Defects in Knitted Fabrics
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Questions and Answers

What is a common cause of barré in knitting machines?

  • Different stitch lengths (correct)
  • High humidity levels
  • Over-tightening the needle
  • Excessive use of dye

    • Which factor can minimize the occurrence of barré in knitwear?

  • Mixing yarns from different shipments
  • Increasing machine speed
  • Changing dye lots frequently
  • Using yarn from the same spinning lot (correct)

    • What primarily causes spirality in knit fabrics?

  • Poor dye application
  • Use of unbalanced yarn (correct)
  • Incorrect machine calibration
  • Uneven yarn tension

    • Which condition does NOT contribute to barré?

    <p>High fiber content in yarn</p> Signup and view all the answers

    How can spirality be somewhat alleviated during knitting?

    <p>By steam setting an unbalanced yarn</p> Signup and view all the answers

    What aspect of knitting machines can lead to variations in take-down or spreader systems causing barré?

    <p>Improper threading of yarn</p> Signup and view all the answers

    What typically does NOT lead to the occurrence of spirality in knit structures?

    <p>Using balanced yarn</p> Signup and view all the answers

    What is a characteristic feature of spirality in knitted fabrics?

    <p>Wales being misaligned</p> Signup and view all the answers

    What is the primary effect of spirality in knitted fabrics?

    <p>Wales tend to bend over and are no longer perpendicular.</p> Signup and view all the answers

    Which finishing step can help correct loop spirality in knitted garments?

    <p>Setting with resins</p> Signup and view all the answers

    What causes facing-up in knitted garments?

    <p>High surface abrasion forces</p> Signup and view all the answers

    Which factor does NOT contribute to the tendency of facing-up?

    <p>Production cost of the fabric</p> Signup and view all the answers

    What is the formula used to calculate the percent change in spirality?

    <p>X = 100 x (AA’/AB)</p> Signup and view all the answers

    How does yarn twist affect the migration of surface fibres?

    <p>Low or irregular twist permits fiber migration.</p> Signup and view all the answers

    Which of the following factors does NOT increase inter-fiber friction?

    <p>Short broken fibres</p> Signup and view all the answers

    What is the main consequence of facing-up in woollen fabrics?

    <p>Change in appearance and possible pilling.</p> Signup and view all the answers

    What is cockling primarily caused by?

    <p>Irregular surface effects due to loop distortion</p> Signup and view all the answers

    Which of the following yarn types is most prone to cockling?

    <p>Wool knitwear made from worsted yarns</p> Signup and view all the answers

    Which type of cockling is caused by a difference in relaxed widths of two structures?

    <p>Rib/plain interface cockling</p> Signup and view all the answers

    What influence does fibre diameter have on cockling?

    <p>Increased fibre diameter increases cockling</p> Signup and view all the answers

    Package dyeing affects loop distortion how?

    <p>It increases loop distortion by creating a 'setting effect'</p> Signup and view all the answers

    Which factor is acknowledged to influence loop distortion, despite little effect from yarn count itself?

    <p>Yarn count regularity</p> Signup and view all the answers

    How does yarn rigidity correlate with loop distortion?

    <p>Greater yarn rigidity increases the tendency for loop distortion</p> Signup and view all the answers

    What type of cockling can generally be assigned to using unsuitable yarn?

    <p>Random all-over cockling</p> Signup and view all the answers

    What is indicated by a run or ladder in knitting?

    <p>A row of dropped stitches</p> Signup and view all the answers

    What is the primary cause of skewing in fabric?

    <p>A design running at an angle</p> Signup and view all the answers

    What typically causes a cloth fall out during knitting?

    <p>Closed latch on an empty needle</p> Signup and view all the answers

    Which defect represents a large hole in the knitted fabric?

    <p>Broken yarn at the needle feed</p> Signup and view all the answers

    What causes needle lines or vertical lines in fabric?

    <p>Tight or loose wales</p> Signup and view all the answers

    What is the effect of bowing in knitted fabric?

    <p>Curvature of a design due to faults</p> Signup and view all the answers

    What can result from mixed needle lots in knitting?

    <p>Uneven fabric quality</p> Signup and view all the answers

    Which condition contributes to the formation of a barre effect in knitting?

