When you switch on an ultrasonic cleaner, it uses high-frequency sound waves in a liquid tank to create microscopic bubbles that scrub dirt from every surface of your parts and lift contamination away from complex components far more consistently than with hand scrubbing alone.
In this guide, we walk through what happens inside the tank, which parameters matter, what you can and cannot clean, and how to use and check an ultrasonic cleaner safely in industrial and workshop settings.
Quick answer: how an ultrasonic cleaner works
An ultrasonic cleaner works by converting electrical power into high-frequency sound waves in a liquid tank, creating tiny bubbles that form and collapse on the surface of your parts and lift contamination away.
Inside the machine, an electronic generator sends a high-frequency signal (often between 20–40 kHz) to ultrasonic transducers bonded to the tank. The transducers vibrate the tank walls, which transmit pressure waves into the cleaning solution. These pressure waves create cavitation bubbles—microscopic voids in the liquid that repeatedly form and implode. When they collapse near a surface, they generate localized jets and shock waves that dislodge oils, chips, polishing residue and other soils.
Because the parts are fully submerged in the tank, this cavitation reaches blind holes, internal passages and fine detail that brushes, cloths or spray jets struggle to reach. The result is a highly repeatable cleaning process that depends on the right combination of solution, temperature, time, frequency and part fixturing.
Inside the machine: main components and their roles
At a high level, every ultrasonic cleaner uses the same building blocks: a tank, a generator, transducers, a basket or fixture, and a suitable cleaning solution. Understanding their roles makes it much easier to specify, operate and troubleshoot a system.
The table below summarizes the main components and what they do:
| Component | Main function | Notes |
|---|---|---|
| Tank (stainless steel) | Holds the cleaning solution and the parts | Size, shape and wall thickness affect energy distribution |
| Ultrasonic generator | Produces high-frequency electrical power for transducers | Controls frequency, power and sometimes sweep or pulse modes |
| Ultrasonic transducers | Convert electrical power to mechanical vibration | Bonded or bolted to tank walls or bottom |
| Cleaning solution | Transmits sound waves and dissolves/loosens soils | Chemistry must match material and contamination |
| Basket/part fixtures | Hold parts in position within the sound field | Prevents parts from touching tank; influences exposure uniformity |
| Heating system (if present) | Raises and maintains bath temperature | Warmer baths often improve cleaning; must respect material limits |
| Filtration (if present) | Removes loosened contamination from the bath | Extends bath life and stabilizes results |
In a well-designed system, the generator, transducers and tank are matched so that power is delivered efficiently into the solution. The basket or fixturing keeps parts away from the tank walls and arranges them so cavitation can reach all surfaces. The solution and temperature are then chosen to complement the mechanical action of cavitation for the specific soils and materials you are cleaning.
Cavitation explained: what really happens in the tank
Cavitation in ultrasonic cleaning is the formation and violent collapse of microscopic bubbles in the liquid, driven by the alternating high- and low-pressure cycles of ultrasonic sound waves.
As the transducers vibrate at ultrasonic frequency, they create regions of compression and rarefaction in the cleaning solution. During the low-pressure phase, tiny cavities or bubbles form. A moment later, in the high-pressure phase, those bubbles collapse. When a bubble collapses near a solid surface, it releases a small jet and shock wave that knocks soils off the surface. Multiply this by millions of bubbles collapsing every second, across the entire tank volume, and you get powerful, fine-scale cleaning action.
Some key points about cavitation in cleaning:
- Bubble size and intensity depend on frequency. Lower frequencies (e.g. 25–30 kHz) tend to create larger, more energetic bubbles, better for heavy soils on robust parts. Higher frequencies (e.g. 40–80 kHz) create smaller, gentler bubbles suited to fine features and more delicate components.
- The liquid matters. Viscosity, surface tension and dissolved gas content all influence how cavitation behaves. Freshly filled baths often need degassing for stable performance.
- Cavitation is not boiling. The bath can run well below boiling temperature; bubbles form because of local pressure changes, not because the liquid is vaporizing in bulk.
