When purchasing an ultrasonic cleaning system, there are ten important ultrasonic cleaner considerations.
1. What Exactly are you Cleaning?
When purchasing ultrasonic cleaning equipment, you must first ask yourself, “What exactly are you cleaning?” Are the parts made of plastic or metal? If metal, what kind of metal? Is it a large or small mass item? Are the blind holes or areas where debris collect on the bottom, top, side, or covering all surfaces?
Generally smaller tanks require more watt density – that is watts per-gallon of fluid. The larger the tank, the less watt density needed. Tanks over 25 gallons usually will work with 25 watts RMS/Gallon or 50 watts peak. At Omegasonics our smallest ½ gallon table top has 90 watts RMS/per gallon, but does not remotely match any of our Omega Pro floor model units for cleaning performance.
You must also think about cavitations. Cavitations refer to the behavior of voids, or bubbles, in a liquid. The more volume you have within your ultrasonic cleaning device, the more room you have for cavitations to occur, bounce, reflect, or re-cavitate. Basically, a larger tank will definitely out perform a smaller tank.
If pieces are made of plastic, keep in mind that plastic absorbs sound — so you may need more ultrasonic power to cavitate through the parts. If items are large, you may need more power to overcome that extra mass.
If heavy mass parts have most of the threaded holes on vertical surfaces, then an ultrasonic unit with side mount transducers is the way to go. If you are talking about a plating line application that is very deep with small parts hanging from a tree style bracket, putting transducers on the bottom will perform very well on the items toward the bottom of the tank. However these same transducers can be somewhat ineffective on the items on the top.
Some applications are complex enough to warrant side and bottom mount transducers. Whatever your needs, Omegasonics has the answers.
2. What is the type of Contamination?
If we are talking about cutting oils, water based coolants and light dirt, either a system with bottom mount transducers or bottom mount direct bond transducers will work for your needs. This is because oil floats and there isn’t much dirt to settle to the tank bottom. However there is a big difference — direct bond transducers are a fixed to the tank bottom so when you look at the inside bottom of the tank, it is flat. With immersibles, the transducers are mounted inside a housing that is 3 – 4 inches thick bolted to the bottom of the tank.
If you are cleaning heavily soiled items with a lot of dirt, grime, carbon etc. the dirt falls to the bottom of the tank. In a direct bond system the dirt will lie on top of the transducers and muffle the sound. This would be like putting a blanket over a stereo speaker – the sound would diminish. In doing so, the cleaning performance erodes rapidly.
Heavy dirt falling to the bottom of the tank with immersibles will accumulate around the transducer sides and will affect performance for a much longer period of time.
3. What Frequency do you need?
There are a multitude of frequencies, such as: 25KHZ, 40KHZ, 68 KHZ, 132 KHZ. Ask yourself, which is the correct one?
40KHZ means 40 thousand cycles per second. That’s 40 thousand cavitation bubbles per second per transducer element. 40KHZ is the most common frequency capturing approximately 95 percent of all applications.
Applications that vary from 40 KHZ are as follows.
25 KHZ works well on hard metal surfaces or larger surfaces contaminated with baked on carbonized dirt. The 25 KHZ bubble is a larger, more powerful bubble. However, these systems do not create as many implosions in a tank. They are generally not used in finer, more precision cleaning applications.
68 KHZ, 132 KHZ, 176 kHz and higher are used in submicron cleaning applications. The bubbles are much smaller, more numerous, but not as powerful. These sizes lend themselves to cleaning delicate equipment such as computer disks, production electronics, fine instrumentation and some medical. This type of ultrasonic cleaning is very specialized.
4. What Functions are Necessary for your Cleaning Equipment?
Well, of course, ultrasonics is required unless we are looking at multistage systems, which we will discuss shortly. Does the unit require heating the fluid and how hot does the fluid need to be? How will the heat be controlled — analog or digitally? How critical is the heat range? Keep in mind ultrasonic activity heats liquid, so if a maximum temperature can not be exceeded, either the ultrasonic circuit, heat circuit or both must shut off. Another option is a constant flow into and out of the tank of cooler flowing fluid.
