Knitted finished fabric may have different type of defects , it may be due to yarn, Knitting, Processing. Here we will discuss about knitting related defects
List of Knitting Faults and their route causes
- Drop stitches
- Needle & Sinker line
- Holes
- Ladders
- Tuck flaw or crow feet
- Oil marks
- Yarn lines
- Iro lines
- Stopping lines
- Foreign contamination/fibre
- Barre
- Abrasion marks
- Slubs
- Snags
- Press/off
- Pulled threads/loop
- Missed loops
- Lycra misplating
- Lycra breaks
- Oil line
- Fleper tension
- Wrong creeling of yarn
23. Winder line (distance between the wales opened or closed)
DESCRIPTION & ROOT CAUSES OF KNITTING FAULTS
1. Drop stitches: – It is a small aperture formed as a result of an inadvertently cast-off loop and where the yarn is not broken. General (All m/c’s)
| Root cause | Checks | Action |
| Feeder/s not down properly. (After lifting feeder to remove fluff) | Check for feeder/s that are not pressed down properly. | Press feeder/s down completely. |
| Extremely weak yarn supply tension. Uneven yarn supply tension ( too high & too low ) | Check if yarn path is correct– i.e. yarn guides, potholes, and feeders. See yarn threading diagram. Check if yarn-feeding unit (Iro) is turning freely.Check if yarn tension is to specification. (Refer to Knitting tension specs) | If not correct rethread according to yarn threading diagram If not turning freely, replace with spare one Adjust according to yarn tension specs. |
| Needles are damaged or bent in cases of drop stitches in a vertical line. | Trace the faulty needles. | Replace with new needles |
| Position of feeders too far from needles. | Use color yarn to identify the feeder/s causing the problem. (See procedure for tracing problem feeders) | Set feeder/s according to Feeder setting specs |
| Loose feeder/s or loose feeder block/s. | Check for loose feeder/s and feeder blocks. | Tighten feeder/s and set according to Feeder setting specs. If feeder block threads are damaged, replace with new ones. |
2. Needle & Sinker line: – Vertical lines going down the wale of the fabric different in configuration/appearance from the adjacent wales. General (All m/c’s)
| Root cause | Checks | Action | Comments |
| Needles and sinkers are floating due to lint build up in tracks. | Check for needles and sinkers that are floating due to lint build up in tricks | Take out needles and sinkers in the affected areas and clean up the lint & re-fit needles and sinkers. | If needle and sinker lines are all around the fabric tube, a Strip & Clean might be necessary. Check Rev chart for Strip & Clean. |
| Needles and sinkers are damaged or bent. | Check for damaged/bent needles and sinkers. | Replace needles and sinkers in the affected areas. | |
| Wrong needles and sinkers for the machine gauge. | Check for wrong needles and sinkers for the machine gauge. | Replace the wrong needles and sinkers with the right ones. See needle check-???? | |
| Insufficient oil supply to needles and sinkers | Check if the oil level is not too low. If 1 is ok, check if solenoid is working. If 2 is ok, check if there is compressed air and pressure is set according to specs.If 3 is ok, check if oil drop rate is set according to specs.If 4 is ok, check visually if oil mist are moving through the oiler pipes.If 5 is ok, check if the nozzles in the cam boxes are not blocked. | If too low, fill up to the maximum level with the correct oil. (See refill procedure)If not working, fix or replace solenoid.If not to specs, set air pressure according to specs.If not to specs, set oil drop rate according to spec.If not moving, unblock oiler nozzles.If blocked, clean and unblock nozzle | |
| Tight or damaged tracks | Check for tight needle and or needle movement. | If tricks are tight, loosen and polish with trick file where necessary. |
3. Holes: – Small aperture in the fabric. General (All m/c’s)
| Root cause | Checks | Action |
| Weak yarn. | Check for weak yarn. | Replace faulty yarn. |
| Incorrect threading. | Check if yarn path is correct– i.e. yarn guides, potholes, and feeders. See yarn threading diagram. | If not correct rethread according to yarn threading diagram |
| Excessive yarn supply tension. | Check if yarn tension is to specification. (Refer to Knitting tension specs) | Adjust according to yarn tension specs. |
| Fluff – Poor house keeping | Check for fluff/house keeping.Check if flutter blower is operating.Check if all fans are turn on and turning. | Clean where necessary.If not operating, fix.If not on, switch on. If not, call electrician. |
| Thick and thin yarn & slubs. | Check for faulty yarn. | Replace faulty yarn. |
| Hand tied knots too big. | Knitters to use splicer where possible and do proper hand knots where necessary. ( See Hand knot procedure) | |
| On Double jersey machines, wrong timing might be a problem. | 1. Check machine timing according to timing specs. | Adjust timing to the Timing specs. |
| On Double jersey machines, wrong gating might be a problem. | 1. Check machine gating according to Gating specs. | Adjust gating to the Gating specs. |
4. Ladders: – A vertical line of unformed stitches caused by a broken needle hook or a needle with a closed latch. General (All m/c’s)
| Root cause | Checks | Action |
| A longitudinal line caused by one or more broken needle hooks. | Check for one or more broken needles. | Replace the damaged needles. |
| A needle with a closed latch(maybe a stiff latch) | Check for a needle with a closed latch. ( or a stiff latch) | Replace the affected needle. |
| Needles are floating due to lint build up in tricks, touching the feeders. Thus damaging the needles. | Check whether needles are not floating due to fluff and dirt behind the needles. | Take out needles in the affected areas and clean up the lint & re-fit needles. |
