Fixing, stitching and bonding are some popular techniques we use to connect two materials. However, we cannot deny that welding can provide the best results.
Welding can provide a strong bond that is much longer than most other forms of joints. Today, a variety of welding methods are used. Each type has its own different methods and is used according to the requirements and the type of materials involved.
One of the most modern welding methods used is ultrasonic welding.
Ultrasonic welding uses ultrasonic vibration to connect different materials together. One of the biggest advantages of ultrasonic welding is that it can be used for materials other than metals, such as thermoplastics.
By applying ultrasonic vibration to the contact point, high vibration can cause the material to melt. The typical frequency range used in ultrasonic welding is between 15 and 40 kHz.
Since the ultrasonic welding equipment can concentrate the vibration in a very local position, the welding is very precise.
Parts of ultrasonic welding
Power supply: High-frequency ultrasonic welding machine requires high-voltage power supply.
Transducer: The transducer absorbs high voltage current and converts it into high frequency vibration.
Booster: It works like an amplifier, it absorbs high frequencies and then makes it more powerful.
Ultrasonic welding head or welding head: As we all know, ultrasonic welding head or welding head is the medium between the material to be welded and the machine. It focuses the ultrasonic vibration to a local point.
The material to be welded is usually fixed to the anvil or some type of fixing device that holds them together. Pneumatic presses are usually installed on the machine, so a horn can be used to transmit pressure to the material.
How does ultrasonic welding melt materials?
Ultrasound is used for welding to provide small but rapid vibration. When the horn or sonotrode is connected to the material, the ultrasonic vibration will cause the material to vibrate about half a millimeter in back and forth movement.
This tiny movement is enough to melt the material because the vibration rate is very high. These vibrations cause materials to rub against each other, and the friction between them generates heat.
You can recreate a similar environment by quickly rubbing your hands. You will feel the heat generated between your palms.
Moreover, if you continue to rub quickly, it will become very uncomfortable. Imagine the heat generated inside when materials rub against each other at speeds that are imperceptible to the human eye!
Friction raises the temperature to the point where the contact points between the materials melt, paving the way for molecular bonding. This is how ultrasonic welding welds plastic.
However, it is slightly different when welding metals. Ultrasonic welding is used to heat metal to one third of its melting point temperature.
At this time, the molecules between the two metals will cross each other to form a strong molecular bond. The metal did not melt.
Advantages of ultrasonic welding
Compared with traditional welding technology, ultrasonic welding has many advantages. Because of the combination of these advantages, many industries use ultrasonic welding.
No need for external heat source: The main advantage of ultrasonic welding is that no external heat source is required. Heat is self-generated between materials.
Fast: Due to the high vibration frequency, ultrasonic welding is one of the fastest welding methods in the industry.
The possibility of automation: Ultrasonic welding is not complicated in many aspects and is easy to automate. Ultrasonic machines have sensors that constantly monitor the temperature.
Clean and strong joint: the contact surface melts/fuses during welding, resulting in a very clean and strong joint.