1. What is cavitation?
”Cavitation" is the rapid formation and collapse of
millions of tiny bubbles (or cavities) in a liquid. Cavitation is
produced by the alternating high and low pressure waves generated by
high frequency (ultrasonic) sound. During the low pressure phase, these
bubbles grow from microscopic size until, during the high pressure
phase, they are compressed and implode.
2. What is degassing, and why should it
”Degassing" is the initial removal of gases present
in the solution. Useful cavitation occurs after gasses have been removed
from the cleaning solution, leaving a vacuum in the formed bubble. When
the high pressure wave hits the bubble wall, the bubble collapses; it is
the energy released by this collapse that will assist a detergent in
breaking the bonds between parts and their soils.
3. How do I get the
best ultrasonic cleaning?
There are many considerations important to ultrasonic
cleaning. Optimizing these variables will produce the best cleaning. The
most important decisions to be made are choosing the proper cleaning
solution, cleaning at the right temperature for the correct amount of
time, and choosing the right size and type of ultrasonic cleaner.
ultrasonic cleaning damage my parts?
With certain cautions, ultrasonic cleaning is
considered safe for most parts. While the effects of thousands of
implosions per second is very powerful, the cleaning process is safe
since the energy is localized at the microscopic level. The most
important cautionary consideration is the choice of cleaning solution.
Potentially adverse effects of the detergent on the material being
cleaned will be enhanced by the ultrasonics. Ultrasonic cleaning is not
recommended for the following gemstones: opal, pearl, emerald,
tanzanite, malachite, turquoise, lapis and coral.
5. What is direct and indirect cleaning?
Direct cleaning occurs when the parts are cleaned in
a cleaning solution which fills the cleaner, usually inside a perforated
tray or mesh basket. The limitation of direct cleaning is that a
solution must be chosen that will not damage the ultrasonic cleaner.
Indirect cleaning involves placing the parts to be cleaned in an inner
non-perforated tray or beaker that often contains a solution that the
user may not want directly filling the ultrasonic tank. When choosing
indirect cleaning, make sure that the water level inside the tank itself
is maintained to the fill line (about 1" from the tank top) at all
6. Why is a special
solution required for cleaning?
Soils adhere to the parts... if they didn't, the soil would just fall
off the parts! The purpose of the solution is to break the bonds between
parts and their soils. Water alone has no cleaning properties. The
primary purpose of the ultrasonic activity (cavitation) is to assist the
solution in doing its job. An ultrasonic cleaning solution contains
various ingredients designed to optimize the ultrasonic cleaning
process. For example, increased cavitation levels result from reduced
fluid surface tension. An ultrasonic solution will contain a good
wetting agent or surfactant.
7. What cleaning solution should I use?
Modern ultrasonic cleaning solutions are compounded from a variety of
detergents, wetting agents and other reactive components. A large
variety of excellent formulations are available, designed for specific
applications. Proper selection is crucial for acceptable cleaning
activity and to preclude undesirable reactivity with the part being
8. What cleaning solution shouldn't I
Flammables or solutions with low flash points should
never be used. The energy released by cavitation is converted to heat
and kinetic energy, generating high temperature gradients in the
solution, and can create hazardous conditions with flammable liquids.
Acids, bleach and bleach by-products should generally be avoided, but
may be used with indirect cleaning in a proper indirect cleaning
container, such as a glass beaker, and appropriate care. Acid and bleach
will damage stainless steel tanks, and/or create hazardous conditions.
should solutions be changed?
Cleaning solutions should be replenished when a noticeable decrease in
cleaning action occurs, or when the solution is visibly dirty or spent.
A fresh batch of solution at each cleaning session is usually not
10. Why must I keep solution at the
tank's level indicator?
The solution level should always be maintained at the level indicator in
the tank, with trays or beakers installed. The ultrasonic cleaning
system is a 'tuned' system. Improper solution levels will change the
characteristics of the environment, can affect the system frequency,
decrease effectiveness, and potentially damage the cleaner. Maintaining
the proper solution level provides optimum circulation of solution
around parts, and protects heaters and transducers from overheating or
11. What is the
length of cleaning time?
Cleaning time will vary, depending on such things as
soil, solution, temperature and the degree of cleanliness desired.
Highly visible removal of soils should start almost immediately after
the ultrasonic cleaning action begins. Cleaning time adjustment is the
easiest (and most often misapplied) factor used to compensate for
process variables. Although new application cycle duration can be
approximated by an experienced operator, it usually must be validated by
actual use with the chosen solution and the actual soiled parts.
12. What is the purpose of the unit heater?
The primary purpose of the unit heater is to maintain
a solution temperature between cleaning cycles. The tremendous energy
released by cavitation will generate the heat for cleaning.
13. How do I know if the unit is
Most poor cleaning usually results from improper
control of one or more process variable(s); such as choosing the wrong
detergent solution, insufficient heat, or not allowing enough time for
the particular soil to be removed. If you suspect that your ultrasonic
cleaner is not cavitating properly, there are two simple tests you can
perform: the "glass slide" test and the "foil" test.
14. How do I perform
the glass slide test?
Wet the frosted portion of a glass slide with tap
water and draw an "X" with a No. 2 pencil from corner to corner of the
frosted area. Making sure that the tank is filled to the fill line,
immerse the frosted end of the slide into fresh cleaning solution. Turn
on the ultrasonics. The lead "X" will begin to be removed almost
immediately, and all lead should be removed within ten seconds.
15. How do I perform
the foil test?
Cut three small pieces of aluminum foil about 4" x 8"
each. Fold each piece over a rod that you will use to suspend the foil
in the tank. A clothes hanger works well. Your cleaner should be filled
with an ultrasonic cleaning solution, degassed, and brought up to normal
operating temperature. Suspend the first "square" in the center of the
tank and the other two a couple of inches from each end of the tank.
Make sure that the tank is filled to the fill line, and turn on the
ultrasonics for about ten minutes. Remove the foil and inspect: All
three pieces of aluminum foil should be perforated and wrinkled to about
the same degree.
16. Why must trays or
beakers be used?
Items being cleaned should never be placed directly
on the tank bottom. Transducers (which produce the ultrasound) are
bonded to the bottom of the tank. Items resting directly on the tank
bottom can damage the transducers and/or reduce cavitation.
Additionally, a tray or beaker will position the item within the optimal
cleaning zone of the tank. The tray or beaker will also hold the load
together and allow for easy, no-touch removal, draining and transport of
the items to the next step in the cleaning process.
17. What is the
optimum cleaning temperature?
Heat usually enhances and speeds up the cleaning
process, and most detergent solutions are designed to work best at an
elevated temperature. The best way to find the optimum temperature,
which will give you the fastest, cleanest and safest results, is to run
tests. Usually, the best results are within the 50°C to 65°C range.
18. Is rinsing required after cleaning cycles?
Rinsing is recommended to remove any chemical
residue, which could be harmful to the part. Parts can be rinsed right
in your ultrasonic cleaner, using a clean water bath, or in a separate
tub containing tap, distilled or deionized water.
19. Why shouldn't I leave my cleaner on constantly?
Low solution levels can seriously damage your
cleaner. Running your unit continuously runs the strong risk of lowered
levels as the solution evaporates, especially when heated. Getting into
the habit of shutting off the ultrasonics when not in use, and
monitoring the solution level when in use, will yield many years of
trouble free service from your ultrasonic cleaner.