What is autoleveller? It is a online monitering device in spinning process. It has become an integral part of the spinning process for production of high quality yarn. It helps in achieving consistent count cv%.
Need of autoleveller To survive in this age of high competition, it has become necessary to produce an internationally accepted standard yarn quality. Carded slivers fed to drawframe to drawframe have high degree of uneveness that cannot be tolerated. Comber contains infamous piecings. Higher CV% affects the appearence of dyed fabrics by absorbing the dye unevenly.
Norms for CV% at different stages Material Wrapping length Without With (yards) autoleveller autoleveller Yarn 120 2.5 – 3 1.5 - 2 Roving 15 1.5 – 1.8 0.9 – 1.2 Drawframe 5 0.7 – 0.8 0.4 – 0.5 Sliver Drawframe 1 1.5 – 1.6 0.9 – 1.1 Sliver
Object of autolevellerTo maintain consistent hank of sliver.Principle: Adjust the Draft continuosly, which will depend on thickness of material fed.
Types of autoleveller Open Loop Closed LoopThis system is effective for This system is effective forshort, medium and to some long term variationsextent long term variationsLack of self monitering SelfmoniteringMore popularly used Rarely used
Various parts of autoleveller Scanning roller Signal convertor Levelling processor Servo drive Quality monitor sensor
Important parameters for qualitylevelling Levelling intensity Levelling action point
Levelling Intensity It indicates the amount of correction to be done. It is to decide the amount of draft change required to correct feed variation. The correlation between mass and volume for different fibres is not same.
Levelling action point The calculated correction should be done on the corresponding defective place. The time required for the defective material to reach the correction point should be known. Levelling action point depends on break draft, main draft roller setting and delivery speed
A% test Sliver weight in ktex (n-1) slivers n slivers (n+1) slivers 1 2 mean A% 0 Over-compensation:For (n-1) slivers Reduce levelling intensity by A% For (n+1) sliversA% = (ktex(n-1) – ktex(n) X 100 levelling intensity by A% ktex(n) X 100 Under-compensation: Increase A% = (ktex(n+1) – Drawframes ktex(n) maintained in good conditions achieve ktex(n) between 0 deviationand 0.5 or between -0.5 and 0A% + : over-compensation A% + : under-compensationA% - : under-compensation A% - : over-compensation
Quick test for levelling action point a) Levelling action is OK. b) Levelling action is too late c) Levelling action is too early
Quick test for levelling intensity a) Ideal diagram. b) Under compensation, increase levelling amplification by A% c) Under compensation, increase levelling amplification by A%
Calibration Need of calibration: Calibration is required because even the best instruments drift and loose their ability to give accurate measurements. On autolleveller callibration is done for Scanning rollers Pressure on scanning rollers Servo motor
Calibration for scanning rollers For rieter RSB-D30 scanning roller calibration is as followsScanning roller current levelling Value Distance guage 3mm 3.3 V 4mm 5V 5mm 6.7 V 6mm 8.4 V
Pressure on scanning rollers Material Scanning roller pressure in KGSmooth, elastic fibres, Combed cotton 100 Cotton carded 120High crimp and bulky fibres, such as 130 acrlyic, polyester (W-type)Extremely high bulk, and micro fibres 140 Polypropylene 160
Calibration for Servo motor Trim potentiometer “Tacho” is adjusted in such a way that actual value equals target value.1) Calibration servo drive -25% deviation > yes target 1487 actual 14862) Calibration servo drive +25% deviation > yes target 892 actual 890
Laser based autoleveller Laser beam is used for measuring the sliver thickness. LDR is used for sensing the intensity of laser beam. Fast in response, No fibre rupture, no mechanical parts High cost
Advantages of autoleveller All variations are corrected. Count CV% will be consistent. Thin places in sliver and hence in the yarn will be low. Higher efficiency in further processes.
Conclusions For obtaining good yarn quality, installation of autoleveller is a must. As long as the autolevelling system is set properly, advantages mentioned above can be achieved. Otherwise, the negative impact will be very big compared to working without autoleveller
References RSB D-30 & RSB D-45 manual A project on “ Assesment of autoleveller on breaker and finisher drawframe” under guidance of Prof. S.D. Mahajan & Prof. M.S. Kulkarni A practical guide to Combing and Drawing – W. Klien www.textilespinning.blogspot.com Trützschler HSR 1000 brochure Technological study of autoleveller at drawframe on cotton yarn quality – nasir mahmood, journal of applied sciences, vol 6, year 2006, pages 287-291 Studies on autoleveller in drawframes – M.S.Indradoraiswamy, P.Chellamani, SITRA, 34th Joint technological conference page 13- 19