ULTRASONIC WELDING

ULTRASONIC WELDING

       Ultrasonic welding is a welding technique uses ultrasonic vibrations locally applied on the work pieces being held together under pressure to create a solid state weld. The two components are subjected to a static normal force and an oscillating shearing stress. The shearing stress is applied at the tip of a transducer. Ultrasonic assembly uses ultrasonic vibratory energy which is transmitted through the parts to melt and bond thermoplastic material and joining thin sheet gauge metals and other light weight metals. This technique is fast, economical and contaminate the work piece.  In ultrasonic welding, there are no connective bolts, nails, soldering materials, or adhesives necessary to bind the materials together. In this welding frictional heat is produced by the ultrasonic waves and force is used for the joining process, the waves are transferred to the material under pressure with a sonometer.

Set up

Parts

1. Transducer : Produce high frequency ultrasonic vibrations.

2. Converter : Converts the electrical signal in to a mechanical                                 

                        vibration.

3. Booster : Modifies the amplitude of vibration

4. Sonotrode : Applies the mechanical vibrations to the parts to be 

        

                        welded 

Ultrasonic transducers are of two types

A. Piezo electric type: Vibrations are produced by piezocrystal

     by “Reverse peizo electric effect.PZT – LeadZicronate  

     Titanate Crystals  are used

B. Magnetostrictive type : it is a property of ferromagnetic 

    materials that causes them to change their shape or dimensions 

    during the process of magnetization.

Ultrasonic welding Mechanism

 A static clamping force is applied perpendicular to the interface between work pieces. the contacting sonotrode oscillates parallel to the interface. combined effect of static and oscillating forces produces deformation which promotes welding.

Advantages of  ultra sonic welding   

1.The process permits welding of thin to thick sections as well as       joining a wide variety of dissimilar metals.

2. Since, the temperatures used are low and no arching or current      flow is involved, the process can be applied to heat sensitive            electronic components with better efficiency for many

    electronic components.

3. Intermediate compounds very rarely form as there is

    no contamination of the weld under surrounding areas.

4.The required penetration is less than most competing processes      for example, resistance welding and correspondingly 

  lesser energy is needed to produce the welds.

Disadvantage

1.Ultrasonic welding is restricted to the lap joint welding of; thin       sheets, foil and wires and the attaching of thin sheets to heavier       structural members. The maximum thickness of weld is about 2.5     millimeter for aluminum and about 1 millimeter for harder                materials.

Applications of USW

  •  Aerospace and automotive industries

  •  Medical industry

  •  Packaging industry

  •  Electrical and electronics industry

  •  Toy’s

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