Knitting:
Knitting is defined as interlacing of yarn into loop to form fabric. There are different ways that yarn can be subjected to needle for fabric formation. In knitting there basically two system these are –
Weft knitting:
Weft knitting is a completion by loops formed a horizontal manner by adjacent needle. The most common machine is used for weft knitting is the circular knitting machine. This machine creates such able fabric in spiral configuration by run the cylinder. The width of the fabric is determined by the number of needle on the machine. One revelation of the machine complete one course for each yarn feed.
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| Fig 1: Circular knitting machine |
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| Fig 2: Flat bed machine |
A second type of machine can be used to produce weft knit. This machine produces fabric a needle beds that are flat so is called flat bed machine.
Regarding the types of machine used in weft knitting, needles place next to each other, knit one up to another in sequence to produce one raw of loops from the same yarn that show on the figure.
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| Fig 3: Loop formation in circular knitting machine |
On the figure here is an illustration of loops yarn created by weft knitting machine that next yarn horizontal manner, so the loops are formed from right to left
Course:
The horizontal raw of loops produced by adjacent needle to the same knitting cycle is known as a course. The course can be measured by the number of courses per linear unit. Expressed as inch per centimeter. In the figure a pattern of loop range in raw in color that is course. If drawing represent one inch by one inch area we identify these three courses per inch.
The vertical column of loops produced by same needle knitting at successive knitting cycles is referred to as wale. The wale can measure by the number of
Wales per linear length. In the same drawing three Wales per inch.
Stitch density
Stitch density refers to the total number of loops in a measured area of fabric and not to the length of yarn in a loop (stitch length). It is the total number of needle loops in a given area (such as a square inch, or three square centimeters).The figure is obtained by counting the number of courses or pattern rows in one inch (or three centimeters) and the number of Wales in one inch (or three centimeters), then multiplying the number of courses by the number of Wales. (Using a measurement of three centimeters rather than one is preferable for accuracy in counting). Stitch density gives a more accurate measurement than does a linear measurement of only courses or only Wales. Tension acting in one direction might produce a low reading for the courses and a high reading for the Wales; when they are multiplied together this effect is cancelled out. Pattern rows rather than courses may be counted when they are composed of a constant number of courses.
Loop formation:
There are only three types of loop or stitches possible in weft knitting. They are –
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| Fig: Knit loop |
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| Fig: Tuck loop |
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| Fig: Float loop |
Knit loop:
Just look at the first, one the knit stitch. If every needle is feed a yarn and goes to basic knitting cycle the product referred to as single jersey. All loops are knitted and all loops look exactly alike. Look closely at this drawing a back ground of knit loop the length of yarn in neck loop is called the stitch length. Notify each loop has what can identify as legs and crown. The fabric in the left is technically face side, and the stitches has an over all vertical apparent. And this side we see primarily legs rather than crown. The fabric at the right is technically in the back, which takes on horizontal appearance. In this view we see mainly crown. Referred to a jersey stitch, stitches arrange in this pattern have a distinguishly different look and feel face to the back.
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| Fig: Technical face |
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| Fig: Technical back |
Tuck loop:
Another types of stitch is referred to as the tuck stitch. Because one yarn is tuck behind another and hide. The pattern on the left shows the technical face for tuck stitch. Follow the green shaded course of yarn across the pattern and looks like a loop has been tuck behind another. The pattern on the right shows technical back, for a tuck stitch from the back tuck is more visible to the eye.
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| Fig: Technical face |
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| Fig: Technical back |
How is a tuck stitch made?
During the tuck cycle at feed one the needle move up from the rest position and old stages that has been formed is held and not allowed to close latch. At the needle moves up found up to grab a second yarn which is put into tuck position. Both yarns are then griped at the rest position. The knit cycle of course with a next feed of yarn at this time, both yarn are cleared the new yarn is feed and pull through both the held and tuck loop forming the tuck stitch. This stitch caused by holding one elongated stitch for an extra course caused more length shrinkage. The tuck loop makes the fabric wider and thicker and slightly extensible.
