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4/13/2016 6
Needle Technology
• Until relatively recently warp knitting machines used four types of needle:
– The bearded needle
– The latch needle
– The compound needle
– The carbine needle
• Bearded and compound needles were used on tricot machines, the latch needle on raschel and crochet machines and the carbine needle on crochet machines.
4/13/2016 10
Knitting Technology
• Recently the bearded needle has been
dropped and development has focused on the
compound needle due to its greater rigidity
and ability to withstand higher yarn lapping
forces (see Loop formation) than the bearded
or latch needle.
4/13/2016 11
Knitting Technology
• Furthermore at the highest speeds (above
2,500 cycles/minute) the issue of latch impact
on the hook starts to become a problem with
latch needles.
• In contrast the compound needle can be
closed gently in a controlled manner even at
the highest knitting speeds.
4/13/2016 12
Warp Knitting Technology
• Warp knitting machines--needles are mounted
collectively and rigidly in a horizontal metal
bar (the needle bar that runs the full knitting
width of the machine).
• Equally the yarn guides are also set rigidly into
a horizontal metal bar (the guide bar that runs
the full width of the machine).
4/13/2016 13
Knitting Element Displacements
• The diagram
summarizes the
somewhat confusing
displacements made by
the guide bar. The front
of the machine lies to
the right of the
diagram.
4/13/2016 14
Knitting Element Displacements
• The diagram shows the individual yarn guides set in a solid bar. The front-to-back movements are called swings. The first swing from front to back is followed by a lateral shog: the overlap, which wraps the yarn in the needle hook.
4/13/2016 15
Knitting Element Displacements
• The next movement is a
swing from back to
front followed by the
underlap that may be
from 0 to 8 needle
spaces depending on
the fabric structure
being knitted.
4/13/2016 16
Tricot Knitting
• In diagram (1.3 a & b)
the guide bar swings
from the front of the
machine (on the right
hand side of the
diagram) to the back of
the machine taking the
yarn through the gap
between two adjacent
needles.
4/13/2016 17
Tricot Knitting
• Diagram (1.4 c) shows the guide bar moving laterally towards the observer. This is known as a shog movement, specifically the overlap that wraps the yarn around the beard of the needle.
• Diagram (1.4 d) shows the second swing in the cycle taking the yarn between adjacent needles back to the front of the machine. At this time the needle bar moves upwards to place the overlap below the open beard on the shank of the needle.
4/13/2016 18
Tricot Knitting
• Diagram (1.5 e) shows the presser bar moving forward to close all the needles and in (1.5 f) the closed needle passes down through the old loop and the sinkers move backwards to release the old loops so that knock-over can take place.
4/13/2016 19
Tricot Knitting
• In figure (1.6 g) the sinker
bar moves forward to
secure the fabric prior to
the needle rising in the
next cycle and at this
stage the guide bar makes
a second shog, this time
an overlap which may be
of 0 to 8 needle spaces
depending on the
structure being knitted.
4/13/2016 20
Tricot Knitting
• The machine type in this series of diagrams is a tricot machine and on this type of machine there is no continuous knock-over surface.
• The belly' of the sinker provides support to the fabric by preventing the underlaps from moving downwards.
• For this reason it is not a good idea to knit fabrics with few underlaps such as net or lace on a tricot machine.
• They are much better knitted on a Raschel machine with a continuous knock-over trick plate.
4/13/2016 21
Tricot Knitting
• The diagrams you are about to see illustrate a tricot machine with compound needles.
• The sequence of events is almost exactly the same as for the bearded needle with the exception that the overlap lays the yarn into the open hook and not onto the beard, and the compound needle is closed by relative displacement between the needle and the closing element.
4/13/2016 25
Guide Bar Shog, Overlap and Underlap
• The displacements shown for the needle,
sliding latch, guide bar swing and sinker bar
are the same irrespective of the type of fabric
being produced by the machine.
4/13/2016 26
Guide Bar Shog, Overlap and Underlap
• The shog movements determine the type of fabric produced and they need to be changed each time the fabric structure is modified.
• Crucially the shog movements must place the guides at the centre of the gap between adjacent needles with 100% accuracy every knitting cycle for the entire lifetime of the machine.
• If there was a failure in the shog displacement and the needle bar moved by less than a full needle pitch then in all likelihood the yarn guides would collide with the needles during the swing movement causing serious damage to the machine.
