Spring back in bending

Spring back in bending :

        Spring back increase in included angle of bent part relative to included angle of forming tool is removed. reason for spring back is when pressure is removed the elasticity energy remain in bent causing it to recover partially toward is original shape .

   Spring back in bending show itself that decrease in bend angle and increase in band radius in fig 1 during bending the work is forced to take radius with Rb and included angle Ab' of the bending tool punch in v bending in fig 2 after the punch is removed the work spring back to the radius R and angle A'.

The amount of spring balance increase with increase in modulus of elasticity and increase in yield strength Y of yield of the work . 

Compression of spring balance is over bending the punch angle and radius are slightly smaller than the specified angle on the final part so that the sheet metal springs back to desired value . 

WHAT IS BENDING

Bending :

       Straining a sheet metal around a straight axis to take a permanent bend this is called bending in manufacturing process.

1) Metal on inside of neutral plane is compress, while metal on out side of the plane is stretched.

2) The metal is plastic ally deform so that the bend take the permanents set with no changes in the thickness.

           

  Types of bending :

There are two types of bending.

1) V bending 

2) edge bending .

V bending :

•   For low production.
• Performed on a press break 
• v dies are simple and in expensive .

Edge bending :

• For high production .
• pressure pad required 

dies are more complicated and costly.