Basic Knitting Technology
A discussion about knitting technology must be dealt both as an analysis of the technical cycles
of knitting as regards the machines used and the mechanisms involved in the process, and as an
analysis of the technology of knitted fabrics in terms of their structures and their physical and
mechanical properties.
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| Picture 1 - Knit fabric |
of the same element, the loop, which is the basic element of the fabric.
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| Picture 2 - The Loop |
The loop (picture 2) is a length of yarn that is forced to assume a curvilinear shape. It can be
divided into three main sections:
a: loop top
b: loop side and bottom
c: half interloop
The interloop is the yarn that links two consecutive loops together. The horizontal or vertical
repetition of loops forms the typical structures of knit fabrics, which can be divided into WEFT
KNIT FABRIC and WARP KNIT FABRIC, respectively.
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| Picture 4 - Warp knit fabric |
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| Picture 3 - Weft knit fabric |
In weft knits (picture 3) the interloop links two consecutive loops placed horizontally; when one
loop breaks, the entire fabric can be undone simply by pulling the free end of the yarn.
In warp knits (picture 4) the yarn is knitted vertically or diagonally and loops are formed
accordingly; to knit the fabric, it is necessary to use many threads simultaneously, allowing the
loops formed by the different threads to bind together.
In this case, the knit fabric is run-proof . Therefore, the warp knit fabrics are also called “nonrun“
or “ladder-proof “.
From a physical point of view, a fabric can be described as a flexible structure, made up by the
vertical and horizontal repetition of two elements: the course and the wale.
The word “course” defines a row of horizontal loops, belonging or not to the same yarn; “wale”
means a row of loops laid vertically one upon the other (picture 5).
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| Picture 5 - Course and wale of a weft knit fabric |
Classification of Knitting Machines
The machines used for the manufacturing of knit fabrics can be divided into machines with
individually driven needles and needle bar machines.
The former type of machine incorporates needles which are moved individually by cams acting
on the needle butt; they are used for producing weft knits and are subdivided into circular
knitting machines and flat-bed knitting machines.
The needles used can be latch needles or compound needles.
The needle bar machines incorporate needles which move simultaneously, since they are all
fixed to the same bar; we distinguish full-fashioned knitting machines and circular loop-wheel
machines for the production of weft knit fabrics, which only use spring-beard needles, and warp
knitting machines which use spring-beard needles, latch needles and compound needles.
The Three Main Types of Needle
The needle is the basic element of loop formation.
be looped;
the loop.
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During the loop formation the hook must be closed in order to transfer the previous stitch
already formed on the new thread; this operation takes place in different ways according to the
type of needle used.
With the latch needle, the latch is hinged at a certain distance from the hook and can revolve:
- the anticlockwise rotation, produced by the pressure of the loop, which is originally inside the
hook, opens the hook to allow a new thread to be fed;
- the clockwise rotation, produced by the pressure of the loop on the stem, allows the hook to be
closed and subsequently knocked over on the new thread.
In spring-beard needles, the hook is closed by an external device, the presser, which, at a
specific time during the stitch formation, comes in contact with it and makes it bend and close.
When the presser is pulled away, the hook springs back and opens the needle automatically.
The compound needle includes (inside the internal groove of the stem) a sliding closing element,
which opens and closes the hook through its upward and downward motion.
The use of the latch needle for knitting machinery has become increasingly widespread over the
last few years; the main advantage of this needle is that has a reduced stroke, which means a
higher speed and increased production capacity without stressing the thread during the transfer
steps. In addition, it offers a wider sampling potential and a better quality of the fabric
manufactured. The main drawbacks include higher costs and a more complicated operating
technology.
The Latch Needle
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| Picture 7- The latch needle |
The elements which characterise this type of needle (picture 7) are the following:
- the stem: the stem is the main part of the needle and its thickness is proportional to the
machine gauge; the stem is arranged between the rods and the pockets of the
needle bed, which acts as a guide; the stem can be bent to allow the needle to
keep the position set by the selection mechanism.
- the butt: the butt is the stem section in contact with the cams or the selection
butts, arranged at different levels.
- the hook: the hook is the upper end segment of the stem. It picks up the yarn fed by the
thread guide to form the stitch. Height, diameter, length, thickness, shape and
- the latch holder: the latch holder is the part of needle carrying the latch pin.
1. it can be screwed (this manufacturing technology is rather complex);
2. it can be “R” standard pressed (when it has a straight hole);
3. it can be “A” angle pressed (when it has a slant hole).
- The latch: it is shrunk on the pin and it can freely rotate in both directions; its length
Screw pin “R” standard “A” angle pressed
pressed pin pin
Picture 8
From a manufacturing point of view we can have two different types of needle:
- wire needle
- die-cut needle
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| Picture 9 – Wire needle Picture 10 – Pressed butt |
to create a flat profile and form a hook, the section accommodating the latch, and an end butt
with tail; sometimes the butt is not obtained with a bending process but by a pressing one
(picture 10).
Die-cut needles (picture 11) are made from a steel plate of the desired thickness, which is die cut
so as to create the shape of a butt with or without a tail; the hook and latch fitting are created
with a special process.
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The manufacturing process with the wire needle is the simplest and most cost-effective one,
while the die-cutting process gives better technical results and imparts greater stiffness to certain
sections of the needle.
A critical feature of all needles is the gauge; it is directly connected to the strength of the needle
which must bear the stress and strain generated during the various technical cycles of the
knitting process.
The gauge of the needle is directly proportional to the gauge of the machine; the needle must be
neither too thick (if so there would not be enough space between a needle and the next one for
looping the yarn) nor too fine since in this case the needle, besides being too weak, could
compromise the resistance of the binding pattern which would result poorly balanced.
