How is face mask ultrasonic welded?

Do you know ultrasonic welding, a welding technique which is commonly applied in face mask production?

What is ultrasonic welding? Two objects friction and their surface molecules fuse due to the high frequency vibration wave and pressure on both objects.

Actually, we can see some indentation on our face mask, especially at the seal, ear belt and breathing valve. It is because they are all ultrasonic welded. During face mask production, nose bridge bar welding, edge folding welding, breathing valve welding, multi-layer roll welding and ear belt welding are all processed through ultrasonic welding.

Ultrasonic acts on thermoplastic surface and generates vibration in high frequency of over 10,000Hz. Such high frequency vibration will transmit ultrasonic energy to the welding area. Then high temperature in some parts will be caused due to large sound resistance in welding area.

However, plastic has poor thermal conductivity. Therefore, thermal energy accumulates in welding area, instead of emitting. In this case, the contacting surface of plastic will melt rapidly and fuse under specific pressure.

Pressure will last several seconds longer than ultrasonic act for plastic solidification and molding. At last, firm molecular chain is formed and the product intensity approaches to raw material intensity.

Besides, ultrasonic welding can be classified into insertion welding, rivet welding, spot welding and molding.

                                                         insertion welding                     rivet welding                              spot welding                              modling

Insertion welding refers to the technique with which metal parts are inserted into plastic holes under the pressure of horn.

Rivet welding means that vibrating horns press the object protrusion and weld it to rivet so that two objects can be riveted mechanically.

Spot welding can weld object whose welding line is difficult to be designed. The object is welded in spot and then fused.

Molding is similar to rivet welding. Concave horn presses on plastic object and generates high frequency ultrasonic vibration to melt plastic. A metal object can be then coated and fixed and its surface is smooth and beautiful. Such a technique is usually applied in mirror fixing in cosmetics or horn molding and fixing...

Except for face mask, ultrasonic welding is also used to produce the following articles for daily use:

All in all, ultrasonic welding makes use of vibration of 15kHz-50kHz to melt and weld plastic. Ultrasonic vibration transmits to the connection of upper and lower objects. Alternating stress is generated and plastic is frictioned, heated and melted. After ultrasonic, the two objects are still pressed until they stick to each other.