Power and torque needed- Shedder machine

Hello to everybody, im a mechanical engineering student in Bogota Colombia and im building a shredder machine for my final project and i have 2 questions:

  1. Ive seen that the average power needed for the system is 2-3HP but why is that the minimum power you need, why not 10 or 20HP or less than 2HP?
    2)How can i get a proper design for the blades, i saw the ones for the laser cut but i wanna know why is that geometry a proper one.
    also why 70RPM is a good angular velocity for the motor.
    Thanks a lot for any response.

Hello @juanbravo1992 !

I will try to answer your questions.

A motor with lower then 1.5-2kW seems to be to weak for shredding thicker plastic (thou this depend on your reducer).
You can use a motor with higher power then 2kW, but they usually cost more, and is most likly to be 3-phased. Most households do not have 3-phase current.

I believe that this was the best/most functional design to use. Others were tried, but this seemed to be the best. @davehakkens may know this?

If you shredd to fast the plastic can start to melt, and if you shredd slower then well, it goes slow…

I am aiming for something between 40-60 rpm for my shredder.

Hope this help you.

answered this with equations in thread i made for shredder calc. Shredder Calculations