Where to Use Ultrasonic Cleaning Technology
The word “contamination” or “contaminant” when used in conjunction with ultrasonic cleaning has a much broader definition than pollution, mold, or radioactivity. Instead, it is a much simpler definition, expressed in Wikipedia as the presence of an unwanted constituent or impurity. In terms of ultrasonic cleaning techniques, a contaminant is anything unwanted but is present due to exposure to ambient conditions, due to manufacturing processes, due to use, neglect, or similar circumstances.
Ultrasonic cleaning technology is one of the fastest, most effective, and environmentally friendly means of removing contaminants. However, it is not universally applicable. For example, since the technology is based on immersing products in an ultrasonic cleaning solution – generally water based – parts being cleaned must be resistant to water damage. In our opening sentence we mentioned pollution in the sense of water pollution and radioactivity. Ultrasonic cleaning is not applicable here.
Ultrasonic Cavitation – The Key to Effective Cleaning
The widespread use of ultrasonic energy in research labs, manufacturing, maintenance and restoration, the surgical suite, and even in the home – is due to the power of what is called ultrasonic cavitation. This post will provide some examples of parts that can best be cleaned by cavitation. For our readers curious about cavitation here is a brief explanation on how it works.
Cavitation is the implosion, not bursting, of extremely minute vacuum bubbles created by the ultrasonic vibration of transducers bonded to the bottom or sides of an ultrasonic cleaner tank. Equipment includes ultrasonic generators operating at frequencies measured in kilohertz (kHz) or thousands of cycles per second. Widely used ultrasonic frequencies are 25, 37, 45, 80 and 130 kHz; several other frequencies are also in use. Some cleaners are designed to operate at dual frequencies.
When activated the transducers cause the tank bottom to vibrate as a membrane creating the bubbles, which implode when in contact with objects being cleaned to quickly and thoroughly remove tenacious contaminants.
What is the result? Damage-free cleaning provided this source of energy is properly applied. “Properly” includes the ultrasonic frequency used. Low frequencies create relatively large bubbles that implode more vigorously against surfaces than the smaller bubbles created at high frequencies. But smaller bubbles are better able to access surfaces of complex configurations that include crevices, cracks, machined and blind holes. Higher frequencies are also recommended for highly polished and delicate surfaces.
“Properly” also includes the ultrasonic cleaning solution formulation. This is a subject onto itself but a short list of examples is found on our cleaning solutions web page. Specific recommendations as to equipment, cleaning solutions and procedures are quickly obtained by contacting our professionals.
Now on to where we use this marvelous method of removing contaminants.
Parts Best Cleaned by Ultrasonic Energy – A Sampler
Delicate and Easily Damaged Surfaces
Common parts cleaning alternatives include the use of wire or soft brushes, coarse or fine steel wool and strong solvents to mechanically remove contaminants such as paint, ink, burned on residues, polishing media, soldering fluxes and carbon deposits. In some instances these surfaces may not necessarily be delicate. But the application of mechanical scrubbing can cause scratching or other surface imperfections that impact the quality of a finished product. Examples include high resolution printing plates, plastic injection molds, inkjet cartridges, printed circuit boards, and decorative components to be painted, electroplated, anodized or powder coated. Scratch-free, residue-free surfaces are critical to superior quality cleaning and product performance.
Other examples where cavitation offers superior results include cleaning and restoring heavily painted antique hardware such as exquisitely designed richly embossed hinges, locks, door knobs and back plates as well as classic faucets and vintage bathroom fixtures. As an aside on this particular use there is a semi-aqueous, micro-emulsion solution that can be used to remove paint in two ways (1) a pre-wash chemical to safely remove oil and water based paints by lifting them off the metal surfaces. Or (2) using it full strength in an ultrasonic cleaner operating at about 70?C. An advantage of the formulation is that it can be reused by filtering it to remove paint debris.
Cleaning or restoring polished surfaces on softer metals such as aluminum, copper and brass requires special care. Examples include musical instruments, clock assemblies, decorative lighting assemblies, restoring decorative antique brass and copper, cleaning laboratory and decorative glass, optical glass and crystal pendants. For damage-free cleaning of these surfaces the use of higher ultrasonic frequencies is recommended.