When designed and controlled correctly, this cavitation reaches into small holes, narrow gaps and complex geometries, which is why ultrasonic cleaning is so valuable for precision hardware, medical instruments and intricate mechanical parts.
Key parameters: frequency, temperature and cleaning time
The same ultrasonic cleaner can behave very differently depending on the operating parameters you choose. Frequency, bath temperature and cleaning time are three of the most important levers.
Frequency
Generally:
- Lower frequencies (around 25–30 kHz) produce larger, more aggressive bubbles and stronger mechanical action. They are well suited to removing heavy oils, carbon or baked-on contamination from robust metal parts.
- Mid frequencies (around 35–45 kHz) balance power and finesse and are widely used for general industrial parts cleaning.
- Higher frequencies (above ~60 kHz) produce smaller, gentler bubbles that are less likely to damage delicate features but still effective for fine particles and thin films.
If you are cleaning thick, robust components with stubborn contamination, a lower frequency system is often appropriate. If you are cleaning fine precision parts, delicate features or thin-walled components, a higher frequency—and sometimes even megasonic technology—may be preferable.
Temperature
Temperature affects both the chemistry and the cavitation:
- Warmer baths generally speed up chemical reactions and help dissolve oils and greases.
- Most industrial cleaning solutions operate best in a moderate temperature range (for example, 40–60 °C), but you must respect both the solution supplier’s data and the part material limits.
- Extremely high temperatures can reduce cavitation intensity and may risk distorting or damaging sensitive parts, plastics or adhesives.
Cleaning time
Cleaning time is another trade-off:
- Too short and soils remain; too long and you risk wasting cycle time or over-exposing sensitive parts.
- Typical cleaning times range from a few minutes for lightly soiled parts to 10–20 minutes or more for heavily contaminated items.
- It is good practice to validate cleaning time with test pieces and cleanliness checks rather than guessing.
In practice, you tune frequency, temperature and time together: robust, heavily contaminated metal parts might use lower frequency, higher temperature and longer cycles; delicate optics or medical devices might use higher frequency, moderate temperature and carefully limited exposure.
Liquids and solutions: what to use and what to avoid
The liquid in the tank is just as important as the ultrasonic energy. The right solution works with cavitation to lift soils away; the wrong one can damage parts, equipment or operators.
At a minimum, you need a compatible water-based solution with a chemistry that matches your materials and contamination. You also need to avoid unsafe liquids, particularly flammable or strongly corrosive ones.
Safe liquids and detergents for ultrasonic cleaning
For most applications, the starting point is clean water plus a purpose-formulated cleaning agent.
Typical examples include:
- Alkaline detergents for ferrous and non-ferrous metal parts with oils, greases or machining fluids.
- Neutral pH detergents for mixed materials, sensitive alloys or assemblies that include different metals and plastics.
- Enzymatic or specialised formulations for medical and laboratory instruments, where bioburden or specific soils must be removed before disinfection or sterilisation.
- Mild glass and optics cleaners for lenses, filters and optical components, used at appropriate concentrations.
Whichever chemistry you choose, make sure it is:
- Compatible with the part materials and any seals, coatings or adhesives.
- Approved for ultrasonic use by the chemical supplier.
- Supported by clear instructions on concentration, temperature and safety precautions.
Liquids you should never use in an ultrasonic cleaner
There are some liquids and chemistries that should never be used in open-tank ultrasonic cleaners because of fire, explosion, corrosion or material damage risks.
As a rule of thumb, avoid:
- Flammable solvents such as gasoline, kerosene and many hydrocarbon or alcohol-based solvents in open tanks. Cavitation plus heat can create vapours and ignition risks.
- Strong acids or alkalis that can attack the stainless steel tank, seals or part materials unless the system is explicitly designed for them.
- Chemistries incompatible with your parts, such as solutions that attack certain aluminium alloys, zinc, magnesium or sensitive coatings.
- Any liquid not supported by the tank manufacturer and chemical supplier for ultrasonic use.
If a process genuinely requires aggressive or flammable chemistries, it usually calls for closed-system equipment or alternative process designs—this is not a case for improvisation in a standard benchtop or open industrial tank.