You must also ask yourself, “Is filtration needed?” Does the filtration skim only floating,suspending particulates or both? If only floating oils is the case, an overflow weir allows the pump to push fluid in from the top surface of the bath over an overflow weir or dam. The pump then pulls from the overflow tank through a set of filters in a closed loop process. If you are filtering suspended dirt or dirt that has sunk to the tank bottom, then the pump must pull from the main tank.
A diverter valve can accommodate filtering from the overflow weir, the main tank or both simultaneously depending upon the position of the valve.
The ability to control the volume or intensity of the ultrasonic action is sometimes necessary if wide assortments of parts are being cleaned. Delicate items must have the power turned down so not to damage parts such as gold inlay ribbon on fine china.
If at all possible, portability is practical function that simply makes life easier. Why not add wheels when at all possible. They allow the unit to be easily moved in a cell-manufacturing environment as long as the generators are securely enclosed. Lack of maneuverability when it comes to extremely large machinery is a huge hassle. It means that you will most likely need a forklift, or possibly a pallet jack, to transport your ultrasonic cleaning equipment to its destination.
However, there is a solution if you need to use huge non-portable units. You can utilize convenient auto-fill and auto-drain options. They accommodate more automated changing of cleaning and rinsing fluids.
Options such as bells, alarms, and dual output timers that automatically cycle a filtration or flush after an ultrasonic cycle will work if the application calls for it. However, basic batch machines are best left to be simple, low option units as these make them easier to work with.
5. What is the Environment of the Cleaning Facility?
Remember you are dealing with an ultrasonic generator, which is a piece of electronic gear. The generator should never be in a room that has strong atmospheric acids such as a plating line which will corrode the surfaces. In this case, generators should be fitted withhave extendoax cables and be housed i separate room.
The same environmental worries apply to extreme moisture or excessive dirt or dust in the air. If the room is particularly dirty or dusty and the generators have no choice but to live in this area, then care should be taken to vacuum off the fan and exhaust monthly. You should also see to it that the circuit boards are Occasionally blown off.
Ideally, generators should be self contained in the ultrasonic equipment housing to protect them from the environment and to keep coax cables from being exposed. Exposed coax cables have a way of getting tripped on, cut, run over by forklifts, or damaged, which could result in damage to the generators.
Remember that the equipment must be built to handle overall moisture in a room if that exists.
6.What Voltage is Required?
Typically ultrasonic generators come in single -phase, 120Volt AC or single-phase 240Volt. If the facility supply is a 3 phase, 240 volt or if the heating circuit necessitates so much heat that a 3 phase is required, the equipment can be built so that it is fed into the 3 phase/240VAC, but internally the generators tap off from 2 legs of the 3 phase legs.
If a 3 phase, 480 Volt power system is the only one available, then a step down transformer is necessary. If a single phase/208VAC is the only thing available, the 240V ultrasonic system will operate without harm, though it will operate 10-17% below peak performance. This can be remedied with a buck-boost transformer, which is not terribly expensive.
7. Multi-Stage Systems
Many applications require more precise cleaning and rinsing. Because of this they require several stages. Two stage systems are common and don’t affect simplicity of use or portability. The first stage ultrasonic wash can use either a detergent followed by either a heated rinse to remove soap residue or a heated ultrasonic water rinse to ensure better final cleanliness. The bottom line is that the number of stages is dictated by the application and should be discussed with an ultrasonic application engineer. It is very important to consult an application engineer as they can help you in many ways. For example they determine how many stages of cleaning you should go with, which stages should have ultrasonics, the type of filtration necessary in each stage, and if at all possible whether the final hot air dryer stage is needed.
When using multi-stage systems your planning isn’t finished after talking with your application engineer. Next, you must decide if the project needs to be manual or robotic. The advantage of going with a robotic system is that the parts baskets are moved seamlessly from stage to stage with minimal labor.
Many applications, either due to the complexity of the part or the chemical make-up of the contamination, may require multiple wash cycles differing in chemistries or rinse cycles.
