Wednesday, December 21, 2016

Defects Due to Problem of Stitch Formation in Apparel Industry

In the apparel industry defects is the common word during apparel manufacturing. Various types of defects are occurring in the production time. Quality inspector always tries to follow about garment defects, because any single defects may be completely destroying company profit and reputation also.

What is Defects?
A defect is an unwanted feature in a product or absence of a desired feature or a feature existing in distorted or wrong way.

Types of defects:
There are 2 main types of defects. Such as:
  1. Sewing defects
  2. Non-sewing defects
Sewing defects:
In the clothing industry during sewing, frequently occur different types of sewing defects. Sewing defect that occur may be categorized in the following way:
  • Defects due to problem of stitch formation
  • Defects due to fabric distortion or puckering
  • Defects due to fabric damage along stitch line
Defects due to problem of stitch formation:
These are the defects that occur due to problems related with stitch formation in garments industry. Such rejects may be enumerated below with causes and remedy.
  1. Slipped or skipped stitch
  2. Staggered stitch
  3. Unbalance stitch
  4. Variable stitch
  5. Thread breakage
Defects due to problem of stitch formation
Fig: Defects due to problem of stitch formation
Here I will mention the defects due to problem of stitch formation with their causes and prevention.

1. Slipped or skipped stitch: They occur when the bobbin hook or looper of the machine cannot pick up the loop in the needle thread. Slipped stitch with a lock stitch machine leads to creating a gap in a seam and a poor appearance in top stitching.

  • Unsuitable thread
  • Defected needle
  • Wrong needle size
  • If needle thread loop size is too small
  • Poor feed of fabric
  • Use right thread
  • Replace defected needle
  • Use right needle
  • Needle size and thread size must be adjusted
  • Control thread tension
  • Use right feed mechanism
2. Staggered stitch: It is caused by the yarns in the fabric deflecting the needle away from a straight line on a hard, thick woven fabric.

  • Comparatively thin needle
  • Blunt needle
  • Needle size and thread size not matching
  • Defected motion of feed mechanism
  • If fabrics are not controlled properly in the feed mechanism
  • Use bias sewing
  • Use right needle
  • Change blunt needle
  • Motion of feed dog to be adjusted
  • The pressure of pressure foot must be adjusted accurately. Feed mechanism to be changed.
3. Unbalance stitch: Thread tensions generally cause unbalanced stitches and give poor appearance.

  • Thread tension
  • Thread passes through wrong path
  • Bobbin case and positioning finger snagging
  • If the threads are not lubricated
  • Control thread tension
  • Control thread twisting
  • Make bobbin case smooth and reset positioning finger
  • Better qualities of Lubricate threads must be used
4. Variable stitch: It occurs, especially, with sticky or slippery materials and also when material feeding is uneven.

  • Sticky slippery fabric
  • Wrong feed mechanism
  • Use of low quality thread
  • Twisting of needle thread in the bottom of thread package
  • Twisting of thread in the thread guide
  • More tension to the thread.
  • Fraying of thread in the needle.
  • Becoming more heated of thread and hook.
  • Use right feed mechanism
  • Adjust feed mechanism with fabric
  • Thread to be changed.
  • Foam pad must be used to the bottom of thread package.
  • Proper threading of sewing thread during sewing.
  • The tension of thread should be less or use of higher strength threads.
  • Finer threads must be used or to be used heavy needle.
  • For thread, high quality needle, needle lubrication, and needle cooler must be used. For hook, examine the distance between needle and hook, lubricant must be available.
5. Thread breakage: Needle and bobbin or looper threads break mainly due to metal surfaces being chipped or otherwise damaged and then causing damage to the thread. The guard over the hook in a plain machine or the needle hole in the throat plate can become chipped as a result of needle deflection. This causes thread breakage. Thread breakage is a time-consuming problem arresting productivity.

  • If the metal surface of hook point, bobbin case, needle guard, needle groove and needle hole in throat plate etc with sharp.
  • If thread fails to unwrap from thread package
  • If obstructed in the thread guide;
  • Snarling before tension disk.
  • Wrong fitting of bobbin case
  • Changed the hook point, bobbin case, needle guard, needle groove and needle hole in throat plate etc with sharp hole and to be smooth.
  • Set thread guide above thread package having a distance 2.5
  • Re-set tension disk
  • Examine the size, type of bobbin, damaging of bobbin case.