bobbin as a matter of fact it is only necessary to take such relation for a suitable plural number of the layers during spinning from the beginning until completion of winding in this case the relation between the number of layers n and the bobbin r p m n u00b0 n may be directly inputted to the micro computer for the roving of a specific description alternatively the relation between n and n u00b0 n is recorded in advance and the relation thus recorded is inputted occasionally to the micro computer so as to be used in a subsequent spinning operation which is to be effected under the same spinning conditions still alternatively the relation between n and n u00b0 n is stored in advance in a micro computer for each of plural descriptions of the roving so that a desired one of such relations may be resorted to when the occasion may demand the preparatory step for the actual spinning is now completed the control process for the bobbin r p m in the course of the actual spinning operation is now described in detail it is assumed that nn designates the bobbin r p m as measured for a certain number of the roving layers n the value nn is inputted to the micro computer for.