slmjim n Z1BEBE
CB750 Enthusiast
Long, geeky post ahead.
Some years ago we were looking for an ultrasonic tank for our Kawasaki Z1 restoration hobby. The breadth & depth of info was daunting, with some conflicting claims & info spread across the interwebs. So, we proceeded to write the article we wish we could have found that covers the basics. The following article we wrote was kindly published in the VJMC NA magazine in 2016 shortly after we submitted it to the Editor. Hope y'all enjoy.
Note - we had to break this up into five parts, as the site software is limited to 10,000 characters per post.
Ultrasonics 101
PART 1
FOREWORD:
Ultrasonic cleaning units sized and priced affordably for individuals and small shops are a commodity in a market where some sellers try all sorts of advertising hype in an attempt to set their equipment apart from others.
In this article I hope to, in plain language, describe what ultrasonic cleaning is, simply distill the theory of operation, define the hardware features most useful to home and small workshops, identify best practices, and cut through the hype that permeates internet marketing.
Information is available regarding every aspect of ultrasonic cleaning to anyone with an internet connection. Much of the information in this article comes from the support and FAQ sections of ultrasonic equipment manufacturers themselves. Where there is sometimes conflicting info between sellers on the same subject, every effort has been made to arrive at a factual consensus based on additional research.
This article is in no way intended to be definitive. It is meant simply to offer anyone who might be contemplating a purchase for themselves or a small shop some basic knowledge to help make a decision.
OVERVIEW:
Ultrasound is defined as any sound frequency that is above the perception of human hearing, generally accepted to be twenty thousand cycles per second, or twenty Kilo Hertz (20 KHz).
To put it simply, ultrasonic cleaning uses the effects induced within an appropriate liquid cleaning solution by high-frequency sound waves (most commonly 40 KHz) to remove many types of contamination from the workpiece being cleaned. The components of an ultrasonic cleaning system are the ultrasonic generator(s), the ultrasonic transducer(s) (driven by the generator) which are solidly attached to the tank, and the tank filled with cleaning solution. Most tank designs are all stainless-steel construction and come in a variety of shapes and sizes, from one pint to hundreds of gallons.
Ultrasonic cleaning utilizes ultrasonic transducers to create cavitation bubbles (aka cavitation, vacuum cavities or bubbles, used interchangeably throughout) within the liquid cleaning solution. This is accomplished by inducing high frequency pressure (sound) waves into the liquid that agitates it at a microscopic level to produce cavitation. The vacuum cavities cannot be seen by the naked eye because they are microscopic in size and exist for only a split second before imploding. Cavitation exerts extreme yet gentle force on the contaminants adhering to the workpiece. Ultrasonic cleaning can be used for many workpiece materials, shapes and sizes, and some items may not even require disassembly prior to cleaning. Ultrasonic cleaning has the ability to clean the INSIDE of complex objects which cannot otherwise be reached by manual spray or brushing. The ultrasonic process penetrates blind holes, cracks, and tiny internal passages and orifices, provided those areas are flooded with cleaning liquid while in the tank. Most materials respond well to ultrasonic cleaning. Ultrasonic cleaning is inherently gentle, although there are exceptions; soft polished metals such as aluminum, some plastics, painted surfaces and a few precious stones. More on that later. Water, specialized detergents or solvents are used, depending on the material of the workpiece and the type of contamination. Contaminants can include insoluble particles such as dust and blast media debris, soluble compounds such as fuel residue (gum & varnish), grease, oil, fingerprints and wax, and contaminant mixtures consisting of insoluble particles embedded within a binder of soluble compound.
Different types of equipment use various ultrasonic frequencies to achieve the desired cleanliness. Lower frequencies aggressively “scrub” larger particles from simple, massive items that have heavily soiled surfaces. Higher frequencies result in gentler cleaning of intricate exterior and internal surfaces on smaller items, and remove smaller particles:
25 KHz creates fewer, larger vacuum cavities that produce aggressive cleaning action. This is because the longer time between alternating positive and negative pressure waves allow larger, more energetic vacuum cavities to form. 25 KHz devices are used to clean large, relatively massive items that;
• are not of complex shape and intricate detail, and;
• are not delicate, and;
• need to be relieved of bulk particulate surface contaminants, and;
•are not easily damaged by the coarser, more aggressive scrubbing action of low ultrasonic frequencies.
