Ultrasonic Cleaner experiences...and DIY?

[Ed_Dinning]

Hi Gents, the Kerry and similar types used a proper transducer with compressed PZT discs, either singularly or in multiples that was bonded to the bottom of the tank and looked like a miniature Dalek.
The cheaper and less effective ones use a single flat disc, with no effective back mass, bonded to the tank base. Avoid these.

Ed

[Bazz4CQJ]

I was always told that you must never place any object directly on the bottom of an ultrasonic cleaner as that will damage the transducer on the other side of the metal. That's repeated on a number of websites, e.g. https://toolboom.com/en/articles-and...onic-cleaning/.

B

[David G4EBT]

The commercial ones come with a wire basket.

If I’ve got small items to clean that would fall through the mesh, I do as others has mentioned and put them in a small glass dish placed in the basket and immersed in the fluid.

In my earlier post I mentioned that a good test of effectiveness is to hold a piece of ‘aluminium’ in the bath, and within minutes, pinholes should appear - if they don’t, it’s just a toy.

Oooops - I’d meant to say ‘aluminium foil’ (ie, cooking foil).

[Lloyd 1985]

Funny you should mention keeping things spaced off the bottom of the tank, I read that when I got mine, i think it might even be printed on it somewhere! When I saw people using the ones at work I was a bit shocked to see them just bunging things straight on the floor of the tank, and with less than 1” water depth! When I said you should have something to keep things off the floor of the tank they just looked puzzled at me, same about filling it to the minimum fluid level... so far only one has broken down and been chucked out! Stuff where I work isn’t well looked after at all.

Regards
Lloyd

[Bazz4CQJ]

Originally Posted by Lloyd 1985

Funny you should mention keeping things spaced off the bottom of the tank, I read that when I got mine, i think it might even be printed on it somewhere! When I saw people using the ones at work I was a bit shocked to see them just bunging things straight on the floor of the tank, and with less than 1” water depth!
Lloyd

This is the big problem if you buy a really good model secondhand; how well has it been treated?

Re penetrating Al foil, that's something I've never attempted. I think the precise test conditions need pinning down a bit. I'm not sure I've ever seen a "self-test" method suggested by any of the makers.

B

[Refugee]

Originally Posted by Ed_Dinning

Hi Gents, the Kerry and similar types used a proper transducer with compressed PZT discs, either singularly or in multiples that was bonded to the bottom of the tank and looked like a miniature Dalek.
The cheaper and less effective ones use a single flat disc, with no effective back mass, bonded to the tank base. Avoid these.

Ed

Mine has got a hefty red polo mint shaped transducer on the bottom of the tank.
I once tried to measure the capacitance of the transducer and scrawled the result on the under side of the tank. I may also have tried to reverse engineer it at the same time.

[Trigon.]

Originally Posted by Bazz4CQJ

I'm not sure I've ever seen a "self-test" method suggested by any of the makers.

Bandelin is a very well established German manufacturer. Here's their page on foil tests:-

https://bandelin.com/service/applica..._test/?lang=en

Cheers

[Bazz4CQJ]

Originally Posted by Trigon.

Bandelin is a very well established German manufacturer. Here's their page on foil tests:-
https://bandelin.com/service/applica..._test/?lang=en

Cheers

Ooh...that's interesting and wonderfully detailed too!
It's now on my "To Do"list. I've always treated my machine with great care, but after 20 years, it seems to clean well, but a test would get me some.... data

B

[Uncle Bulgaria]

Thank you all for the interesting reading. I had no idea valve ones existed. That is tantalising...! A lot of deliberation here, but when one's time rich and cash poor that's all right. There seems a general expression of utility and that it's worth having one with the right fluids.

I've got the circuit from EPE mentioned earlier by Terry (thanks also for the input, Lloyd! The Armitage Shanks Experience?) The project page is here.

DIY is tempting, as ever. The hitch is the casing. I would prefer a self-contained, easily stored rectangular unit like the stainless commercial options rather than a collection of wires, as I haven't a workshop where odd shapes can be stuffed away under a bench. Finding a suitable chassis and tank is likely to be pricey.

However, the EPE circuit does include features that only start appearing on units which cost thousands. Frequency sweep, for example. Having a programmable circuit with a microcontroller could be handy. Being able to adjust the power, and a fast de-gas could be added as well...

"Mission creep"?

It would be interesting to try higher frequencies than the ones usually used (a thread on record cleaning discusses 120kHz for the microgrooves) but it seems difficult enough to buy 40kHz transducers. eBay has them, but the usual big suppliers are silent.

The units from the 'reputable' suppliers and the knock-offs look extremely similar, down to the control panels. Whether that means significant differences of quality, I don't know, but as I endeavour not to buy from a certain far eastern country because of humanitarian differences of opinion there are some qualms there, despite the tempting prices!

I think a 6l tank will be suitable for car bits, records, Rotring pens (top tip, G6Tanuki!) as well as delicate watch parts, so bigger is more capable in that regard.

Maybe the way to go is to buy one, then fiddle with the circuitry for extra features...

[David G4EBT]

Re ‘foil tests’, ultrasonic cleaners are used extensively for decontaminating dental instruments and in the NHS. There are protocols for regular foil tests - typically at three monthly intervals, with the foil retained for comparisons with previous tests, with the dat and other data marked on the foil.

