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Why Choose Ultrasonic Plastic Assembly Process

Ultrasonic assembly is an extremely cost-effective and popular technique whose benefits include speed (most welds take less than a second), no consumables, minimal or no setup time, low cost of capital equipment, and easy integration into automation.

It utilizes a series of components—power supply, converter, booster, horn (or stack), and actuator—to deliver mechanical vibration and force to the parts. This generates heat at the interface of the mating parts, melting the plastic and creating a strong bond.

In these systems, the power supply, converter, booster, and horn function together to create mechanical vibration. The power supply takes standard electrical line voltage and converts it to an operating frequency (in this illustration—20 kHz). Power-supply frequencies are set but are available between 15 and 70 kHz. The most common frequencies are: 20, 30 and 40 kHz.

This electrical energy is sent through an RF (radio-frequency) cable to the converter. The converter utilizes piezoelectric ceramics to convert the electrical energy to mechanical vibrations at the operating frequency of the power supply. This mechanical vibration is either increased or decreased based on the configuration of the booster and horn. The proper degree of mechanical vibration, known as amplitude, is typically determined by an application engineer and is based on the materials being welded.

In a typical bench-type system, the actuator base and column can be removed, providing an excellent configuration for integrating into automation. The actuator is used to deliver the converter, booster, and horn to the parts being welded and applies force. Weld forces can range between 50 and 750 lb. The actuator also can have other components such as a linear encoder to measure weld distances.

The limitations of this process derive primarily from the materials being welded and the size of the parts. With an easy-to-weld material such as ABS, a part up to 10 x 10 in. could be welded with a 15-kHz welder. For a more difficult-to-weld material such as nylon, a part approximately 3.5 in. square or 3.5 in. diam. would be the largest that could be welded. Deep contours or reliefs in the horn may also limit its range.