Large DIY Vibratory Tumbler

This instructable is a guide on how to design a vibratory tumbler. I couldn´t find a lot of information on how to build one, so I experimented and here are my findings that hopefully help you. This is somewhat of a advanced build, so I keep this simple and only show the important details.

There are two types of tumblers, rotarry like a barrel filled with stones and vibratory which is more like a bathtub. They come in any size. I needed one for 1.2m long parts, so I made mine 130cm long. Aparently vibratory tumblers are more efficient than rotaty tumblers. The oder advantage is that you can see the parts as they are spinning and you can easily remove them. I was thinking about using a barrel first, but baralles are not long enough and getting the parts out would have been very difficult. So I went with the tub design.

Where to place the Motor?

Most industrial machines have two motors on either end of the tub. That makes a lot of sense to me, but the space in my workshop is limited so I wanted to keep it as compact as possible. Two motors are also more expensive than one and I belive that the industrial machines get custom made motors. Not standard industrial motors as I have used. Thats why I decided to mount the motor on the frame and independently from the tub. Otherwise I was affraird it would shake itself to bits.

Where to place the weight?

Somewhere in the middle! Not sure if underneath the tub or at the side is better. But it needs to be in the middle.

What material to use?
I work with aluminium profiles a lot and accumulated a selection of scraps over the years. These are all parts with blemishes or holes, so I cannot use them for customers anymore. So I didn´t have to buy material and I got rid of scraps. Win win. Ideally you should use steel. It would be easier to weld and the slots in this case don´t add any value to the machine. You could also rivet the frame together instead of welding it. Using Aluminium has the advantage that it is easier to move around the workshop.

How to connect aluminium extrusions?

There are a lot of options. Check out my other instructable if you need ideas. https://www.instructables.com/id/Bandsaw-Stand-Ou...

How big should I make the frame?

I made mine 150cm long. So the tub has 10cm space to either side.

I didn´t make this. My sheetmetal supplier owed me one, so he made it for free. Its 4mm mild steel. Everything was bend and only the front and the end were welded on. I wasn´t sure if I could weld it watertight on my own, so that was one unknown out of the equation.

Its important that the tub is super ridgid. If I could do this again, I would add more braces on the outside. Maybe even a complete square pattern out of ribs. That way all the force from the vibrations will go into the media and not into the steel tub that flexes. In the video you sometimes see me use a clamp across the opening of the tub. That is there to keep the front side from flexing.

What Motor to chose?
I had a rough idea on how much power I would need, but no clue as to what speed would be right. So I went with 2.2kW which is somewhat of a standard size in Germany and then selected 1440RPM which is the median model. There was also 700RPM and 3000RPM available. I figured that I can change this with some pulleys if it was wrong. The VFD of course adjusts the speed, so I was only focusing on the power.

What VFD?

The VFD makes it possible to adjust the motor speed. Otherwise it would just run on full speed like a table saw does. On cordless drills you can change the speed by altering the voltage. That only works at low voltages and DC power. With 230V, you need a VFD. In brushless cordless drills there is a miniature version of a VFD. It kinda manipulates and changes the power as it comes in in such a way that the motor achieves a certain speed. Complicated stuff and I am no expert. However if you want variable speed, you need a VFD. Variable speed is important to get the right vibrations.

My VFD is from Yaskawa. It was on sale and it is made in Japan. So I can be confident that it will work great. I cannot reccomend cheap knockoff VFDs at all!

How to wire it up?
If you are buying from a proper motor dealer, just ask them for advice. I learned that shielded motor cables are important for VFDs. They can eliminate issues, but you could be lucky without one.

Overall design:

The motor is connected to a sliding universal joint. That way the tub can move independently from the tub. Without this setup, this machine would not run at all. You could of course mount the motor directly to the tub, but then it might shake itself to bits, or the shaft of the motor could break. These motors are not designed to have large radial forces on their shafts. If they are running a table saw or similar, the radial forces are tiny compared to when they are flying around a huge unbalanced weight.

Parts to use:

The main goal here is to make everything beefy. My shafts are all 25mm thick and I wouldn´t go smaller than this.
The U-Joint is an awesome piece of machinery and extremly high quality. If you cannot find one as cheap as this, you can try sourcing one from farming equipment or from a car. They have a similar part at driven front wheels.
For the pulleys I used taper locks. Amazing stuff. No need for keyways and super easy to assemble and tighten.
I used 10mm V-Belts which is one of the smallest sizes. I think its the same as on any drill press. They work fine.

Counterweight:
I used whatever I had lying around. I ended up with 1.5kg. Safety is key, so make sure it is on there properly. In terms of coupling the mass to the shaft, I found that it will always spin with the shaft. You don´t need to clamp it on tightly like a pulley or gear. A zip tie would probably add enough clamping force to make it spin. Obviously you want some steel to hold it on. A zip tie allone would snap, but it is enough clamping force to keep it going. I kept it so simple and crude because I was doing trial and error. Now that I know how heavy it needs to be at 50Hz, I can make a proper weight that looks nicer.

Ultimately you are going to need a drain and a water hookup. The tumbling generates dust and it needs to be washed away. So add a drain at the bottom and also a fresh water supply. Check with your local muncipality on how to dispose the water.

There is a wide array on media out there. I recommend calling a supplier and asking for advice.

I chose a medium grit so it is rough enough to quickly remove a burr, but also not as aggressive to keep a smooth finish. This is plastic media which is a little bit more leightweight than ceramic media. That reduces the swinging mass on the tumbler so the forces on the shafts and bearings don´t have to be as great.

This stuff is expensive. I payed €1200,- for 150kg of media. But I know it will last a long time and just a few loads will pay for this machine. Sending my pallets to a tumbling company and back would cost €200 alone plus the work of course.