Defects in woven fabric are can be a result of yarn imperfections, incorrect weaving process or errors in the finishing process. They can be categorized into 3 groups: Yarn related defects, defects occurringin warp direction and defects in the filling direction.
Yarn Related Defects
Mixed End/ Thick End:It can be identified as the warp end having larger diameter than the other warps.
- Occurrence of excessive count variation
- Accidentally missing up of counts in winding and warping
- Piecing up of broken ends with wrong count thread
- Conduct frequent inspection to make sure count mixing does not happen
Slub or Slug:Abnormally thick place occurring in the yarn that affects the fabric’s appearance.
- Occurrence of undrafted portions or sections in the yarn
- Ensure proper yarn spinning and yarn cleaning during the winding processes Warp
Warp direction defects
Reedy fabric marks:
Appearance of fine cracks across the fabric between warp end groups which resemble enting pattern in the reed
- High warp tension
- Insufficient shade toughing
- Late shed timing that causes tension imbalance at beat-up
Broken / Missing End:
It can be identified as the space created in the fabric when a yarn partially or completely is missing from the fabric.
- Weaver fails to attend the warp breaks immediately
- The warp stop motion isn’t working properly in the machine
- Use spare ends on the loom to substitute missing ends
- Instruct the weaver to attend to the warp breakages attentively and fast
- Check the warp stop motion assembly before weaving starts
- Inspect the drop pins and replace any defective ones when putting on a new beam
Weft direction defects
Thick or thin places occurring in fabric due to pick density variation when starting the loom, causing starting marks.
- Anti-crack motion not functioning properly
- Fell of the fabric is very close to the reed due to faulty take-up motion
- Training of the weaver to follow the correct procedure
- Ensure take-up motion is working correctly
- Periodic variation in the count of the weft yarn due to spinning defect
- Missing of different counts or different twist yarns
- Incorporate count identification and rectification processes
- Properly segregate yarn to avoid lot mix-up of weft during weaving
Broken pick:Broken pick defect can be identified as the weft inserted to only a partial portion of the pick.
- Weft breaks in ordinary looms
- Faulty weft fork mechanism on automatic looms
- Inspect the shuttle for any loose fitting pirn or any form of roughness of surfaces, as friction might cause weft breakages
- Check the shuttle and shuttle box for settings and surface smoothness to prevent weft cuts
- Ensure weft fork mechanism is running smoothly
- Check for any loose picks before starting the loom
This defect occurs on drop box looms for fabrics that have patterns. If the sequence of weft yarn colour breaks or pattern width of particular colour is distorted, broken pattern defect appears.
- The pattern cards or lattices are not properly adjusted
- Weaver fails to adjust the pattern chain after mending or break
- Pick being inserted in wrong shed when mending a break
- Train the weaver to be vigilant regarding the design needs and to find picks before restarting the loom
- The pattern cards should be checked and adjusted as needed at the start of the beam
This defect happens when more than one pick is inserted in the single shed.
- In ordinary looms, when restarting the loom, weaver might fail to find out the correct shed for inserting the pick
- On automatic looms, if the pirn change gets affected by the weft form then double pick defect appears
- Pick finding every time the loom is restarted
- Proper pirn change with weft feeder mechanism
Appearance of foreign matter or contamination like lint, waste, etc woven into the fabric.
- Ensure warp tension as required
- Early shed timing
- Back rest should be raised by around 2 cms above the front rest level
Warp streaks can be identified as the warp way stripes of shade variations occurring between groups of threads.
- Uneven reed dents spacing
- Variations in warp
- Coarse count and tight ends spacing appear lighter in shade, shereas, finer count and wider spacedappear darker in shade
- Use of good quality warp thread
- Periodic checking of the reed’s condition
- Metal reeds give better results than the pitch bound reeds
- Ensuring proper material handling and storage will help us avoid any yarn count mixing
Misdraws/ Wrong draw:
Design or stripes in the final fabric being damaged due to drawing of incorrect ends.
- The fault in drawing-in of beam or drawing-in of the broken-ends by the weaving operator
- End of different colour than needed being drawn
- Proper training of the drawing-in operator is necessary
- Fabric inspection on the loom
- Waste disposed off randomly by the weaver
- Foreign matter or waste getting into the weaving shed
- Ensure the machine’s and shed’s maintenance and cleaning
When a bunch of or coil of yarn slips from the pirn during weaving then thick yarn bunches or coils appear on the fabric.
- Pirn winding done without the proper tension being maintained during the winding process
- Due to harsh picking
- The humidity settings in the pirn storage or shed are not set as required
- Maintaining proper tension during pirn winding
- Check the picking mechanisms condition the weft yarn appropriately before using it
When yarn doubles back on itself especially of high twist yarn are used snarling appears. It can be found randomly spread across fabric width or only in a region nearby the selvedge.
- Use of high twist weft yarn
- Keeping the weft tension extremely low
- The weft fork is not set correctly
- Shuttle rebounds between its way
- Weft conditioning before using it
- Ensuring needed drag in the shuttle
- Propel shuttle and weft fork setting monitoring
Now we know some of the common defects that can appear in woven fabric that can hamper the quality of the final garment produced out of it. With the knowledge of what causes these defects and how we can avoid them during the weaving process, we can ensure the fabric produced is as per the quality and appearance intended.