Vibration Welding
Vibration Welding is a very efficient welding method. Vibration
Welding requires no additional materials beyond the two pieces
of material to be bonded and uses relatively low energy. Vibration
Welding has the advantage of being able to handle relatively
large parts. It is also a highly cost effective process and
has short cycle times. However, because it relies on movement
or rotation of the pieces of material to be welded, it is
only possible to apply Vibration Welding to 2-dimensional
joint contours.
Vibration Welding works through friction and
pressure. The two pieces of plastic to be welded are rubbed
against each other at a relatively low frequency, usually
between 80-300hz. The friction between these pieces of material
causes heat, and eventually melting. However, an important
distinction to note between Vibration Welding and Ultrasonic
Welding is that though like in Ultrasonic welding vibration
is used, the pieces are physically moved, and not vibrated
through sound. Typically, only one part of the two plastics
is moved or rotated, while the other is held stationary. A
constant pressure is also applied to the two parts of plastic.
As the surfaces of the plastics melt, the pressure forces
them to bond. Once the two parts are sufficiently bonded,
the vibration stops, and the parts are allowed to cool while
smaller "holding pressures" hold the pieces together. The
result is one very securely welded piece of plastic. The relatively
low pressures involved ensure low rates of pressure-related
distortion.
There are three main motions involved in vibration
welding. Only one is typically used in any one welding job.
Lateral vibration welding involves moving one piece against
another in a line- it is also known as "linear" vibration
welding. Angular vibration welding rotates a piece on a specific
axis. Orbital vibration welding involves rotating one of the
parts along a central axis.
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