    <p>Inconsistent yarn blends</p> Signup and view all the answers

    Study Notes

    Defects in Knitted Fabrics

    • Skew or Bias: A line or design running at a slight angle across the fabric. This is caused by an uneven distribution of forces during knitting.

    • Bowing or Twisting: A line or design curving across the fabric. The distortion results from a faulty take-up mechanism on the knitting machine. This can be seen as different types of bowing (double, hooked, reverse side etc)

    • Knots: Visible knots in the fabric structure; this is an irregularity in the yarn flow.

    • Thick and Thin Yarn: Uneven thickness in the yarn used in knitting, creating noticeable variations in the fabric texture.

    • Uneven Yarn Structure: An inconsistency in the yarn's thickness throughout the fabric.

    • Course Yarn: A significant change in the width/spacing of the wale rows.

    • Slub: A noticeable unevenness in the fabric resulting from irregularities in yarn during knitting, forming an irregular, thickened area.

    • Needle Lines: Vertical lines due to a wale being tighter or looser than neighboring wales. The distortion can be caused by improper needle fit in its slot, or a defective sinker.

    • Needle Run: A defect caused by bent, broken or dirty needles, dial/cylinder needle misalignment, improper yarn guide setting or machine vibration. This often causes holes

    • Fabric Run/Ladder: A row of dropped stitches in the wale; this is caused by a dropped or loosely knitted stitch either from the yarn carrier not being set properly, or the stitch being knitted too loosely. This forms a ladder-like structure.

    • Holes: A large hole in the fabric from a broken yarn during knitting. Causes may include mechanical issues with the machine, high friction between yarn/guides, insufficient lubrication or wax, poor quality yarn, excessive yarn tension, knots, or inappropriate yarn size for gauge (dimension).

    • Cloth Fall Out: This is typically caused by a dropped stitch, and when an empty needle (with closed latch) clashes with the yarn feeder, which then pulls the yarn out of the hooks of the following needles.

    • Bunching Up: A result of the fabric take-up system not working correctly.

    • Shade Bar/Barre: A fabric imperfection that creates stripes with shaded edges on the knit. Horizontal in weft knits and vertical in warp knits. Causes can include yarn count variations, uneven yarn twisting, wrong yarn size/color or improper conditioning.

    • Fly Yarn Contamination: A defect where extra fibers are incorporated into the fabric during the knitting process.

    • Fabric Weight out of Tolerance: The fabric's weight deviates from the specified standard.

    • Fabric Elongation not as Approved: The fabric's stretching abilities do not meet the standards.

    • Dye Mark: Marks or blotches of an uneven dye in the garment.

    • Stain(s): Marks or blotches from dirt/oil on the garment.

    • Missing Plush Loop: A defect caused by the malfunctioning of the loop mechanism in the knitting machine.

    • Pin Marks: Marks left by poorly adjusted stenter pins on the garment.

    • Spirality: A regular distortion of the knit structure caused by yarn twisting within the structure. This results in the wales not being perpendicular to the courses, creating a spiral appearance. Often caused by an "unbalanced" yarn.

    • Facing-up: Accumulation of loose, surface fibres leading to a change in appearance. This could be a result of fibres from the yarn being dislodged to the surface as a consequence of wear, often during tumble drying. Factors influencing this include fiber length, fiber diameter, and yarn twist. Factors like yarn density and softener content also influence facing-up.

    • Cockling and Loop Distortion: Irregular surface effect caused by loop distortion, commonly appearing as localised groups of skewed loops. This is often caused by the use of unsuitable fiber and/or yarn.  The problem shows in plain knit structure more than other knit structures, and is especially prevalent in yarns spun from animal fibers such as wool or mohair. Types include rib/plain interface cockling, panel-edge cockling, and random all-over cockling. Factors affecting these defects include yarn diameter, method of dyeing, yarn count, yarn twist, yarn rigidity, steam setting and cover factor.

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    21 Defects in Knitted Fabrics PDF

    Description

    This quiz covers common defects found in knitted fabrics, such as skew, bowing, and knots. Understanding these imperfections is crucial for improving fabric quality and production techniques. Test your knowledge on the various types of knitting defects and their characteristics.

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