Vibratory Parts Cleaner for Under $10 From Scrounged Parts.

In our attempts to be green, we sometimes overlook that recycling is the last option for unwanted items. Before recycling, re-use and re-purpose should come into play if possible.

I repair old electronic gear as a hobby and sometimes have a need to clean up small rusty parts. A wire brush works but is time consuming if you have more than just a couple of parts to clean. Vibratory parts cleaners have been around for a long time. It's basically a container you put an abrasive material in along with the parts you wish to clean. You turn it on and it vibrates causing the cleaning media and parts to move around, thus cleaning them up.

This homebrew parts cleaner can be made for as little as zero dollars! Take a cruise on garbage day and you may just find what you need. What's needed?

1) a medium sized woofer

2) a plastic container that fits inside the woofer

3) silicone RTV adhesive

4) an old cellphone that can still install apps

5) an audio amp

Worst case you have to buy the RTV adhesive and spend a couple of dollars on a small Chinese class D amp board. That set me back $10 in total and most of it was the RTV adhesive. You will need basic hand tools and the ability to solder may be helpful.

You are looking for a woofer in the 5"-8" range. Something bigger will work but will also take up more work bench space. Many small subwoofer boxes use this size. If you find one that has a
built in amp, test the amp if possible. You can re-use the amp and speaker for this project.

Probably the best source for a suitable woofer will be a small subwoofer enclosure like those used with low end home theater systems, old BOSE Acoustimass systems, and gaming computer sound systems. A woofer pulled from a regular speaker system may work as long as it have sufficient excursion (cone travel) and the suspension is firm enough that it doesn't easily give when a little force is applied to the cone.

The best candidate will have a black rubber surround (flexible edge that connects speaker cone to speaker frame) instead the of the foam type I used. The black rubber (butyl) surrounds are typically found on better quality speakers and resist more abuse.

The next item you will need is a container with a screw lid that fits inside the speaker and sits as closely as possible to outer edge of cone (pic 1). I had a bunch of ice cream containers I reuse for storing small parts laying around and found that they served this purpose well.

It's very important that the container fit inside the woofer but as close as possible to the edge of the cone. This adds strength and longevity to this contraption who's purpose it is to shake things. Why a screw lid? Trying to pop a snap lid on and off a container mounted in a woofer will likely result in a torn woofer cone. The screw lid can be removed by grasping container with one hand and turning the lid with the other, thus lessening uneven forces on the woofer cone.

In order to glue it down I used silicone RTV adhesive. Why? It sticks well and is flexible. Those are perfect qualities for this application. I had to buy a tube of the stuff as I was out. If you already have some laying around you can cut the cost of this project down to just a couple of dollars.

Clean the bottom of the container with alcohol to remove all traces of oils and apply the glue as you see in picture 2, set the container down onto the cone and center it. Let it set up for a few minutes then reapply a thin bead around the edges. Notice how I left 2 small areas with no glue (pics 3 & 4)? This helps with the drying process so air can get all around the bead of adhesive. Let it dry per instructions on your glue choice.

Why no glue sticks, gorilla glue, etc? You need something flexible yet strong. Silicone RTV adhesive is the best product for the job.

Here you have tons of flexibility. Got an old stereo amp laying around that works? That'll do. Found a powered subwoofer and the amp still works? You're doing good! You just need a way to amplify an audio signal that provides at least 20W or more.

In my case, I had plenty of discarded stereo amps in my pile-o-junk but wanted to make this contraption small. I decided to use a Chinese class D mono amp board. This little board does 35w and cost just a couple of dollars. The downside to using one of these little boards is you have to source a power supply but thankfully most of these boards have a pretty wide power input range. A search through my pile of junked laptop adapters and I had what I needed. Don't have a pile of laptop adapters laying around? I've seen them at local Goodwill stores in the electronics dollar bin quite regularly. Ask a friendly computer geek and they may have what you need.

