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106
Dukane Manual Part No. 403–566–01
DPC
™
II Plus and EZ Welder System – User’s Manual
Ultrasonic Horn
The horn transfers the ultrasonic mechanical vi-
brations (originating at the transducer in the probe
housing) to the plastic parts through direct physi-
cal contact. The horn is precision machined and
designed to vibrate at either 20kHz, 30kHz,
40kHz, 50kHz or 70kHz. The tuning is accom-
plished using electronic frequency measurement.
Inherent variations in material composition pre-
vent tuning by dimensional machining alone.
There are many different horn profile styles de-
pending upon the process requirements. Factors
which affect the horn design are the materials
to be welded and the method of assembly. Horns
are usually constructed from aluminum, hard-
ened steel or titanium. As the frequency in-
creases, vibration amplitude typically decreases,
but internal stress in the horn increases. Higher
frequencies are used for delicate parts that can-
not handle a lot of amplitude. Some factors to
keep in mind for high–frequency (e.g. 40kHz)
ultrasonic welding versus low–frequency (e.g.
20kHz) ultrasonic welding are listed here.
1. Stress in the horn is higher at high frequencies.
2. Wear on the horn is greater at high frequencies.
3. Clean and flat mating surfaces between the
horn, booster and transducer are more critical
at high frequencies.
Booster
The function of a booster is to alter the gain (i.e.
output amplitude) of the probe. A booster is am-
plifying if its gain is greater than one and reducing
if its gain is less than one. A neutral or coupling
booster is used to provide an additional clamping
location for added probe stack stability. A probe
designed to be mounted in a fixture along with a
booster and horn is shown in Figure 10–2. This is
commonly referred to as a stack. As indicated, the
components are secured with threaded studs.
Probe
Housing
Booster
Horn
Figure 10–2 Probe, Booster and Horn