| Feeder too close to the needles. Thus damaging the needles. | Check if feeder setting is correct. (See Feeder stetting specs) | If not correct, set feeder/s according to Feeder setting specs |
| Thick slubs in the yarn causing the needle hooks to break. | Check whether knot catchers are not missing. Check yarn for excessive thick slubs. | If missing, fit appropriate knot catchers. (See Knot catcher table)If there are excessive thick slubs, report to manager. |
| Fluff – Poor house keeping | Check for fluff/house keeping.Check if flutter blower is operating.Check if all fans are turn on and turning. | Clean where necessary.If not operating, fix.If not on, switch on. If not, call electrician. |
5. Tuck flaw or crow feet: – A fault with a loop that has been held on the previous course. General (All m/c’s)
| Root cause | Checks | Action |
| A needle with a bent latch causes them. | Check for a needle with a bent latch. | Trace the affected needle and replace. |
| A needle with an open hook. | Check for a needle with an open hook. | Trace the affected needle and replace. |
| Not enough takedown or not enough pressure on takedown roller. | Check if takedown is not slipping. Check if takedown is enough.(See Takedown specs) | Check and adjust according to specs.Increase takedown according to Takedown specs. |
| Chipped needle and/or sinker butt. | Check for chipped needle and /or sinker butt. | Open all cam boxes and look for butt piece/s.Blow all the cam boxes.Replace damaged needle.Close and tighten all the cam boxes. |
| Bad gating on double jersey. | Check if gating is correct. (See Gating specs) | If not correct, set according to Gating specs. |
| Feeders not properly adjusted, causing bent latches. | Check if feeder setting is correct. (See Feeder stetting specs) | If not correct, set feeder/s according to Feeder setting specs |
6. Oil marks: – Deposited oils that has been absorbed on the fabric and has caused discoloration on the fabric. General (All m/c’s)
| Root cause | Checks | Action |
| Overflowing oil from the machine bed. | Check if drainpipe is blocked. Check if there are no oil spills on the takedown rollers. | Unblock drainpipe. Clean bottom of machine bed. Clean takedown rollers. |
| Too much oil from the oiler, produces light oil stripes | Check if oil drip rate is not too much. (See Oil drip rate specs). Slightly reduce the quantity. | Adjust according to specs. |
| Knitter not blowing the machine after manual flushing. | Check machine for fluff accumulation between the sinker cap ring and the cylinder cams. | Knitter must blow after each and every manual flushing. |
| Insufficient oil leads to dark longitudinal stripes, caused by abrasion of the needles | Check the setting of the oil is correct.The oiler is not blocked. | Increase the lubrication quantity.Flush manually with oil at intervals |
7. Yarn line: – A horizontal line that goes around the fabric tube for more than one revolution. General(All m/c’s)
| Root cause | Checks | Action |
| Thin yarn – thinner Tex than required. | Check if yarnTex are different. | Trace wrong yarn & replace with correct one. |
| Thick yarn – thicker Tex than required. | Check if yarnTex are different. | Trace wrong yarn & replace with correct one. |
| Wrong yarn –Mixed type | Check if yarn type is mixed. | If mixed, replace with correct yarn type. |
8. Iro lines: – A horizontal line that goes around the fabric tube continuously. The stitches are smaller on that course than the others. General
(All m/c’s)
| Root cause | Checks | Action |
| Unlock IRO or out of tape/belt. | Check it Iro is unlocked.Check if belt is in the right position. | Lock IRO into positionPut tape/belt in the right position. |
| Empty Iro – one or two wraps around the spool only. | Check if there are enough wraps around the spool. See Iro Drawing) | Fill according to Iro drawings. |
9. Stopping lines: – A horizontal line that goes around the fabric tube for one revolution. The stitches are smaller on that course than the others. General (All m/c’s)
| Root cause | Checks | Action |
| Positive belts slipping – tension on belts not enough. | Check if belt tension is to specs. | Tighten tension of belts according to Specs. |
| Positive belts slipping – too many Iros running on one belt. | Check if there are too many Iros one belt. | Re-arrange Iros so that load is split on two belts. |
10. Foreign Contamination/fibre: – Color specks/fibre in the fabric. General (All m/c’s)
| Root cause | Checks | Action |
| Foreign fibre i.e. non-cotton fibres spun in the yarn. | Check if the contamination is visible on the cones. | Very difficult to trace offending yarn cones. Report to supervisor/manager |
11. Barre: – A horizontal stripe lighter or darker than the rest of the fabric. Width of the stripe might vary. General (All m/c’s)
| Root cause | Checks | Action |
| Mixed merges and/or batches are knitted together. | Check yarn on the creel for mixed merges, batches and/or week no. | If mixed merges/batches/week no. are found, replace with correct yarn.If merges/batches/week no. are ok, send a meter piece of fabric for dyeing in the washing machine & a meter piece to the dyehouse for dyeing.If no barre after above procedure, continue knitting. If barre, report to manager and planning. |
| Wax barre – Yarn with different wax level on the yarn. ( Yarn merges/batches are not mixed) | Check yarn on the creel for mixed merges, batches and/or week no. | Send a meter piece of fabric for dyeing in the washing machine & a meter piece to the dyehouse for dyeing. If no barre after above procedure, continue knitting. If barre, report to manager and planning. |
12. Abrasion marks: – An area of localized wear characterized by the presence of excessive surface hairiness or denuded fibre. It is a surface fault on the fabric.
