New blade's design

i’m trying to design a blades for the shredder which seen it in a shredder … so i want to know your opinion …

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another photos

Oh NVM I used the correct number.

Also on that computation I think I used umm HDPE taught instead of stainless steel. I will amend the calculations above or double check it.

I will compelete it and send it to u

you would also use FEA but you will need to know how thick the max cross section of the material you will cut. So like a 1 inch by 1 inch rectangle or 2 inch by 2 inch rectangle. Then what material are you cutting HDPE, PET, PP, LDPE etc.
So if you would want me to help you would have to tell me the cross section cut. or let me calculate the maximum cross section area cut by sending me the file of the rest of the housing.

@thegreenengineers thx for your advice … so if i want to know how good the blades with plastic ,which analysis i must do ?

My personal opinion on the shaft (the cylinder part) is to have it turned down to the same diameter as the width of the square shaft. So 1.181 inch that will leave you with the strongest shaft rather than turning the shaft down.

case hardening only effects the “case” which is the surface up to like 10 thou thick
it does not effect the interior of the steel
however if it is “through” hardened steel then it is hardened all the way through.
the through hardened steel will handle a lot more force yest that would be better.

anyways equation for the size of the cross section is this.
Also what i am talking about is the thinner cylindrical cross section that connects to the motor not the square section. The square section is strong enough.
tau = (T*(radius))/J
J for circle cross section = ((pi)*(D^4))/32
So solving for D you get:
((T*(16))/(tau*pie))^(1/3) = D (diameter)
T = 535 N.m (3HP at 40RPM)
tau = 215 MPa * .80 = 172MPA = 172,000,000 PA
D = .025 meters
= .0828 feet
= 1 inch
so currently you are at .945 inches
so you need to increase by .055 inches
otherwise known as 55 thou
Enjoy.

What about running case hardened mild steel blades?

That will make the assembly better. that has nothing to do with how big of a section of plastic you can cut. i did not run FEA on that as i need to see the housing that that assembly rotates in.

@thegreenengineers so the design will be correct if i increase the diameter of shaft ?… btw i have a 3 hp motor

Ok so
if using 304 Stainless on everything in your model
Under the scenario that you try to cut to much plastic and your motor stalls
you will be able to use around a 2 hp motor before your center shaft fails in TORSION
So you will have to increase the cross section area of your main drive shaft to be able to handle more power.
Image bellow is of the S.F. safety factor which basically means that if the number is 1 it is going to break.
Mabye going to look at some other senarios

@thegreenengineers here is a link for the files … can u write your account on FB or email to contact u … https://www.mediafire.com/file/iajbtm56zdtq1t0/Shredder%20development.rar

Yes. Send me all the individual files and the assembly of the solidworks files i will import them into fusion360 and run the FEA. what grade of stainless? 316L?

@thegreenengineers i want to make it with stainsteel … i can pass u the files of solidworks and u make the analysis cause idk do that

have you run FEA (Finite Element Analysis)? to see if it could handle the stresses of cutting that large of cross section of plastic. And what material would it be made out of?