Knitting Doc

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KNITTING The term knitting describes the technique of constructing textile structure by forming a continuous length of yarn into columns of vertically intermeshed loops. It is the interloping of yarns, which are interlaced in a variety of ways to form a fabric. It is a process of manufacturing a fabric by the intermeshing of loops of yarns. When one loop is drawn through another loop, a stitch is formed. Types of knitting 1. Weft knitting 2. Warp knitting Comparison between weft and warp knitting:WEFT KNITTING The loops are formed across the width of fabric. It is possible to knit with one thread. Staple as well as filament yarns can be worked successfully. Latch needles are used. WARP KNITTING The loops are formed vertically down the length of fabric. Warp beam is used. Filament yarn can be worked successfully. Latch, beard, or compound needles are used. More versatile machines. Change in pattern does not affect the speed of machines. Fabric quality is consistent. Loops are uniform. Stretch in widthwise direction. More dimensional stability. Costlier to produce. E.g. tricot & raschel machine.

Less versatile machines. Speed reduces with design change in cams. Fabric quality is not consistent. Loops are not uniform. Stretch in both direction. Less dimensional stability. Cheaper to produce. E.g. circular knitting machine.

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1. Weft knitting The loops are made in a horizontal way from a single yarn and intermeshing of loops in a circular or flat form on a course-wise basis. In this method, one or more yarns are being fed (called Feeds) one at a time, to a multiplicity of knitting needles, placed in either lateral or circular fashion (Tubular). Each weft thread is fed, more or less, at right angles to the direction in which the fabric produced.

Course Wales

It is possible to knit with only one thread or cone of yarn, through production demands have resulted in circular weft knitting machines being manufactured with upto 192 threads (feeders).

Course horizontal row of successive loops. Wale vertical column of loops produced by the individual needles. Gauge it express the number of needles/inch. Stitch length length of yarns required to form a single loop. Types of weft knitting

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1. Single jersey 2. Rib 3. Interlock 4. Purl

1. Single jersey This structure is produced by using one set of needles placed in the needle bed. It is done by drawing all the loops towards the technical face side.

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Back side Properties:

Simplest form of knitted structure. V shaped loop on face sideSemi circular loops at backside. Widthwise extensibility. Non reversible. If the single loop gets breaks, they tend to run or ladder. Production rate is high because of stitch simplicity and its cost is low because of machine simplicity. If the yarn breaks, needle loops successively unmesh down a wale and sinker loops unmesh up a wale. Stitch length can be varied with cam setting. Rigidity, air permeability, weight per unit area, bursting strength changes with the stitch length. The fabric may appear thick of flimsy if the stitch length is reduced or increased. The fabric can be unroved from either end and if a stitch is broken, the wale will be disintegrate causing the stitches in that line to undo or ladder.

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Fabric tends to curl as the ends and side unless it has been heat set during the finishing.

The knitting action

Tucking in the hook for rest position :The sinker is forward, holding down the old loop whilst the needle rises from the rest position.

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Clearing :The needle has been raised to its highest position clearing the old loop from its latch.

Yarn feeding :The sinker is partially withdrawn allowing the feeder to present its yarn to the descending needle hook and also freeing the old loop so that it can slide up the needle stem and under the open latch spoon.

Knock-over :-

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The sinker is fully withdrawn whilst the needle descends to knock-over its old loop on the sinker belly.

Holding-down :The sinker moves forward to hold down the new loop in its throat whilst the needle rises under the influence of the upthrow cam to the reset position where the head of the open hook just protrudes above the sinker belly.

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Cam

Plain knitting

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Rib

This structure is produced by using two set of needles (arrangement of needles side by side). Cylinder needle Dial needle

It is done by drawing the loops towards the technical face side and backside alternatively.

