It is caused by the interaction between the material's compression on the inside of the neutral axis and its expansion along the outside of the neutral axis. With a profound-radius bend, springback-the material's attempt to return to its original flat position-increases dramatically (see Figure 1). If the bend radius exceeds 10 times the material thickness, it is considered a large-radius orprofound-radius bend. If the bend radius is less than 63 percent of the material thickness, it is considered a sharp bend. Under normal press brake bending conditions, an inside bend radius that falls between 63 percent of the material thickness and 10 times the material thickness is defined as a radius bend.
With a profound-radius bend, springback increases dramatically.