Defects in Knitted Fabrics

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.