What you can (and cannot) clean with an ultrasonic cleaner
Ultrasonic cleaning works best on hard, non-porous, water-tolerant materials and assemblies that can be safely submerged. It is particularly valuable when parts have internal passages, blind holes or fine features.
However, not everything belongs in the tank. Some materials and assemblies are at high risk of cracking, delaminating, swelling or losing their finish when exposed to cavitation and chemistry.
A simple way to think about suitability is in the table below:
| Item / material type | Typically suitable? | Notes |
|---|---|---|
| Machined metal parts (steel, stainless, Ti) | Yes | Ideal for removing oils, chips and polishing compound |
| Hard plastics rated for immersion | Often yes | Check chemical compatibility and temperature limits |
| Glass, ceramics, some optics | Yes, with care | Use appropriate chemistry and frequency to protect surfaces |
| Jewelry (solid metal, some stones) | Yes, with caveats | Avoid soft/porous stones and weak settings |
| Porous stones (opal, pearl, emerald, etc.) | Usually no | Risk of cracking, discolouration or moisture ingress |
| Glued or poorly bonded assemblies | Risky | Cavitation can weaken adhesive bonds |
| Unsealed electronics and MEMS | Often no | Moisture ingress and cavitation can damage internals |
| Coated or very thin-walled parts | Case-by-case | Validate carefully; risk of coating damage |
If you are handling critical or high-value components, it is always worth running sample tests and consulting both the equipment manufacturer and the component supplier before committing to a new ultrasonic process.
Jewelry and watches: when ultrasonic cleaning is a good idea
Ultrasonic cleaners are widely used for jewelry because they reach behind stones and into complex settings where dirt builds up. For solid metal jewelry (e.g. gold or stainless rings and bracelets) and water-resistant watch cases, they can be very effective.
However, you need to be careful with:
- Soft or porous stones, such as opal, pearl, turquoise and some emeralds, which can crack or absorb fluids.
- Heavily included or fracture-filled stones, where cavitation can exploit internal weaknesses.
- Non-water-resistant watches, where moisture ingress is a bigger risk than the cleaning itself.
As a rule, jewelry that a professional jeweler is happy to clean ultrasonically in their shop is a good candidate. If in doubt, check manufacturer guidance for the watch or jewelry and start with gentle settings.
Automotive and mechanical parts: ultrasonic cleaning in the workshop
In workshops and industrial maintenance, ultrasonic cleaning is often applied to carburetors, fuel injectors, hydraulic components, brake parts and precision mechanical assemblies.
Here, the benefits are clear:
- Cavitation reaches internal passages, jets and galleries that are hard to access mechanically.
- Heavy oils, carbon and varnish can be softened and removed using appropriate alkaline cleaners and elevated temperatures.
- Consistent exposure in the tank reduces the variability you get from manual scrubbing.
You still need to watch for:
- Seals and elastomers that may not tolerate the chosen chemistry or temperature.
- Coatings or plated layers that could be undercut if the solution is too aggressive or cycles are too long.
Testing on scrap parts or less-critical components before standardising a process is good practice.
Other specialised use cases (retainers, dental devices, gun parts)
Ultrasonic cleaners are also used with:
- Dental retainers and mouthguards, usually with consumer or dental-office devices and chemistry designed specifically for oral devices.
- Gun parts, where ultrasonic cleaning can remove carbon and fouling from small passages and surfaces more thoroughly than simple soaking.
In these cases, the mechanism is the same, but the risk profile and regulatory environment can be different. It is important to follow the instructions for the specific device and chemistry being used and, where applicable, to align with professional or regulatory guidance in your region.
How to use an ultrasonic cleaner step by step
Using an ultrasonic cleaner correctly is mostly about following a consistent sequence and respecting the limits of your parts, solution and equipment.
