Ultrasonic cleaners are unsurpassed when it comes to removing contaminants from virtually any hard surface that can be safely immersed in a cleaning solution. The challenge is selecting the correct ultrasonic cleaner; its accessories, cleaning solution formulations, and cleaning procedures to accomplish tasks in the most efficient manner. That s why we put together this guide. While it should be helpful, you may have additional questions concerning your particular requirements. If so, please contact us for the answers. Before digging into the 10 things you should know let s start with a brief explanation of the process. Ultrasonic cleaners are fitted with transducers attached to the bottom of a tank filled with the cleaning solution. Transducers create vibrations at high frequencies measured in thousands of cycles per second (khz) and send sound waves through the cleaning solution. These waves produce millions of tiny vacuum-filled bubbles that shoot out powerful jets of liquid when they implode. The force of the implosions, called cavitation action, lifts contaminants off objects being cleaned. The process is tough enough for carburetors but gentle enough for electronics and surgical instruments. Got that? Now let s get into equipment selection.
1. What are you trying to accomplish? While we use the term ultrasonic cleaner these devices do a lot more than clean parts, be they engine components, injection molds or surgical implants. For example, they are used to degas solvents, disperse nanoparticles, and emulsify, dissolve, disperse and otherwise prepare lab samples. If you are cleaning parts, to get started you need to consider the following before making a selection: Type of contamination to be removed. There s a big difference, as you can imagine, between removing coolant from machined parts, varnish deposits from a carburetor, ink from printing rolls, and blood and tissue residues from surgical instruments. The composition of products being cleaned. Different parameters apply to cleaning aircraft engine components and glass capillaries. You ll need compatible cleaning solution and ultrasonic cleaning frequency. How will the parts be used after cleaning? How do you define clean? Will you be cleaning batches or individual parts? Component size and weight Once you define exactly what you re trying to accomplish the following points will help narrow down your equipment selection. Armed with information you are then ready to contact Tovatech for specific recommendations.
2. How large are the parts you ll be cleaning? Measure the dimensions of largest parts to be cleaned and make sure to select a tank that will accommodate these parts. In addition, pay attention to the internal dimensions of the parts basket, since this is most likely where you will put the parts during cleaning. We ll discuss the importance of the basket in the next section. You ll also need to know the working depth of the cleaning fluid as it relates to the size of parts you re cleaning. The working depth is the distance from the inside bottom surface of the basket to the surface of the liquid in a filled tank. It s important because parts being cleaned must be fully immersed in the liquid. Product specifications for benchtop ultrasonic cleaners may not include this information. If they do not, feel free to contact us for this information.
3. Yes! You need a parts basket. Why? Baskets are used to support parts in an ultrasonic cleaner. They affect cleaning efficiency and the lifetime of the tank. Baskets with insulated handles facilitate placing and removing parts being cleaned in hot liquid. They also keep parts off the tank bottom where they suppress vibration and lower cleaning effectiveness. In terms of tank life, keep in mind that the bottom of the tank is a vibrating membrane. Any solid item, particularly a metal part, can act as a drill while the ultrasound is operating. Over time this can wear a hole in the tank. That s a good enough reason to use baskets. Parts positioned on the bottom of the tank can also damage transducers. Some baskets hang on the tank rim; others are equipped with rubber- coated feet positioned near the corners of the tank bottom where there is minimal vibration. Fine mesh baskets for small parts can be positioned in beakers or inside standard baskets. The industrial Elmasonic X-tra basic unit has brackets to hang the basket in two different positions: while cleaning or while draining the liquid from the parts after cleaning.
4. Do you need a heater? Most cleaning operations are much more effective with heating. It s a lot like doing laundry. A hot cleaning solution is best for removing oils, machining coolants and a whole host of other contaminants from just about any surface you can think of. Although heat is a natural byproduct of ultrasonic cavitation, cleaning efficiency increases when you give it a boost by using ultrasonic cleaners with thermostat-controlled heaters. Examples are the Elmasonic E, S and P series. These can be adjusted in increments to 80⁰C above which cavitation is inhibited and cleaning efficiency levels off. On the other hand if you are removing blood, don t use heat at all.
5. Do you need Sweep mode operation? We re not talking about brooms here. Sweep mode is a small continuous variation of the ultrasonic frequency around a central value, such as 40 khz±3 khz. When an ultrasonic cleaner operates at a fixed frequency without Sweep there are three potential problems: hot spots, dead zones, and harmonic vibrations. Hot spots are areas with a high concentration of cavitation bubbles, i.e. a stronger ultrasonic effect. If the ultrasonic cleaning is too intense this can cause etching on delicate parts with fine features, and on polished surfaces or thin layers of soft metals. Dead zones are areas where there is no cavitation, i.e. no cleaning. Nearly all Elma models have Sweep mode for uniform cleaning. This can be critical for demanding applications such as cleaning precision parts or surgical instruments. Harmonic vibration can develop when the fixed ultrasonic frequency causes parts to resonate. This is potentially damaging to sensitive components such as fine wires or crystals. Harmonic vibration is particularly undesirable when cleaning electronics and printed circuit boards. Always operate an ultrasonic cleaner in Sweep mode to protect sensitive electronics.
