• After basic shearing operation, we can bend a part to give it some shape.
• Bending parts depends upon material properties at the location of the bend.
• Some of the things that may/do occur in bends,
- material at the outer bend radius undergoes tensile plastic deformation
- material at the inner bend radius undergoes compressive plastic deformation
- the width (along the bend axis) will reduce in length based on poissons ratio
- if the bend radius is too small the plastic deformation at the outside of the bend will result in fracture.
• The basic calculations for a bend radius are shown below,
• The strain on the outermost fibers of the bend is,
• After sheet metal is bent it will tend to spring back to a lesser angle. The following formula relates bend radius before and after release.
• There are a variety of methods for springback compensating,
- trail and error to over bend
• The maximum bending forces may be calculated using the relationship below,
• Press Brakes a small presses that will bend a sheet metal piece over several feet.
• Some other operations done to sheet metal parts,
beading - the edges of the sheet metal are bent back (in a rounded shape) to stiffen the edges and eliminate the sharp edge.
flanges - a hole can be formed by punching through, and a lip (the flange) remains about the edge of the hole
Hemming - like a bead, but the edge is bent back as a flat.
Roll Forming - Bends can be made along long axes by using rollers.
• When planning to bend a piece, car must be take not to punch holes too close to the bend.