A typical cycle looks like this:
- Inspect the tank and equipment
Check that the tank is clean, free from damage and correctly installed. Verify that any filters, lids and safety devices are in place. - Choose and prepare the cleaning solution
Select a solution compatible with your materials and soils. Mix to the recommended concentration using clean water, and fill the tank to the indicated level. - Degas and warm the bath (if required)
Run the cleaner without parts for a few minutes to drive off dissolved gases. If your process calls for a certain temperature, use the heater to bring the bath into the recommended range. - Load parts in baskets or fixtures
Arrange parts so they do not touch the tank walls or each other excessively. Avoid stacking parts in ways that create shadowed surfaces where cavitation cannot reach. - Set frequency and power (if adjustable)
Choose appropriate settings based on the robustness of the parts and the soils you are removing, following your validated process parameters. - Set cleaning time and start the cycle
Use a timer to control exposure. Start with validated times from previous tests or supplier recommendations and adjust only based on cleanliness checks. - Rinse parts after cleaning
Remove parts from the tank and rinse them with clean water (or the specified rinse solution) to remove any remaining chemistry and loosened soils. - Dry and inspect parts
Dry parts with air, heated dryers or other methods suitable for your material. Inspect key features to confirm that required cleanliness levels are achieved. - Maintain the bath and equipment
Skim or filter out solids as needed, monitor solution condition, and change or filter the bath according to your process plan to maintain performance.
Following these steps consistently will give you much more stable ultrasonic cleaning results and makes process validation easier.
Do ultrasonic cleaners really work? Advantages and disadvantages
When correctly specified and used with the right solution and parameters, ultrasonic cleaners are highly effective at removing oils, particles and residues from complex parts. They do not solve every cleaning problem, but they are a powerful tool in the right context.
Advantages
- Deep cleaning of complex geometries – Cavitation reaches internal passages, blind holes and fine features better than hand tools or simple soaking.
- Consistency and repeatability – Automated cycles with controlled parameters reduce variability from operator technique.
- Reduced manual labour – Less time spent scrubbing and more predictable throughput.
- Good compatibility with multi-stage lines – Ultrasonic stages integrate well with pre-wash, rinse and drying steps.
Disadvantages and limits
- Equipment and setup cost – Industrial ultrasonic systems and appropriate chemistry represent a real investment.
- Not a sterilisation method – Ultrasonic cleaning removes soils but does not disinfect or sterilise on its own; medical devices still require validated disinfection/sterilisation stages.
- Sensitivity to process control – Poor solution choice, over-loaded baskets or incorrect parameters can lead to inconsistent results.
- Potential for damage – Certain materials, coatings or assemblies are at risk if mis-processed.
Overall, ultrasonic cleaners do work extremely well when the chemistry, parameters and equipment are matched to the application and when the process is validated rather than improvised.
Safety and delicate parts: managing risk with ultrasonic cleaning
Ultrasonic cleaning is safe when used correctly, but cavitation and chemistry can cause damage if applied blindly, especially to delicate components. Managing risk means understanding what can go wrong and building that awareness into your process.
Key safety themes include:
- Material and assembly compatibility – Cavitation can exploit weak bonds, thin sections and fragile finishes.
- Chemistry hazards – Some solutions are corrosive or harmful if mis-handled; others can produce hazardous vapours at elevated temperature.
- Operator safety – Proper lids, ventilation and PPE should be used when recommended by the solution supplier and equipment manufacturer.
If you are unsure about a new application, the safest path is to consult both the equipment documentation and the part/component manufacturer and to run controlled tests on representative samples.
Delicate electronics, optics and MEMS: when ultrasonic cleaning is appropriate
For delicate electronics, optical components and MEMS devices, ultrasonic cleaning can be either very helpful or very risky, depending on how it is used.
Cases where ultrasonic cleaning is often acceptable (with care):
- Certain printed circuit boards (PCBs) and assemblies designed for cleaning, when processed with compatible chemistry and parameters.
- Optical lenses and filters made from glass or appropriate materials, using mild solutions and higher frequencies.
- Some MEMS or sensor components specifically designed for wet cleaning processes.
Cases where ultrasonic cleaning is often not recommended:
- Unsealed electronics not intended for immersion, where moisture ingress and cavitation can cause latent failures.