The board I used uses a TDA8932 chip. These are common on ebay and Amazon for just a few bucks. The power input range on the chip is 10-30v making it pretty easy to find something that will work, just make sure it can supply at least a couple of amps of current.

Since I went with the little amp board and laptop supply, I had to wire the stuff up (pic 2). You'll need to be able to solder to do this. There are amp boards with screw terminals for a few extra dollars. I used zip ties as you can see in pic 3 to cinch the cables down and keep them from flopping around and breaking at the connection points. In order to connect to the speaker I used an old alligator clip lead and cut it in half. This allows me to disconnect the amp from the speaker/shaker when not in use. It also allows me to use the little amp setup for other projects if needed.

At this point you should have a screw top container attached to a suitable woofer and some kind of audio amp to make it move. Here's where an old cellphone comes into play.

There are countless audio tone generator apps out there for Android and Apple (pic 1). Find one with good reviews and download it. These apps turn your phone into an audio signal generator. Some apps even allow you to pick the type of waveform. When working with speakers, always use the sine wave setting (looks like a smooth wave going up and down). Don't use triangle or square wave as they can destroy speakers.

I mentioned an old cellphone as one of the needed items. The reason is you can plug it in and let it do it's thing. Can you use your daily driver phone? Certainly but then every time you get a notification or call, you'll be tethered to the shaker and have to interrupt the process.

You'll need to get the audio from the phone to the amp. In the case of the amp board I used an old headphone cable (pic 2), stripped it, and soldered one channel to the amp input. Why only one channel? I've discovered some phones don't take lightly to having left and right audio shorted together and will shut off. Use just one side and leave the other disconnected (pic 3).

If you are using an actual old receiver or stereo amp to do this, the standard RCA Y cable will do the trick. Run wires from one amp channel to the shaker speaker and leave the other channel unused. Adjust balance control on amp to the channel you are using so you aren't needlessly running a signal to an unused channel.

You folks with phones that use special connectors will surely benefit from doing this with an older phone that still has the industry standard 1/8" stereo jack.

How to set volume? If using the amp board I used, all volume adjustments are done via the phone. If you are using an old home stereo amp, turn amp all the way down, turn phone audio up to almost max, then carefully bring up volume on stereo amp.

In pic 1 you see some random rusty hardware I decided to test this on. In pic 2 you see the hardware in the container along with my poor choice of abrasive material, random sand and small pebbles collected from backyard. In pic 3 you see the result after running this contraption long enough for me to eat a sandwich for lunch. Finally I've attached a video of it in operation. The cellphone camera distorts movement a bit but look at the flow of material as it's vibrating. You're shooting for this churning action with as little power as possible. To get it churning you need to play with volume (power) and frequency.

A word on abrasives..

There's plenty of proper abrasives on the market for this but we're looking at keeping it cheap. I used sand and small pebbles collected right from were rainwater washes off my roof. A better abrasive might have been clean white sand or dry beach sand. There are also abrasives made from crushed walnut shells that wont work as fast but may polish things up. Don't be afraid to test different things on random nuts and bolts to get a feel for it.

In the vid you'll see what that little class D amp board is capable of when cranked up. It was fun to watch but the little woofer wasn't too happy and I quickly started smelling unhappy overheating things.

When you first run it watch it closely, feel, and smell for overheating. I ended up crazy gluing (yes, I know it's not an ideal method) a small heatsink onto the amp chip to keep it cool. Had I been using a big stereo amp, this wouldn't be an issue. Once the amp was happy, I had to be careful not to toast my woofer. Run yours for a few minutes and sniff the woofer. You'll know if you're running it too hard.

What about keeping it from dancing around? Place it in a plastic bowl with a towel in it. This should suffice to keep it in place for temporary use.

If you blow it up, its not a big loss. The woofer is likely to take the hit. Peel off your container, find another junked speaker and stick it on.