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Ultrasonic Welding: Definition, Working Principle, Applications, Advantages, and Disadvantages [Notes with PDF]

In this article we’ll learn in-depth about Ultrasonic Welding, how it’s works, its applications, benefits and so much more in detail.

What Is Ultrasonic Welding? 

Ultrasonic welding is a process commonly used in many industries for welding small parts with high rates of production. The welding is done with the help of high-frequency vibration in the order of 20kHz to 40kHz. When welding is done using ultrasonic vibrations between 2 workpieces then it is called ultrasonic welding. Ultrasonic welding is a clean and fast process for creating welds between the workpieces. It is a type of spot welding in which the weld is created due to the mechanical vibrations and intermolecular bonding. 

Characteristics Of Ultrasonic Welding:

Ultrasonic welding is a solid-state welding process. Certain characteristics make ultrasonic welding different from traditional welding methods. 

  • There are no electrodes used in ultrasonic welding as in the case of traditional welding two electrodes are used to weld the two workpieces. 
  • No filler metals are used in ultrasonic welding. The weld formed is due to the intermolecular bonding of the working metals. Hence no foreign filler metal is used in the process. 
  • No spark is produced in the case of ultrasonic welding unlike in traditional welding methods there are sparks produced. 

History Of Ultrasonic Welding:

Ultrasonic welding was first used in the 1940s to weld thermoplastic materials together. In the year 1965 ultrasonic welding for thermoplastics was patented by Seymour Linsley and Robert Soloff. With the evolution of time, the application of ultrasonic welding became wider. And now it is used for various industrial applications. It can be used to weld plastics as well as metals. 

Construction Of Ultrasonic Welding:

The construction of ultrasonic welding equipment is quite simple. The column is attached on a cast iron base. A transformer is attached to the column on one side. The transducer-horn arrangement is attached to the other side of the column. A 240V Power supply is connected to the transformer. The column also provides a mechanical movement to the horn to apply force on the joint. Fixtures are attached to the base to hold the workpiece. 

The parts used in ultrasonic welding equipment are:

  • Transducer:

A transducer is a device that converts electrical signals to mechanical vibrations. In the case of ultrasonic welding equipment, a Transducer is used to convert high-frequency electrical signals to high-frequency mechanical vibrations. 

  • Booster:

The booster acts as an amplifier it is used to amplify the mechanical signals obtained from the transducer. This is an important element as the amplitude required to create a weld is fulfilled by the booster. 

  • Horn:

The part that is in direct contact with the workpiece is called the horn. Horn has a decreasing area of the cross-section to concentrate the pressure on the given workpiece. 

  • Fixtures:

Fixtures are used to restrict the degrees of freedom of the workpiece. Fixtures used in the case of ultrasonic welding must be accurate because the high frequency of vibration may dislocate the workpiece from its actual position. 

  • Transformer:

A transformer is used to supply Alternating current to the transducer. This is done by the principle of mutual inductance.

  • Column:

The column is the beam used to support the transformer and the transducer-horn arrangement. The column must be rigid enough to survive the mechanical vibrations. 

  • Base:

A cast iron base is used in the case of ultrasonic welding equipment. This base acts as a damper and absorbs the vibrations generated. This helps in keeping the whole setup stable. 

Ultrasonic Welding Construction or Parts
Diagram of Ultrasonic Welding, Learn Mechanical

Working Principle Of An Ultrasonic Welding Equipment:

As soon as the power supply is switched on, Alternating Current is generated by the transformer because of the mutual inductors present in it. This alternating current reaches the transducer where it is converted to high-frequency mechanical vibrations. There is a transfer of vibration from the transducer to the horn.

The horn applies pressure along with mechanical vibrations on the workpieces in contact. Because of the mechanical vibrations friction is created between the workpieces which causes a localized increase in the temperature between the workpieces. This temperature is sufficient enough to create an intermolecular bond between the two workpieces and as a result of which the workpieces get welded. 

Advantages of Ultrasonic Welding:

  • High production:

production rate while working on ultrasonic welding equipment is quite high when compared to conventional welding methods. The only thing that needed to be done is, place the workpiece in the correct position and start the machine. Around 50-60 workpieces can be welded in a minute. 

  • Welding thin materials:

Welding thin sheets and other thin materials can be done easily using ultrasonic welding. It is difficult to weld thin materials using conventional methods as they may burn thin sheets or wires. 

  • Less heat affected zone:

Heat-affected zones in the case of ultrasonic welding are less than traditional welding. Heat Generation is responsible for the development of thermal cracks and thermal stresses. These may cause the workpiece to fail. Hence less heat generation results in increased strength of the workpiece. 

  • Cost-efficient:

 there are no electrodes and filler metals used in the process of welding workpieces using ultrasonic welding. This makes the welding process cost-efficient and simple. 

  • Flexibility:

One of the advantages of ultrasonic welding is that dissimilar metals can be welded together using the ultrasonic welding method. This is because the weld formed is due to the intermolecular bonding of the working metals. 

Limitations Of Ultrasonic Welding:

  • High initial investment:

One of the major disadvantages of ultrasonic welding is the high initial cost of the equipment. The whole setup is very costly but the cost of running is low when compared to traditional welding methods. 

  • Joint limitations:

Only lap joints can be welded with the help of ultrasonic welding. Other joints such as vee joints, butt joints, etc cannot be welded using ultrasonic welding. 

  • Size limitations:

Another limitation of ultrasonic welding is that it cannot be used for welding heavy and large materials. Hence cannot be used for heavy industrial purposes. 

  • Loading:

The process involves fatigue loading of the workpiece. This decreases the life of the workpiece under the application of forces. 

Applications Of Ultrasonic Welding:

  • It is widely used in electrical industries for welding different circuits, PCBs, hard drives, and semiconductor devices. Ultrasonic welding is suitable for such an application because there are no sparks produced in the process which may burn electrical components. 
  • Another important application of ultrasonic welding is that it is used in the automotive industry for welding steering parts, door panels, and many engine components. 
  • As there are no chemical reactions involved in the process of ultrasonic welding, this makes ultrasonic welding a clean process, hence it is used for welding many medical equipments. 
  • Ultrasonic welding can also be used for packaging industries. It can be used for welding different thermoplastic containers and tubes. 

Ultrasonic welding has many industrial applications. It can be used for welding thermoplastics and thin metals. The weld produced is clean and without the use of filler metals. Though the initial cost of the equipment is high the running cost is low. It has numerous disadvantages but also has great advantages which make the process fit for different purposes. 

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Aayush Rao

Aayush is a Mechanical Engineering aspirant completing his degree from Rajiv Gandhi Institute of Technology, Mumbai. He has a keen interest in Manufacturing Technology, Thermal Engineering, and Workshop technology. He is now working as an Intern writer at Learn Mechanical.

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