- Very fragile optics or coatings with unknown resistance to both chemistry and cavitation.
- Components where the manufacturer explicitly forbids ultrasonic cleaning.
The key is to use validated recipes and to follow manufacturer guidance closely rather than assuming that any delicate device is safe to immerse. When in doubt, consult standards and industry guidance, and consider referencing external resources such as more detailed background on ultrasonic cleaning to support your internal procedures.
Troubleshooting: how to check if your ultrasonic cleaner is working properly
A well-set-up ultrasonic cleaner gives consistent results; when it does not, you need a few simple checks to distinguish equipment issues from process variables.
Some practical checks include:
- Observe cleaning performance on sample parts
If previously easy-to-clean test pieces suddenly come out with visible residue under the same conditions, something has changed. - Look at the bath surface and sound
A working cleaner typically shows a fine, energetic pattern on the surface and a characteristic ultrasonic hum. A completely still surface may indicate a problem, though visual cues alone are not enough. - Perform a simple foil test
Suspend a piece of thin aluminium foil in the bath and run a short cycle. In an active sound field, the foil will show a pattern of pinholes and pitting where cavitation occurs; large untouched areas may indicate dead zones. - Check solution condition and temperature
Old, contaminated or incorrectly mixed solutions, as well as baths far outside the recommended temperature range, can significantly reduce performance even when the hardware is functioning correctly. - Verify load and fixturing
Overloaded baskets, tightly nested parts or contact with the tank walls can reduce effective cavitation on the parts you care about.
If these checks point to a persistent issue despite fresh solution and correct loading, it may be time to consult maintenance or the equipment supplier about transducer, generator or tank health.
Where ultrasonic cleaning fits in an industrial cleaning line
In many industrial environments, ultrasonic cleaning is not a standalone step but one stage in a multi-stage cleaning line. A typical line might look like this:
- Pre-wash or pre-degrease
- Ultrasonic cleaning
- Rinse (possibly multiple stages)
- Drying
In this context:
- The pre-wash stage removes bulk contamination and protects the ultrasonic bath from being overwhelmed by heavy soils.
- The ultrasonic stage then focuses on removing remaining films and particles from difficult geometries.
- Rinse stages remove chemistry and any remaining loose contamination, ensuring residues do not remain on critical surfaces.
- The drying stage stabilises cleanliness and prepares parts for subsequent processes (assembly, coating, sterilisation, etc.).
Ultrasonic cleaning also sits alongside other technologies:
- Spray and jet-washing systems for high-throughput cleaning of less complex geometries.
- Megasonic systems (higher frequencies, gentler cavitation) for extremely delicate substrates like semiconductor wafers.
- Manual cleaning stations for special cases, rework or areas where inspection and manual intervention are required.
For engineers, the key decision is where ultrasonic cleaning adds the most value in the line. For deeper safety and procedure details in regulated environments, you can refer to resources such as this technical guide on ultrasonic cleaning in sterile processing.
If you want to explore equipment options or custom line designs, you can review our ultrasonic cleaning machines and systems on the Ultrasonic CleanTech website.
Summary and key takeaways
An ultrasonic cleaner works by sending high-frequency sound into a liquid bath, creating cavitation bubbles that collapse against your parts and scrub away contamination—even in blind holes and fine features. The real performance comes from correctly matching equipment, solution and parameters to your specific materials and soils.
When evaluating or running an ultrasonic process, keep these points in mind:
- Choose appropriate chemistry and avoid unsafe liquids; water-based, purpose-designed solutions are the norm.
- Confirm that parts and materials are suitable, and treat delicate electronics, optics and porous or glued items with particular care.
- Control frequency, temperature and time based on validated tests—not guesses—and monitor solution condition.
- Use simple checks and tests to verify that the cleaner is working and that your line integration (pre-wash, ultrasonic, rinse, dry) supports consistent results.
Used correctly, ultrasonic cleaning is a powerful tool for industrial parts cleaning and maintenance. If you need help matching a system to your application, our team can work with you to translate these principles into a validated, repeatable process.
