Saturday, April 15, 2017

Sewing Defects Caused by Needles in Garments

Maximum garments defects occur in sewing section. Among them sewing defects caused by needles is one of the major defects for garments. It is found in the sewing room is the defects caused by the interaction between the needle and the fabric. Because it hampers for quality of garments. 

Sewing defects caused by needles:
This can cause different types of damages in the fabric, namely:
  1. Rupturing of fabric yarns due to the collision with the needle tip.
  2. Friction between the fabric yarns and the needle.
  3. Thermal aggression of the needle on the fabric yarns.
  4. Friction between the fabric yarns and the sewing thread.
The frictional properties of fabrics are one of the major factors affecting needle penetration forces, and can be improved with appropriate finishing processes. The other main variable is the sewing needle size. The fabrics producing high penetration force values were generally those that exhibited more sewing damage using standard sewing tests.
Sewing defects caused by needles
Fig: Sewing defects caused by needles
An important aspect to consider for fabric damage caused by needles is needle heating. Long seams at high speed tend to produce high needle temperature, which can cause damage to the fabrics, especially when sewing synthetic fabrics. Hot needles not only cause damage to the fabric but they may also deteriorate the sewing thread, causing thread breakage or a reduction in the strength of the seams, a problem that is again worse when using synthetic sewing threads. Temperature may increase at 1800C. At 1400C, the threads suffered a reduction of about 40% in breaking strength. The researchers determined that the sewing speed, the type of material being sewn and thread tension were the main factors influencing needle heating.

This problem can be reduced by using lubricants or air cooling of the needle and sewing threads. Some sewing machine manufacturers provide devices for this purpose. A more straightforward solution is to reduce sewing speed and/or thread tension.

Needle manufacturers offer many options to minimize the problems related to needle penetration. The main factor for good performance is the needle point, which can have different shapes according to the materials sewn. The needle points can be divided into two main classes: cloth points and cutting points. The latter are used for leather and other continuous materials that have to be cut to achieve penetration (see in figure-1 ).
Figure-1: Examples of cloth points, from left to right: sharp round point, round point with rounded tip, light ball point and heavy ball point.
Cloth points are designed to penetrate between yarns of structured fabrics. These can coarsely be divided into round points and ball points. Round points are generally used for woven fabrics, whilst ball points are designed for knitted fabrics. However, many exceptions exist, and often only experience and case-to-case analysis allows an adequate choice of the needle tip. A proper choice of the needle type and size (along with the use of an adequate-quality thread size and type, with good frictional characteristics) is important to avoid a certain type of sewing faults promoted by the needle, while penetrating the fabrics to form the stitch, damaging the fabrics by rupturing the yarns due to contact with the needle tip.

Other characteristics of needles that manufactures try to optimize are the design of the needle’s cross-section and the needle’s surface finishing. Both have a direct effect on the friction between the fabric and the needle, thus contributing to manage the problem of needle heating. Surface finishing of the needle is also very important to avoid thread breakage during high-speed sewing.
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  2. Garment Defects Causes and Remedies
  3. Fabric Seam Strength Analysis
  4. Fabric Seam Slippage Mechanism, Process and Way to Improve
  5. Working Process of Sewing Department in Apparel Industry