I am far from an expert on the technology, but I will share some info.
The basic principles are documented on Wikipedia:
http://en.wikipedia.org/wiki/Ultrasonic_cleaningThe way it was described to me is that ultrasonic cleaners use sound waves and are more efficient than many other cleaning methods.
I started off with a cheap ultrasonic cleaner off eBay and was somewhat disappointed with it. I now keep it under the sink in my master bathroom, and about once a month as I jump in the shower of a morning, I throw my glasses in it, filled with warm water and a single drop of antibacterial hand soap, and when I get done, after a warm water rinse, my glasses are refreshed, no more skin oils/grease/whatever gets in every little nook and cranny. Some jewelers use them. But, the $40 USD ultrasonic cleaner just didn't cut it for pin parts.
The ultrasonic I cleaned these parts with was around $250 USD, and honestly, until yesterday, I thought I may have wasted my money. A friend who is quite heavily involved with the technology suggested I was using the wrong cleaning solution - there are many out there, and depending on what you are cleaning, apparently you can adapt the cleaner you use. One challenge I have giving you an idea of what I use - what I used to clean these parts probably isn't available on your continent. However, I'm sure there's something close.
The cleaners come in all sizes too. Some engine re-builders have one with a tank large enough to stick an entire engine block in.
They make solutions for cleaning things in an ultrasonic cleaner, and they make different varieties depending on what sort of stuff you'll be cleaning. But, what I've done is just experimented with stuff around the house. Mainly cleaners that I've known to work when cleaning parts by hand - because I already had some of those to try.
The degreaser I use is heavy on alcohol - after cleaning parts for 2 days, my hands are very dry and chapped. I had to slather them down with lotion several times, and my hands just absorbed it like a sponge. Next time around, I may use some gloves. The degreaser I am using is citrus based, smells somewhat like oranges. Orange smelling citrus cleaners are pretty common over here. I'm using the degreaser undiluted - but am curious to try it diluted. A 64 oz bottle of this degreaser is $1-2 at a local dollar store, and after cleaning all the metal hardware, I've still got enough of it left to fill the ultrasonic tank once more.
I am also curious to see how windex would work, both straight and diluted. I've used 'mean green' in the ultrasonic, but diluted it pretty heavily as all I had left was a little left in the bottom of a bottle. I've also tried a few drops of dish washing detergent in a ultrasonic full of water. Really, it's a trial and error thing, find what you can get locally and test it out.
One thing that I wonder - is the 'green' movement popular in Australia as it is over in the US? Meaning, environmentally? One challenge I have had over here is that all the manufacturers of cleaning solutions and other things are going very environmentally friendly with their products and reformulating them. The manufacturers swear they work as well, but I'm not convinced yet.
When I bought a jug of windex the other day, it made comments about its green formulation, and it doesn't seem to smell the same and work the same. I cleaned a PF glass with it, and it cleaned the glass just fine, but the other non-intended cleaning purposes of the windex may have been changed. The flitz I use in my tumbler is now in a new 'green' formulation and I'm not convinced it's the same as the flitz I bought 5 years ago - it smells different and I don't know if it works as well when I go to my spares and look at brackets I tumbled years ago.
Some ultrasonic cleaners have a heater built in, so the solvent can be used at a warmer temperature. If run for about 5 minutes, this one gets the solution warm to the touch - and it seems to get warmer the dirtier the solution gets.
Some cleaners have seemingly nice parts baskets in them, like a deep fryer, so you can lift the parts in and out of them easily. The problem with the one I had with a basket is that the basket absorbed a lot of the waves and didn't clean so efficiently. I still use that one for my glasses, but I don't use the basket in it. With metal parts, you can use a big magnet to fish them out. I imagine to get a cleaner with a basket with tight enough mesh that the smaller parts didn't fall through into the tank, you'd probably lose the majority of the waves, and it'd be ineffective.
