Why can the notch of the cutting backing plate heal automatically

I think strictly speaking, it's not healing. The material of the cutting backing plate is a kind of anisotropic rubber, which is relatively hard in the vertical direction, but relatively soft in the horizontal direction. After cutting, because the horizontal direction is very soft, the stress distribution of the cut section does not change much, and the plate will not have large deformation, so the section can be well matched. Under the action of van der Waals force, many molecules on the cross section establish connections, so the macro cross section adheres together again.