Parts of Complex Configuration
Ultrasonic cleaning cavitation bubbles go where hands and brushes cannot. As an example, consider that a bubble created at 40 kHz has a radius of 83 microns and one created at 80 kHz has a radius of 41 microns*.
As noted in our opening paragraphs lower ultrasonic frequencies create bubbles that implode more vigorously than higher frequencies, but in some cases the smaller higher frequency bubbles can provide more thorough (in addition to more gentle) cleaning.
A great example of a well-known piece of hardware with complex configurations is the automotive transmission. Check out “auto transmission components” in the web for examples. You’ll find a seemingly limitless variety of configurations where ultrasonic cavitation cannot be beat when it comes to cleaning and reconditioning this complex component in the family car.
Cleaning small diameter thin-wall glass or metal tubing is easily accomplished in an ultrasonic cleaner with sonic energy penetrating the tubing walls which causes cavitation action on interior surfaces. A caution is to position tubes on a slant in the solution, thereby permitting contaminants to drop out.
Removing coolant residues and metallic contaminants from small diameter drilled and machined holes, blind or extending through parts, requires special care in an ultrasonic cleaner. Techniques include allowing the cleaning solution to access the interior surfaces, avoiding trapped air and providing a means for contaminants to exit confined spaces. We treat this topic in more detail in our post sonic cleaning tubing and blind holes.
Reusable industrial filters are also characterized as having complex surfaces. High-pressure water and detergent sprays have the potential to damage these filters whereas immersing them in an ultrasonic bath will quickly remove grease, dust, dirt and other contaminants from filter fibers and other filtering elements.
No, we’re not talking about heavy metal bands but instead parts fabricated of iron and steel – those types of heavy metals – typically ferrous but not necessarily.
Machining, grinding, welding, forming and casting operations leave residues on the products that must be removed before further processing that can include painting or other final finishing. Contaminants include grinding residues, metal fines and machining coolants.
These are among the reasons why metalworking and machine shops include ultrasonic cleaning systems that can be comprised of pre-rinsing, cleaning, post-rinsing and drying equipment to bring their products up to specification before further processing.
Engine and Drive Train Components
On-road, off-road, land, marine, air, farm, sports, recreation, lawn and garden equipment powered by gasoline or diesel engines and drive trains comprise a tremendous market for ultrasonic cleaners from benchtop to floor-mounted industrial units. Engine blocks and headers, crankshafts, camshafts, carburetors, transmissions, brake assemblies, and differentials are among the myriad mechanical assemblies now being cleaned by cavitation rather than with aerosol sprays or in solvent-based wash tanks.
In nearly every instance users ranging from shade-tree mechanics to full-scale professional service providers voice the same praises: increased productivity with superior cleaning results. The ultrasonic cleaners eliminate many if not all permitting and disposal issues associated with solvent washers and ventilation requirements that may arise through heavy use of aerosol sprays. Other advantages expressed (that apply as well to other applications) is that timer-equipped ultrasonic cleaners let mechanics set up the procedure, activate the units then devote attention to other maters while the cleaning cycle proceeds.
Getting Started on an Ultrasonic Cleaning Regimen
This post provides a number of examples of parts best cleaned using ultrasonic cavitation. If you see opportunities to apply this technology in your business, be in repairing PBCs or reconditioning engines or adding efficiency to your production methods you can start by giving a call to the iUltrasonic cleaning professionals.
But before you call please establish to the best of your ability the answers to the following points. The answers will help us serve you better.
1. What is being cleaned
2. What is it made of – include all components that will be immersed in the cleaning bath
3. What contaminants are to be removed
4. Are there industry standards that apply to your product in terms of cleanliness and if so what are they.
5. Post-cleaning treatments if any, along the production line. Painting, plating and powder coating are examples.
We will provide recommendations on the cleaninga equipment, cleaning solution, cleaning procedures and equipment maintenance that will get you on your way to a faster, more efficient and environmentally friendly cleaning operation.
*Bubble size in water. Measurement varies based on the cleaning solution.