Home Site Map What's New Company Info Contact Us
Industrial Resonators

Up ] Bar horns ] Block horns ] Spool horns ] Slotted cylindrical horns ] Boosters ]


Industrial resonators deliver high energy density in order to substantially affect the materials with which they are in contact. Common uses include welding of plastics and nonferrous metals, cleaning, abrasive machining of hard materials, cutting, enhancement of chemical reactions (sonochemistry), liquid processing, defoaming, and atomization. Usual frequencies are between 15 kHz and 40 kHz, although frequencies can range as low as 10 kHz and as high as 100+ kHz.

Krell Engineering can design many variations of the resonators shown below, including carbide face inserts and other wear resistant materials. (Note: not all resonators are shown to the same scale.)

Find the resonator below that most closely meets your needs. Then click on "details" to get detailed information, which often includes an animation of the actual resonator vibration.

A typical industrial ultrasonic stack consists of a horn, booster, and transducer (converter).

Ultrasonic stack

Ultrasonic stack

The horn contacts the load and delivers power to the load. The horn's shape depends on the shape of the load and the required gain. Horns are typically made of titanium, aluminum, and steel. Horns are also called sonotrodes. Small diameter horns are sometimes called probes.
The booster adjusts the vibrational output from the transducer and transfers the ultrasonic energy to the horn. The booster also generally provides a method for mounting the ultrasonic stack to a support structure.
The transducer (converter) converts electricity into high frequency mechanical vibration. The active elements are usually piezoelectric ceramics although magnetostrictive materials are also used. Transducers are also called  converters.



Cylindrical horns


Typical shape Description

Ultrasonic horn -- simple

Solid horns with a simple geometry (stepped, exponential, or catenoidal). May have a replaceable tip. Can have high gain.
Used for plastic spot welding and inserting and liquid processing.

Ultrasonic horn -- spool

Solid horn with a spool shape and large diameter (up to 1/2 wavelength). Has good amplitude uniformity across the face (generally >= 90%) and relatively low stress. Face must be flat or have only minor relief. Low gain.
Used for plastic welding of circular parts and liquid processing.



Ultrasonic horn -- bell

3/4 section

Unslotted horn with a cavity that extends to the node. Maximum diameter is generally <= 0.4 * wavelength. Moderate gain. May have considerable radial face amplitude.
Used for plastic welding of circular parts and liquid processing.

Ultrasonic horn -- slotted cylindrical

Large diameter horn with radial or cross-slots. Diameter usually >= 0.4 * wavelength. May have a face cavity. Low gain.
Used for plastic welding of circular parts.


Bar horns

A bar horn has a rectangular output face and is either unslotted or has slots in one direction only. The horn thickness is generally <= 0.35 * wavelength.


Typical shape Description

Ultrasonic horn -- unslotted bar

Horn width is generally <= 0.4 * wavelength. Moderate gain.
Used for plunge and scan welding and for some liquid processing applications (e.g., ultrasonic soldering).

Ultrasonic horn -- slotted bar

Horn width is generally >= 0.4 * wavelength. Special design techniques give optimum face amplitude uniformity. Moderate gain.
Used for plunge and scan welding.


Block horns

A block horn has a rectangular output face and has slots in two perpendicular directions.


Typical shape Description

Ultrasonic horn -- block

Width and thickness are generally >= 0.4 * wavelength. Unity gain.
Used for plastic welding of  large, flat, rectangular parts.


Special horns


Ultrasonic horn -- composite

High gain tip horns are driven by a common mother horn.
Used for spot welding of plastics and for liquid processing.


A horn that has a complex, often irregular shape machined into its face.
Used for plastic welding.



Full-wave bell

Ultrasonic horn -- full-wave rigid mount bell

This bell horn has an integral booster and is designed for liquid processing. The rigid mount flange provides a hermetic seal against the wall of the pressure vessel.
Metal welding

Ultrasonic horn -- metal welding

Metal welding tip and nut

Tip and nut details

Metal welding horns have a replaceable annular tip (typically tool steel) that is secured by a nut. The tip has multiple welding lobes.


Radial disk

Ultrasonic horn -- radial disk

The resonator is driven axially but the disk vibrates radially. Designed for use with a rigid mount booster.
Used for rotary seam welding of plastics.
Flexure disk

Ultrasonic horn -- flexure disk

The flexure disk is driven axially at its center but vibrates in bending with circular nodes. The amplitude decreases from the center to the edge. Compared to conventional horns, the disk has a large surface area with low mass. With the proper contour, the disk can produce a very narrow, intense acoustic beam.
Used primarily for airborne ultrasound  (drying, defoaming, agglomeration, etc.).
Radial sphere

Ultrasonic horn -- radial sphere

The resonator is driven axially but the sphere vibrates with a uniform radial motion. The sphere's diameter is approximately twice the axial thin-wire half-wavelength (about 250 mm at 20 kHz).
Used for atomization and cavitation.



Typical shape Description


The mounting ring is isolated from the booster body by O-rings.




Rigid mount

Ultrasonic rigid mount booster

Because the rigid mount booster is constructed only of metal (no compliant elastomers), it has excellent axial and lateral stiffness.
Used with heavy loads or where precise positioning is required and for rotating applications (e.g., seam welding; see radial disk). Also used where a hermetic seal at the mounting ring is required (e.g., for mounting through the wall of a pressure vessel); for an example, see the full-wave bell horn.






Ultrasonic cross-coupled booster

With a cross-coupled booster, the input and output surfaces are at 90 degrees, so the booster can essentially transmit ultrasound "around a corner". As with conventional boosters, various gains are possible. For the illustrated booster, the output amplitude from the top surface is 2.5 times greater than the input amplitude from the left surface. Note: the cross-coupled booster can also be used directly as a cross-coupled horn.

Transducers (converters)


Typical shape Description

Ultrasonic transducer

3/4 section

Typical transducer with four piezoelectric ceramics, center-bolt (Langevin) design. The housing and electrode leads are not shown.

For industrial applications, available power can range from 10 watts to 3000 watts, depending on the operating frequency, duty cycle, cooling, ceramic volume, and other factors.

Also see resonator design by finite element analysis.


Top | Home | Site Map | What's New | Company Information | Contact Us

Krell Engineering
212 E. Medwick Garth    Baltimore, MD  21228    USA

e-mail: info@krell-engineering.com