Modified (larger) shredder
My name is Wes. I am an engineer with quite a bit of product development experience, and I decided to build the shredder machine. After reviewing the documentation, I decided I wanted something larger (mainly so I could throw in a whole trash bag full of plastic instead of feeding it a few pieces at a time). I basically took the same concept that you could download here, and used my CAD software to re-design and make everything larger. I also did some FEA to confirm the component sizing and ensure nothing is going to break.
This is powered by a 5HP (3-phase) motor and a 22:1 reduction gear box (about 76 RPM). I am using a VFD basically as a phase converter so that the motor can be powered on either single phase or 3 phase (I am using 240V single phase from my house). It turns out that 3-phase motors are a lot cheaper than single phase motors, so it was almost (within $100) the same price to get a 3-phase motor + VFD compared to a single phase motor, plus then all my controls are built into the VFD to keep wiring simple.
Plus, I programmed the VFD so that if it detects an overload, it will reverse the direction for a specified time period (to clear a jam), and then start rotating the opposite direction.
So far, I’ve found a couple things based on my experience. First, I designed the teeth using a 3-bladed tooth, and kept all the teeh the same. I found this doesn’t work very good (because you have so many teeth cutting at the same time), so I will design the teeth with 2 blades so that you can alternate them so only 2 teeth are cutting simultaneously. Secondly, I found that 76 RPM is a little faster than I’d like, as shredded particles tend to get thrown around quite a bit. Third, I found (after subsequent FEA) that my machine can handle a lot more torque than my motor/gearbox was supplying. I plan on getting a higher reduction ratio and keeping the motor HP the same, so I’ll have more torque and slower speed, plus if I wanted to speed it up a little bit the VFD can safely turn up the speed.
See attached images. If anyone would be interested in purchasing a kit, I would be happy to help out. I have some pretty good suppliers for the motor setup and the laser cutting/forming, and everything can fit on a single pallet for easy shipping…