Introduction:
Fabric quality is very important for customer satisfaction. About 90% of the fabric defects in the grey fabric originate during weaving. Denim fabric is highly sensitive for defects, mainly like starting marks (crack and thick place), broken pick, snarl and missing end etc. These kinds of defects are broadly responsible for deterioration of fabric quality. In this article I will discuss different types of denim fabric defects, their causes and remedies.
Different Types of Denim Fabric Defects:
Denim fabric is a fabric that is woven with warp yarns dyed and sizing with indigo dye. During the manufacturing process of denim fabric, defects may occur in any process.
Denim fabric defects can be classified as:
- Yarn defects (both warp and weft)
- Weaving defects and
- Dyeing and finishing defects
A. Yarn defects:
Yarn defects are warp slub, weft slub, foreign fiber, coarse pick, yarn fly and yarn irregularity.
B. Weaving defects:
Weaving defects are knots, weaving fly, loom stop, stack end, snarl, broken pick, miss pick, tangle, double warp, hole, sizing defect, oil spots, drawing defect and broken warp yarns.
C. Dyeing and finishing defects:
Dyeing and finishing defects are more complex damages than physical damages. Problems often seen are poor fastness, uneven and poor washdown, abrasion or scrub marks in prewashed denim fabrics, uneven shrinkage, stiff hand after dyeing, dye streaks, side to center shading caused by the loom, poor stabilisation and corrugation in sanforization. It is easy to confuse many causes of unevenness of color in indigo denim fabrics. It can be created in preparation of the yarn, including inadequate and uneven boil off, bunching of the yarn during dyeing, uneven squeezing in the dyeing and uneven wash off. It may also be due to poor sizing, poor weaving, loom settings or uneven tensions.
Major Denim Fabric Defects with Causes and Remedies:
1) Starting mark:
Thin place: A small but abnormal gap between the two picks is seen while starting the loom after a stoppage and where the pick density is lower than normal.
Thick place: A stripe in the fabric where the pick density is more than the normal.
Causes:
Improper back re stand drop box setting, head frame height and shed angle set not properly, warp beam calibration not ok. If let-off and take-up unit is disturb. If back rest bearing is damage and TSF (Tension system of filler roller) problem.
Remedies:
Set the back rest and drop box setting properly according to quality. Check let-off and take-up unit is disturbed or not. Proper warp beam calibration is eliminating tension variation on warp ends. Head frame height and shed angle set not properly.
2. Broken pick:
A pick missing from a portion of the width of the fabric.
Causes and Remedies:
Filling detector OFF during working. Filter value of filling detector is high. Dust accumulated on filling detector. Check working of feeler. Filter value should be low as possible. Clean Feeler head.
3. Loose / slack warp:
This type of fault is produced in woven fabrics when the tension of warp yarn is slow.
Causes:
Uneven or insufficient tension in the warp yarn during the weaving process.
Remedies:
Regular maintenance of weaving machinery to ensure consistent and appropriate tension.
4. Streaky mark:
Streaky mark is a common and major problem in denim fabric which is also known as ‘line mark’. Generally, buyers don’t accept such type of defects of denim fabric.
Causes and remedies:
Streaky mark can occur due to dyeing, weaving, finishing problems etc. Dyeing parameter like gpL, Hydro, ORP, pH should be aligned with the program. Machine roller pressure should be optimum with the parameters. Every part of the machine should be cleaned regularly.
5. Snarl:
Small loops of weft yarn are weaved in the fabric along with the normal pick.
Causes:
Air pressure of relay valve is low than main valve. Improper catch cord drawing. Improper stretch valve pressure and timing. Improper heald frame height and shed crossing. Play in heald frame. Improper binding of leno yarn.
Remedies:
Air pressure of all nozzles. Check catches cord drawing in and its position. Check stretch nozzle timing and position. Heald frame height and shed crossing. Reed dent gap opposite to stretch nozzle. Filling detect or head condition to check for any damage etc. Binding of leno yarn.
Conclusion:
Denim fabric defects encompass a range of issues, including broken ends, starting mark, slubs, snarls, stains, streaky mark and fading, originating from various production stages like weaving and dyeing. Selection of quality of raw material, work skills and proper machine settings can reduce denim fabric defects during manufacturing.
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