• –Staple length:-.

More the staple length more will be the fibre friction & more difficulty for opening roller to separate fibres.

•This will lead to fibre shortening & then rotor fauling.

• Hence comparitively ( comparing with ring  spinning) shoter staple lengths are used[ for polyester fibres 32mm.].

• –Fibre fineness:-.

• The advantage of finer fibres is that, while maintaining the minimum number of fibres in the cross section, one can raise the fine-yarn count limit for rotor spun yarn considerably.

• Further advantages are the ability to reduce yarn twist & increase breaking tenacity.

• But use of extremly fine fibres may lead to fibre damages during preparation especially during carding.[Ideal linear density =1.5 denier].

• –Fibre crimp:-.

•Highly crimped fibres have greater resistance to extraction from the sliver by opening roller,which leads to fibre damage & rotor fauling.

• Also they do not flow smoothly in the duct between the opening roller & the rotor; Furthermore they do not lie in a compact mass in the `v` of the rotor groove.

•While the fibres with low crimp levels give higher yarn strength, fewer yarn defects & a reduced number of ends down.

• But the fibres with too low crimp level or performance will have poor card-web cohesion & result in a poorly drawn sliver.

• –Tenacity :-.

• High tenacity fibres are reported to perform  better than lower-strength versions because they minimize the strength loss of open end spun yarns, suffer less breakage & therefore produce fewer rotor deposits.

• –Relative humidity & temperature:-.

•Relative humidity should be between 50-55% & temperature should not be lower than 23 deg. Celsius.

• –Sliver preparation :-.

• •Rotor spinning parameters :-.

• –Combed sliver do not much improve the yarn quality as compared to the carded sliver.

• – Blending can be done by flock-blending & draft sliver blending methods.

• –However, with draft-sliver blending, even after the second passage of drawing, the sliver is still basically in a stripe form.

• – If the sliver blending is used, autolevelling should be therefore carried out at the card with two or three drawframe passages prior to spinning.

• –1] opening roller parameters :-
  • .•Inclination of teeth of clothing = 90 degrees, the tooth height = 1.2 mm. , THE DISTANCE BETWEEN THE TEETH = 4 mm. , Density of teethes =14 teethes per  square centimeter. , Opening roller speed= 6000 - 7000 rpm.
• – 2] rotor parameters :-.
  • •Twist factors = 120 - 140;
  • •Spinning tension must not exceed 60 % of the yarn strength ;
  • •Ratio of rotor diameter to fibre length should not be less than 1;
  • •Smaller rotor diameters require higher rotor twist;
  • •Higher rotor speeds leads to a steep rise in yarn tension, & resulting yarn friction against the doffing tube may cause localized melting of synthetic fibres.

   

• – 3] Doffing tube parameters :-.
  • Smooth doffing tubes are recommended in preference to the notched type in order to keep stresses on the yarn within acceptable limits