Production batching process of mutual collusion can not use the closed mixing and loading system automatic weighing, still need to manually weighing, batching. There are weighing accuracy depends on the operator's responsibility, details can not be retained, historical data traceability and other issues. The reliability of manual weighing is directly related to the stability of the quality of the entire dosage. This paper describes the use of force control configuration software combined with Siemens S7-200SMARTPLC development of manual weighing and dosage computer monitoring system, to achieve the manual weighing and dosage process data collection and objective preservation and real-time data display, query of the historical operating data guide, curve display, alarm, system parameter settings and other functions.

1 system design

1.1 Demand for batching process

The artificial weighing part of the dosage consists of three scales distributed in different locations on the site, weighing different alloys in the dosage process for feeding. The specific process requirements are:

1) Weighing mode: the three weighing modules can weigh at the same time or separately, with manual mode and automatic mode switching;

2) Input process parameters: ingot number, alloy grade, alloy name and other process parameters can be input and saved corresponding to the weight;

3) Report query function: it has the function of filtering and querying according to scale number, alloy grade and date respectively, and it can be exported to Excal document;

4) Trend curve: real-time curve and historical curve of the weighing process to support the analysis of the records after the event;

5) Operating privileges: different privileges for different users. And with event records.

1.2 Hardware design

The whole feeding system contains two parts: local weighing site and remote host computer. The weighing site contains weighing instrument, electronic scale, photoelectric switch, weighing control system, field input and alarm indication part.

1.2.1 Weighing detection

There are three weighing modules on site. The actual operation requires each scale to judge the start and end of weighing. In order to meet the reliability of the two sides of the platform installed in the counter-reflective photoelectric switch. When an object is placed on the scale, the photoelectric switch is blocked to give the PLC input signal. At this time, it starts to collect and process the data, at the same time, in order to give feedback to the current operator weighing status, it installs a status indicator module next to the platform scale, which contains the status light display of weighing in progress, collection completed, and entering into the range of the process requirements, and so on.

1.2.2 Data transmission

Considering that the three weighing modules in the field belong to different locations in the batching area are far away from each other, it is not easy to wire, therefore, the physical transmission medium is selected as wireless ZigBaa technology [2], this time, we use four RS485 to ZigBee modules based on the TICC2530 chipset, one of which is located next to the main control computer as a Coordinator node to create a ZigBee network, and three of which are located next to the main control computer as a coordinator node to create a ZigBee network. ZigBee network and three of them are located next to the scale as Router. also known as ZigBee full-featured nodes. The ZigBee configuration is simple and requires only the node attributes of the module to be configured.

On-site platform scale weighing instruments use Modbus-RTU protocol for weight data transmission, in addition to the site also needs to have a digital input and output, for this reason, each platform scale is configured with a 16-channel Modbus-RTUDI/D0 module and weighing instrumentation connected to the ZigBeeRouter network via RS485, PLC connected to ZigBeeCoordinator node via RS485. ZigBeeCoordinator node through RS485.

1.2.3 Data processing

The status indication and weight data distributed in various places of the site are in Mod-bus mode, and Siemens S7-200SMART itself has a RS485 hardware interface, and at the same time, it has an Ethernet interface that can be used to conveniently interact with the configuration software of the host computer. Therefore, the SR30 series is used as the Modbus data processing master to communicate with the field modules and communication instruments and logic operations.

1.3 Software Design

The software platform uses Windows 7 operating system. The human-machine interface of the application software is developed by the ForceControl monitoring and control configuration software, and the Access database of Microsoft Corporation is used as the embedded database to connect with the configuration software.

1.3.1 Screen configuration

Using Draw, the graphic development environment of ForceControl configuration software, and the graphic interface running system View, it is easy to develop the above functions of the weighing and monitoring system, including the main weighing interface, the process parameter modification interface, the trend interface, the report interface, and the system management interface.

Power control configuration software itself with a historical database, can be collected on-site, in addition to the use of writing script programs can realize the complex alarm functions and system parameter settings.

1.3.4 PLC program

PLC is mainly responsible for the data transfer of Modbus devices and digital input and output logic operations, this time the choice of Siemens S7-200SMART series PLC, which itself has a rich library of Modbus commands, can carry out the initialization of the field module and logic processing.

