#weft knitting

A machine used to make knitted fabrics or garments. A knitting machine forms loops of yarn and connects them into various knits.

Knitting machines differ in purpose, design, and type of knitting needles. All knitting machines may be classified according to the number of knitting needles per unit length of the needle cylinder. The most widely accepted system uses the English inch (1 inch = 25.4 mm) to measure the length of the needle cylinder. Machines produced in the USSR range in gauge from 3 to 36. The higher the gauge, the finer the fabric produced. For example, 34-gauge machines are used for knitting fine stockings; here, the gauge corresponds to the spacing of the needles 0.75 mm apart in the needle cylinder.

The principal working parts of a knitting machine are the looper, the yarn feed motion, and the take-up motion. The looper contains the needle cylinder with the needles, sinkers, a presser (for spring needles), yarn guides, and other elements. The sinkers, blades with complex shapes, bend the yarn into loops and move the yarn along the shaft of the needle (if the needles are stationary) or hold it (if the needles are moving); one sinker is usually positioned in each space between the needles. The presser, in the form of a wedge, plate, or disk, presses on the needle hook and prevents the loops from falling into the hook.

When the yarn is laid on the needles, the yarn feed motion maintains a specific and constant tension, with the aid of the yarn guides, brakes, take-up motions, and other attachments. In some yarn feed motions, the length of yarn is measured off for each loop row. The yarn may be fed in individual strands (in weft-type machines) or in groups (in warp-type machines). The take-up motion draws the finished knitwear off the needle cylinders while maintaining a constant tension. The material may be drawn off by means of tension created by the weight of the take-up motion or a separate weight, or it may be accomplished by means of rollers.

The knitting processes are automated by mechanisms that control the consistency of feed and yarn tension and the proper working order of the needles; they also rectify any defects that may appear, such as running loops. In full-fashioned machines, various special mechanisms transfer the loops when the width of the cloth is altered, form separate loop rows, introduce reinforcing yarn, alter the density of the knit, and form complex, three-dimensional shapes in such articles as hosiery and gloves. Electronic control devices have been developed for selecting or introducing the needles in knitting patterned and open-work weaves. In knitting artificial fur, circular knitting machines are used that have miniature carding devices in each loop-forming system; these devices knit the tufts of long fibers into loops to form a nap.

The productivity of knitting machines, in million loops per min, ranges to 3.74 for warp-type machines, 5.94 for circular knitting machines, and 1.44 for automatic circular hosiery knitting machines. Knitting machines manufactured in the Federal Republic of Germany, the USA, Great Britain, Czechoslovakia, and the German Democratic Republic are widely used. The further development of knitting machines is aimed at increasing the gauges available, increasing the number of loop-forming systems, and automating the knitting process.

Answer:

Weft knitting: One type of knitting method where fabric is formed by making loops in horizontal way. Loops are formed by using a single yarn and inter-meshing of loops take place in a circular or flat form.  Most of the weft knitting is made in tubular form. For example; Tee shirts are made with weft knitted fabric.

What is Knitted Fabric

What is knitted fabric?

Knitted fabric:

Knitted fabrics provide comfortable wear to almost any garment. For getting comfortable wear we first think about knitted garments. Though it has open structure so most of the knitted garments contour to the body’s silhouette. That’s why knitted garments are so much popular as inner-wear, body wear and sportswear.

A nice comfortable wear made by knitted…

Experiment Name: Study on V-bed knitting machine. Objects: § To know about the passage of yarn and fabric of the machine. § To know about the different parts and their functions of the machine. § To know about the cam arrangement of the machine. § To know about the different types of cam and their functions.

 Specification:

Brand: PROTTI

Feeder no: 4

Gauge: 8

Width: 48 inch

Cam per bed:

Knit cam- 2 no.s

Tuck cam- 2 no.s

Stitch cam- 2no.s

Main parts: 

Yarn package

Front needle bed

Yarn guide 

Needle spring

Tension spring

Fabric

Cymbal tension

Dead weightening system

Yarn take-up 

Latch needle

Fabric comb

Yarn carrier

Back needle bed

M/c description: 

 In the following figure shows a cross section of a simple hand powered and manipulated V-bed rib flat machine. The trick walls are replaced at the needle bed verges by fixed, thinner, polished and specially shaped knock-over bit edges. In rib gating, a knock-over bit in one bed will be aligned opposite to a needle trick in the other bed. During knitting, the edges of the knock-over bits restrain the sinker loops as they pass between the needles and thus assist in the knocking over of the old loops and in the formation of the new loops. The cover plate is a thin metal blade, located in a slot across the top of the needle bed tricks. It prevents the stems of the needles from pivoting upwards out of the tricks as a result of the fabric take down tension drawing the needle hooks downwards whilst allowing the needles to slide freely in their tricks. Latch opening brushes are attached to the cam plates of both needle beds to ensure that the needle latches are fully opened. The supports of the brushes are adjustable to ensure precise setting of the bristles relative to the needles. The cam-carriage either slides or runs on ball bearings or wheels, along guide rails, one of which is fixed over the lower end of each needle bed. It is propelled either by hand or from a motor driven continuous roller chain or rubber belt. Each yarn carrier is attached to a block which slides along a bar, which, like the carriage guide rails, passes across the full width of the machine. Two levers are usually provided, one at each end of the needle bed. One is for racking the back needle bed, to change the gating of the needle beds for changes of rib set out or rib loop transfer. Cam system of the V-bed hand flat machine: The following figure illustrates the knitting action of a V-bed hand flat machine and the another figure shows the underside of the cam carriage and the cams forming the tracks that guide the needle butts through the knitting system. The needle butts will enter the traversing cam system from the right during a left to right carriage traverse and from the left during a right to left traverse. For each needle bed there are two raising cams (R), two cardigan cams (C) and two stitch cams (S). The arrangement as shown in the following figure is referred to as a knitting system. A single system machine will knit one course of rib in one traverse whereas a double system machine will knit two courses of rib per traverse. Sometimes a set of cams in one bed is referred to as a lock. A (L) – Raising cam (left) B (R) – Raising cam (right) C – Tuck cam (left & right) D (L) – stitch cam (left) D (R) – stitch cam (right) E – Guard cam The knitting action of the V-bed hand flat machine: 

  The rest position: The tops of the heads of the needles are level with the edge of the knock over bits. The butts of the needles assume a straight line until contacting the raising cams R (R) because the leading stitch cams S and AS (L) are lifted to an inactive position. The lifting action is an alternating action that always lowers the trailing stitch cams and raises the leading stitch cams in each system as the traverse commences. This action prevents needles from being unnecessarily lowered and strain being placed on the old loops prior to the start up of the knitting action.

Clearing: 

The needle butts are lifted as they contact the leading edge of cams R (R), which raises the needles to ‘tucking in the hook’ height with the undersurface of cams S (L) acting as guard cams. The needles are lifted to full clearing height as their butts pass over the top of cardigan cams C (R) and C (L). Yarn feeding: The yarn is fed as the needles descend under the control of guard cam (G). The required loop length is drawn by latch needle as it descends the stitch cam S (R). Knocking over: 

To produce synchronized knocking over of both needle beds simultaneously, the stitch cam S (R) in the front system is set lower than the auxiliary stitch cam AS (R), so that the latter is rendered ineffective.

Conclusion: