Ultrasonic Welding of Plastics

Ultrasonic welding is perhaps the most common welding technique for plastics.  Possible reasons include speed, relatively simple fixture design, modest capital costs, and applicability to a wide range of thermoplastics.  In UW, the weld energy is provided in terms of a horn that vibrates at high frequencies ranging from 15-35 kHz; the vibrations are transmitted through the parts being welded by suitable part and horn design.  When the energy travels across the weld interface, it produces localized softening of the plastics which then bond under the action of the applied force.  Other applications of UW apparatus to create a bond include Ultrasonic Swaging and Ultrasonic Staking.

Once the horn and fixture are properly aligned, the process has few variables to control including energy, power, pressure, and/or time.  Proper design of the horn is critical and becomes more important as the weld size increases.  Frequent aligning checks and tuning checks should be conducted to ensure proper process control.  One good aspect of the welding process is that with experience, one can hear a good or bad weld based on how the long the weld is on and what kind of sound it makes.

Common applications include assembling enclosures such as transformer housings, telephone handsets, and battery pack casings.  UW is also used for sealing food cartons and also finds applications in "sewing" garments that have greater than 50% synthetic content such as lab gowns.

For additional information or consulting services, please contact us.