1. Roller Slip
The bottom rollerisindirectcontact withthe bottomsurface A of the fibers,&the motion
reachesB whichinturn movesthe toprollerconsequently,thereisacertainamountof slippage
occurring,& the topsyntheticcoveredrollerdoes notexactlyshow the same surface speedwith
whichthe bottomflutedrollerisrunning.
Thisfall insurface speed of top roller,whenmaterialispassingbetweenthem, istermedas
“rollerslip”
Causes:
The amount of rollerslipdependsmainlyupon:
Bulkof fibers&nature of fibers
Centertocenterdistancesof the two pairsof rollers.
Degree of orientationof the fibersinthe material.
The amount of draft betweenthe twopairs.
Conditionof the rollersincludinghardnessof topsyntheticcovering.
Amountof weightingonthe toprollers.
Remedies:
By usingnarrowflutedroller.
By usingclosersettinginthe middle zone of draftingsystem.
Use correct rollertorollerpressure.
RollerSetting
Factors consider for selection of roller setting:
1. Staple lengthof the fiber.(staple length+allowance)
2. Amountof draft required. ↑ Allowance ↑
3. Thickness/Bulkof the material.↑ Allowance ↑
Measurement of roller setting:
Front Zone (FZ)=SL+1/8inch
2. Middle Zone(MZ)=SL+1/4 inch
Back Zone(BZ)=SL+1/2 inch
SL= Staple length
Auto levelling
Draw frame isthe bestautomaticcontrol of sliverregularity.Indrawingdraftiscontrolledbyservo
motor forconstantcount. The programme of controllingdraftbyservomotor iscalledauto
levelling.Itisdone bytwo ways:
1. Openloopautoleveller
2. Close loopautoleveller
Open loop autoleveller:
Whensensorsense the feedcount&actionis done onthe feedmaterial tochange the draftis
calledopenloopautoleveller.
Close loop autoleveller:
In thisprocesssensorsense the deliverycount&sendthissense tofeed & draftis changed
accordingly
Defects/Faults of Draw frame
1. End missing/Fine sliver:When5or6sliverare doublinganyslivermaybreak.Thisisendmissing.
Causes:
(i)Faultystopmotiondevice
(ii)Operatorcarelessness
2. Irregularsliver
Causes:
1.Rollerslip
(a) Improperrollerpressur
(b) Worn top roller
(c) Eccentrictop roller
(ii) Defective draftingsystem
3. (iii)Improperrollersetting
3. Long fiberinthe waste
4. Rollerlapping
Causes:
(a) Impropercleaningof the roller
(b) Impropertemperature &RH
5. Excessive sliverbreaks
Causes:
(a) Feedzone:Feedtension
(b) Draft zone:(i)Rollerlapping
(ii)Entanglementof sliverincan
(c) Deliveryzone:(i)Improperselectionof trumpet
(ii) Impropersurface of trumpet
6. Improperstockfilling.
Draw Frame(Calculation)
1. A certainDraw frame witha 56 teethdraftchange pinionisdelivering a48 grain/yardsliver
from45 grain/yardfed.Whatwill be the pinionrequiredif 52grain/yardslivertobe produced
2. Calculate the productionpershiftof 8 hoursof a draw frame whichisrunningat 85% efficiency.
Speedof 1.25 inch front
Chayan
