Edge Trimming of Aluminum Sheets Using Shear Slitting at a Rake Angle

Edge burr is inevitably present at a slit edge when an aluminum web is shear slit by a pair of rotary knives (or blades) engaged and rotated in opposite directions. This paper presents a new method of shear slitting for an aluminum sheet to produce very low edge burr height, for use in edge trimming. The method uses the same bottom rotary blade as in the traditional shear slitting, but a revised top blade that forms a rake angle with respect to the bottom blade. The top blade edge is chamfered so that the surface of the top blade edge is parallel to the surface of the bottom blade edge to produce a pair of shearing surfaces to shear slit the aluminum sheet. A sequential set of micrographs of an aluminum slit edge are taken to visualize different stages of the shear slitting process. The observation indicates that this new slitting configuration induces a local tension as a result of blade relative motion so that a combined tension∕shear is applied to the aluminum sheet to facilitate early separation in the aluminum sheets. As a result, a clean edge with very small burr height is produced consistently. Edge trimming of aluminum sheet over a wide range of slitting conditions indicates that the new configuration is insensitive to blade gap and overlap, and can lead to a clean cut with very low edge burr height even when two blades are separated by a gap that is a few times of the sheet thickness.