ULTRASONIC WELDING

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ULTRASONIC WELDING
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Ultrasonic Welding

• Learning Activities
• View Slides
• Read Notes,
• Listen to lecture
• Do on-line workbook

• Lesson Objectives
• When you finish this lesson you will understand
• Ultrasonic Welding Definition, Characteristics,
  Process Applications
• Ultrasonic Power Generation
• Interfacial Interactions Dissimilar Metals
  Welding

Keywords Ultrasonic Welding, Transducer,
Sonotrode, Anvil
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Definition of Ultrasonic Welding

• A solid state welding process in which
  coalescence is produced at the faying surfaces by
  the application of high frequency vibratory
  energy while the work pieces are held together
  under moderately low static pressure.

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Ultrasonic Welding Process
Clamping force

• Process Description
• Components of ultrasonic welding system include
• Transducer
• Sonotrode
• Anvil

Mass
wedge
Transducer
Sonotrode tip
Vibration
Weldment
Anvil
Force
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Ultrasonic Welding Mechanism
Clamping force

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

Mass
wedge
Transducer
Sonotrode tip
10-75 KHz
workpiece
Anvil
Force
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Process Variations

• Spot Welding
• Ring Welding
• Line Welding - Linear Sonotrode
• Continuous Seam Welding - Roller Sonotrode
• Microminiature Welding

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Typical 1500 ultrasonic spot-type welding machine
Courtesy AWS handbook
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100 W Lateral Drive Ultrasonic Welder
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Typical Ring Welding Applications Tip in Shape of
Weld
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Attachment for Continuous Ring Welding
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Tip
Traversing Head for Continuous Seam Welding
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Ultrasonic Welding Variables
Welding Variables

• Ultrasonic power
• Clamping force
• Welding time
• Frequency
• Linear Vibration Amplitude

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Ultrasonic Welding Power Generation
Power Generation

• Electrical power of 60 Hz is supplied to the
  frequency converter.
• The frequency converter converts the required 60
  Hz signal to the welding frequency (from 10 to 75
  kHz).

Frequency converter
Electrical energy
Transducer
Vibratory transducer
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AWS Welding Handbook
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Ultrasonic Welding Power Generation
Power Generation

• Frequency is transformed to vibration energy
  through the transducer.
• Energy requirement established through the
  following empirical relationship.
• E K (HT)3/2
• E electrical energy
• H Vickers hardness number
• T thickness of the sheet

Frequency Converter
Electrical energy
Vibratory transducer
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Power Requirements
Where E electrical energy, Ws (J) k a
constant for a given welding system H Vickers
hardness number of the sheet T thickness of
the sheet in contact with the sonotrode tip, in.
(mm)
The constant K is a complex function that
appears to involve primarily the
electromechanical conversion efficiency of the
transducer, the impedance match into the weld,
and other characteristics of the welding system.
Different types of transducer systems have
substantially different K values.
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Source AWS handbook
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Sonotrode Tip and Anvil Material

• High Speed Tool Steels Used to Weld
• Soft Materials
• Aluminum
• Copper
• Iron
• Low Carbon Steel
• Hardenable Nickel-Base Alloys Used to Weld
• Hard, High Strength Metals and Alloys

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Ultrasonic Welding Interfacial Interaction

• Localized temperature rises resulting from
  interfacial slip and plastic deformation.
• Temperature is also influenced by power, clamping
  force, and thermal properties of the material.
• Localized Plastic Deformation
• Metallurgical phenomena such as recrystallizing,
  phase transformation, etc..... can occur.

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Ultrasonic Welding Materials Combinations
Source AWS handbook
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Extreme Interpenetration Nickel Foil (top) to
Gold-Plated Kovar Foil
Local Plastic Flow Dark Regions are Trapped
Oxide Nickel Foil (top) to Molybdenum Sheet
Very Little Penetration, Thin Bond Line, Fiber
Flow Molybdenum Sheet to Itself
AWS Welding Handbook
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Comparison With Resistance Spot Weld
AWS Welding Handbook
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Advantages of Ultrasonic Welding

• No heat is applied and no melting occurs.
• Permits welding of thin to thick sections.
• Welding can be made through some surface
  coatings.
• Pressures used are lower, welding times are
  shorter, and the thickness of deformed regions
  are thinner than for cold welding.

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Limitations of Ultrasonic Welding

• The thickness of the component adjacent to the
  sonotrode tip must not exceed relatively thin
  gages because of power limitations of the
  equipment.
• Process is limited to lap joints.
• Butt welds can not be made because there is no
  means of supporting the workpieces and applying
  clamping force.

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• Other Process Variations
• Ultrasonic Welding of Non-metallic
• Ultrasonic Plastic Welding

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Welds Can Be Made to Non-Metallic Substrate
Materials Coated with Thin Layers of Metal Films
Material Welded
Metal Film
Non-Metallic
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AWS Welding Handbook
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Ultrasonic Welding of Plastics

• Advantages
• Fast
• Can spot or seam weld
• Limitations
• Equipment complex, many variables
• Only use on small parts
• Cannot weld all plastics

0.1.1.2.5.T25.95.12
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Questions
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Applications of Ultrasonic Welding

• Assembling of electronic components such as
  diodes and semiconductors with substrates.
• Electrical connections to current carrying
  devices including motors, field coils, and
  capacitors.
• Encapsulation and packaging.
• Plastic parts

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AWS Welding Handbook
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Note weld progression (no weld in center)
AWS Welding Handbook
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Starter motor armature with wires joined in
commutator slots by ultrasonic welding
Ultrasonically welded Helicopter access door.
Courtesy AWS handbook
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Field coil assembled by ultrasonic welding
Courtesy AWS handbook
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AWS Welding Handbook
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Wire Bundle Placed in Jaws
Ultrasonic Tying Tool
Metal Tape Fed Around bundle of Wires and welded
once, then cut and welded again.
Ultrasonic Horn
Bundled Wires
Welds
Cut and Second Weld Made
First Weld Made
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Ultrasonic Stitch (Clad) Welding
Sonatrode
Anvil
Louks, et al Ultrasonic Bonding Method US
Patenet 6,099,670 Aug. 8, 2000
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Ultrasonic Welding of Eraser Holder on Plastic
Pencil
Coinon, A, Trajber, Z, Pencil Having and
Eraser-Holding Ferrule Secured by Ultrasonic
Welding US Patent 5,774,931 July 7, 1998
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Explosive Gas Generator For Auto Air Bag (Plastic
Ultrasonic Weld)
Gas Generating Explosive Powder
Plastic Cap Welded to Plastic Base
Primer
Ultrasonic Weld
Avory, et al Electrical Initiator US Patent
5,763,814 June 9, 1998.