Automatic Material Control System Based on PLC

The automatic control system of continuous batching conveying 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. It is an important link in CIMS and has been widely used in the world. This technology is also being gradually applied to many industries in China.

After joining the WTO, China's commodity distribution and distribution service market will gradually expand the open areas and scope. And logistics is the key issue of enterprise development, logistics will affect the overall survival and development of enterprises. In 2000, the logistics cost accounted for 16.7% of the gross domestic product (GDP), while in the United States it was only below 10%. In particular, there is a huge gap between the logistics equipment level of enterprises and developed countries, mainly manifested in the low transportation efficiency and the astonishing waste in the logistics process. We know that the gap is the 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 the transportation distribution in the logistics system. It is a system that can automatically store and take out materials.

Material automatic control system Process production control

The logistics automatic control system is mainly to control the conveying system to complete its material conveying tasks. There are elevators and conveying lines at the entrance and exit of materials. In this way, a closed circulation conveying line system is formed within the scope of the warehouse, production workshop and packaging workshop, which can reach each production location smoothly and at the same time. All relevant materials and finished products used in the production process must be packed in boxes with barcodes for transportation and loading. Under the action of the production order issued by the production management system, the material enters the conveying system from the designated entrance.

Overall control requirements: the system consists of hoppers, conveyor belts, and detection systems. The batching device can automatically identify the status of the trucks and automatically batch the trucks. When the trucks are full, the batching system will automatically stop batching. Stop batching and automatically feed when the material in the hopper is insufficient.

The process control requirements are as follows:

(1) Initial state

       After the system is started, the red light L2 is off and the green light L1 is on, indicating that the car is allowed to drive into the load. The outlet D2 of the hopper is closed, if the material level sensor S1 is set to OFF (the material in the hopper is not full), the feed valve is opened to feed (D4 is on). When S1 is set to ON (the material in the hopper is full), stop feeding (D4 is off). 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, start the motor M4, after 2S, then start M3, and then after 2S Start M2, then start M1 after 2S, and then open the discharge valve (D2 is on) after 2S, 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 M1 stops for 2S, M3 stops after M2 stops for 2S, and M4 finally stops after M3 stops for 2S. At the same time, the red light L2 goes out and the green light L1 is on, indicating that the car can be driven away.

(3) Shutdown control

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

The structure of the PLC control program of the system

In the automatic batching and loading control system programmed with basic logic instructions, the feed valve is controlled by the material level sensor S1. S1 has no monitoring signal, indicating that the material is not full, and feeds after 5S; S1 has a monitoring signal, indicating that the material is full. Stop Feed. The start of the batching system can be realized through the limit switch SQ1 under the platform scale. When the car enters the loading position, under the action of its own weight, turn on SQ1, and the batching system starts; when the car is loaded to the tonnage, the limit switch SQ2 is turned off, and the batching stops.

Use the ladder diagram language to compile the PLC control program. The control program embodies the logistics control method and structure in a clear linear modular approach. It can be divided into the following parts:

①. Motion equipment/conveying path control

Operate all belt conveyors, roller conveyors and elevators in the required mode to ensure smooth and continuous movement of containers on the conveyor line. According to the path identification code of the container, control the conveyor line and other conveyor line exchange devices to realize the path selection in the container 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 the boxes on the conveyor line.

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

It mainly deals with the information exchange with the upper computer, including communication protocol, message format, communication encoding and decoding, and error diagnosis, etc. Use the data block to establish a record storage area to store the information of the container. Use the function block to realize the operation of the database, and provide the control basis for the path identification of the conveying system.

④. Data processing of MCGS configuration monitoring

Cooperating with MCGS monitoring, data processing mainly includes alarm processing, data processing of equipment operation status, etc.

⑤. Lack of material replacement warehouse

When the batching process is completed, the warehouse number has been dispensed, and the system will automatically prompt an alarm for lack of materials. Press the [Shortage Material Change] button, a dialog box will pop up, enter the warehouse number to be replaced, confirm, and then press the [Clear Fault] button to complete the warehouse change and enter the automatic batching state. Note: After changing bins, the order of ingredients must be changed. Set the shortage warehouse to 0, and set the newly replaced warehouse number to be consistent with the original order, which is convenient for report statistics.

It can be seen from the analysis that this system is a control process that operates in a certain order. Using the method can make each work step act in strict order. If the program is programmed with step instructions, the program is easier to understand and read.

The material automatic control system has been debugged and operated, and its production material automatic distribution capacity can meet the production needs of various products, and can meet 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, continuously transporting materials in strict accordance with the program instructions. The investment in this system has enabled the enterprise to completely abandon manual operations, and the batching method has entered into scientific and data-based production, and individuals have also been freed from harsh working environments such as dust and noise. Not only that, the stable high-quality ingredients have brought about the improvement of product quality. After the system is put into use, the main technical indicators such as product density and false specific gravity have been greatly improved. Therefore, the automatic logistics control system is indeed an important tool in the field of manufacturing and processing, especially in large-scale, high-efficiency, and continuous production logistics companies. A technology worth promoting. The whole system has been put into use now, and it has important reference value for the development and design of the logistics automation system such as the computer integrated manufacturing process of enterprises and enterprises in the network information age and the network sales field.