| Root cause | Checks | Action |
| Severe physical contact or pressure with a rough surface causes this fault. | Check whether spreader height is not too low, thus rubbing onto the takedown rollers.Check whether spreader wheels on the Inspection machine are turning freely. | Raise and set spreader at specified height.(See specs) Clean and ensure that turning freely. |
13. Slubs: – A thickened place in the fabric of different length where the yarn knitted in that area is at least 50 % thicker than the normal diameter of the yarn used. General (All m/c’s)
| Root cause | Checks | Action |
| Bad yarn clearing from the yarn supplier. | Check whether problem started with a new week no. Or merge.If 1 is no, trace the bad yarn/s if possible. | If yes, creel with a fresh week no. or merge. If no improvement, report to manager.If bad cones are found, replace with fresh cones. If no improvement, report to manager. |
14. Snags:- Yarns or filament in the form of long loops that are protruding from the surface of the fabric. General (All
| Root cause | Checks | Action |
| Sharp or protruding objects pulling on the fabric surface. | Trace back the fabric route and check for sharp or protruding corners and ends. | Polish where necessary |
15. Press-off: – Partial or complete breakdown of the fabric structure. General (All m/c’s)
| Root cause | Checks | Action |
| Fluff in the feeders. | Check knitting machine for cleanliness. | Clean the knitting machine. |
| Yarn tension too high. | Check if yarn tension is to specification. (Refer to Knitting tension specs) | Adjust according to yarn tension specs. |
| Weak yarn. | Check for weak yarn. | Replace faulty yarn. |
| Cuts or nicks in the feeder hole. | Check for damaged feeders. | Replace the damaged feeder/s and re-set according to Feeder setting specs. |
| Too little yarn wraps around the spool. | Check if there are enough wraps around the spool. (See Iro Drawing) | Fill according to Iro drawings and procedure. Half -way full |
16. Pulled threads/loops: – An area on the loop/piles side of the fabric where the loop/pile has been pulled. S/Jersey m/c’s
| Root cause | Checks | Action |
| Sharp or protruding objects pulling the loop/pile on the fabric surface. | Trace back the fabric route and check for sharp or protruding corners and ends. | Polish where necessary |
17. Missed loops: – An area on the loop/pile side of the fabric where the loop has not been tucked in. Single Jersey m/c’s
| Root cause | Checks | Action |
| Feeder setting not correct. | Check feeders according to Feeder set-up specs. | Check feeders according to Feeder set-up specs. |
18. Lycra misplaiting: – Little horizontal indentations of various lengths on the surface of the fabric. General (All m/c’s)
| Root cause | Checks | Action |
| Wrong feeder setting. | 1. Check feeders according to Feeder set-up specs. | 1. Check feeders according to Feeder set-up specs. |
| Lycra feed wheel/rollers dirty & not turning. | Check if Lycra wheels are turning freely. | Clean the lycra wheels. |
| Lycra wrapped at the end of the feeder. | Check yarn path from the elastane spool to the feeder. (See threading diagram) | Correct threading according to threading diagram if necessary. |
19. Lycra breaks: – A horizontal fault of various lengths where the lycra has been broken. General (All m/c’s)
| Root cause | Checks | Action | Comments |
| Bad winding – Lycra breaking constantly. | Check whether it is the same spool breaking all the time. | If same spool breaking all the time, replace the faulty spool. | |
| Tension too high. | Check if yarn tension is to specification. (Refer to Knitting tension specs) | Adjust according to yarn tension specs. |
20 Needle breaks
| Root cause | Checks | Action | Comments |
| Size of yarn carrier correct | |||
| Size of slub catcher correct | |||
| Fluff dropping from the roof | |||
| Fans not working, positioned correctly…build up of fluff. | |||
| Air flutters not working, build up of fluff |
21 Winder line – Distance between the wales closed, or wales opened too much
| Root cause | Checks | Action | Comments |
| Fluff between the needles | Check if any fluff evident, especially the airlines (usually 1 or 2), blowing through the cylinder | Remove fluff | |
| Fabric wound too tight on roll | Check tension of fabric by hand, compare to other machines | Reduce tension, until line disappears | Too less tension will cause problems with winding the roll |
| Edge of expander damaged | Check for sharp points, damage to the frame | Call engineers for repairs | |
| Edge line of fabric not between segments of take down roller | Check if the edge of the fabric is approx 1cm over the end of the segment | Move segments | |