If you’re lucky, some applications simply require a single ultrasonic wash in a free rinsing soap. Automotive, power-sports, or light duty industrial application is easily handled in a single batch system. Complex industrial items with intricate multi-threaded blind holes or requiring a higher degree of final cleanliness should then go through a rinsing process — preferably heated. Depending upon the level of cleanliness needed, the secondary rinse may be helped by adding ultrasound.
Ultrasound gets rid of residual debris left from the first stage process as well as removing soap residue for total cleanliness.
Typical processes have a dual stage filtration system to remove debris and possible oil contamination using a skimming overflow weir. Oils float to the surface and are forced over an overflow weir through a pump and dual filter system.
Primary filters range from 10 to 50 micron to remove dirt particles before passing into a charcoal secondary filter to eradicate oils. Charcoal filters have a 3-micron discharge so it is optimal to pre-filter as much dirt as possible before beginning the cleaning process. In application dealing with primarily suspended dirt, it is best to use micron filters in both cartridges.
Once the parts are taken to the second stage rinse, there is usually only a single stage filter which is necessary because charcoal filters are most advantageously applied there. Charcoal filters will remove smaller particulate left over from stage 1 cleaning but additionally do a better job of removing soap residue.
Third and fourth stage systems are sometimes required but are not as common as the more common single stage or even two stage systems. Testing parts that a manufacturer does not have a cleaning procedure for or application experience with is always recommended before purchasing a system. During the system testing process, soap concentration, the number of cleaning and rinsing tanks can be better defined.
8. Type of Basket or Parts Racking Required
Most applications make use of immersion baskets with 1″x1″ mesh. Smaller parts will necessitate either a tighter mesh basket or a sub-basket with a tighter mesh to fit inside the larger basket. Baskets should be made from round rod material to more efficiently reflect sound waves. The importance of reflecting sound waves is that flat solid surfaces absorb sound and don’t impart nearly the performance upon the parts being cleaned.
There are others considerations when choosing they type of basket. If parts are easily scuffed and cannot have metal-to-metal contact, baskets can be lined with vinyl. If parts can’t touch each other, the basket will require spacers or guides to avoid parts contact.
There are also solutions to cleaning singular parts. Plating lines use a branch like apparatus to hang parts on as they are dropped into a tank. These applications are usually deep tanks with side mount transducers.
9. Is the Equipment Easy to use or Easy to Service?
A machine with controls that need to be programmed through endless key-strokes and mode changes renders the equipment useless if the operators can’t understand and operate it. Controls must be simple, remote and easy to understand. Limiting programming options is much safer for a majority of locations.
Serviceability is also very important. If equipment breaks, does it need to be sent back to factory for repair — that can be an expensive proposition when it comes to larger machines? Or do you need a technician to come out to your facility — also costly with the increased cost of travel due constantly rising gas prices.
Components that are modular — the term “plug and play” is a favorite of mine, allow for swapping out in the field with limited labor. Do components slide in and out of plug-in-sockets or do they require tedious screw-driver adjustments? This is just something else to consider when choosing your ultrasonic cleaning system.
10. Where is the Equipment Manufactured and Where is it Supported?
Of course we all expect that products made overseas are cheaper due to lower manufacturing labor costs. But is the product as reliable as a US made product? Who do you speak with for service, somebody who speaks only a little English? Buying the equipment is easy — servicing if you have an issue can turn out more costly in lost time and productivity than the original machine.
Interviewer’s Questions
Frank, concerning the 10 questions you have posed to the consumer when buying a piece of ultrasonic cleaning equipment, what is the number one question you would have if you were the consumer buying the product and why?
Explain to me the term “plug and play” a bit more?
How many international manufacturing companies exist versus domestic entities?
How does voltage come into play when choosing a cleaning system?
How do you prevent contamination in the equipment at Omegasonics?
What is the singular most common contaminant equipment owners must combat?
Frank, do you have anything else to add that could help guide a novice like myself through the intimidating process of purchasing cleaning equipment?
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