Spinning Total draft limitation

DRAFTING:
The break draft should depend upon the following,

• fibre type
• fibre length
• roving T.M
• main draft

Some examples are given below,

Normally 1.13 to 1.18 break draft is used for

• 100%cotton , Poly/cotton blend, 100% synthetic
• roving T.M. upto 1.3 for cotton and .80 for Poly/cotton blend, 0.5 to0.7 for synthetic
• ring frame back zone setting of 60mm for fibres upto 44mm and 70mm for fibres upto 51mm
• total draft in ringframe upto 35

1.24 to 1.4 break draft is used for

• 100%cottton, poly/cotton blend, 100%synthetic fibre
• strongly twisted roving i.e higher than the above mentioned T.M.s
• total draft from 33 to 45
• back zone setting(R.F) around 52mm for fibres upto 44mm and 60mm for fibres upto 51mm-

If the total draft is more than 45 or the fibre length is more than 51 and the fibre is a fine
fibre(i.e more number of fibres in the cross section)with a very high interfibre friction, break draft
more than 1.4 is used.

Please note that for most of the application, lower break draft with wider setting is used. With higher break
drafts, roller setting becomes very critical. Higher the break draft, higher the chances for thin places
i.e. H1 classimat faults.

Higher draft with improper back zone setting will lead to thin places and hence more end breaks
even though more twist flows into the thin yarn.

MAIN DRAFT ZONE:

Mostly for cotton fibres, short cradles are used in the top arm. Front zone setting is around 42.5 mm to 44 mm depending upon the type of drafting system. The distance between the front top roller and top apron should be around 0.5to 0.7mm when correct size top roller is used. This is normally taken care of by the machinery manufcturer. If a technician changes this setting, this will surely result in more imperfections, especially with karded count the impact will be more. Therefore when processing cotton fibres, care should be taken that the front zone setting should be according to the machinery manufacturers recommendation.

For synthetic fibres upto 44 mm , it is better to use short cradles. Even with 42.5 mm bottom roller
setting, 44 mm fibre works well without any problem. Because, the clamping distance will be around 52 mm or 50 mm. The imperfections and U% achieved with short cradle is better than with medium cradle(52mm setting).

Instead of using medium cradle for processing 44mm synthetic fibre, it is always better to use
short cradle with 1 or 2mm wider setting than the recommended to avoid bottom apron damages.
If a mill has got a problem of bottom roller lapping, the apron damages are extremely high, it is better to use short cradle for 44 mm fibre and widen the setting by 1 or 2mm. This will minimise the complaints and improve the basic yarn quality also.

Please note that if the bottom apron breakages are high, then the mill is working with a lot of
bottom apron which is defective and with a lot of top roller which is defective. Both the defective
parts produces a defective yarn, which can not rejected by older version of yarn clearers, and improperly set new type of clearers. This yarn will very badly affect the fabric appearance.

Therefore it is always advisable to use a wider front zone setting upto 2mm , if the mill faces a problem of excessive bottom roller lappings. Please note that the defective bottom apron and top roll will not only affect the quality, but also the production, because the defective bottom apron and top roll make the  spindle a sick spindle which will be prone to end breaks. A wider front zone setting will increase the imperfection and uster, but there will not be major deviations of yarn quality.
Nose bar height setting is very important. Depending upon the design, it is 0.7mm or .9 mm. Variation in heigh setting will affect the yarn quality and the apron movement. The distance between nose bar  and middle bottom roller should be less than apron thick ness or more than 3 mm to avoid apron buckling if there is any diturbance in apron movement.