the legs of the triangle formed between the grooved roller 14 and the collector c 1 is largely reduced minimizing the detrimental influence of tension of the legs on the quality of the carding sliver as shown in fig3 the drafting system d is shown to be a 3 over 4 roller drafting system wherein the second drafting zone is pre set at a constant draft the draft ratio of the first zone is determined by control signals input to a controller 16 the controller 16 includes the motor and gear system not shown where the rotating speed needed for each roller 18 19 20 and 21 is controlled by a respective output thereof sensors 15 and 17 are each installed in grooved rollers respectively located at the input and the output of the drafting system for measuring the linear density of the input and output carded slivers the controller 16 uses the input linear density g 1 and the output linear density g 0 in comparison with the ideal linear density g to provide adjustment for correction of long term unevenness and prevention of fly away fiber conditions during the drafting process moreover the output speeds v 1 and v 2 of the.