Weighing and loading of granular fillers in industrial production is a common production process. Some bulk materials such as gunpowder are highly hazardous to fill manually. There is also lime, which generates a lot of dust, and when manual filling is used, the operator will inhale the dust into his lungs, which is very harmful to the human body. Therefore, the realization of automatic weighing and filling of bulk materials can improve production efficiency, reduce the labor intensity of workers and ensure the personal safety of operators. Automatic weighing and filling process is a key and complex process in the whole filling production line. This paper introduces Siemens S7-300 PLC in the granular filler weighing and filling system applications, equipment can be realized such as lime, urea, gunpowder and other granular filler automatic weighing and loading, can be widely used in petrochemical, fertilizer, feed, building materials, and other industries, automatic weighing and packaging of bulk materials.

2. Filling system composition and working principle of granular filler automatic weighing is divided into two steps: coarse weighing and fine weighing. First set the weight to be weighed. When the conveyor carrying the filling cylinder is accurately transported to the station under PLC control, the filling cylinder is locked. The ② butterfly valve closes and the ① butterfly valve opens completely, and the granular filler in the hopper starts to leak from the top of the ① butterfly valve to the space above the ② butterfly valve, which is equipped with an electronic weighing system underneath the space. When the electronic scale indicates that the weight is 90% of the set weight, the butterfly valve closes 80% to complete the rough weighing. No. butterfly valve open 20%, continue to leak material when the value indicated by the electronic scale and the set value match, complete the fine weighing, PLC will control the pneumatic switch action, so that the butterfly valve closed. After ① butterfly valve closes, the system carries out automatic detection (for example, to determine whether the filler is clamped or not), if it meets the discharging conditions, ② butterfly valve opens, and starts to fill the filler until the weighed granular filler is loaded into the filler cylinder, then ② butterfly closes, and the work of weighing and packing station is completed.

Granular filler weighing station consists of filling hopper, butterfly valve, weighing system, support frame, stepping motor, cylinder, filling cylinder, fixture, manipulator, and receiving plate.

The weighing control system circuit is Huygens circuit. The function of the circuit is to transform the resistor resistance into voltage output. When there is bulk material weighing, the circuit resistance strain gauge resistance value R, R, R: R changes so that the weight signal into the bridge output voltage signal, and then through the A/D conversion, into a binary digital quantity, through the digital input module into the PLC.

3. Metering filling machine hardware design

Automatic filling machine control using semi-automatic and manual control. The system is controlled by Siemens S7-300 PLC, which is widely used in the field of industrial control and has high electromagnetic compatibility, strong vibration and shock resistance, and can be adapted to many production environments. It can be adapted to many production environments.The biggest feature of S7-300 PLC is its modular function, which is convenient for users to master. The main modules of this control system are as follows: power supply module PS307; CPU module CPU315; digital input module SM321; digital output module SM322; analog input module SM331: analog output module SM332. In order to communicate with the industrial computer, there is also an interface module IM365; communication processing module CP341 which has 13 input points. Output points 13. Output points 13. Reserve 5 input points, 5 output points.

4. Weighing and filling machine software design

Explosion-proof filling machine software is based on Siemens PLC development platform STEP7 development completed S7-300 programmable controllers using STEP7-Micro/WIN32 programming software for programming. STEP7-Micro/WIN32 programming software is a Windows-based application software, powerful, mainly used for the development of the program, but also can be used for timely monitoring of the It can also be used to monitor the execution status of the user's program at the right time. Together with the Chinese version of the program, it can be operated under a fully Chinese interface. This system adopts the statement table (STL) development method, which can realize the function that cannot be realized by ladder diagram. Similar to assembly language, the program is composed of individual statements. the most important feature of S7-300 PLC is modular programming. The main application program of this system is stored in the module FC220, which realizes the functions of clamping, releasing, weighing, filling manually, automatically and alarming.

The control software of the industrial control machine in this system uses the WINCC language, through which the software is programmed to realize the functions of controlling, comparing and analyzing the human-machine interface. To significantly reduce such costs, it is necessary to use simple and efficient configuration tools, as well as an intuitive and user-friendly system. once again, WINCC shows the way. the WINCC configuration software is very easy to use for the realization of animations, as well as for the connection of a screen object to an internal PLC variable. Once a new object has been placed on the screen, an easy-to-edit dialog box appears, and the WINCC graphic designer makes it very simple to animate and preview any of the object properties you require. For overall flexibility, it is even possible to enhance an object with a script.

The first step is to set the weighing weight in the interface. Under automatic control, the operator can monitor the weigh filler from the control interface. Observe the colors of the indicator lights.

Butterfly valve No. ① has three states: green is the butterfly valve fully open for rough weighing; half-red and half-green is the butterfly valve incompletely open for fine weighing; and red is the butterfly valve closed.

Butterfly valve No. 2 has two states: red is closed and green is open. The filling cylinder also has two statuses: red color lights up for locking; green color lights up for releasing. There is also a manual operation button in the interface to realize manual control under special circumstances.

5.Conclusion

Automatic filling machine is an important station in the automated production line. The use of PLC to control the weighing and loading of bulk materials is of great significance to industrial production. Can be extended to the assembly of ammunition (loading gunpowder), the production of milk powder, urea packaging and other industrial occasions, can improve production efficiency, reduce labor intensity, ensure personal safety and other advantages.