How to set the welding parameters of ultrasonic plastic welder

How to set the welding parameters during ultrasonic welding? First of all, we need to understand the main welding parameters of ultrasonic welding, including: power required, vibration frequency, static pressure, welding time, etc., one by one described below.



1. Power required

The factors that have the greatest influence on the power required are the thickness and hardness of the weldment, which can be determined by the following formula:

P = KH3/2 delta l

Where, P is the power required (W).

K is the coefficient, depending on the thickness and hardness of the weld, as shown in Figure 1.

S is the thickness of weldment (mm).

H is weld hardness (HV).



In view of the great difficulty in the measurement of ultrasonic power, the power is expressed in terms of amplitude in practice, as shown in the following formula:

P=μSFυ = MSF2A Ω /π = 4μSFAF

Where P is ultrasonic power (W);

F is static pressure (N);

S is solder joint area (mm2);

V is the relative velocity (m/min);

A is the amplitude (μm);

μ is the friction coefficient;

Ω is the angular frequency (Ω =2πf);

F is the vibration frequency (kHz).



2. Vibration frequency

The frequency of ultrasonic resonance depends on the thickness of the weld and its physical properties. High frequency should be used for thin parts (up to 80KHz), and low frequency should be used for thick parts and materials with low hardness and yield point, such as 15-20KHz. The ultrasonic wave below 15kHz is less used because of noise.



3, the amplitude

Adjusting the power output of the generator can adjust the amplitude, the common amplitude is 5-25μm. Due to the great load variation in the welding process, there may be detuning phenomenon, which leads to the joint strength reduction and instability, so maintaining the resonance stability of the acoustic system is the basic guarantee of the solder joint quality stability!



4. Static pressure

Static pressure is an important factor affecting the power output and the deformation condition of the weldment, and its magnitude depends on the thickness and hardness of the weldment. Generally, the static pressure at the minimum available power and the power slightly higher than the minimum available power are selected for welding. In order to determine the mutual influence of each parameter, we can draw a critical curve to judge.