EG:

https://www.qcs.co.uk/regular-mainte...rasonic-baths/

Neither the Lidl nor Maplin cleaners I tried had any impression on foil, but then they shut off after 3 mins, which is no time at all. Further cycles had no effect.

This was some years ago - maybe small cheap baths are now more powerful. Whether or not they state the ultrasonic power, I’ve no idea. I suspect not. Clearly there are those on the forum who are happy with the performance of such small baths. It would be interesting to see how they perform in a foil test.

I think a minimum of 50 Watts ultrasonic power is needed to be truly effective.

[Lloyd 1985]

I remember dunking the foil wrapper of a KitKat in mine once, and it obliterated it! It was only very thin foil though.

Regards
Lloyd

[stevehertz]

I fail to see the significance of all this 'British Standard' level of testing etc when for most of us all that's needed to know is that the unit will remove encrusted 'chicken fat' from age old knobs etc. It depends on an individual's take on this. Me, I'm not that interested in my cheap and cheerful Aldi unit's credentials, power, ability to punch hoes in foil etc it's just another useful too in my workshop. It does what I want it to do and has done with no maintenance for over five years. Personally I wouldn't even consider making one, but again I accept that we're all different. I don't even have the time to restore my collection of radios and vintage hifi let alone construct an ultrasonic cleaner!

[Trigon.]

I'm inclined believe that many of the very low cost so called 'ultrasonic cleaners' are effectively no more than agititators which actually don't cavitate to any signifcant degree.

If they 'shake' the fluid enough they will appear to work by breaking down the boundary layers and making the cleaning solution work better than simply soaking, but in the absence of direct comparison with a 'real' ultrasonic cleaner the average user won't be any the wiser.

If one performs adequately for your needs then that doesn't really matter, but the foil test is a sure indicator that cavitation is present.

Cheers

[Bazz4CQJ]

I've just tried the foil test on my old Ultrawave and did see holes within the first minute. There weren't has many as shown in the Bandelin video, but the machine is only being used for hobby purposes now, so I think that's good enough.

B

[AC/HL]

To be fair, the cheapies are sold as jewellery or spectacle cleaners. What we want is stretching things a bit, although knob cleaning should be possible with patience.

[Ed_Dinning]

Hi Folks, Refugee's transducer does seem to have somev mass associated with it, but it is not clamped up as the better commercial ones are so is limited in its power handling capability.
Al foil ~ available in many grades and thicknesses. One of the senior managers at Kerry's would test our tanks with thin, soft foil and compare it to the opposition using a non annealed Al foil.
Kit kat foil will act as a standard soft foil and should be "eaten " quickly.

The transducer is the resonant element and was coupled with a valve and a tuned tank circuit. Kerrys often used a TYT-3 triode and a few 100 volts on the anode.
Later units used a push-pull transistor module based on early SMPS principals .
As one side of the transducer is connected to the frame of the tank insulation is of vital importance.
Disc transducers normally operate in radial mode, mass loaded types in piston mode, putting more energy into the fluid. Water, direct from the tap often contains dissolved air. This reduces the ultrasonic activity until it is expelled.

Many of these stainless steel tanks were commercial kitchen food containers, easily and cheaply available. The larger Kerry tanks were fabricated, one of our largest had about 30 transducers fitted, fan cooled and was driven by a 3KW transistor generator.
The generators used unsmoothed Dc supplies which caused a slight sweeping of the frequency, avoiding dead spots in the tank.

Ultrasonics works well to clean hard stones in jewelry but should not be used for pearls or opals. It may not work that well on plastic knobs, but cleans twin gang caps well.

Generally the higher the frequency the more gentle the cleaning (80Khz for Ferranti Gyro parts); 20KHz for hospital instruments and Lucas alternators.

Ed

[MotorBikeLes]

Uncle B, if you do a search you will find the stuff posted on my "Mullard" ultrasonic cleaner. There is a circuit there too.
I originally had TWO U/S generators and THREE tanks (approx 1 gallon). Two of the tanks failed to respond, with some damage to one or more of the transducers. Either 6 or 8 per tank. My third tank had holes which had been for some sort of piped system which I eventually got welded up.
My second generator proved to have a faulty mains transformer, so I scrapped it, retaining all the components. I thought I had a second failed transformer recently, but it proved to be the valve, but meantime we concluded that a microwave transformer would probably make a good replacement.
If you really want to build one, this could be the basis.
Les.

[knobtwiddler]

Do you know if it was a B3 or C3? Did it have a Leslie speaker?

[AC/HL]

Hammond? is this in the correct thread?

[Uncle Bulgaria]

Originally Posted by Ed_Dinning

Hi Folks, Refugee's transducer does seem to have somev mass associated with it, but it is not clamped up as the better commercial ones are so is limited in its power handling capability.

The transducer linked below has a threaded hole, though I would have thought sealing it would be awkward if it were screwed through the tank. The designs I've seen recommend epoxy.

Originally Posted by Ed_Dinning

Many of these stainless steel tanks were commercial kitchen food containers, easily and cheaply available. The larger Kerry tanks were fabricated, one of our largest had about 30 transducers fitted...

A good tip on the stainless steel food containers - I've just been perusing them. They look just the ticket and reasonably priced. I think for a larger bath they would be ideal as for the smaller ones they're still a large proportion of the cost.

If the circuit is tuned, can more transducers be added for more power? I've read some information about the impedance of the liquid, which must be greater at higher volumes.

This kind of transducer appears to be the only suitable type available on a relatively thorough investigation of the usual suspects.