If you skimp on cost when purchasing an ultrasonic cleaning system for your business, you may find that while you save money up front, you will end up spending more money down the road on such things as electricity, detergent, replacement parts, time and energy

In today’s video, Frank shares characteristics that vary between makers of ultrasonic cleaning systems, which can result in higher costs if you decide to go with a less expensive system.

A Wide Variety of Ultrasonic Cleaning Systems

Remember that in today’s market, there are hundreds of different ultrasonic cleaning systems that are made and sold by dozens of different manufacturers and at wildly varying cost points. Here are some of the important factors to keep in mind when choosing an ultrasonic system.

Tank Size

Smaller capacity units cost less than those with bigger tanks, but may crowd parts and be less efficient at cleaning, which can result in dirty parts, or longer running times to get parts clean.

Wall Thickness.

Most cleaning systems are constructed of stainless steel, which is very expensive. Going with a cheaper, thinner wall tank, however, will result in the walls being more susceptible to the high frequency vibrations used in the cleaning process, and eventually will erode, crack, and leak.

Ultrasonic Transducers

In an ultrasonic system, the more transducers acting on the fluid, the more clean the parts will be. Lower cost cleaners use fewer transducers which requires a longer run time, or results in parts that aren’t fully cleaned.

Temperature Control

Ultrasonic cleaning systems work best when the detergent solution is maintained at an even 110-150 degrees. Cheaper systems may use lower-quality thermostats which don’t maintain a consistent temperature, so heating and run time will vary from batch to batch. As with other aspects of less expensive units, this can result in longer run times, or even possibly damaging parts if the temperature runs too hot.

Circulating Filtration Systems

When an ultrasonic cleaning system cleans, the removed contaminants fall to the bottom of the tank as sludge, or float to the top if oil and grease. These contaminants can interfere with the cleaning process. Higher end cleaners are usually fitted with filtration systems that can remove contaminants. Cheaper ones don’t always have built-in filtration, and will cost extra money in draining and detergent.

Accessories for Ultrasonic Cleaning Systems

Finally, higher-end systems have accessories included that usually have to be purchased separately with less expensive units. These accessories include baskets and trays, which are essential for keeping parts elevated during cleaning, and tank covers, which help keep the solution at a constant temperature and prevent evaporation.

When deciding between different ultrasonic cleaning systems, you don’t have to go with the most expensive one on the market, but if you go with the cheapest option available, you may find yourself spending more money in the long run.

Both work effectively, however each has some pluses and minuses; as a result, designers over the years have debated which type is preferable for use in an ultrasonic cleaner.

Piezoelectric and magnetostrictive transducers are used to generate sound waves in ultrasonic cleaning systems. Omegasonics compares each type of ultrasonic transducer.

We’re going to look at how each type of ultrasonic transducer works, the pros and cons of each type, and then let you decide which type would best suit your needs.

How Each Ultrasonic Transducer Works

The two types of ultrasonic transducers work in completely different ways to achieve the same result. In piezoelectric transducers, a crystal with special electrical properties (originally it was quartz, today it’s a modern ceramic called lead zirconate titanate) is connected with electrical wires attached to opposite faces of the crystal.

The crystal and wires are housed between two metal plates. When voltage is passed through the crystal, it changes shape. When the electricity is taken away, it returns to its original shape.  And when there’s no voltage at a given frequency, the crystal and the metal housing around it will resonate.

Magnetostrictive transducers work on the principle that iron-rich metals (originally it was iron and steel, today it’s Terfenol-D) expand and contract when they are placed in a magnetic field. To make a magnetostrictive transducer, many thin plates of this material are stacked up side by side to make a “core.” Copper wire is then wrapped cylindrically around the core, and the whole assembly is placed in a canister, with the top and bottom plates of the canister touching the ends of the core.

Since electricity produces a magnetic field, as soon as current is applied to the copper coil, the core grows in length. When the current is turned off, the core returns to its original shape. By using an alternating current source to power the transducer, it expands and contracts, causing the canister in which it’s housed to resonate.

Pros and Cons Related to Ultrasonic Cleaning

Method of Attachment – Piezoelectric transducers are attached to an ultrasonic cleaner housing using an adhesive, while magnetostrictive transducers are usually attached by welding the housing to the tank. Early on, magnetostrictive transducers had an advantage in this area, because the adhesives available were not very strong, and piezoelectric transducers would become detached. Today, however, with the advent of modern engineered adhesives developed for aircraft, the difference is negligible.

Transducer Frequency – For most parts and contaminants, ultrasonic cleaning is best done between 40 and 70 kHz, although some ultrasonic cleaners use frequencies as low as 25 kHz and as high as 170 kHz or higher. The highest reasonable frequency achievable in a magnetostrictive transducer is around 30 kHz, because in order to change the resonant frequency, the core must be made shorter and shorter, and the system eventually reaches such a low mass that no transmittal of the vibration occurs to the tank.

Piezoelectric transducers are not limited by this restriction, and can therefore accommodate the entire frequency range. Because of this, magnetostrictive transducers are usually limited to low frequency ultrasonic cleaning applications where the parts are large and contaminants are difficult to remove, but complete cleaning is not required.