4/13/2016 28
Warp Knit Structure
• Warp knitting is defined as a stitch forming process in which the yarns are supplied to the knitting zone parallel to the selvedge of the fabric, i.e. in the direction of the wales.
• In warp knitting, every knitting needle is supplied with at least one separate yarn.
• In order to connect the stitches to form a fabric, the yarns are deflected laterally between the needles.
• In this manner a knitting needle often draws the new yarn loop through the knitted loop formed by another end of yarn in the previous knitting cycle.
4/13/2016 29
Warp Knit Structure
• A warp knitted structure is made up of two parts. The first is the stitch itself, which is formed by wrapping the yarn around the needle and drawing it through the previously knitted loop.
• This wrapping of the yarn is called an overlap. The diagram shows the path taken by the eyelet of one yarn guide traveling through the needle line, making a lateral overlap (shog) and making a return swing. This movement wraps the yarn around the needle ready for the knock-over displacement.
4/13/2016 30
Warp Knit Structure
• The second part of stitch formation is the
length of yarn linking together the stitches
and this is termed the underlap, which is
formed by the lateral movement of the yarns
across the needles.
4/13/2016 31
Warp Knit Structure • The length of the underlap is defined in terms
of needle spaces.
• The longer the underlap, the more it lies at
right angles to the fabric length axis.
• The longer the underlap for a given warp the
greater the increase in lateral fabric stability,
• conversely a shorter underlap reduces the
width-wise stability and strength and
increases the lengthways stability of the
fabric.
4/13/2016 32
Warp Knit Structure
• The length of the underlap also influences the fabric weight.
• When knitting with a longer underlap, more yarn has to be supplied to the knitting needles.
• The underlap crosses and covers more wales on its way, with the result that the fabric becomes heavier, thicker and denser.
• Since the underlap is connected to the root of the stitch, it causes a lateral displacement in the root of the stitch due to the warp tension.
• The reciprocating movements of the yarn, therefore, cause the stitch of each knitted course to incline in the same direction, alternately to the left and to the right.
4/13/2016 33
Warp Knit Structure
• In order to control both the lateral and longitudinal properties, as well as to produce an improved fabric appearance with erect loops, a second set of yarns is usually employed. The second set is usually moved in the opposite direction to the first in order to help balance the lateral forces on the needles. The length of the underlap need not necessarily be the same for both sets of yarns. – Run-in: the yarn consumption during 480 knitted courses
– Rack: a working cycle of 480 knitted courses
• The run-in
………….is the yarn consumption for one rack.
4/13/2016 34
Warp Knit Structure
• For a given machine with a given warp:
– A longer run-in produces bigger stitches and a
generally slacker, looser fabric
– A shorter run-in produces smaller and tighter
stitches
– With more than one guide bar the ratio of the
amount of yarn fed from each warp is termed the
run-in ratio
4/13/2016 35
Lapping Diagrams
• With the exception of the
very simplest structures,
it is too time consuming
to represent warp knitted
fabric using stitch or loop
diagrams. For this reason
two methods of fabric
representation are
commonly used.
– Lapping diagrams
– Numerical representation
4/13/2016 36
Looping Diagrams
Actual Guide Movement
• This is the symbolic image
of the technological process
of lapping. This diagram can
also be derived from a stitch
chart by not drawing in the
stitch legs but only the head
and feet of the stitches.
4/13/2016 37
Looping Diagrams
• The needle heads are represented on paper as dots. The path of the guide bars is drawn in front of and behind the needles
• The yarns will not lie as straight in the fabric as they do when they are conducted through the guide bars and around the needles on the machine. The yarn path in the lapping diagram is rounded off to represent this
4/13/2016 38
Looping Diagrams
• Each dot represents one needle and each horizontal row of dots a single stitch forming process, i.e. one course. Several rows of dots from bottom to top represent the succession of several stitch-forming processes or courses recording a complete repeat of the fabric structure.
4/13/2016 39
Numerical Notation Related to Chain Link
Height
• The numerical notation
is best understood in
relation to the
mechanical system that
is used to generate the
lateral displacements
(shogs) of the guide
bars.
4/13/2016 40
Numerical Notation Related to Chain Link
Height
• If the pattern drive is on the right hand side of the machine, then the movement of the guide bar from the smallest chain link height (0) is only possible towards the left. With a chain link (1), the guide bar is moved to the left by one needle space (division), with a chain link (2) by two needle spaces, etc.
