Establishing Ultrasonic Cleaning Cycles

Many of our posts describing an ultrasonic cleaning process contain a caveat along the lines of “with experience you’ll develop your own routine.”  And that is true because even if you clean similar parts the conditions of those parts may vary from slightly to substantially dirty.  Parts themselves react differently to cavitation action.  You’ll need more vigorous cavitation remove grease and grime from heavily soiled engine parts than to finish clean precision optics.

This post takes a brief look at variables that go into establishing an ultrasonic cleaning cycle and presents some suggestions that should help you refine your own cleaning procedures to secure the best results.

Ultrasonic Cleaning Temperatures

Cavitation action in water is most intense at 35⁰C (95⁰F).   But higher temperatures may be required to remove oils, greases, waxes and other contaminants.  This is where cleaning chemistries come into play.  Cleaning chemistries and cleaning temperatures together define the most effective ultrasonic cleaning process.  There is an upper limit, however.  Above 80⁰C (176⁰F) cavitation loses its effectiveness.  That’s why temperature controls on ultrasonic cleaners do not exceed 80⁰C.

Biodegradable cleaning formulations come with instructions including proper dilution with water and recommended cleaning temperatures.  For example, the cleaning temperature for elma lab clean A20sf for lab glassware and instruments of stainless steel, ceramics and plastics is 50 to 70⁰C.   The widely used elma tec clean A4 to remove oil, grease, combustion residues and other organic contaminants has a recommended cleaning temperature of 50 to 80⁰C.

The temperature range provides leeway.  As you “develop your routine” remember that lower temperatures consume less energy, so it is a tradeoff between cleaning time and thoroughness.

On the other hand medical and surgical instruments contaminated with blood should be cleaned at room temperature because heat causes blood to set on surfaces and becomes very hard to remove.

Ultrasonic cleaning temperatures can be controlled on Elmasonic and other cleaners available from Tovatech.  Keep in mind, however, that cavitation action in itself raises the temperature of the cleaning solution.  Cooling coils are available as an option if high solution temperatures should be avoided.

Ultrasonic Cleaning Time

It won’t surprise you that the dirtier the part the longer the cleaning cycle.  When cleaning heavily contaminated parts such as automotive gears and other products with built-up deposits take a few minutes to carefully scrape away loosely adhering deposits.  The same applies to removing grinding dust, shavings and powder residues from newly fabricated metal parts.  Not only will this shorten the cleaning cycle but it also helps prolong the effectiveness of the cleaning solution.

Here are some suggested cleaning times in our posts relating to specific products, but again referring to our caveat actual time will depend on the condition of the parts.  We also suggest that when cleaning medical and surgical instruments and implants you should be guided by the recommendations of professional associations.

The position of parts in the cleaning solution is important and can affect cleaning time.  All surfaces must be exposed to cavitation action.  Parts with slots, blind holes and tiny crevices, and narrow aperture tubing should be positioned to allow full penetration of the cleaning solution but without “trapping” thereby keeping contaminants from draining away.  This may call for removing the basket and repositioning the parts, then continuing the process.  Slight vertical agitation such as provided by the Elmasonic Flex 1 ultrasonic cleaner and Flex 2 system combining cleaning and ultrasonic rinsing greatly assists this process.

Selecting Ultrasonic Frequency

Ultrasonic frequency in kHz produces bubbles that implode on contact with parts being cleaned thereby carrying away the contaminants.  Low

Ultrasonic frequency, time, temperature and power can be selected on the Elmasonic P ultrasonic cleaners

frequencies such as 25 kHz produce relatively large bubbles that implode more violently than those created at higher frequencies such as 37, 80 or 130 kHz that produce progressively gentle cleaning action.

Removing gross contaminants from robust parts such as fabricated or cast metals requires lower frequency cleaners.  Softer metals, plastics, and products with polished surfaces should be cleaned at higher frequencies.  In addition to protecting polished surfaces smaller bubbles are better able to penetrate tight areas such as seams, crevices and blind holes.

The following table provides a representative selection of ultrasonic cleaners available from Tovatech and their frequencies. Additional options are available.  Contact us for information.

And Finally Ultrasonic Cleaning Power

Power, usually presented in watts per gallon of cleaning solution, is another variable to be considered when selecting an ultrasonic cleaning system.  Since this post is already long enough we direct you to another post on tips for selecting ultrasonic cleaner power.  As always, the ultrasonic cleaning professionals at Tovatech are ready to help.  Simply contact us to get the discussion started.