1. 1.Introduction

The Tunnel furnace is an industrial heating equipment, it is widely used in food processing, electronic assembly, chemical and pharmaceutical baking, heating process. Usually is is used with circulating hot air. The circulating hot air system is divided into horizontal type and vertical type. Both type need to be calculated accurately by the wind motor which is driven by the wind turbine and electric heater. The hot air goes to the oven from the air-duct, and the hot air will goes into the air-duct again to realize the reuse of the cycle of heating. This can improve the temperature uniformity.

If the system is closed during the operating, this system can restore the operating temperature value quickly by the air circulation system. The whole system need to be controlled by the automation system, with the use of WECON PLC and HMI can realize the following functions: manual automatic control, status monitoring, PID self-tuning calculus control, automatic temperature, over-temperature power alarm, leakage protection, motor overload Protection, temperature curve and many other functions.

2. 2.Program

This system use the WECON LEVI700L HMI, the LX3V 1212MT PLC, and the temperature control module: LX3V-4PT.

3.Brief Introduction of the Program

1）Manual screen: this screen is for making the outputs of main equipment, and check the possible existence of the fault.

2）Automatic screen: automatic screen need to set the temperature and working time, and need to monitor the working state, make the machine work in constant temperature.

3）PID Parameters: PID self-tuning calculus control, and set the temperature power alarm value.

4. 4.Conclusion

The tunnel furnace system, aim at controlling the temperature, to keep the furnace temperature stable. With the use of WECON HMI touch screen and PLC control system, PID algorithm can meet this requirement perfectly.