The ultrasonic welding machine for two thermoplastic parts requires ultrasonic vibration to be transmitted to the upper half of the assembly through the welding head, and finally to the joint or interface of the two halves. Here, vibration energy is converted into heat energy to melt plastic. When the vibration stops, the plastic solidifies under pressure, resulting in welding on the joint surface.

　　The design of the two bonding surfaces is very important for obtaining the best welding results. There are various connection designs, each with its own characteristics and advantages. The use of various designs depends on many factors, such as plastic type, part geometry, welding requirements (ie, viscosity, strength, sealing, etc.).

　　Fixture device:
　　An important factor in ultrasonic welding of plastics is the fixture device. The main purpose of the clamp device is to fix the parts, align them with the welding head, and provide appropriate support for the assembly. The material being welded, the geometry of the part, the wall thickness and the symmetry of the part can all affect the energy transfer to the interface, so it must be considered when designing the fixture.
 

　　Some applications, such as riveting and embedding, require a hard supporting device under the contact area of ​​the welding head. The aluminum fixture device can provide the necessary rigidity, and can be chrome plated to prevent scarring and improve wear resistance.

　　In some applications, the clamp must have a certain degree of flexibility to ensure that the out-of-phase state occurs in the connection area. The out-of-phase state generally appears at the worst joint, which is the range to be welded; however, due to certain parts materials and geometric shapes, the two halves of the joint may become a whole and vibrate up and down at the same time. If this state occurs, it will Changing the bearing groove from a rigid material to an elastic material, or changing the durometer from a soft material to another material, is often sufficient to re-establish the out-of-phase state in the connection zone.

　　Simple experimental fixtures can be built with wood, epoxy or plaster of paris. For more precise and longer-life fixtures, aluminum, steel, brass, cast urethane, or other elastic materials will be used. The range of fixture design is wide, from quick disassembly fixtures to simple metal plates. Application requirements and productivity usually determine the design of the fixture.

　　Welding:
　　Simple butt welding connection and ideal connection time-temperature curve with energy-oriented part. The energy-directed part allows rapid welding while achieving maximum strength. The material in the guide part flows throughout the bonding area as shown.