pivoted in the direction of the arrow b by reversing the operation of the cylinder unit 62 the drafting arrangement is again closed and again locked by reversing the operation of the cylinders 10 upon starting the machine at creep speed the drafted material is inserted into the funnel or trumpet 53 and then into the pair of calender rolls 54 thereafter the drafting arrangement can be switched to its normal production speed under the term 34 short to long staple fibers 34 there also are to be understood cotton and man made fibers of a staple length of up to 80 mm for those bottom rolls which from the beginning of the pre drafting zone and the main drafting zone a diameter of 90 mm is chosen so that also when processing fibers of 80 mm staple length there can be ensured a wrapping angle of the fiber sliver upon said bottom rolls of maximum 45 angle degrees as practical experience has shown at wrapping angles exceeding an angle of 45 u00b0 the friction due to the cord wrapping angle between the fiber sliver and the bottom roll becomes too great with conventional fluting of the bottom rolls the initially mentioned high sliver speeds cause high centrifugal forces i e high values of angular or radial acceleration at a sliver speed of for instance 1000 m min at the delivery or outlet point of the drafting arrangement and with a diameter of 90 mm of the first bottom roll 13 of the main drafting zone and at a draft ratio of 4 1 the angular or radial acceleration reaches a.