A new method of burr-free slitting

Abstract

Conventional rotary slitting is now widely used for dividing a wide strip into a plurality of narrow strips or for trimming the unnecessary and/or unacceptable edge portion of relatively wide sheet metal stock. However, with conventional slitting, burr formation on the slit edge is inevitable. To eliminate this drawback associated with conventional slitting, a new slitting method has been developed by the authors which causes no burr at all to occur on the slit edge. This new slitting method consists of two stages, namely, (i) that of first subjecting the flat-rolled material to a shearing action along the longitudinal axis of the material to cause it to be partially sheared, by use of a pair of circular slitting cutters set at a distance apart of less than the thickness of the material, and (ii) then transferring the partially-sheared material to the nip of a pair of cylindrical rolls which are preset to a gap which is substantially equal to the thickness of the material, in order to push back and separate the material into a number of strips without any burr on their edges. The process is very simple, in that the horizontal cutter clearance can always be set at zero value, regardless of the material and the thickness. Apart from the simple operation of setting the second-stage flattening rolls to a gap which is substantially equal to the material thickness, only the adjustment of cutter spacing is needed, to suit the type and thickness of the material. This feature will result in a reduction of operational cost. Moreover, the wear of cutter discs according to this method is found to be very small when compared with that for the conventional slitting method. In addition, the second stage rolls show hardly any wear at all. Further, industrial significance of the method resides in that it is applicable to various kinds of ductile material which would be liable to cause relatively high levels of burr as the cutter is worn away.