What is knitting?
A knitted fabric is formed through loops and stitches. The loop is the fundamental element of all the knitted fabrics. A stitch is the smallest stable unit of all the knitted fabrics. It is the basic unit consisting of a loop which is held together by being intermeshed with the previously formed loops. It is formed by interlocking loops with the help of hooked needles. According to the purpose of fabric the loops are loosely or closely constructed. As the loops are interlocked in the fabric, it can easily stretched in any direction even when a low grade yarn having little elasticity is used. The construction of knitted fabrics is assessed by the no. of stitches or loops per square inch used.
When the interlocking loops run lengthwise, each row is called a wale that corresponds to the direction of warp in woven fabrics. When the loops run across the fabric, each row is called a course that corresponds to the filling or weft in woven fabrics. A knitted fabric that has more wales will be rigid and stable in width while a fabric that has more courses will be rigid and stable in length.
Warp and Weft Knitting:
Warp Knitting
Warp knitting is the process of making a fabric by forming the loops in a vertical or warp-wise direction; the yarn is prepared as warp on beams with one or more yarns for each needle. The fabric has a flatter, closer, less elastic knit than weft knit and is very often run resistant.Weft Knitting
Weft knitting is the most common type of knitting, it is the process of making a fabric by forming a series of connected loops in a horizontal or filling-wise direction; produced on both flat and circular knitting machines.Differences in Warp and Weft Knitting
1. In weft knitting only one set of yarn is used that form courses along the weft wise direction of the fabric, while in warp knitting many sets of yarns is used coming from the warp-wise direction of the fabric.2. Warp knitting differs from weft knitting, basically in that each needle loops has its own thread.
3. In warp knitting the needles produce parallel rows of loops simultaneously that are interlocked in a zigzag pattern, while in weft knitting the needles produces loops in the widthwise direction of the fabric.
4. In warp knitting the stitches on the face of the fabric appear vertically, but at a slight angle. While in weft knitting the stitches on the face of fabric appears vertically straight having v shaped.
5. Warp knits can yield cloth with a dimensional stability almost equal in woven fabrics, but in weft knits their very low dimensional stability and fabric can be stretched easily.
6. The production rate of warp knitting is very high than that of weft knitting.
7. Warp knits do not ravel or run and are less susceptible to sagging as compared to weft knits which are easily susceptible to snagging.
8. In weft knitting the needles move in the cams having tracks in a circular direction, while in warp knitting the needles are mounted on a needle board that can only move up and down.
9. In weft knitting the needles moves alternatively while in warp needles moves simultaneously.
10. Preparation of sectional beams are required for warp knitting whereas in weft knitting the yarn is directly taken from cones.
Faults in weft and warp knitting
Weft Knitting Faults
1. Barre: is a fault occur in circular weft knits, which is caused by mixing of yarn, having different luster or dye affinity, into machine. In this fault fabric will appear to have horizontal streaks.2. Birds-eye: caused by un-intentional tucking from malfunctioning needle. Here usually two small distorted stitches, side by side.
3. Broken color pattern: usually caused by color yarn out of place on frame.
4. Drop stitches: results from malfunctioning needle or jack. Will appears holes or missing stitches.
5. Hole: caused by broken needle.
6. Missing yarn: occurs in circular knit, which is caused by one end of yarn missing from feed and machine continuing to run.
7. Needle line: caused by bend needle forming distorted stitches, which are usually vertical lines.
8. Press-off: results when all or some of the needles on circular knitting fail to function and the fabric either falls of the machine or design is completely disrupted or destroyed.
9. Sinker mark: caused when sinker corrodes due to abrasion then sometime cannot hold a new loop as result sinker mark comes.
10. Oil stain: caused when oil lick through the needle trick then it pass on the fabrics and make a line.
Warp knitting faults
1. End out: occurs due to knitting machine continuing to run with missing ends.2. Hole: caused by broken needle.
3. Broken color pattern: usually caused by color yarn out of place.
4. Mixed yarn: results from wrong fiber yarn (or wrong size yarn) placed on warp. Fabric could appear as thick end or different color if fibers have different affinity for dye.
5. Runner: usually caused by broken needle and will appear as vertical line.
6. Slub: usually caused by a thick or heavy place in yarn or by lint getting on to yarn feeds.
7. Straying end: caused when an end of yarn breaks and the loose end strays and is knit irregularly into another area.
8. Yarn contamination: results from foreign fibers mixing, it remains in the fabric even after finishing or by mixing of different count yarns.
Applications:
Weft Knitting:
1. Tailored garments, like jackets, suits, or sheath dresses are made from weft knitting.2. Interlock knit stitch is wonderful for making T-shirts, turtlenecks, casual skirts, dresses and children's wear.
3. Seamless hosiery, knitted in tubular form, is produced by circular knitting machines.
4. Circular knitting is also used for the production of fabrics used in sports having high stretch ability and also dimensional stability.
5. Flat knitting is used for knitting collar and cuffs.
6. Sweaters are also made from flat knitting and are joined to sleeves and collar necks by using special machines.
7. Cut and sewn garments are also made from weft knitting which includes T-shirts and polo shirts.
8. Highly textured fabrics with complicated patterns are made using tuck stitch.
9. Knitted hats and scarves are used in the winter season are made through weft knitting.
10. Industrially, metal wire is also knitted into a metal fabric for a wide range of uses including the filter material in cafeterias, catalytic converters for cars and many other uses.
Warp Knitting:
1. Tricot knit a type of warp knitting is used in the making of light weight fabrics usually inner wear like panties, brassieres, camisoles, girdles, sleepwear, hook & eye tape, etc.2. In apparel warp knitting is used for making sportswear lining, track suits, leisure wear and safety reflective vests.
3. In household warp knitting is used for making mattress stitch-in fabrics, furnishing, laundry bags, mosquito nets and aquarium fish nets.
4. The inner linings and inner sole linings of sports and industrial safety shoes are made from warp knitting.
5. Car cushion, head rest lining, sun shades and lining for motorbike helmets are being made from warp knitting.
6. For industrial uses PVC/PU backing, production masks, caps and gloves (for the electronic industry) are also made from warp knitting.
7. Raschel knitting technique a type of warp knitting is used for making as an unlined material for coats, jackets, straight skirts and dresses.
8. Warp knitting is also used for making three-dimensional knitted structures.
9. Fabrics for printing and advertising are also produced from warp knitting.
10. The warp knitting process is also being used for the production of bio-textiles. For example, a warp knitted polyester cardiac support device has been created to attempt to limit the growth of diseased heart by being installed tightly around the heart.
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