PRINCIPLES
OF ULTRASONIC WELDING
In the ultrasonic welding process oscillation energy is supplied to the part to be welded
by the welding tool, the so-called sonotrode. The very briefly occuring friction of the
material particles causes the material to plasticise very quickly in the desired areas. If
the process is supported by a defined mechanical pressure, a tight joint of material is
obtained.
The order of magnitude of the plasticizing depends upon the amount of ultrasonic energy
supplied. Subject to proper application it is almost impossible for the material to be
altered or detrimentally affected in any way in areas outside the welding zone. Depending
upon the type of plastic material, different solidification times are required for the
"at the joint plasticized material" to resolidify under the effect of the still
present mechanical pressure. The process called the cooling or holding time.
The sequence of an US-weld is as follows:-
The machine moves the tip of the sontrode into very close contact with the component to be
oscillated. The component must be able to resonate relatively freely and undamped within
the expected amplitude of oscillation.
The ultrasonics pulse starts immediately. Fast plasticizing now takes place at the points
of contact of the part welded. When the optimum degree of plastification has been reached,
the mechanical pressure first applied, just before that moment is intensified to the
preselected required order of magnitude. When the ultrasonic impulse has stopped, the
mechanical pressure is further intensified but only to a minimal extent. The cooling time
begins and at the end of this process the machine returns to its starting position; the
welding process is completed.
The whole cycle takes place within a relatively short period of time. The individual cycle
time for a complete welding process vary from 0.1 to 5 seconds, depending on the
application. In most cases the cycle time are between 0.5 and 2 seconds.
Our machines or ultrasonic component parts are built in a module system and can be easily
integrated into automated manufacturing system should there be a requirement. The
microprocessor control unit is already equipped with all the necessary hardware and
software elements to be able to control the more common rotary table units.
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