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Using a Buffer Sheet in the Ultrasonic Welding Process


Ken Holt

Using a Buffer Sheet in the Ultrasonic Welding Process

Appearances matter, and your reputation may depend on that. These days every edge in making consistently appealing and attractive parts is important. So, here’s where the idea of using a buffer sheet in the ultrasonic welding process comes in.

What is a buffer sheet anyway? Basically it is a thin film – think sandwich bag type material, a heavy-duty clear plastic wrap – positioned between the ultrasonic machined tool (horn) and the part that is being welded. Material used as the buffer sheet should not be the same as that of the parts being welded. For instance, polyethylene film could be used with ABS plastic parts. Polyethylene film is used in most cases. Sometimes Mylar is considered as buffer sheet material, but it tends to be pricier.

What does the buffer sheet do? The buffer sheet provides a protective cushion to prevent the part from being marked during the welding process. The buffer sheet helps minimize the effects mold imperfections or variations might have as the ultrasonic horn meets the part. Essentially the buffer sheet fills voids due to contouring where the molded part does not match precisely with the horn. The sheet helps alleviate marking that might be caused by mold imperfections such as sinks and warpage and other variations.

What kinds of parts would benefit? Many kinds of parts will benefit from use of a buffer sheet during the ultrasonic welding process. In general electronics that have high internal costs are good candidates. Examples are; parts associated with personal electronics, medical devices, and automotive controls and instrumentation. Consumer goods with high appearance requirements such as appliances can also benefit. Welding painted or decorated parts can also be done with a buffer sheet and reduce the concern of marking those surfaces. Whenever there is a critical need for superior quality appearance, using a buffer sheet when welding makes sense.

Machine Equipped with Film Feeding System

Film Feed Device A cost-effective option that provides a solution to position and dispenses buffer sheet material is Dukane’s film feeder  at approximately $4,300*. A 6” wide by 500’ roll of film costs about $20* or $.04 per foot.

Some advantages in using this film feeder:

  • Timing adjustments allow consistent film advance.
  • This rugged, long-lasting unit will fit nearly any ultrasonic welder.
  • Quality and consistency pay off.
  • Higher quality parts reflect positively on company reputation and on sales.
  • Positive return on investment.

For more information about Dukane’s film feed system, please go to