production management system, the materials enter the conveying system from the designated entrance. The logistics automatic control system is shown in Figure 1.

Overall control requirements: As shown in the figure, the system consists of a hopper, a conveyor belt, and a detection system. The batching device can automatically identify the presence of a truck and automatically batch the truck. When the truck is full, the batching system automatically stops batching. When the hopper is insufficient, the batching stops and the material is automatically fed.

The process control requirements are as follows:

(1) Initial state

After the system is started, the red light L2 goes out and the green light L1 comes on, indicating that the car is allowed to drive in for loading. The hopper outlet D2 is closed. If the material level sensor S1 is set to OFF (the hopper is not full of material), the feed valve opens to feed (D4 is on). When S1 is set to ON (the hopper is full of material), the feed stops (D4 goes out). Motors M1, M2, M3 and M4 are all OFF.

(2) Loading control

During the loading process, when the car enters the loading position, the limit switch SQ1 is set to ON, the red signal light L2 is on, and the green light L1 is off; at the same time, the motor M4 is started, and after 2S, M3 is started, and after another 2S, M2 is started, and after another 2S, M1 is finally started, and after another 2S, the discharge valve is opened (D2 is on), and the material is discharged through the hopper.

When the car is full, the limit switch SQ2 is ON, the hopper is closed, M1 stops after 2S, M2 stops after 2S of M1, M3 stops after 2S of M2, and M4 stops last after 2S of M3. At the same time, the red light L2 goes out and the green light L1 turns on, indicating that the car can drive away.

(3) Shutdown control

Turn off the start SD switch and the entire system of automatic batching and loading will stop running.

3. System Hardware Design

1. System Schematic Diagram

2. I/O configuration and wiring

In order to improve the reliability of the automatic control system and the working efficiency of the equipment, the system uses MITSUBISHI's FX1N-40MR PLC as the controller. According to the requirements of automatic batching and loading control, the designed I/O configuration and wiring are shown in Figure 3.

Motors M1~M4 are controlled by contactors KM1~KM4; in order to facilitate operator monitoring, signal lights can also be used to display the operating status of the motor.

4. System software design

1. Main program flow chart

2. Structure of the system's PLC control program

In the automatic batching and loading control system programmed with basic logic instructions, the feed valve is controlled by the material level sensor S1. If there is no monitoring signal from S1, it indicates that the material is not full, and the material is fed after 5S; if there is a monitoring signal from S1, it indicates that the material is full, and the feeding is stopped. The batching system can be started through the limit switch SQ1 under the scale. When the car drives into the loading position, under the action of its own weight, SQ1 is turned on and the batching system is started; when the car is loaded to the tonnage, the limit switch SQ2 is disconnected and the batching is stopped.

The PLC control program is compiled using ladder diagram language. The control program reflects the logistics control mode and structure in a clear linear modular method. It can be divided into the following parts:

①. Motion equipment/transport path control

All belt conveyors, roller conveyors and elevators are operated in the required mode to ensure that the cargo boxes can run smoothly and continuously on the conveyor line. According to the path identification code of the cargo box, the conveyor line and other conveyor line exchange devices are controlled to realize the path selection in the cargo box transportation.

②. Data processing of automatic identification system

The barcode laser scanner communicates with the real-time database of the PLC to complete the automatic identification of cargo boxes on the conveyor line.

③. Communication interface of host computer production management system/real-time database management system

It mainly handles information exchange with the host computer, including communication protocol, message format, communication encoding and decoding, and error diagnosis. It uses data blocks to establish a record storage area to store the information of the cargo box. It uses function blocks to operate the database and provide control basis for the path identification of the conveying system.

④. Data processing of MCGS configuration monitoring

In conjunction with MCGS monitoring, the data processing carried out mainly includes alarm processing, data processing of equipment operating status, etc.

⑤. Change warehouse due to lack of materials

During the batching process, if the material in the bin number has been fully prepared, the system will automatically prompt a material shortage alarm. Press the [Change bin due to material shortage] button, a dialog box will pop up, enter the bin number to be replaced, confirm, and then press the [Clear fault] button to complete the bin change and enter the automatic batching state. Note: After changing the bin, the batching order must be changed. Set the bin with material shortage to 0, and set the newly replaced bin number to be consistent with the original order for easy report statistics.

After analysis, it can be known that this system is a control process that moves in a certain sequence. The use of step instructions can make each step move strictly in sequence. If the program is programmed using step instructions, the program will be easier to understand and convenient to read.

V. Conclusion

After debugging and operation, the automatic material distribution capacity of the material control system can meet the production needs of various products and the high-level and high-efficiency operation of the equipment and production of related logistics companies. In modern industrial control, the system is like a tireless porter, which continuously transports materials in strict accordance with program instructions. The investment of this system has enabled enterprises to completely abandon manual operation, and the batching method has entered scientific data production, and individuals have also been freed from the harsh working environment such as dust and noise. Not only that, stable and high-quality batching has brought about improved product quality. After the system was put into use, the main technical indicators such as product density and false specific gravity have been greatly improved. Therefore, the logistics automatic control system is indeed a technology worth promoting in the field of production and processing, especially in the field of large-scale, high-efficiency and continuous production of logistics companies. The entire system has been put into use, and it has important reference value for the development and design of logistics automation systems such as computer integrated manufacturing processes of enterprises and institutions in the network information age and network sales.