The evolution of ultrasonic machines over the last twenty plus years has allowed for overseas manufacturing and “attempted” commoditization of ultrasonic transducers and electronic circuitry. How does an ultrasonic cleaner work? The truth behind the evolution of ultrasonics is explained below.
How do ultrasonic machines work?
Ultrasonic cleaning tanks generate high frequency sound waves through the use of transducers and electronic ultrasonic wave generators. Typical transducers are made from piezoelectric crystals which convert electrical energy into mechanical / sound wave energy because piezoelectric crystals change geometric size when electrical voltage is applied.
The high frequency sound waves generated by the electrical wave generators and transducers are transmitted in a liquid solution of water or solvent base and cause the cavitation of the solution molecules. Cavitation is simply the implosion of the solution molecule resulting from the high frequency sound (pressure) waves transmission through solution. This extremely high pressure variation over a very small area causes a great amount of surface agitation on the surface of parts. The part surface agitation or “micro-scrubing” is very uniform throughout blind holes, part internals, etc since the agitation is formed in the volume of solution which the part is placed in.
How do high quality ultrasonics differ than low quality “off the shelf” ultrasonics?
The great reach of the internet and overseas manufacturers have brought “off the shelf” ultrasonic machines to the United States over the last ten plus years. The competitive problem that exists with this combination is, in order to offer the lowest prices sacrifices were made in the production of these machines. Many end users don’t understand nor see such sacrifices, so they purchase the low-priced ultrasonic tank thinking it is the same as a U.S.A. made ultrasonic parts washer / cleaner tank. Unfortunately, that couldn’t be any further from the truth.
Let’s look at a few of these sacrifices:
- Piezoelectric crystal transducers can vary greatly in quality and can be made so only inexpensive. Due to the sheer nature of the crystalline formation, transducers will naturally decay over time (3-6 years typically) in their ability to convert electrical energy to mechanical/sound energy. Inexpensive, lower quality transducers will decay much faster than those made with higher quality crystals. This degradation or decay will greatly change the cleaning quality of an ultrasonic cleaning tank. Inexpensive tanks which seem to perform well when new can often show decreased cleaning quality affects in as little as 3-6 months.
- Ultrasonic generators can be made from various electrical components and will not have the expected longevity that an end user demands. The combination of accelerated piezoelectric transducer decay and low quality ultrasonic generator components results in extreme variations of ultrasonic tank cleaning performance over time and in different solutions. This cleaning variation will cause quality differences in cleaned parts and result in more scrapped and reworked parts. This is often not only a major cost problem for a business, but in medical device, aerospace, and other fields this causes the process to fail validation protocols and specifications.
- Decreasing the ultrasonic cleaning power can significantly reduce the cost of an ultrasonic machine, but decreasing the power too much can result in reduced cleaning effectiveness and a compromise in the transducers ability to evenly cavitate a solution.
How Are Best Technology’s Ultrasonics Different?
- Our ultrasonic transducers are made of the highest quality piezoelectric crystals. While the price to produce the transducers is more expensive due to raw material cost, there will be a much longer duration before the transducers begin to decay (5+ years of manufacturing use typically)
- Our ultrasonic generators are self tuning meaning they can sense the load of parts in the ultrasonic cleaner tank and adjust power output based on the load. This also means also the generators sense the decay in the transducers and increase the power output to ensure continuously even power delivered to the parts over time.
- The generators are made with MOSFET transistors and other high quality components which are designed for continuous manufacturing condition use not just laboratory occasional use.
- Ultrasonics are measured by power output, but more importantly they should be measured in power/volume or watts/gallon. We typically keep all our tanks 100 watts/gallon for any tank under twenty gallons. This ensures that the ultrasonics are properly transmitted and distributed over the entire volume of the tank. Tank geometry can play a critical role in smaller tanks, so staying with 100 watts per gallon ensures eliminating tank geometry effects.
Ultrasonic Tank Myths
– Frequency sweeping will clean your parts better – Frequency sweeping or slightly varying the frequency produced by the generators will help even out the ultrasonic cavitation throughout the depth of the tank. Often times, lower quality ultrasonic tanks have frequency sweeping because the true resonance frequency of the transducers vary greatly from transducer to transducer which ends up causing some negativation of ultrasonic energy by out of frequency transducers. Frequency is swept trying to reach the true resonant frequency of each transducer, but in reality all the transducers are not reaching resonance at the same time. Our transducers are tested and matched based on exact resonance frequency and the ultrasonic electronics are then tuned to this exact frequency.
– More surface movement / agitation from ultrasonics is better – Many think that surface “dancing” means a lot of power in the tank, but surface movement is just ultrasonic energy reflecting off the surface of solution and it has nothing to do with the uniformity of the ultrasonic energy. The easiest way to test of uniformity of ultrasonic energy is to hang a piece of aluminum foil in the tank and observe the cavitation pin holes in the foil throughout the depth of the tank.
– As long as tanks have ultrasonics, power doesn’t matter– Having the right ratio of watts per gallon is essential to proper distribution of ultrasonic energy throughout the tank (see #3 above). Many low priced tanks sacrifice ultrasonic cleaning power for the sake of price typically less than 50 watts/gallon. Our tanks are typically at least 100 watts/gallon for tanks under twenty gallons. Higher volumes do not require as high power density due to tank geometry.