To optimize the cleaning of cotton in a spinning milk, there is entered into a control original data concerning fiber characteristics and proportions of different types of contamination inherent to the origin of fiber cotton bales. Also there is entered into the control a desired degree of cleaning and a throughput quantity of the carded fiber sliver. The control delivers predetermined control signals based upon the entered original data, the throughput quantity of the carded sliver and the desired degree of cleaning. These control signals set adjustable operating members governing the rate of opening of the cotton bales by bale opening machines, the degree of cleaning of the cotton fibers by cleaning machines and the rate of processing of the cotton fibers by at least one carding machine.