11-05-2012, 12:16 PM
In another thread, Colin (‘Retired’), recently said that perhaps I’d like to outline my experiences with an ultrasonic bath which I treaded myself to for Christmas 2010, so here goes:
Ultrasonic cleaners rely upon what’s termed ‘acoustic cavitation’ generated in the liquid during the cleaning process. Cavitation forms when ultrasonic waves travel through the liquid, which stretches and compresses the medium to transmit the sound waves. When the amplitude of the sound waves reach a level at which the water cannot contain the stretch, the sound literally tears the water apart, forming millions of tiny vapour bubbles under negative pressure which loosens the contamination on the surface of the object being cleaned. This cleaning process can reach cavities, recesses and orifices that other cleaning methods cannot, which is why the process is used very effectively for cleaning clogged up carburettors which have inner chambers and small orifices.
Ultrasonic cleaners can be used to clean just about anything including taps, dies, milling cutters, paint guns, ceramics, jewellery, air brush nozzles, dentures, expanding watch straps, coins, small machined parts, and so on. There are exceptions - some plastics and precious stones for example. To check the effectiveness of the bath, if you hold a piece of cooking foil in it, and within minutes, the foil is full of pinholes. Although you can just use water as the cleaning fluid, there is a wide range of solutions available. I use a general purpose fluid, which I then store in a plastic bottle. The dirt settles to the bottom during storage, and I carefully pour off the fluid into the tank next time I want to use it. It does of course become so discoloured in time and have to be discarded.
I became interested in ultrasonic cleaning way back in 1981 there was an article in Everyday Electronics about making a small ultrasonic bath from a kit. I saw the bath being demonstrated at an electronics show and was intrigued by it, thinking that I might make one. However, shortly afterwards the factory that made the kits burnt down and that was the end of that. (I've never seen a project since in electronics magazines, which is a bit surprising, but I think the transducer used is the complication, rather than creating the oscillator circuitry).
About five years ago, small inexpensive ultrasonic baths started to appear, which made impressive claims about their capabilities. On impulse, I bought one for a tenner from Lidl – it went back for a refund the same day – useless for anything other than maybe cleaning a pair of earrings or such like. They cut out after three minutes, and the cavitation action is barely visible. Having not learned from that experience I bought a ‘professional’ bath from a certain High Street electronic gimmickry store, thinking that one might be better. It wasn’t, so it too went back. The problem with such ‘toy’ baths is that though they may oscillate at ultrasonic frequencies, they don’t do so with sufficient amplitude to be very effective. I don't think they achieve anything that couldn't be achived just as quickly, and probably more effectively, with a toohbrush and detergent.
Towards the end of 2010, full page ads started appearing in EPE Magazine by a firm called Allendale Electronics, for professional small ultrasonic baths used in labs and by the NHS etc. One that seemed to suit my needs was just over £100 – not cheap, it has to be admitted, but not expensive for what it does and how its made. The one that I bought was model PS-10A, which has a tank size of 150mm (6”) x 135mm (5.3”) x 100mm (4”) deep, which holds 2 Litres of cleaning fluid. The ultrasonic power (at a frequency of 40 kHz) emitted by the transducer to the bath is 70 Watts, and the thermostatic heater, which heats up to 80 C is 60 Watts. It has a built-in timer for up to 80 minutes, and all the settings are displayed on a digital display. It presently costs £102 inc VAT:
http://www.allendale-ultrasonics.co.uk/u...acity.html
I haven’t used it often, buy when I have, it’s proved effective. In use, you must not allow articles to come into contact with the metal base of the tank – you have to place them in a wire basket. If the articles are so small that they’d fall through the mesh of the basket, you can place them in a glass container (small dish or whatever), immersed in the cleaning fluid, resting in the basket.
For another £20, a 3.2 Litre model is available, which has 120 Watt ultrasonic power and 100 Watt heating:
http://www.allendale-ultrasonics.co.uk/3...ntrol.html
At that Allendale website a range of cleaning fluids can also be viewed.
There’s no set time that it takes to clean an object, but on average, 20 minutes should be enough. Here’s an example of cleaning a carburettor, including before & after pics:
http://www.youtube.com/watch?v=Lk5JEgPHo9c
(I notice that they didn't put the carb in a wire basket as recommended, but straight into the tank).