Energy Consumption – Piezoelectric transducers convert low voltage electrical energy into mechanical energy in one step, making them very efficient. Magnetostrictive transducers convert electrical energy into magnetic energy, and then to mechanical energy. A lot of energy is lost in the form of heat during this process, and as a result, these transducers are less efficient. That means for equal amounts of ultrasonic cleaning, piezoelectric transducers will consume much less power

Inherent Noise Level – Since most piezoelectric transducers operate at 40 kHz and above, the first sub-harmonic frequency is above 20 kHz, which is beyond the range a human can hear. Magnetostrictive transducers operate at 30 kHz or less, which puts the first sub-harmonic in the audible range for humans (20 Hz to 20 kHz). The sound is identical to the hum emitted from a high-tension electrical line or transformer. When multiple magnetostrictive transducers are mounted to the same ultrasonic cleaner tank, the noise level is such that hearing protection is usually required.

Life Expectancy – When piezoelectric transducers were first designed (using quartz crystals), their strength would drop off over a period of time. Magnetostrictive transducers had no such issues, and as a result were the transducer of choice for a long time in ultrasonic cleaning systems. Later, as engineers began to develop the semiconductor ceramic materials used in piezoelectric transducers, they learned that “aging” the material before converting it to piezoelectric wafers eliminated 99 percent of the strength degradation. Because of this practice, piezoelectric transducers do not lose effectiveness with age like they once did, and magnetostrictive transducers lost their biggest advantage.

Having an integrated ultrasonic cleaning system in a facility allows for a smaller footprint for the machine, opening up the factory floor for other equipment and working space, provides a single point of electrical connection for all stages of the process, and makes the unit mobile so it can be moved around the facility as needed.

Complete ultrasonic cleaning stations are typically arranged as three- or four-stage systems. In a three-stage unit, the ultrasonic cleaner, rinsing station, and drying station modules are built into a single housing so parts can be quickly moved from cleaning process to cleaning process. The four-stage unit also adds a pre-wash module ahead of the ultrasonic cleaner in facilities where removing any loose scale, grease, oil, or dirt is helpful before parts are placed in the ultrasonic cleaner.

Multistage ultrasonic cleaning systems are compact, portable, and convenient. Omegasonics makes the DX3 and DX4 three- and four-stage ultrasonic cleaners.

Here’s a general overview of how each of the stages function

Pre-wash – This cycle is used to remove gross contamination from the surface of parts. This keeps the majority of sludge out of the ultrasonic cleaner, so it doesn’t need to be cleaned as often and allows the unit to do its job more efficiently. Designs vary, but the pre-washer may include a heater or spray nozzles to facilitate contaminant removal.

Wash – This stage is the heart of the ultrasonic cleaning unit. This provides the actual final cleaning to remove any residual contaminants from the surface, hidden passageways, blind holes, and cracks and crevices in the parts. These units are heated to optimize cleaning and have a programmable timing cycle to minimize the power and time used for cleaning.

Rinse – This cycle removes remaining detergents from the parts after they’ve been washed. Rinse stations are heated, and typically use de-ionized water or other specialized cleaning agents to ensure no residue is left behind.

Dry – A recirculating hot air dryer is the final stage, used to dry the parts quickly so they can be moved on to the next process. The drying step is also critical for parts that may oxide or rust quickly if moisture is not removed.

Automation – Some ultrasonic cleaning systems also come with automated pick-and-place systems. While this is useful for highly automated production systems, it is very expensive—often doubling the price of an integrated unit.

Omegasonics builds three- and four-stage ultrasonic cleaning systems—the DX3 and DX4, respectively. Our units are designed for maximum portability with built-in casters and a single point of connection for utilities, and fabricated from corrosion-resistant materials. They do not include automation, so they are reasonably priced and economical for even small and midsize businesses.

The high-efficiency hot air dryer is contained within the system to maximize space and improve convenience. We highly recommend them to any facility that uses ultrasonic cleaning regularly as a portion of its processes.

Contact us if you or your facility is looking for a convenient, compact, and economical solution for your ultrasonic cleaning system needs. You can also find us on LinkedIn and Twitter.

Every time a cleaning solution is handled—whether by the manufacturer during filling or processing, or by us when we pour it into our ultrasonic cleaners—it picks up small amounts of air that dissolve into the liquid.

These gasses—nitrogen, oxygen, and carbon dioxide, among others—stay dissolved in the solution until it is excited in some way and they get released, such as by heating, shaking, or yes, turning on our ultrasonic cleaning machine. And when they get released in this manner, they wreak havoc in the process, and render it ineffective until all of the gas is gone.

When we turn on our ultrasonic cleaners after filling them with fresh cleaning solution, the high-frequency pulsations begin to heat the gasses dissolved in the liquid. They start to collect and form large bubbles that eventually rise to the surface and escape, but while still in the tank, act like shock absorbers to prevent the pressure pulsations from forming the tiny, imploding bubbles necessary for effective ultrasonic cleaning.

Until all of the dissolved gas is gone, all of the energy created by the transducers goes into heating the gasses and gets absorbed by the bubbles they form, and as a result parts can’t be cleaned.

We can easily remedy the problem, however. We just have to remember to degas our solution anytime we add more or replace the existing cleaner. To degas the solution, we simply turn the ultrasonic cleaning system on with the new cleaner in the tank without any parts, and run it through a complete cleaning cycle. Adding a little heat, where possible, will speed up the process and remove the gasses more thoroughly and completely.

Ignoring the degassing step will not save time. In fact, it will cost time, since we will have to run parts through multiple cleaning cycles if we don’t first take the time to remove the dissolved gasses from the cleaning solution in our ultrasonic cleaning systems. It’s more efficient and effective to take the time as soon as new solution is introduced to degas it and get that step behind us, so we can clean parts properly later in the process.

Contact us for more information on ultrasonic cleaners. You can also find us on LinkedIn and Twitter.