Presentation on: Circular knitting M/C

Prepared By:Tanvir Ahammed Rana

Id. 201200040003819th Batch, Textile Department.

SouthEast University.

Introduction

Due to the ever increasing demand for quality products a high quality standard is importantfor the circular weft knitting industry. The highquality standard can be guaranteed by carefulplanning, incorporating appropriate quality assurance ensure and by accurate allocation ofincurred overheads to their origins. Industrial analyses indicate that product quality can be improved, and defect cost minimized, by real-time monitoring of the circular knitting process. The important function of such a concept lies not only in detecting process interference but also in identifying their sources and ensuring their quick and cost effective elimination.

What is knitting:

Knitting is the process of manufacturing fabric by transforming continuous strands of yarn into a series of interlocking loops, each row of such loops hanging from the one immediately preceding it. The basic element of knit fabric structure is the loop intermeshed with the loop adjacent to it on both sides and above and below it.

Circular knitting

Circular knitting or knitting in the round is a form of knitting that creates a seamless tube. When knitting circularly, the knitting is cast on and the circle of stitches is joined. Knitting is worked in rounds in a spiral. Originally, circular knitting was done using a set of four or five double-pointed needles. Later, circular needles were invented, which can also be used to knit in the round: the circular needle looks like two short knitting needles connected by a cable between them. Longer circular needles can be used to produce narrow tubes of knitting for socks, mittens, and other items using the Magic Loop technique. Machines also produce circular knitting; double bed machines can be set up to knit on the front bed in one direction then the back bed on the return, creating a knitted tube. Specialized knitting machines for sock-knitting use individual latch-hook needles to make each stitch in a round frame. Many types of sweaters are traditionally knit in the round. Planned openings (arm holes, necks, cardigan fronts) are temporarily knitted with extra stitches, reinforced if necessary. Then the extra stitches are cut to create the opening, and are stitched with a sewing machine to prevent unraveling. This technique is called steeking.

Diagram of circular knitting machine

Machine parts

1 – Legs2 – Cylinder3 – Dial4 – Needle5 – Cam Parts6 – Feeder guide7 – Cam8 – Supply Package9 – Creel

10 – Top Stop motion11 – Anti Snarl Device12 – Tensioner13 – Positive feeder14 – Knitted fabric15 – Fabric spreader16 – Fabric withdrawal roller17 – Fabric winding roller

Process flow chart of circular knitting machine:

Yarn in package form ↓

Place the yarn package in the creel ↓

Feeding the yarn ↓

Set the m/c as per design & GSM ↓

Knitting ↓

Withdraw the roll fabric and weighting ↓

Roll marking ↓

Inspection↓

Numbering 

Types of circular knitting machine:

Circular Knitting Machine

Large diameter circular m/c Small diameter circular m/c

Single Jersey (U.K) Double Jersey (U.S.A) Single Double Dialand

Cylinder Cylinder Cylinder

Single tract Multi tract Circular Rib Circular intrlook

Jacquard Non-Jacquard

Some circular knitting machine description:

Single Jersey Machines:Single Jersey machines are equipped with a single “cylinder”, about 30 inch diameter, of needles that produce plain fabrics (single thickness).Wool production on single jersey machines tends to be limited to 20 gauge or coarser, as these gauges can use two-fold wool yarns which will give spirality-free fabrics. An additional inherent feature of wool single jersey fabrics is that the fabric edges tend to curl inwards. This is not a problem whilst the fabric is in tubular form but once cut open can become so if the fabric is not finished correctly.

Double jersey machines Double jersey machines are single jersey machines with a “dial” which houses an extra set of needles positioned horizontally adjacent to the vertical cylinder needles. This extra set of needles allows the production of fabrics that are twice as thick as single jersey fabrics. Typical examples include interlock based structures for underwear/base layer garments and 1 x 1 rib fabrics for leggings and outerwear products. Much finer yarns can be used as singles yarns do not present a problem for double jersey knitted fabrics as the “double layer” construction works to cancel out the residual torque between the face and reverse sides, the net effect being no spirality.

Rib circular knitting machine.

