The welding head of an ultrasonic metal welding machine is an acoustic device that directly transmits mechanical vibration energy to the products to be bonded. The vibration is transmitted through the workpiece to the bonding surface, generating heat through friction that melts the plastic. The vibration stops when the molten material reaches the interface. Briefly maintaining pressure allows the molten material to solidify at the bonding surface, forming strong molecular bonds. The entire cycle is typically completed in less than a second, yet the weld strength is close to that of a single, continuous piece of material.
Amplitude Parameter
Amplitude is a critical parameter for the materials to be welded, analogous to the temperature of a chrome iron. Insufficient temperature will result in incomplete welding, while excessive temperature will cause the raw materials to char or lead to structural damage and reduced strength. Because each company chooses different transducers, the output amplitude of the transducers varies. By adapting the amplitude transformer and welding head to different ratios, the working amplitude of the welding head can be corrected to meet the requirements. Typically, the output amplitude of the transducer is 10-20 μm, while the working amplitude is generally around 30 μm. The amplitude transformer ratio of the amplitude transformer and welding head is related to factors such as their shape and front-to-back area ratio. For example, exponential amplitude transformers, functional amplitude transformers, and stepped amplitude transformers have a significant impact on the ratio. The front-to-back area ratio is directly proportional to the overall ratio. Since your company uses welding machines from different brands, the simplest method is to manufacture them according to the proportional dimensions of the welding heads already in use, which will ensure the stability of the amplitude parameters.
Frequency Parameters
Every ultrasonic welding machine from any company has a center frequency, such as 20kHz or 40kHz. The operating frequency of the welding machine is mainly determined by the mechanical resonant frequencies of the transducer, booster, and horn. The generator frequency is adjusted according to the mechanical resonant frequencies to achieve consistency, ensuring the welding head operates in a resonant state. Each component is designed as a half-wavelength resonator. Both the generator and the mechanical resonant frequencies have a resonant operating range, typically set at ±0.5kHz. Within this range, the welding machine can generally operate normally. When manufacturing each welding head, we adjust the resonant frequency to ensure the error between the resonant frequency and the design frequency is less than 0.1kHz. For example, for a 20kHz welding head, our welding head frequency is controlled between 19.90 and 20.10kHz, with an error of 0.5‰.
