Welding plastics is typically done with an ultrasonic assembly. Ultrasonic plastic welding occurs when a vibrating tip comes into contact with a workpiece. When pressure is applied, energy from the stack flows into the workpiece and raises the contact area’s temperature. This heat starts to melt the plastic. When you remove the vibrating tip, the material will solidify and form a bond. Before beginning this type of welding, it is important to know the different parts of the stack. Basic stacks consist of ultrasonic boosters, transducers, and horns.
The transducer supplies your vibration by converting electrical energy into movement. It is made from polycrystalline ceramic pieces and metal plates pushed together under pressure. When you apply a current to these pieces, an electric field is generated because the ceramic parts start changing in thickness. This creates a pressure wave. The metal reflects this pressure and lets it flow through the transducer. The amplitude output of this current is relatively low. The energy can be shifted into the booster for further development. This piece can require anywhere from 50 to 3,000 Watts to operate.
Boosters are located between the transducer and the horn. It is the last part of the stack found inside your welding machine. This piece alters the output amplitude of the stack. It takes the energy created by the transducer and sends it to the horn. They are available as amplifiers and reducers. If no alteration is needed, neutral boosters can be found to connect the transducer and horn.
The horn is responsible for amplifying and focusing the current created by the transducer. Aside from this, it is also responsible for applying the vibrations to the workpiece and creating pressure. Horns are tuned through electronic frequency measurement. This is because they are designed to work with various plastics. Horns are manufactured from titanium or aluminum alloys. These metals are capable of transmitting energy with slight loss.
These machines are designed to operate at anywhere from 15 to 70 kHz. The higher the frequency, the smaller the acoustic wavelength and the horn. Also, horns come in numerous shapes based on their operations. These shapes can produce different kHz outputs. The materials and assembly method are important factors to consider when choosing the correct part.
Anyone considering ultrasonic welding should understand the components of a stack. The transducer, booster, and horn are responsible for providing the energy needed to weld plastic together.