The table in Picture 12 shows the gauge of needles according to their thickness.
The values are indicative, as the real value of the needle gauge is only given by the
manufacturer’s specifications.
Needle Specifications
The typical “European” specifications for a needle includes a word, a number (usually a fourdigit
number) and a final combination of letters and numbers.
For example: Vota 78.60 G.02
The capital letter at the beginning of the word ( “V”), identifies the origin of the needle
(obtained from a wire, pressed or die-cut), the type, the number of butts and the type of tail.
The other capital letters have a very precise meaning, except for the vowels “e” and “a” which
are added to make the word pronounceable, and indicate the shape and the height of the butt, the
eventual existence of a groove and its size, the length of the tail and some other features of the
needle.
The next group of numbers identifies the needle according to the length and the gauge.
The first part (78 in the example) indicates the whole length rounded off to the mm (in our case
that makes 78 mm); the second part indicates the gauge of the needle in hundredths of
millimetres (in our case the gauge of the needle is equal to 0.60 mm).
The final group of letters and numbers has to be read as follows.
The first capital letter indicates the needle manufacturer
(For example Z for Torrington, E for Exeltor, G for Groz-Beckert).
The next number is used to distinguish a specific needle among all the needles produced by the
same manufacturer.
The next letter refers to some particular features of the needle: for some needles an “A”
indicates that the latch has been fixed with an angular pressed pin while an “R” means that the
latch has been fixed with a straight pressed pin.
For other needles, the latch fixing method is indicated by a “0” before the last number.
A “0” indicates that the latch has been fixed with a standard pressed pin; no “0” means that the
latch has been fixed with a screw pin.
The Stitch Formation Cycles with the Three Types of Needles
Stitch Formation with a Latch Needle
At the beginning of the process, the needle is positioned on the knock-over plane with the loop
thread inside the hook, closed by the latch.
Once the needle has reached its maximum height on the looping plane, the latch opens wide and
the stitch moves along the stem.
The needle now begins to move downward. On reaching the tuck-stitching plane, it catches a
new loop thread.
latch on the hook.
Stitch Formation with a Spring Beard Needle (picture 13).
The needle moves upward and the loop thread, originally inside the spring beard, moves along
the stem.
Once the needle has been fed, the thread is introduced inside the spring beard, by means of an
external device; at this point, the presser closes the spring beard.
While the needle is in the non-knitting position, the stitch can move on the hook. Then, when
the needle begins to move downward, it slides on the hook and knocks over on the new yarn fed
at the end of the stroke.
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| Picture 13 - Stitch formation with spring beard needles |
The hook is opened by the upward motion of the needle and by the insertion of the slide in the
groove on the stem; the stitch moves on the stem, going below the tip of the slide.
The needle, now completely open, is fed with new thread and then starts to move downward.
The slide moves with a certain delay in relation to the needle and this makes the hook close and
the previous stitch to be knocked over on the new thread.
The Needle-bed
The needle-bed of a knitting machine is made up by the needles. As we said before, the needles
can be all fixed on the same needle bar (picture 14) or can be driven individually in a grooved
plate, according to the type of knitting machine.
All knitting machines can be equipped with one or two needle-beds, according to the model.
Picture 14 - A needle bar with
Picture 15 - The needle-bed of
The needle-bed of a knitting machine can be flat (picture 15) or circular (picture 16). It is made
up of a steel body provided with grooves where the needles with hook and butt turned upward
slide. The milled grooves guide the needles during the knitting process.
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| Picture 16- The needle-bed of a circular knitting machine |
The needle-bed is characterised by two elements:
- the operating width
- the gauge
The operating width is the maximum working area and varies according to the type of machine
(picture 17): for example in a flat-bed machine the operating width is the distance between the
first and the last needle while in circular knitting machines the operating width is the needle-bed
diameter.
The gauge is the population of needles on a certain length of bed.
The English Gauge is the number of needles included in an English inch, that is to say how
many are included in 2.54 needle-bed centimetres.
From a conceptual point of view, the English inch is measured from the centerline of a needle
but usually it is the distance corresponding to 1 inch, measured from one side of the needle to
the same side of another needle within 1 inch. For example: if we start from the right side of
the first needle we will have to reach the right side of the last needle.
The gauge refers always and only to one of the two needle-beds.
The English gauge is indicated with a capital E and is used for all the weft knitting machines
and warp knitting frames.
There are also other types of gauges used for other machines and specifically:
- the English Raschel Gauge for Raschel looms is indicated with the capital letters
“ER” and refers to the number of needles included in 2 inches, that is to say in 5.08
centimetres;
- the GG Gauge is indicated with the capital letters GG and refers to the number of
needles included in 1.5 inches, that is to say in 3.81 centimetres. This gauge is used
for flat-bed full-fashioned machines and for English circular machines.
- French Gauge is indicated with the Gros symbol and refers to the number of needles
included in 1.5 French inches, that is to say in 4.16 centimetres. It is used for loopwheel
circular machines.
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| Flat needle-bed width Circular needle-bed diameter |
Picture 17 - Operating width
Flat Knitting Machines
The flat knitting machine is a two-bed machine.
The most important mechanical features of a flat knitting machine are:
- the supporting frame
- the yarn feeding system
- two needle-beds made up of flat grooved plates
- a carriage provided with cam-locks for needle control
- a transmission system
- a fabric take-down motion
- a central programming unit
- a needle-bed racking system
2 comments:
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AKASH coxs` Bazar
World University of Bangladesh
Textile technology 3rd year
01818766765
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