Design and application of Constant-current Control System for Ultrasonic Seam Welding Machine
Abstract: Ultrasonic seam welding is a process in which high-frequency mechanical vibration and pressure are used to weld two pieces of material.The traditional manual welding process requires high welding efficiency and good welding quality, but manual operation is labor intensive, and the process is complicated and inaccurate.So we designed a constant current control system for ultrasonic seam welding machine, the system is built on SCM microcontroller, the welding parameters are set by the keyboard.The welding work frequency, welding current and time is set conveniently and accurately, which can guarantee the stability and welding quality.It not only improves the welding quality and production efficiency, but also reduces the labor intensity.
Keywords: ultrasonic seam welding; constant current control; SCM microcontroller.
1 Introduction
Ultrasonic seam welding is a welding method that uses high-frequency alternating current to generate and transmit high-frequency mechanical vibration and pressure, which melts and bonds two pieces of material.It has many advantages, such as short weld time, good appearance, few and small defects, no additional material consumption and easy to automate.So ultrasonic seam welding is widely used in the fields of electronics, automobile and home appliance industry[1].
In order to control the welding parameters accurately, a constant current control system is needed for the ultrasonic seam welding machine.Based on the SCM microcontroller and its integrated development environment, we designed a constant current control system for the ultrasonic seam welding machine.The system can accurately set the welding work frequency, welding current and time, so as to make the welding process more efficient, accurate and stable.
2 System design
2.1 System block diagram
Fig.1 is the block diagram of the constant current control system for the ultrasonic seam welding machine.The system mainly consists of keyboard, LCM, SCM, current sensor, power converter and drive unit.All the signals of the system enter and leave the SCM microcontroller.The control signals are then output to the drive unit to drive the ultrasonic welding machine.
Fig.1 System block diagram
2.2 Control process
Fig.2 is the flow chart of the control process.Start the power and set the system parameters, then enter the welding state. Firstly, step 1 will enter the welding state and issue a start signal. Then step 2 will start the motor, and send a signal to read the voltage and current sensor value. In step 3, the current sensor value is read, and the adjustment signal is sent out according to the feedback value, to adjust the current value of the welding workpiece. Step 4 monitors the welding time and current values. When the current is greater than the set value, or the welding time reaches the set time, the system will enter the switch state, and step 5 will cut off the power supply and end the welding operation.
Fig.2 Control flow chart
3 Prototype verification
3.1 System hardware
In order to verify the performance of the system, a prototype is designed. In the prototype, the CPU uses STC11F04S microcontroller, and LCD display, keyboard and encoder are used for data input. The current sensor signal is connected to the ADC module, and finally the drive array is used to drive the ultrasonic welding machine.
3.2 Welding experiments
The stainless steel plate is used as the welding material. The welding parameters of the welding process are set to 800 Hz, 30 A and 6.5 s. The stability of the welding current and the welding quality are observed during the welding experiment. The experimental results show that the control system can control the welding current accurately and stably.The welding quality is good, and no weld defects can be found.
4 Conclusion
A constant current control system is designed for the ultrasonic seam welding machine based on the SCM microcontroller.The system can set the welding parameters accurately and conveniently, improve the welding quality and production efficiency, and reduce the labor intensity.Experimental verification shows that the designed system has good performance and high accuracy, and can meet the welding requirements.
References:
[1] H. L. H. 郭, W. T. S. 杨, X. L. 陆, et al. A Brief introduction of Ultrasonic Seam Welding[J]. 航空制造技术, 2016, 36(2): 10-14.
