The correct interface design of ultrasonic plastic welding interface is very important for successful ultrasonic welding. In order to achieve the best effect, people have developed a variety of interface forms, but there are three main types: docking interface, shear interface and oblique interface, and other forms of interface are improved on this basis.
(1) the docking interface (Butt Joint) with the energy guide wedge (Wedge-Shapes Energy Director) is suitable for the welding of non crystalline plastics, but for semi crystalline plastics, the welding quality is not good. Due to the narrow flow temperature range of the semi crystalline plastic in the melting state, the energy guide wedge will quickly solidify after melting. It is difficult to spread to the surface of the entire docking interface, which leads to the formation of the weld only near the energy guide wedge, and the welding strength is very low.
(2) the shear interface (Shear Joint) is the most effective interface form for welding semi crystalline plastics. During the welding process, the initial contact material is melted, and then melts continuously between the material of the interference part (Interference) of the two parts. Under the action of pressure, the two parts are connected along the side wall and then joined together. This form of interface is also suitable for non crystalline plastics, and is most suitable for cylindrical parts, and can form highly dense air tight welding.
(3) Scarf Joint is also suitable for semicrystalline plastic because the melting process takes place on the surface of the whole interface and does not involve the flow of molten plastic. Often used in thin-walled parts at the upper end, the interface is a ring or elliptical profile to avoid mating and contact problems at the oblique corners.
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