How important is the welding horn of the ultrasonic metal welding machine?
Ultrasonic horn design and production are delicate and strict. When using an improperly processed or untuned welding horn, it will bring expensive losses to your production, it will destroy the welding effect, or even more serious, will directly cause damage to the transducer or generator, so The design of the ultrasonic horn is by no means as simple as its appearance, on the contrary it requires a lot of professional knowledge and skills. The material, end shape and surface condition of the ultrasonic welding head will affect the strength and stability of the solder joint. When ultrasonic metal welding is generally used for welding softer metals such as copper, aluminum, nickel, gold and silver, the ultrasonic welding head is generally made of high-speed steel. Ball bearing steel.
1. Amplitude parameter of the horn: Amplitude is a key parameter for the material to be welded. It determines the size of the welding power and is related to the removal of the oxide film on the surface of the welding material, the state of plastic flow, and the temperature of the joint surface. The selected transducers have different output amplitudes. After adapting horns and welding heads with different transformation ratios, the working amplitude of the welding head can be corrected to meet the requirements. Usually the output amplitude of the transducer It is 10-20μm, and the working amplitude is generally about 30μm. The transformation ratio of the horn and the welding head is related to the shape of the horn and the welding head, the front-to-rear area ratio and other factors. The shape is like exponential amplitude, functional type Variable amplitude, stepped variable amplitude, etc., have a great influence on the transformation ratio, and the front and rear area ratio is directly proportional to the total transformation ratio.
2. horn frequency parameters: any company’s ultrasonic welding machine has a center frequency, such as 20KHz, 40 KHz, etc. The working frequency of the welding machine is mainly composed of the Transducer, Booster, and the Horn is determined by the mechanical resonance frequency. The frequency of the generator is adjusted according to the mechanical resonance frequency to achieve consistency, so that the welding horn works in resonance, and each part is designed as a half-wavelength resonant body. Both the generator and the mechanical resonance frequency have a resonance working range, which is generally set to 0.5 KHz. The welding machine can basically work normally within this range. When we make each welding horn, we will adjust the resonance frequency and require The error between the resonance frequency and the design frequency is less than 0.1 KHZ.
3. Vibration node welding horn: both are designed as a half-wavelength resonator with a working frequency. In the working state, the amplitude of the two end faces is large, the pressure is small, and the node amplitude at the middle position is zero. high pressure. The node position is generally designed as a fixed position, but the thickness of the usual fixed position design is greater than 3mm, or the groove is fixed, so the fixed position is not necessarily zero amplitude, which will cause some calls and some energy loss. Calls are usually isolated from other parts by rubber rings or shielded by sound insulation materials. Energy loss is considered when designing the amplitude parameters.
4. Ultrasonic welding horn processing accuracy: because it is working under high-frequency vibration, a symmetrical design should be maintained as much as possible to avoid unbalanced stress and lateral vibration caused by the asymmetry of sound wave transmission. Unbalanced vibration can cause heat and fracture. Ultrasonic welding is used in different industries to have different requirements for machining accuracy. For particularly thin workpieces, such as the welding of lithium-ion battery pole pieces and tabs, and the coating of gold foil, the requirements for machining accuracy are very high.