Think cast iron blocks or large plates of stainless steel.
40 KHz creates more numerous, smaller cavities that are gentler and remove smaller particles. This is because the shorter time between the alternating positive and negative pressure waves only allow smaller, less energetic vacuum cavities to form more often (higher frequency). 40 KHz devices are the most common, and are the focus of this article. They are available in sizes ranging from one pint home-use units to industrial units with capacities of hundreds of gallons. 40 KHz offers the best combination of cleaning power and speed, gentleness of action, and variety of devices sized and priced for the home or small shop. Consumer items lending themselves to this cleaning frequency can be as delicate as jewelry and eyeglasses, up to carburetors and firearms. 40kHz units are efficient at at removing insoluble particles larger than about 0.7 microns and above.
At 80 KHz – 200 KHz frequencies, correspondingly smaller vacuum cavities of steadily diminishing power are created more often, but the resulting tiny cavities yield the most gentle and finest cleaning power down to sub-micron size contaminants. Devices that run in the 80 KHz through 200 KHz ranges are specialized units typically found in medicine, research and aerospace. Think removing bio-contaminants (blood cells, bacteria etc.) from medical equipment, molecular-level mixing, cleaning delicate solid-state devices that could be damaged by the vibrations of lower frequencies, and achieving ultra-clean-room results needed with delicate aerospace components.
Some high-end units offer multiple frequencies, as in both 40KHz and 80KHz operation simultaneously in the same unit.
Think of frequencies as sandpaper; 25KHz as being coarse, with higher frequencies as becoming rapidly finer. When ultrasonic energy is more evenly distributed in the tank at higher frequencies, cavitating force at any one location in the tank is reduced, although it happens more often and in tinier areas. In other words, cavitation intensity is inversely related to frequency, because as as frequency is increased, cavitation intensity diminishes due to the smaller size of the cavitation bubbles and their less energetic implosions.
THEORY OF OPERATION:
An example virtualization of the cavitation process:
During liquid cavitation, millions of micron-sized vacuum cavities (bubbles) are continuously formed, grow and implode (at 40,000 times per second in a 40 KHz unit) during the alternating positive and negative pressure waves induced in the cleaning solution by the ultrasonic transducer(s). Think cold boiling. Some marketing materials indicate that at 40 KHz, just prior to implosion the cavities are approximately 8 microns (8 µm) in diameter. To put that in perspective, natural spider silk is 2.5 – 4 µm. These vacuum cavities are stretched and compressed at the design frequency and amplitude of the device, growing during the the low pressure phase and being compressed during the high pressure phase when compression causes them implode. Just prior to implosion, the vacuum cavity has an enormous amount of energy stored within itself. Different marketing materials offer sometimes conflicting information, but the numbers seem to be centered around 5,000° F. as the estimated localized, instantaneous energy release of an imploding cavity, with estimated vacuum pressure of 10,000 PSI. Note that these millions of tiny temperature spikes are what causes the temperature of the solution to gradually rise during the cleaning process. (We'll discuss the advantages of heated cleaning fluid later.) The implosion of the vacuum cavity, when it occurs on a hard surface, transforms the cavities' relatively enormous negative pressure into a jet of liquid a fraction the size of the cavity at the time of it's implosion. The resulting very energetic, sub-micron-sized jet impinges on the hard surface at estimated speeds up to 300 ft./sec. With this happening tens of thousands of times a second, soluble contaminants are dissolved and insoluble particles are displaced, quickly and non-destructively from the workpiece. Due to the microscopic size of the jet and the relatively enormous energy it exerts impinging on the surface, ultrasonic cleaning has the ability to reach into tiny internal areas flooded with cleaning liquid that are otherwise inaccessible to manual cleaning, and remove tightly adhered contaminants very effectively.