In a dial cylinder rib machine there is one set of needles on the circumference of the vertical cylinder and another set of needles on a horizontal dial. So two sets of needles remain at the right angle with each other. In dial cylinder machines the dial and cylinder rotates but the cam systems with the feeders remain stationary.

The dial needles get its motion from its butt which is placed on the cam truck. This cam truck is formed by different cam placed on a cam plate.

During the rotation of the cylinder, cylinder needles moves vertically and dial needles moves horizontally. Cylinder needles also get its motion from it. There is a cloth tale up roller which also rotates with unison to dial and cylinder and fabric is wound on it. 

Knitting action: The knitting action of a circular rib machine is shown:

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

2. 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.

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

Interlock circular knitting machine: 

The yarn is supplied from cone, placed either on an integral over head bobbin stand or one free standing creel through tensioners stop motion & guide eyes down to the yarn feeder guides.

The fabrics is tube form is drawn downwards from inside the needle cylinder by tension rollers & is wound on to the fabric batching roller of winding down fabrics.

The winding down mechanism revolves in unison with the cylinder & fabrics tube & in rock lever operated via cam followers running on the underside of a profiled cam - ring.

The sinker cam plate is mounted outside on the needle circle, the center of the cylinder is referred to as an open top or sinker top m/c.

Knitting action:

The knitting cycle of a interlock machine can be divided in to eight headings. They are discussed below,

• Position – 1: Rest position: The head of these needles are in the range of the knock over edges of cylinder & dial respectively.

• Position – 2: Tucking position of dial needle: The dial needles are brought into the tucking position.

• Position – 3: Tucking position: The cylinder needles are brought in the tucking position.

Knitting action:• Position – 4: Clearing position of dial needle: The dial needles are come into the clearing position.

• Position – 5: Clearing position: The cylinder needle are come into the clearing position.

• Position – 6: Yarn presenting position: Both cylinder & dial are moved to the yarn presenting position.

• Position – 7: Cast on position: Both cylinder & dial are moved to their cast on position.

• Position – 8: Knock over position: Both cylinder & dial are reaches to the knock over position.

Features of circular knitting machine:

1. Frame: The frame, normally free-standing and either circular or rectilinear according to needle bed shape, provides the support for the majority of the machines mechanisms. 

2. Power supply: The machine control and drive system co-ordinates the power for the Drive of the devices and mechanisms.  3. Yarn supply or feeding: The yarn supply consists of the yarn package or beam accommodation, tensioning devices, yarn feed control and yarn feed carriers or guides.

Features of circular knitting machine:

4. Knitting action: The knitting system includes the knitting elements, their housing, drive and control, as well as associated pattern selection and garment- length control devices (if equipped).

5. Fabric Take-away: The fabric take away mechanism includes fabric tensioning, windup and accommodation devices.

6. Quality control: The quality control system includes stop motions, fault detectors, automatic oilers and lint removal systems.

Uses of circular knitting machine:

Fabric machines: Jackets, ladies tops, spots & T-shirt, casual wear, suits, dresses, swimwear, bath robes, dressing gowns, track suits, jogging suits, furnishing, upholstery, automotive & technical fabrics, household fabrics.

Advantages of circular knitting machine:

Less load by high precision Perfect gaps between all

parts. Smooth passing of Needles

between cylinder and cams better quality of plated

fabric Less friction for each part Longer needle’s life Save power consumption Fantastic Machine Speed

Awesome Specification of Rib

Immediate restart after Setting

Save Maintenance Cost Life time guaranty of

Ceramic yarn carrier. Longer needle life Special servomotor for

take-up system

Conclusion:

Modern circular knitting machines feature on-board computers (CPU) complete with a display and a keyboard to monitor and control the most important functions: Speed Number of machine revolutions (R.P.M) Working hours Causes of machine stops Detector of the yarn length fed into the machine

On modern microprocessor-controlled machines, the LCD display (TOUCH SCREEN) is equipped with an alphanumeric keyboard for entering the operator’s settings. The whole system is controlled by an electronic circuit which signals the status of the machine and the possible causes of machine stops by means of flashing lights.