Hope these notes are of interest.
Ultrasonic cleaners rely upon what’s termed ‘acoustic cavitation’ generated in the liquid during the cleaning process. Cavitation forms when ultrasonic waves travel through the liquid, which stretches and compresses the medium to transmit the sound waves. When the amplitude of the sound waves reach a level at which the water cannot contain the stretch, the sound literally tears the water apart, forming millions of tiny vapour bubbles under negative pressure which loosens the contamination on the surface of the object being cleaned. This cleaning process can reach cavities, recesses and orifices that other cleaning methods cannot, which is why the process is used very effectively for cleaning clogged up carburettors which have inner chambers and small orifices.
Ultrasonic cleaners can be used to clean just about anything including taps, dies, milling cutters, paint guns, ceramics, jewellery, air brush nozzles, dentures, expanding watch straps, coins, small machined parts, and so on. There are exceptions - some plastics and precious stones for example. To check the effectiveness of the bath, if you hold a piece of cooking foil in it, and within minutes, the foil is full of pinholes. Although you can just use water as the cleaning fluid, there is a wide range of solutions available. I use a general purpose fluid, which I then store in a plastic bottle. The dirt settles to the bottom during storage, and I carefully pour off the fluid into the tank next time I want to use it. It does of course become so discoloured in time and have to be discarded.
I became interested in ultrasonic cleaning way back in 1981 there was an article in Everyday Electronics about making a small ultrasonic bath from a kit. I saw the bath being demonstrated at an electronics show and was intrigued by it, thinking that I might make one. However, shortly afterwards the factory that made the kits burnt down and that was the end of that. (I've never seen a project since in electronics magazines, which is a bit surprising, but I think the transducer used is the complication, rather than creating the oscillator circuitry).
About five years ago, small inexpensive ultrasonic baths started to appear, which made impressive claims about their capabilities. On impulse, I bought one for a tenner from Lidl – it went back for a refund the same day – useless for anything other than maybe cleaning a pair of earrings or such like. They cut out after three minutes, and the cavitation action is barely visible. Having not learned from that experience I bought a ‘professional’ bath from a certain High Street electronic gimmickry store, thinking that one might be better. It wasn’t, so it too went back. The problem with such ‘toy’ baths is that though they may oscillate at ultrasonic frequencies, they don’t do so with sufficient amplitude to be very effective. I don't think they achieve anything that couldn't be achived just as quickly, and probably more effectively, with a toohbrush and detergent.
Towards the end of 2010, full page ads started appearing in EPE Magazine by a firm called Allendale Electronics, for professional small ultrasonic baths used in labs and by the NHS etc. One that seemed to suit my needs was just over £100 – not cheap, it has to be admitted, but not expensive for what it does and how its made. The one that I bought was model PS-10A, which has a tank size of 150mm (6”) x 135mm (5.3”) x 100mm (4”) deep, which holds 2 Litres of cleaning fluid. The ultrasonic power (at a frequency of 40 kHz) emitted by the transducer to the bath is 70 Watts, and the thermostatic heater, which heats up to 80 C is 60 Watts. It has a built-in timer for up to 80 minutes, and all the settings are displayed on a digital display. It presently costs £102 inc VAT:
http://www.allendale-ultrasonics.co.uk/u...acity.html
I haven’t used it often, buy when I have, it’s proved effective. In use, you must not allow articles to come into contact with the metal base of the tank – you have to place them in a wire basket. If the articles are so small that they’d fall through the mesh of the basket, you can place them in a glass container (small dish or whatever), immersed in the cleaning fluid, resting in the basket.
For another £20, a 3.2 Litre model is available, which has 120 Watt ultrasonic power and 100 Watt heating:
http://www.allendale-ultrasonics.co.uk/3...ntrol.html
At that Allendale website a range of cleaning fluids can also be viewed.
There’s no set time that it takes to clean an object, but on average, 20 minutes should be enough. Here’s an example of cleaning a carburettor, including before & after pics:
http://www.youtube.com/watch?v=Lk5JEgPHo9c
(I notice that they didn't put the carb in a wire basket as recommended, but straight into the tank).
Hope these notes are of interest.
Regards, David.
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