6. What ultrasonic frequency do you need? Most ultrasonic cleaners operate between 35 and 45 khz. This frequency range is well suited to the vast majority of cleaning tasks. A lower frequency such as 25 khz produces larger cavitation bubbles. When these bubbles implode they release a larger amount of cleaning energy. For coarse cleaning such as removal of lapping abrasives or polishing paste, a lower frequency will be more effective. Note that the lower the frequency, the louder the cleaning operation. Sound-deadening tank lids with insulation are a good idea when operating at 25 khz. A higher frequency produces smaller cavitation bubbles. These cover fine featured complex surfaces more thoroughly and are gentler than low frequencies. For fine cleaning of very delicate jewelry, electronics, and soft metals with polished surfaces consider a unit operating at 80-130 khz. If you are cleaning capillary tubes or spectrophotometer cuvettes you will need a unit that operates at 80 khz or higher. If you are cleaning a variety of materials consider a dual-frequency ultrasonic cleaner. An example is the Elmasonic X-tra basic industrial unit that can be set to 25 khz for coarse cleaning and to 45 khz for fine cleaning. Benchtop TI-H MF3 models operate at 35 or 130 khz and TI-H MF2 models operate at 25 or 45 khz. Elmasonic P models operate at 37 or 80 khz.
7. When it comes to ultrasonic power, the important number is watts/gallon (or watts/liter). Which model is stronger? sounds like a simple question but it s really pretty complicated. An ultrasonic cleaner consumes electrical power evenly but it is released in intervals to create sound waves. Some manufacturers report ultrasonic peak power and others report average or effective power. Peak power is defined as the ultrasonic power generated at the summit of the vibration amplitude. In some cases the peak power equals 2X the average power. But in other models peak performance may be 4X or 8X the average power depending on the wave shape. You don t need to understand the physics but you do need to understand that while it makes sense to compare the average power of two different units of the same size, it s not meaningful to compare peak power of one unit to average power of a different unit. You would be comparing apples with oranges. Generally the larger the volume of solution, the more ultrasonic power is needed for cleaning. Most table top cleaners run at an average power of 50 to 100 watts per gallon. Note that high capacity industrial tanks operate efficiently at lower power densities than bench top models. While more power usually indicates faster and more effective cleaning, more power is not always better. Too much power can damage electronic parts, the surface finish on a soft metal (e.g. aluminum), and other delicate items. For cleaning extremely sensitive items, adjustable power is a useful feature. Examples are the Elma TI-H and P series. And a caution: Don t try to increase the effective power of an ultrasonic cleaner by under-filling the tank. Ultrasonic cleaner generators that power transducers are tuned to a particular fill level. Operating the unit with less fluid can damage the generator and will result in less than optimized cleaning.
8. Do you need Degas mode? If you are cleaning parts, keep in mind that every time you fill the tank with fresh cleaning solution you must degas the solution before the unit can clean effectively. Entrained or dissolved air inhibits cavitation, and cavitation is the mechanism that accomplishes the cleaning. A Degas mode will enable you start cleaning sooner after you fill the tank. It does the job by switching on and off causing air bubbles to coalesce and allowing them rise to the surface and burst. Pulse mode provides intermittent spikes of very high ultrasonic power to remove stubborn contaminants. Pulse mode also degasses solutions very effectively. If you are degassing solvents select a model that has either a Degas mode or a Pulse mode. An ultrasonic cleaner without these modes will also degas your solvents, but will do so at a slower rate.
9. If you are preparing laboratory samples it s best to purchase a unit that has both Sweep and Normal (fixed frequency) modes. Examples are the Elmasonic S and Elmasonic P series. Only trial and error will indicate which mode will best dissolve, disperse, homogenize, or mix your samples. If you are disaggregating liposomes, select a unit with adjustable power since you will need to find the power level that disperses your samples without damaging them. If you are dispersing nanoparticles, select a unit with extremely high ultrasonic power such as the Elmasonic P. Similarly, if you are working with difficult to dissolve samples, select a high power unit. Pulse mode, which produces intermittent power spikes, will also assist in dissolving challenging samples. A variety of accessories are available to support the use of ultrasonic cleaners in the lab. Blending, dissolving and dispersing are facilitated when suspending samples in a water bath with a surfactant. Use Erlenmeyer flask holders, flask clamps, test tube holders or specially designed lids to hold beakers. If high bath temperatures are a concern a cooling coil attached to a cold water line serves as a heat exchanger to prevent the bath from heating up.
10. A word on cleaning chemicals. The correct cleaning solution chemistry is as important as ultrasonic frequency, power and other points covered in this selection guide. You should contact Tovatech for detailed information on the correct formulation for your jobs. Most commonly used chemistries fall into three categories: alkaline, acidic and neutral. They are usually supplied as concentrates so a little goes a long way. Their non-toxic biodegradable chemistry eases disposal concerns. Here are brief examples of the three categories: The alkaline elma tec clean A series is produced in several formulations to handle specialized or general purpose cleaning. Elma tec clean A4 and tec clean A1 are our most popular cleaning solutions. Elma tec clean A4 is a universal cleaner and degreaser for all types of metals and most plastics; it s a great choice for cleaning automotive parts such as carburetors. Elma tec clean A1 is a free-rinsing formulation preferred for applications where the parts must be rinsed free of any chemical residue after cleaning. This includes cleaning optics and electronics, especially printed circuit boards. Acidic ultrasonic cleaning concentrates such as elma tec clean S1 are used for removing corrosion, oxidation, minerals and rust. Neutral elma tec clean N1 is a phosphate-free emulsifying cleaning concentrate for gentle cleaning action. It is used for the treatment of highly sensitive pieces. Neutral elma clean 260 dip & splash is a free-rinsing formulation specially developed for cleaning aluminum and laser machined parts.
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