Some years ago we were looking for an ultrasonic tank for our Kawasaki Z1 restoration hobby. The breadth & depth of info was daunting, with some conflicting claims & info spread across the interwebs. So, we proceeded to write the article we wish we could have found that covers the basics. The following article we wrote was kindly published in the VJMC NA magazine in 2016 shortly after we submitted it to the Editor. Hope y'all enjoy.
Note - we had to break this up into five parts, as the site software is limited to 10,000 characters per post.
Ultrasonics 101
PART 1
FOREWORD:
Ultrasonic cleaning units sized and priced affordably for individuals and small shops are a commodity in a market where some sellers try all sorts of advertising hype in an attempt to set their equipment apart from others.
In this article I hope to, in plain language, describe what ultrasonic cleaning is, simply distill the theory of operation, define the hardware features most useful to home and small workshops, identify best practices, and cut through the hype that permeates internet marketing.
Information is available regarding every aspect of ultrasonic cleaning to anyone with an internet connection. Much of the information in this article comes from the support and FAQ sections of ultrasonic equipment manufacturers themselves. Where there is sometimes conflicting info between sellers on the same subject, every effort has been made to arrive at a factual consensus based on additional research.
This article is in no way intended to be definitive. It is meant simply to offer anyone who might be contemplating a purchase for themselves or a small shop some basic knowledge to help make a decision.
OVERVIEW:
Ultrasound is defined as any sound frequency that is above the perception of human hearing, generally accepted to be twenty thousand cycles per second, or twenty Kilo Hertz (20 KHz).
To put it simply, ultrasonic cleaning uses the effects induced within an appropriate liquid cleaning solution by high-frequency sound waves (most commonly 40 KHz) to remove many types of contamination from the workpiece being cleaned. The components of an ultrasonic cleaning system are the ultrasonic generator(s), the ultrasonic transducer(s) (driven by the generator) which are solidly attached to the tank, and the tank filled with cleaning solution. Most tank designs are all stainless-steel construction and come in a variety of shapes and sizes, from one pint to hundreds of gallons.
Ultrasonic cleaning utilizes ultrasonic transducers to create cavitation bubbles (aka cavitation, vacuum cavities or bubbles, used interchangeably throughout) within the liquid cleaning solution. This is accomplished by inducing high frequency pressure (sound) waves into the liquid that agitates it at a microscopic level to produce cavitation. The vacuum cavities cannot be seen by the naked eye because they are microscopic in size and exist for only a split second before imploding. Cavitation exerts extreme yet gentle force on the contaminants adhering to the workpiece. Ultrasonic cleaning can be used for many workpiece materials, shapes and sizes, and some items may not even require disassembly prior to cleaning. Ultrasonic cleaning has the ability to clean the INSIDE of complex objects which cannot otherwise be reached by manual spray or brushing. The ultrasonic process penetrates blind holes, cracks, and tiny internal passages and orifices, provided those areas are flooded with cleaning liquid while in the tank. Most materials respond well to ultrasonic cleaning. Ultrasonic cleaning is inherently gentle, although there are exceptions; soft polished metals such as aluminum, some plastics, painted surfaces and a few precious stones. More on that later. Water, specialized detergents or solvents are used, depending on the material of the workpiece and the type of contamination. Contaminants can include insoluble particles such as dust and blast media debris, soluble compounds such as fuel residue (gum & varnish), grease, oil, fingerprints and wax, and contaminant mixtures consisting of insoluble particles embedded within a binder of soluble compound.
Different types of equipment use various ultrasonic frequencies to achieve the desired cleanliness. Lower frequencies aggressively “scrub” larger particles from simple, massive items that have heavily soiled surfaces. Higher frequencies result in gentler cleaning of intricate exterior and internal surfaces on smaller items, and remove smaller particles:
25 KHz creates fewer, larger vacuum cavities that produce aggressive cleaning action. This is because the longer time between alternating positive and negative pressure waves allow larger, more energetic vacuum cavities to form. 25 KHz devices are used to clean large, relatively massive items that;
• are not of complex shape and intricate detail, and;
• are not delicate, and;
• need to be relieved of bulk particulate surface contaminants, and;
•are not easily damaged by the coarser, more aggressive scrubbing action of low ultrasonic frequencies.