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| Fig: Tuck loop formation process |
Float loop:
The third type of the stitch is the float which is also called miss stitch. The drawing on the left is a technical face. On the face in the middle course of yarn is middle wale. It looks like when a machine not captures or knit with any other stage this is float or miss stitch. In the technical back row the loop float
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| Fig: Technical face |
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| Fig: Technical back |
Float loop formation process:
To produce the float stitch in feed one, a yarn is laid to rest behind the hook of the needle. The needle remains in the rest position. It is not activated in the float cycle. In the knit cycle erase, one a subsequent yarn is knit in the next feed. The missed yarn floats to the technical back of the fabric. Loops can be made float over a series of
Wales. To make the structure secured some float yarn can be tied into the ground with a jerky of tuck stitch. Float loops make the fabric more narrow and less extensible because the floating yarn is in straight configuration.
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| Fig: Float loop formation process |
Circular knitting machine:
The principle for circular knitting machine feed from the knitting elements yarn moves from the yarn supply or creel through guides to stop motions control above the machine, then back down to tension controls and yarn feeding devices to the knitting elements. Quality products can be produced only on stop motion and yarn feeding functions are properly set. Then inter get action knitting and needles form loops. The course at the needle of the machine between the take up and yarn feeding mechanism. Circular weft knitting, needle let one after the other in a sequence for each yarn. Loops are formed horizontally by needle knitting around the cylinder forming a tube. After yarn is knit on the knitting elements the knitted fabric passed over a spiral mechanism through take-up roller and round a roll. This electrical spiral distribute the take-up tension uniformly and reliable to fabric confirm flat tube.
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| Fig: Circular knitting machine |
Different parts of circular knitting machine:
1. Chassis 2. Main foot 3. Side foot 5.Supporting ring 6.Needle cylinder 7. Yarn carrier 8.
Cam box ring
9. Yarn feed device 10. Feeding the yarn 11. Central machine axis 12. Protective cover 14. Working platform 15. Upper step 16. Lowest step 18. Safety railing 20. Holding rods 21. Roller 22. Horizontal axis 23. Guide way
Needle action:
Cylinder
Knitting machines are designed as each needle can be placed in a groove cut into the out side the middle cylinder. The groove may above refer to as slot or trick. The top edge of each groove is called the verge. This cylinder is very precisely manufacture, so the diameter measure the any place is equal. Machines are classified by the number of slot per linear inch. This is referred to as gauge of the machine. For example eight gauge machines have eight slots per inch. The total number of slot around the circumference of the cylinder, which indicate the number of needles in the cylinder. The more needles the wider the fabric.
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| Fig: Cylinder |
Needle:
In the figure shown a latch needle and label it parts. At the top each needle is a hook, below this is a latch attach with a rivet, bottom edge of the latch is curved to feed over in completely close the hook. All the bottom of the needle is the butt, which place a part in controlling how needle activate up or down. A needle with a latch is very efficient, when the latch needles are used to create weft knit the knitting cycle can be complete with out any auxiliary attachments.
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| Fig: Latch needle |
Latch needle works:
At rest or running position a knit loop rest above or on latch as the needle moves up the old loops are ready formed drops below and clears the latch. As the needle moves down every sieve the new yarn to began forming a new stitch. The latch is knock over by the old loop and this old loop is cast off. The needle moves further down to fully form and complete the new stitch. The amount of yarn used to form a new stitch determines the stitch length. This is the important because the stitch length affects the weight, width and static of the fabric.
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| Fig: Knitting action of latch needle |
Causes needle move up or down:
Cam is responsible for needle movement up or down. Each cam is designed to allow the needle to runs straight or moves up and down. Here needle travels through various stages. At the rest or running position the needle runs straight over the rest cam. When it reaches the clearing cam it raises up step angle which forces the needle rise and clear the old loop. Then the needle drops with a contact stitch cam. As a continuous on its parts it catches new yarn. It continuous further down pulling the new yarn forming a new loop or stitch to form and old loop cast off the up through cam returns the needle to reach resting position. So it can begin cycle again.
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| Fig: Needle movement process by cam |
Sinker:
As needle activation a course how the machine controls the movement of fabric as it knit. There is one more part place between each pair of needles. It’s called the sinker. It is steel element with distinctive shape. The sinker has a butt is place to insert a cam. It has a hold, throat and nose.
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| Fig:Sinker |
As the needle goes up the sinker moves to catch the fabric in its throat. When its catch the loop the old loop clear the latch. When the hook catches the feeder yarn as the needle moves down, the sinker moves backward of the way and knock over, cast off and stitch forming takes place. As the new stitch formed the fabric rest on the top of the nose.
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| Fig: Action of the sinker during loop formation |
By: MA
