Quick Guide to Ultrasonic Cleaning

What is ultrasonic cleaning?

Ultrasonics is the term used for vibrations that are inaudible to the human ear. It is commonly used in cleaning applications and for cleaning components with complex geometries, where standard cleaning principles or manual cleaning methods can sometimes fail.

It’s a cleaning method that can effectively reach blind holes while also protecting delicate surfaces, which is why the technology has been a mains tay in the watchmaking and many other precision sectors, e.g. medical, aerospace, for many years. Being non-contact and non-abrasive, it’s a great choice for small components where manual cleaning would increase the risk of damage.

Ultrasonic cleaning machines come in many different sizes and with different levels of automation. However, in all cases, parts are submerged within a basket in a tank fort he cleaning process to be effective.

The science behind ultrasonic cleaning

Ultrasonics uses high-frequency sound waves (20–130 kHz) to create stable or transient cavitation in liquid, lifting off contaminants.

Stable vs. Transient Cavitation

Stable cavitation

Oscillating microbubbles help with rinsing by stirring the fluid and promoting exchange at the component surface.

Transient cavitation

Microbubbles collapse violently, producing shockwaves and microjets ideal for heavy-duty cleaning.

Microbubbles from stable and transient cavitation implode against surfaces, dislodging contaminants like grease and dirt. Naturally, different frequencies produce different levels of cavitation, depending on the strength of cleaning you need:

• 25–30 kHz: Strong cavitation for robust parts with heavy contamination.
• 35–45 kHz: All-purpose cleaning (most common).
• 80+ kHz: Gentle cleaning for fine details and delicate surfaces.

Elma ultrasonic cleaners often feature multi-frequency options for enhanced cleaning flexibility, as well as various modes such as Sweep, Pulse, Eco, and others, tailored to meet your specific needs.

Elma Ultrasonic Cleaning Modes

Sweep Mode

Frequency modulation spreads cavitation zones, compensating for sound field nodes.

Pulse Mode

Temporarily boosts power for stubborn contamination.

Eco Mode

Reduced energy use while still generating transient cavitation—great for everyday cleaning.

Dynamic Mode

Alternates Sweep and Pulse for maximum surface coverage and intensity.

Degas Mode

Prepares the tank by removing excess dissolved gas, especially useful after refills.

Ultrasonic cleaning also requires specialist chemicals

Detergents significantly enhance this ultrasonic cleaning process by reducing the surface tension of water and improving cavitation efficiency:

Surfactants:

These chemicals reduce surface tension, allowing water and other cleaning solutions to get into small crevices and lift dirt more efficiently. They also emulsify fats and oils.

Types of Surfactants:

There are several classes, each suited for specific cleaning tasks:

• Anionic surfactants: Ideal for removing heavy oils and greases.
• Cationic surfactants: Excellent for neutralising certain contaminants and providing anti-static properties.
• Nonionic surfactants: Offer excellent wetting and emulsifying capabilities, suitable for precision cleaning of sensitive components.
• Amphoteric surfactants: Flexible and gentle, typically used for delicate or mixed-material components.

Careful selection and precise dosing of cleaning chemicals will maximise cleaning effectiveness, protect component integrity, and optimise energy usage.

How to effectively implement an ultrasonic cleaning solution

The best approach is to consult with the experts. Turbex is a recognised leader and can help design an ultrasonic package that works for your business.

In general, a successful ultrasonic cleaning solution will need careful consideration to work as intended. Your supplier should cover:

• Choosing the right system or machine for your facility
• Making sure you have the right cleaning chemicals for your application
• Installation and commissioning of the system
• Training and troubleshooting
• Further optimisations to maximise throughput and minimise operating costs.

Of course, this process differs depending on your machine and facility. Successfully implementing a small tabletop ultrasonic system like the P Range is straightforward.

Commissioning a large, custom-built Evo Automated system is an involved process that requires significant consultation and engineering support.

What process parameters might you need to optimise?

Finding the ‘sweet spot’ with ultrasonic cleaning may take some time. Turbex recommend experimenting until you find a balance between cleaning speed, energy efficiency, and cleaning results that suit your needs best. A fast and robust cleaning process may use more energy, but that might suit your production speed best.