Think cast iron blocks or large plates of stainless steel.
40 KHz creates more numerous, smaller cavities that are gentler and remove smaller particles. This is because the shorter time between the alternating positive and negative pressure waves only allow smaller, less energetic vacuum cavities to form more often (higher frequency). 40 KHz devices are the most common, and are the focus of this article. They are available in sizes ranging from one pint home-use units to industrial units with capacities of hundreds of gallons. 40 KHz offers the best combination of cleaning power and speed, gentleness of action, and variety of devices sized and priced for the home or small shop. Consumer items lending themselves to this cleaning frequency can be as delicate as jewelry and eyeglasses, up to carburetors and firearms. 40kHz units are efficient at at removing insoluble particles larger than about 0.7 microns and above.
At 80 KHz – 200 KHz frequencies, correspondingly smaller vacuum cavities of steadily diminishing power are created more often, but the resulting tiny cavities yield the most gentle and finest cleaning power down to sub-micron size contaminants. Devices that run in the 80 KHz through 200 KHz ranges are specialized units typically found in medicine, research and aerospace. Think removing bio-contaminants (blood cells, bacteria etc.) from medical equipment, molecular-level mixing, cleaning delicate solid-state devices that could be damaged by the vibrations of lower frequencies, and achieving ultra-clean-room results needed with delicate aerospace components.
Some high-end units offer multiple frequencies, as in both 40KHz and 80KHz operation simultaneously in the same unit.
Think of frequencies as sandpaper; 25KHz as being coarse, with higher frequencies as becoming rapidly finer. When ultrasonic energy is more evenly distributed in the tank at higher frequencies, cavitating force at any one location in the tank is reduced, although it happens more often and in tinier areas. In other words, cavitation intensity is inversely related to frequency, because as as frequency is increased, cavitation intensity diminishes due to the smaller size of the cavitation bubbles and their less energetic implosions.
THEORY OF OPERATION:
An example virtualization of the cavitation process:
During liquid cavitation, millions of micron-sized vacuum cavities (bubbles) are continuously formed, grow and implode (at 40,000 times per second in a 40 KHz unit) during the alternating positive and negative pressure waves induced in the cleaning solution by the ultrasonic transducer(s). Think cold boiling. Some marketing materials indicate that at 40 KHz, just prior to implosion the cavities are approximately 8 microns (8 µm) in diameter. To put that in perspective, natural spider silk is 2.5 – 4 µm. These vacuum cavities are stretched and compressed at the design frequency and amplitude of the device, growing during the the low pressure phase and being compressed during the high pressure phase when compression causes them implode. Just prior to implosion, the vacuum cavity has an enormous amount of energy stored within itself. Different marketing materials offer sometimes conflicting information, but the numbers seem to be centered around 5,000° F. as the estimated localized, instantaneous energy release of an imploding cavity, with estimated vacuum pressure of 10,000 PSI. Note that these millions of tiny temperature spikes are what causes the temperature of the solution to gradually rise during the cleaning process. (We'll discuss the advantages of heated cleaning fluid later.) The implosion of the vacuum cavity, when it occurs on a hard surface, transforms the cavities' relatively enormous negative pressure into a jet of liquid a fraction the size of the cavity at the time of it's implosion. The resulting very energetic, sub-micron-sized jet impinges on the hard surface at estimated speeds up to 300 ft./sec. With this happening tens of thousands of times a second, soluble contaminants are dissolved and insoluble particles are displaced, quickly and non-destructively from the workpiece. Due to the microscopic size of the jet and the relatively enormous energy it exerts impinging on the surface, ultrasonic cleaning has the ability to reach into tiny internal areas flooded with cleaning liquid that are otherwise inaccessible to manual cleaning, and remove tightly adhered contaminants very effectively.
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