Ultrasonic cleaning is often understood through the lens of cavitation, the rapid formation and collapse of microscopic bubbles that dislodge contaminants at a microscopic level. But cavitation alone doesn’t determine how thoroughly or evenly a part is cleaned. The way a part moves through the tank also plays a critical role. One of the most commonly overlooked contributors to ultrasonic cleaning performance is mechanical agitation.
Unlike passive submersion, agitation introduces controlled movement that helps parts interact more fully with the ultrasonic energy. When components oscillate through the tank—rising and falling through high- and low-energy zones—they experience a more consistent scrubbing action. For parts with internal cavities or complex geometries, agitation can be the difference between a clean surface and one that traps residue out of reach.
Equalizing Energy Exposure Across Surfaces
Within any ultrasonic tank, cavitation energy doesn’t occur in a perfectly even field. High-intensity zones naturally form in certain areas of the tank based on the transducer layout, frequency, watt density, and standing wave patterns. Left stationary, a part may sit in a lower-energy band for the entirety of the cycle, especially if its geometry shields certain surfaces or if contaminants are located deep within cavities or blind holes.
By moving a part vertically through an oscillation or lift cycle, the part passes repeatedly through different bands of energy. The result is a more uniform scrubbing effect, applied not just to exterior surfaces but to internal features that would otherwise receive less cavitational impact. This up-and-down motion is subtle, but it dramatically improves coverage, especially when cleaning complex or irregular geometries. At Zenith Ultrasonics, we engineer agitation cycles with precision, matching motion speed and amplitude to the characteristics of the load and the cleaning chemistry being used.
Protecting Sensitive Materials from Cavitational Etching
Ultrasonic energy is powerful, but like any powerful force, it must be used with control. For certain materials, particularly soft metals such as aluminum or components with polished or machined finishes, excessive or concentrated exposure to ultrasonic energy can lead to cavitational etching. Cavitational etching is a form of micro-abrasion caused when the same surface area is subjected to high cavitational energy for prolonged periods without movement.
Mechanical oscillation provides a reliable safeguard. As the part moves through the cleaning tank, exposure time is distributed more evenly across its entire surface. No single area sits in the peak energy zone for too long, minimizing the risk of damage without sacrificing cleaning effectiveness. This is especially important in regulated industries like aerospace and medical manufacturing, where surface finish integrity is often as critical as cleanliness.
Clearing Cavities and Entrapment Areas
One of the more frustrating challenges in ultrasonic cleaning is residue left behind in recessed features. When contaminants are dislodged but not fully flushed from blind holes, channels, or cavities, they can remain trapped, even after cavitation has technically done its job. This is where agitation transitions from a cleaning enhancement to a necessary fluid dynamic tool.
Oscillating movement causes fluid to flow into and out of recessed areas, essentially pushing contaminants out through repeated changes in hydrostatic pressure. Each rise and fall encourages fresh solution to exchange within the cavity, loosening and removing debris that would otherwise settle back in place or remain suspended in stagnant pockets. Without this motion, even a well-formulated detergent and well-tuned ultrasonic field can fall short in cleaning internal spaces.
Designing for the Right Motion at the Right Time
Not all agitation is created equal. The timing, frequency, and amplitude of part motion need to be matched to the part size, basket design, and process requirements. Aggressive or erratic movement can disrupt cavitation or create turbulence that diminishes cleaning quality. Gentle, controlled oscillation, however, works in harmony with ultrasonic energy while the part remains at a consistent angle and orientation throughout the cycle.
Zenith designs motion into our systems as part of the core mechanical engineering process, not as an afterthought. Whether it’s a simple vertical lift cycle or a programmable multi-stage sequence with precision-controlled dwell and drain points, agitation is tuned to enhance—not interfere with—the ultrasonic process. This attention to motion also carries over to our blow-off and drying stages, where parts may need to rotate, tilt, or pause to facilitate faster, more complete drying.
A Smarter System Is Always in Motion
Ultrasonic cleaning is more than a chemical-and-cavitation equation. Motion—specifically engineered, controlled agitation—is a fundamental part of the process. From preventing cavitational damage to accelerating contaminant removal, agitation transforms ultrasonic cleaning from a static immersion into a dynamic and highly efficient solution.
At Zenith, we design systems that move with purpose. Every agitation cycle, lift stroke, or basket oscillation is engineered to maximize the effectiveness of cavitation, protect delicate parts, and ensure no contaminant gets left behind. It’s one of the many reasons customers in critical industries trust Zenith to build ultrasonic cleaning systems that perform reliably, cycle after cycle.
Let us show you how agitation, when properly integrated, can improve your ultrasonic cleaning results and reduce rework, water usage, and chemical load. Learn more about our customizable Advantage Automation System and request a complimentary demo cleaning.
