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torque for 3 roll bending machine

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anyone knows how to calculate the necessary torque and power for a sheet metal straightener machine or a 3-roller bending machine? 
 
I know material streght, thickness, width, rollers diameters and distance between rollers are factors to consider.
Thanks.
 
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This is a really tough question because plastic deformation is involved. In forming a ring this way, the material must be permanently deformed (partially moved into the plastic state) so that it does not spring back. I suspect you might make some FEA calculations, but the ultimate proof is in the testing. I think I would opt to go straight to testing.

DrD

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In the straightening of steel sheet, it is necessary to calculate the optimal reduction of the steel blank by the working rollers of the straightening machine so that the sheet produced has the minimum residual stress and curvature. In the simulation of sheet straightening in multiroller machines, the curvature and bending torques of the steel sheet at contact points with the working rollers are first calculated and then the straightening forces are determined. In straightening steel sheet, it is important to calculate the forces in the multiroller straightening machine. Such calculations are based on determination of the reaction of the roller bearings and the forces at the upper and lower working-roller cassettes in straightening. With insufficient bending torque, it is impossible to eliminate harmful residual stress and surface defects in the sheet. Extreme roller torques and forces at the roller cassettes often lead to defects of the sheet, fracture of the working and supporting rollers, and failure of the straightening machine. In the present work, an approximate method is proposed for calculation of the optimal cold-straightening parameters of the steel sheet in a multi-roller machine. The calculations permit determination of the curvature of the neutral plane in the sheet on straightening, the residual curvature of the sheet after straightening, the bending torque and the reaction of the working-roller bearings, the residual stress in the sheet, the penetration of the plastic deformation into the depth of the steel sheet, and the relative deformation of the longitudinal surface fibers of the sheet on straightening as a function of the radius of the working rollers, the distance between the rollers of the straightening machine, the reduction of the sheet by the upper rollers, the sheet thickness, and its properties (Young’s modulus, yield point, and strengthening modulus). The results may be widely used at manufacturing and metallurgical plants.

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2 hours ago, Steve Beck said:

In the straightening of steel sheet, it is necessary to calculate the optimal reduction of the steel blank by the working rollers of the straightening machine so that the sheet produced has the minimum residual stress and curvature. In the simulation of sheet straightening in multiroller machines, the curvature and bending torques of the steel sheet at contact points with the working rollers are first calculated and then the straightening forces are determined. In straightening steel sheet, it is important to calculate the forces in the multiroller straightening machine. Such calculations are based on determination of the reaction of the roller bearings and the forces at the upper and lower working-roller cassettes in straightening. With insufficient bending torque, it is impossible to eliminate harmful residual stress and surface defects in the sheet. Extreme roller torques and forces at the roller cassettes often lead to defects of the sheet, fracture of the working and supporting rollers, and failure of the straightening machine. In the present work, an approximate method is proposed for calculation of the optimal cold-straightening parameters of the steel sheet in a multi-roller machine. The calculations permit determination of the curvature of the neutral plane in the sheet on straightening, the residual curvature of the sheet after straightening, the bending torque and the reaction of the working-roller bearings, the residual stress in the sheet, the penetration of the plastic deformation into the depth of the steel sheet, and the relative deformation of the longitudinal surface fibers of the sheet on straightening as a function of the radius of the working rollers, the distance between the rollers of the straightening machine, the reduction of the sheet by the upper rollers, the sheet thickness, and its properties (Young’s modulus, yield point, and strengthening modulus). The results may be widely used at manufacturing and metallurgical plants.

Hi Steve. Thanks.

Yes, I know that. I read this in an article in the web.

I need some formulas to calculate torque and power needed.

Thanks.

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13 hours ago, DrD said:

This is a really tough question because plastic deformation is involved. In forming a ring this way, the material must be permanently deformed (partially moved into the plastic state) so that it does not spring back. I suspect you might make some FEA calculations, but the ultimate proof is in the testing. I think I would opt to go straight to testing.

DrD

 

Yes ! I agree. There are some formulas I could find (even considering plastic deformation) but they are very inconsistent.

Finally, I took this like a rectangular beam and I considered Tensile Strenght for my calculus.

After that, I could find a formula for Power needed. And with the velocity, that I know, I got the Torque.

Unfortunately, I can not test nothing. The machine does not exist yet.

Based on this and some expierence in the field, It was the best I could do.

 

Thank you very much DrD !! you are the best !

 

 

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