The seven key parameters to consider when optimising are:

Temperature:

What is the minimum temperature you need to degrease and clean your parts? Determining this will optimise your cleaning. Higher temperatures accelerate cleaning and enhance the chemical activity, but it may also damage components and cause higher energy bills.

Did you know?

The temperature sweet spot for cavitation is between 30–70°C, balancing vapour pressure, viscosity, and surface tension.

Power & frequency:

Find the mode on your Elma machine that works best. Different frequencies will offer a range of results based on your contamination type. Getting the right frequency is essential for cleaning effectiveness and power consumption.

Cycle time:

Excess time cleaning wastes energy and could harm surface finish. Experiment to find the cycle time that achieves your desired cleanliness levels without using excessive force and energy.

Fixtures & baskets:

Always ensure you use the correct mesh baskets for your machine, and orient the components correctly for effective cleaning. The right basket helps the ultrasonic action access your parts efficiently, while also protecting them from damage.

Did you know?

Water gas content influences cavitation and cycle time? High gas = big bubbles = less effective cleaning.

Positioning parts:

Much like a dishwasher at home, carefully positioning your parts for maximum contact between the cleaning solution and contamination is essential – especially if your parts are complex in geometry. Positioning affects not only the ultrasonic action, but also the rinsing and drying actions.

Bath vs. Individual cleaning:

If your parts are delicate or very complex, cleaning them alone may be the best option. Batch cleaning is most efficient for simpler components.

• To scale throughput, consider larger tanks or multiple machines. Having multiple tanks running different operations can assist in efficiency.
• If you work with mixed loads, bunch similar components together in the same wash cycle. It’s also worth investing in adjustable baskets to accommodate different parts in the same cycle.

Post-cleaning:

Cleaning doesn’t stop after the wash stage. Consider if your parts need a rinsing stage or drying for optimal results. Machines with automated drying systems slash time usage and protect parts.

Real-world example: Cleaning surgical implements using a multi-stage Elma system

Step 1: Preparation

Instruments are carefully arranged in baskets. Items are aligned with space between them to facilitate:

• Complete liquid contact during cleaning and rinsing.
• Efficient drainage during drying.

Step 2: Automated Loading

A conveyor system transports the basket to a pickup point. A robotic gripper lifts the basket and places it into the first cleaning tank. The basket is attached to an oscillation unit, which moves it vertically (~3–5 cm/min) to improve cavitation exposure.

Step 3: Primary Cleaning (Tank 1)

• Ultrasonic Frequency: 25 kHz (low frequency → strong cavitation).
• Mode: Pulse Mode – enhances cleaning power through short bursts.
• Temperature: 60–70°C
• Water Type: Softened or standard town water.
• Cleaning Chemistry: Alkaline, surfactant-based detergent.
• Duration: 10 minutes
• Dirt removal: Mechanical cleaning aided by strong transient cavitation.

Step 4: First Rinse (Tank 2)

• Ultrasonic Frequency: 45 kHz (gentler, effective for residue removal).
• Temperature: 50°C
• Water Type: Softened water
• Purpose: Removes entrained dirt particles and cleaning agent residue.

Step 5–6: Cascade Rinsing (Tanks 3 and 4)

Tank 3:

• Ultrasonic Frequency: 37 kHz
• Water: Deionised water (DI water)
• Temperature: 50°C

Tank 4:

• Ultrasonic Frequency: 130 kHz (fine-detail, non-damaging).
• Water: Fresh DI water

Cascade Setup:

• Water flows from Tank 4 to Tank 3 via overflow (cascade system).
• Ensures final rinse water is always of the highest purity.

Step 7: Drying (Tank 5)

• Method: Hot air drying
• Design: Tank-style dryer with flowing warm air.
• Purpose: Removes residual water, prepares parts for further processing or sterilisation.

Step 8: Unloading

The transporter moves baskets to an unloading unit. Cleaned instruments can now be packed or sterilised.

Additional Processes:

• Degassing: All tanks are degassed during preheating to optimise cavitation.
• Filtration: Each tank filters out the removed contaminants post-process.

Smart Automation:

• Oscillation units in each chamber.
• Cascade flow for water economy and purity.
• Potential for custom features, such as lift-outs or rotational baskets.