Open End Rota Spinning. (OE)
Open End or rotor spinning (OE) has been used to spin wool and wool blend yarns in commercial mills for many years. A technical limit applies with respect to the length of wool fibre that can be used. The maximum fibre length should not exceed a maximum of 1.25 times the rotor diameter, e.g. the longest 1% of fibres (from the Almeter test result) should not exceed 58 mm for a rotor diameter of 46 mm. Schlafhorst recommend an average fibre length of 30 to 40 mm for a 46 mm rotor. The 46 mm rotor diameter has proved especially good for processing 100% wool knitting and weaving yarns. Smaller diameter rotors, e.g. 40 mm rotors, can be used with wool-poor blends, e.g. with cotton.
Wool Rich Blends
Schlafhorst recommend the minimum number of fibres in the cross-section of a 100% wool yarn is 150 to 200 fibres, although this number is largely tied to the larger rotor diameter required for 100% wool and the higher spinning tension applied to the yarn in larger rotors. Following this recommendation, 100% wool OE yarns are limited to counts coarser than 60 Tex (1/10 Ne) from wool fibre with a diameter less than 20 µm. However, for wool poor blends, finer count yarns spun using smaller rotors are feasible resulting in total fibre numbers much less than 150.
Schlafhorst recommend that the percent of antistatic agent not exceed 0.5%. The build up of grease and dust inside the rotor groove leads to detrimental spinning ability (performance). CtnWool™ is delivered with an antistatic agent of 0.3%, giving our spinner customers potential for addition just prior to processing (See Preparation).
Spinning Settings
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Twist multipliers (αe) Weaving = 4.0 – 4.5 Knitting = 3.6 – 4.1
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Winding tension Angle of wind = 39° with a lateral displacement of 1 to 2 mm for parallel cheeses. Set cradle pressure to minimum setting.
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Delivery speeds for wool blend yarns should not exceed 140 m/min.
Components
Schlafhorst have recommended rotors, opening rollers and navels for the spinning of wool yarns. It is recommended that contact be made with the OE machinery manufacturer to discuss the components and settings required to spin wool/cotton blend yarns.
Rotors and Rotor Speeds
Rotor diameters between 40 and 56 mm (80,000 to 60,000 rpm) should be used depending on blend ratio. Boron coated rotors have been found to be most satisfactory. A range of rotor grooves can be used to change yarn characteristics and spinning ability. Of the rotor groves available, the G or T shaped rotor grooves are most suitable for wool blend yarns although selection depends on internal mill trials on yarn type, e.g. bulky and hairy yarns are produced using rotors with open and wide grooves such as the S-groove, whilst tight smooth yarns are produced using T-grooves. Typically, larger rotors are used to spin knitting yarns and smaller rotors are used to spin weaving yarns.
Combing Roller
The S21 combing roller with diamond nickel (DN) or nickel (N) coating has less aggressive teeth and is suitable for blends with wool, polyester and acrylic. It is recommended that the combing roller is run at speeds between 7500 to 8500 rpm depending on yarn type and blend ratio.
Navels
The choice of navel is dependent upon the type of yarn required; a KN (smooth) ceramic navel is suitable for smooth low hair yarns whereas a K8 navel with notches produces a hairier yarn suitable for knitting. The choice of navel also determines somewhat the stability.