As the operation process for manual feeding, so how to identify the stability of the weight data and saved to the database for the transformation of the key for the stability of the data to identify the use of multiple data comparison method is the most commonly used and very effective method, and sampling comparison.

1.3.2 Database

Data to save Yuan to realize the generation of tables, drawing curves and other functions Yuan, but its saved data can not be detached from the configuration environment, in particular, can not be realized according to any conditions to query and delete the data, which can not meet the actual needs of the site, after weighing the amount of data to consider the actual process data and the database easy to use the operability of the Yuan use of the third-party software to adopt.

1.3.3 Database script program

Completed the screen configuration, the dynamic connection between the screen and the data and the relationship between the data table binding Yuan, but if you need to achieve other control functions also need to use the functions provided by the configuration software to write script programs. For example, through the force control statement to realize the establishment of data tables in the database, but also must be connected to the force control and access database, through the value of the feedback variable A can determine whether the database is connected successfully.

Report query function is the main function of the Yuan is also realized through the SQL code function in the script language, according to the time, according to the scale number, according to the process parameters of the combination of query, in order to query the conditions according to the scale number. In addition to writing script programs can be used to achieve complex alarm functions and system parameter settings.

1.3.4 PLC program

PLC is mainly responsible for the data transfer of Modbus devices and digital input and output logic operations, this time the choice of Siemens S7-200SMART series PLC, which itself has a rich library of Modbus commands, can be carried out on-site module initialization and logic processing.

As the operation process for manual feeding, so how to identify the weight data stability and save to the database for the transformation of the key Yuan for the data stability of the identification of Yuan using multiple data comparison method is the most commonly used and very effective method, and the more samples compared to the number of times, the more pronounced the effect, the following is a number of comparisons to determine the stability of the data as an example of the signal into the host computer began to read the scale data and draw the curve. When the actual quality of the single material line description. Quantity and theoretical quality in line with the time (within the process allowable error) data stabilization automatically on the weight data w interval ti time and 1 time sampling, through the comparison with the recipe information saved to the database. After the material leaves the scale, the system stops drawing the curve interval twice whether the data is consistent that is, w (i) - w (i + 1) = 0. If consistent cycle 1 time, if inconsistent reset; here, the interval time and the number of times of sampling, determines the sensitivity and stability of the automatically saved data, the shorter the interval time, the fewer comparisons of the sensitivity of the higher. The shorter the interval time, the fewer the number of comparisons the higher the sensitivity, the worse the stability. The longer the interval time. The longer the interval time, the fewer the number of comparisons, the higher the stability. Sensitivity is worse. According to the actual working conditions in the field after repeated testing, the interval time is selected 500ms, and the number of comparisons is selected 10 times. Under the premise of ensuring stability. Take into account the sensitivity. Because there are three scales on the scene, for simplicity, you can use a unified program to determine the stability of processing.

2 system work process description

The host computer, start weighing when there are materials placed on the platform scale, photoelectric switch detects the signal, the host computer began to read the scale data and draw curves when the actual quality of the single material line description. Quantity and theoretical quality in line with the time (within the process allowable error) data stabilization automatically on the weight data for the interval time and 1 sampling, through the comparison with the recipe information is saved to the database. After the material leaves the table scale the system stops drawing curves the upper computer begins to read the scale data and draw curves. When the actual quality of the single material. When the actual quality of the single material and the theoretical quality in line (within the process allowable error) data stabilization is automatically saved to the database with the recipe information. After the material leaves the scale, the system stops plotting the curve to complete the current weighing.

Data query can be queried through the drop-down menu by scale number, grade, ingot number, time, individually or in combination, and can be exported to CSV or Excel for SPC analysis by process personnel.

Setting of multiple levels of operating privileges. Lower privileges can view the weighing process and retrieve data. Higher authority can change process parameters and data export operations.

3 Conclusion

The manual batching control system designed by using configuration software realizes:

1 weighing and batching process to realize paperless operation;

2 to reduce the dosage error. Eliminate the randomness of manual configuration, to ensure the stability of product quality;

3 accurately trace the weighing process;

4 reduce the labor intensity of the staff. Realize the whole dosage process information integration.

The system has been running for many years, which shows that: the system design is reasonable, the input cost is low, the system can be deployed quickly, and the operation is stable. Can be extended to other related batching needs of the industry. Has direct economic benefits.