Basic Concept of Weft Knitted Structures
Shareful Islam Palash
Lecturer, Institute of Textile Engineering & Information Technology
Email: palash313@gmail.com
Concept of weft knitted structures:
There are many types of knitted fabrics, which produced by different types knitted structure. According to the arrangement of loops in their course and wales, there are four basic groups of weft knitted structures. All types of other weft knitted structures are derived from those basic structures. In a weft-knitted structure, the intermeshed loops touch each other only in a few places, and the fabric can be stretched along the width or the length under a low stress. The graphical and the schematic representations of the four basic weft-knitted structures are described in this article.
Types of weft knitted structures:
The four basic weft-knitted structures are
- Plain / Single knit structure.
- Rib structure.
- Purl knit structure.
- Interlock structure.
Plain structure is made on a single bed machine whereas the other three are made on double bed machines. But the arrangements of needles in the two beds are different for obtaining rib, interlock and purl structures. Further plain is made of only face loops or back/reverse loops whereas rib, interlock and purl are made of both face loops and back loops.
How to represent weft-knitted structures?
Three kinds of methods used to represent weft knitted structure:
a) Loop Diagram: The actual loop of the fabric is drawn. One can see the fabric structure clearly. This is suitable for simple structure.
b) Notation: Special symbols are used to represent a particular stitch. A cross is used to represent a plain stitch and a circle represents a reverse plain stitch (back side of a plain stitch). A blank space is used to represent a miss stitch and a dot represents a tuck stitch. It is quite difficult to use this methods to indicate an interlock fabric which is knitted with two sets of needles lying directly opposite each other.
c) Yarn-path diagram: This is the best way to represent any weft knitted structure. A straight line perpendicular to the yarn path is used to represent a needle. For a single jersey, one set of straight lines is used to represent one set of needles. For double jersey structure, two sets of straight lines are used to represent two sets of needles. A stitch is represented by a loop drawn around the needle. A tuck stitch is represented by the yarn touching the tip of the needle and the miss stitch is represented by the yarn drawn across the needle without touching it.
How can we identify the plain knit structure fabrics?
Plain knit structure is the simplest and most basic structure. It’s also called single knit structure. It’s produced by the needles of one set of needle with all the loops intermeshed in the same direction. We can identify the plain knit structure fabrics as following properties……..
- The fabric is unbalanced and different appearance on face and back side. V shapes on face and Arcs on back.
- Lengthwise extensibility of the fabric is moderate (10-20%) and widthwise extensibility is high (30-50%).
- Fabric shortens in width if the same is extended in length by tension and vice-versa.
- The fabric extensibility area is moderate to high.
- The fabric is thicker and warmer than plain woven made from same yarn.
- The plain knit structure can be easily unravelled from the edge which was knitted last. Unroving either end.
- Properties like rigidity, air permeability, bursting strength, etc. and GSM of the fabric change with change in loop length.
- The fabric has tendency to curl.
- Fabric thickness is approximately two times the diameter of the yarn used.
- Courses per inch and wales per inch in the fabric inversely vary with loop length.
Notation of plain knit structure:
* * * *
* * * *
* * * *
* * * *
Face loop
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
Back loop
End Uses:
Plain knit structures are used for basic T-shirt (men’s and ladies), Under garments, men’s vest, ladies hosiery,fully fashioned knit wear etc.
How can we identify Rib structures fabrics?
Rib is the second family of knit structures. It’s also called double – knit. It’s requires two sets of needles operating in between each other so that wales of face stitches and wales of back stitches are knitted on each side of the fabric. We can identify the Rib structure fabrics as following properties——
- Same appearance in both sides of rib fabric. Like face of plain.
- Lengthwise extensibility of the fabric is moderate and widthwise extensibility is very high (50-100%).
- Each course is made of face loop and back loop in alternative order, the order may be 1×1, 2×2, 3×3, 6×3, etc.
- The fabric extensibility area is high.
- The fabric is much thicker and warmer than plain woven.
- Rib fabrics are double-faced structures as well as balanced structures.
- Rib structures can be unravelled from the edge knitted last. Unroving only form end knitted last.
- Fabric surface is rough or harsh in feel.
- Minimum one yarn is needed to produce a fabric.
- No tendency to curl.
- Fabric surface is vertically corrugated or ribbed.
- Fabric is much thicker, generally double, than single jersey fabric.
- Fabric has good extensibility in length direction, but the width-wise extensibility and the recovery are much higher than single jersey fabric which makes it suitable for neck collar, hand cuff, waist band, etc.
Notation of rib structures:
* 0 * 0
* 0 * 0
* 0 * 0
1*1 Rib structure
End Uses:
Rib structures are uses for–Socks, cuffs, waistbands, collars, men’s outerwear, knitwear, under wear etc.
How can we identify purl knit structures fabric?
Purl knit structures is the third family of knit structures. As with rib structures, it’s requires the participation of both needle beds for the production of the loops. We can identify the Purl structures fabric as following properties….
- Same appearance on both sides. Like back of plain.
- Lengthwise extensibility is very high and widthwise extensibility is high.
- The fabric extensibility area is very high.
- Very much thicker and warmer than plain woven.
- Unroving either end.
- No tendency to curl at the edges because of alternate face and back loop courses.
- Fabric has horizontal corrugation or rib appearance on the surfaces, i.e. opposite to rib fabric.
- Fabric is reversible in appearance and has soft handle.
- Fabric has very high extensibility in length direction, making it suitable for kidswear.
Notation of purl knit structure:
0 0 0
* * *
0 0 0
1*1 purl knit
End Uses:
Purl structures are uses for—Children’s clothing, knitwear, thick and heavy outerwear etc.
How can we identify the interlock structures fabric?
Interlock is another 1*1 rib variant structure which is produced on specially designed machines. Those machines possess two sets of needles (short and long needles) in both cylinder and dial and at least two feeders. We can identify the interlock structure fabric as following properties—–
- Same appearance on both sides, like face of plain.
- Each interlock course is composed of two rib courses
- Lengthwise extensibility is moderate and widthwise extensibility is moderate.
- Extensibility area is moderate.
- Minimum two yarns are needed to produce a fabric.
- Fabric has double faced as well as very stable structure.
- Fabric surface is smooth.
- Fabric is equally thicker to rib but much more compact.
- Fabric neither curls nor ladder.
- Very much thicker and warmer than plain woven.
- Unroving only from end knitted last.
- No tendency to curl.
- Fabrics are dimensional stable, heavy and costly.
Notation of interlock structure:
* 0 * 0
0 * 0 *
Interlock structure
End Uses:
Interlock structures are use for– Underwear, shirts, suits, trouser suits, sportswear, dresses etc.
Conclusion:
Mainly we can identify any types of knitted fabric by appearance. Here I only given some basic knowledge about weft knit structure, by which we can generally identify different types of weft knitted fabric.
References:
- Knitting Technology by David J Spencer
- Fundamentals and Advances in Knitting Technology by Sadhan C. Ray
- Understanding textile for a merchandiser by Engr. Shah Alimuzzaman Belal.
- Advances in Knitting Technology Edited by K. F. Au
- Textile Handbook By The Hong Kong Cotton Spinners Association
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
