Introduction of Warp Knitting | Principle of Warp Knitting | Properties of Warp Knitted Structures

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Warp Knitting
Warp knitted fabric is knitted at a constant continuous width, although it is possible to knit a large number of narrow width fabrics within a needle bed width, usually separating them after finishing. There is considerable potential for changing fabric properties during the finishing process, as well as during knitting. It is also possible to produce length sequences such as scarves with fringed ends, articles produced on double needle bar raschels based on the tubular knitting principle, and scalloped shaping of net designs by cutting around the outline after finishing.

Fig: Warp Knitting
The Properties of Warp Knitted Structures

Warp knitting offers: 
  • Higher production rates than for weaving.
  • A wide variety of fabric constructions.
  • Large working widths.
  • A low stress rate on the yarn that facilitates careful handling of fibres such as glass, aramide and carbon (particularly when using weft-insertion techniques).
  • Conventional warp knitted structures that can be directionally structured.
  • Three-dimensional structures that can be knitted on double needle bar raschels.With weft insertion, uni-axial, bi-axial, multi-axial and composite structures that can be manufactured on single needle bar raschels.
 Principle of Warp Knitting :
Compound lapping movements are responsible for the production of warp knitted fabric. The compound lapping movement is composed of two separate motion.
  1. Swinging motion (backward & forward motion)
  2. Shogging motion (the lateral motion or side way movement )
The swinging motion is obtained from the main cam shaft while the shogging motion isobtained from the pattern wheel or pattern drum provided at one side of the machine.

The no. of pattern wheels or no. of endless pattern chain links will be equal to the no. of guide bars used. The lateral movement of the guide bars along the needle bars or parallel to the needle baris called a shogging motion. The amount of yarn supplied to the guide bar for a definite number of courses iscalled run-in or amount of yarn required (inch ) to 480 courses ( 1 rack ) is termed as run-in.

The ratio of Run-in between two guide bars is termed as

Run-in ratio:
Run-in ratio is related to the loop length & structure of fabric & thus the appearance & knitting performance
 

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