Wes

My guess is that would be a 3600 RPM motor. For the shredders here most use a gear reduction in the 30-60 RPM range. I don’t think you’d have good results trying to use that, for this application you really need low speed/high torque, not high speed/low torque in the case of a motor like you described.

Normally reversing contactors are a pair that are mechanically interlocked so that it’s physically impossible for both contactors to be energized at the same time. On a 3 phase motor, if you swap two of the wires, you will reverse the direction. So for “normal” direction, you’d pair L1-T1, L2-T2, L3-T3. To reverse the direction, you could set…[Read more]

To select the shaft size, I just went with whatever size the gearbox uses. You could do a calculation to determine the minimum shaft size, but I went this route because coupling the gearbox to the shredder shaft being equal size is a lot easier for a variety of reasons.

One thing I will note, it will NOT hurt to oversize the gearbox/motor in…[Read more]

I guess what I don’t have shown here is the 3/4″ diameter pipe is actually a valve (the tank will be pressurized at times), and the valve is actually a 1″ nominal but the bore of the valve is 3/4″ (ball valve). I am concerned that the screw may not be able to push/force the plastic through the reduced diameter, but maybe it’s not enough of a…[Read more]

I used a 5HP 3-phase motor with a VFD running single phase (220V 2-wire), so 2 leads on the input side of the VFD, 3 leads on the output side. 1800 RPM

Gearbox was a worldwide electric inline reducer: http://www.worldwideelectric.net/product-category/gear-reducers/inline-helical-gear-reducers/

First one was a 20:1, 76 RPM gearbox. This didn’t…[Read more]

Just a quick update:

Based on my testing I will need to do a complete redesign of my unit. Originally the gearbox I used was about 75 RPM, which was too fast.. Whenever it would jam it had so much momentum it was very violent. I got a larger gearbox which moved the speed down to about 25 RPM and over doubled the torque, but then it applied so…[Read more]

If you want to save a little money, get the parts made out of A36 steel instead of stainless. That would take quite a bit out of the cost.

For a gearbox, just look up anyone who sells belts, pulleys, bearings, etc. They’ll usually carry a line of gear reducers and motors.

A 3 HP single phase motor will perform the same as a 3 HP three phase motor. The three phase motor will be more efficient and cost less.

I am using a 3 phase motor + VFD with a single phase connection input. Basically you give it single phase input, and it spits out the 3 phase the motor wants. The VFD doesn’t need to special, you just need…[Read more]

On the underside of my machine I have a 1/4″ mesh. I found that it cut everything the proper size, but the material would tend to stay on the mesh and not fall through. Plus, no matter what I did it seems like this thing always makes a mess. So I’m building a hopper to go underneath it to funnel the material close to the inside, and I’m going…[Read more]

Update to my project. I finally got my bigger gearbox in and I modified the frame. In the pictures the blue one is the old one, orange one is the new one. I increased my torque about 3x (under 3,000 in-lb to over 10,000 in-lb), and reduced the speed from about 75 RPM to 25 RPM.

The new gearbox has a bigger shaft, and I didn’t want to have a…[Read more]

I agree that it would be nice for something on the outside of the blades to grab onto the material. I am working on a new set of blades for my machine and I may give this a try.

Another thing that I noticed with mine is that sometimes material likes to get stuck between the blades and spacers. I’m thinking that next go-around I may add some…[Read more]

I’m not really following what you’re going after?

Remember the spacers and the cutting teeth are different thicknesses of metal to allow for clearance between them. In my design the cutting teeth were 1/4″, and the spacers were 5/16″, so you have 1/16″ (or about 1.5mm) total clearance between the teeth. So when everything is put together you…[Read more]

Personally if it were me, I would lean toward oversizing the motor/torque requirements than getting too little. Last thing you want to do is lock-up the motor, and you’ll take a LOT of torque to break any components inside the machine.

I really like my 3-phase motor with VFD, and was about the same price as a single phase motor without a VFD.

I did try offsetting the blades, and while it did help I still think I have issues with it trying to cut too much at a time. For testing purposes, I think I’m going to cut off one of the blades on the teeth so I can offset them more like how the original design (from here) is done.

I also had a failure of the gearbox. Fortunately the MFG is…[Read more]

I suppose it could work, but I’m not really sure of the advantage. Getting parts cut on a laser really isn’t that big of a deal, and my guess it wouldn’t save you a lot of money. Not to mention with wider teeth, you’re going to be making bigger pieces.

I’d be surprised if you could 3D print plastic parts cheaper than having them cut from steel (unless you get free access to 3D printer and 3D print material).

I don’t think zinc (galvanized) steel would gain you much because the zinc wear and you’re left with mild steel. Also keep in mind galvanized steel generally has slightly different…[Read more]