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1x1 Rib

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Rib knits properties

Face & back side having the same appearance (reversible). Used for collar, cuff and neck line. More elastic than the single jersey. Looks alternate vertical cords and thin ridges (1x1 Rib,2x2 Rib). Fabric generally produced on V-bed or circular machines. It is heavier and thicker structure than plain knit structure with similar gauge used. The rib machine also requires finer yarn than a similar gauge plain machine. It is more expensive fabric to produce than plain. The fabric does not curl at the edges due to its balanced nature. It can be unroved from the end knitted last by drawing the free loop heads through the back of each stitch. Rib fabrics are extensively used in the production of outwear garments.

Knitting action

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Clearing :The cylinder and dial needle move out to clear the plain and rib loops formed in the previous cycle.

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Yarn feeding :The needles are withdrawn into their tricks so that the old loops are covered by the open latches and the new yarn is fed into the open hooks.

The dial needle has retracted before the cylinder needle and is in the process of knocking-over the old loop.

Knocking-over :The needles are withdrawn into their tricks so that the old loops are cast off and the new loops are drawn through them.

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Cam

Needle timing It is the relationship between the loop forming positions of the dial and cylinder needles measured as the distance in needles between the two stitch cam knock-over points.

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Collective time adjustment is achieved by moving the dial cam-plate clockwise or anti-clockwise relative to the cylinder; individual adjustment at particular feeders (as required) is obtained by moving or changing the stitch cam profile. Synchronized timing If both the cylinder and dial needles knock over together, to produce loops of equal size, it is known as synchronized timing. Delayed timing The dial knock-over occurs after about four cylinder needles have drawn loops and are rising slightly to relieve the strain. The dial loops are thus larger than the cylinder loops and the fabric is tighter and has better rigidity; it is also heavier and wider, and less strain is produced on the yarn.

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Interlock This structure is produced by using Two set of needles placed opposite to each other.

Cylinder needle Dial needle

It is done by drawing the loops towards the technical face side at front and backside.

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Properties

It looks with the V shaped structure at both front and back. It is called double jersey. Thicker, stronger fabric and similar smooth appearance on each side. Having less elongation than single jersey than & rib. Consequently, finer yarns are usually used to reduced the area density of the fabric. It unroves from the course knitted the last. The fabric becomes costlier due to thickness and less production. It is used for outwear fabrics (dress wear and skirts), often using wool, acrylic and polyester yarns, while cotton and polyester/cotton blends are used for the production of under garment.

Knitting action The needle set out on the machine, with long and short needles alternating on the cylinder. 1 interlock gating, the needles in two beds being exactly opposite each other so that only one of the two can knit at any feeder.

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Two separate cam systems in each bed, each controlling half the

needles in alternate sequence, one cam system controlling knitting at one feeder, and the other at the next feeder. Needles set out alternately, one controlled from one cam system, the next from the other; diagonal and not opposite needles in each bed knit together. Long needle cams were arranged for knitting at the first feeder and short needle cams at the second feeder. At the first feeder, long needles in cylinder and dial knit, at the second feeder short needles knit together; needles not knitting at a feeder follow a run-through track.

Cam

Notation

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Purl Purl fabric has loops knitted to the front and back on alternate courses, in the contrast to a 1x1 rib fabric which is knitted to the front and back on alternative wales. If on both sides of a relaxed weft knitted fabric only reverse stitches are visible, then this is defined as a purl knitted fabric. Purl was originally spelt pearl and was so named because of its similar appearance to pearl droplets. Properties Purl fabric does not curl. Both sides are similar appearance. It extends easily in the lengthwise direction. It can be unroved from either end. The fabric is commonly used for childrens wear.

Knitting action

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Engagement of the head of the receiving slider with the needle hook that was originally knitting from the opposing bed.

Cam action causing the head of the delivering slider to pivot outwards from the trick and thus disengage itself from the other hook of the needle.

Sufficient free space to allow the heads of the sliders to pivot outwards from their tricks during engagement and disengagement of the needles.

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A positive action which maintains the engagement of th