4/13/2016 41
Numerical Notation Related to Chain Link
Height
• On dotted paper, therefore, the numbers read from right to left and are entered between each needle space. The numbering is done from left to right when the pattern drive is on the left-hand side of the machine. The lateral movement of the guides is initiated by chain links of various heights marked with 0, 1, 2, 3, 4, etc. This guide bar movement is an especially important part of the pattern development.
4/13/2016 42
Chain Link Arrangement
• The guide bar is positioned with the follower roller on chain link 0'; it swings through, then moves to the left as the roller moves to chain link 1'. It swings back and returns to its starting position (chain link 0').
– The chain should read: 0
1
– In the opposite direction: 1
0
• The smallest repeating unit (repeat) extends over one course: height repeat = 1 stitch, width repeat = 1 stitch.
4/13/2016 43
Chain Link Arrangement
• Application
– Pillar stitch construction can be employed in the
production of outerwear and for ribbed velour
fabrics (corduroy). Even in these fabrics, the open
pillar stitch is more popular as it provides the
necessary longitudinal stability and runs freely. It
is used in conjunction with the binding element
in-lay' in laces and curtains, though always with a
second guide bar.
4/13/2016 44
Open and Closed Stitches
• The stitch formed has an open or
closed character according to the
direction of the underlap and overlap
motions. The underlaps can be of
differing magnitudes and directions:
– If the underlap and overlap are in
opposite directions then the stitch
formed would have a closed character
– If the underlap and overlap are in the
same direction, then the stitch formed
will have an open character
4/13/2016 45
Open and Closed Stitches
• The stitch is open when the feet do not cross and closed when the feet cross. The structure of a warp knitted fabric depends on the lapping motion of the guide bars, and therefore the structure could be represented by:
– Drawing a stitch or stitch chart diagram, which takes time and is difficult
– Lapping diagram
4/13/2016 46
Yarn Threading Plan
• In warp knitting a yarn guide wraps the yarn around the needle hook, thus forming a loop. However, to form a fabric, the yarn guide must wrap the yarn around a different needle during the next course. The yarn guides, therefore, must be displaced laterally during knitting. Different warp knitted structures are produced by varying the magnitude of their lateral displacement. Therefore warp knitted structures can be described by noting the guide bar displacement.
4/13/2016 47
Yarn Threading Plan
• The actual guide bar
motion consists of an
underlap, swing-
through, overlap and
swing-back movement,
and this motion is
known as lapping.
4/13/2016 48
Yarn Threading Plan
• The yarn is wrapped around the needle hook due to the swing-through, overlap and swing-back movement of the yarn guide, and this forms a stitch. A warp knitted fabric is, therefore, made from stitches (overlap) and connecting underlaps.
4/13/2016 49
Single Bar Structures
• A plain warp knitted structure is produced on a single needle bar. The resulting structures are known as single face fabrics. Rib and interlock warp knitted structures are produced on double needle bars, and these structures are known as double face fabrics.
• In single face structures (plain), stitches are visible on one side, known as the technical face, and on the other side (known as the technical back) only underlaps are visible.
4/13/2016 50
Pillar Lap
• A pillar stitch (or chain
stitch) is a stitch
construction where lapping
of a yarn guide takes place
over the same needle.
• As there are no lateral
connections between the
neighboring wales, the
stitches are only
interconnected in the
direction of the wales.
4/13/2016 51
Pillar Lap
• Due to the absence of underlaps, a fabric is not created, only chains of disconnected wales.
• Single bar pillar lap is technically possible only on Raschel machines where the trick plate acts a knock-over bed.
• On a tricot machine the sinkers are unable to control the position of the old loop when there is no underlap (pillar stitch) and so the knitting of pillar stitch on its own is impossible.
4/13/2016 52
Pillar Lap
• Open or closed pillar
stitches can be
produced depending on
the guide bar
movement.
4/13/2016 53
1 and 1 Lap (Tricot Lap)
• The laps are executed in alternate overlap and underlap motions on two defined needles.
• This stitch creates a textile fabric as the underlaps connect both the courses and the wales.
• The simplest of this group of structures is made between two adjacent needles.
4/13/2016 54
1 and 1 Lap (Tricot Lap)
• The laps are executed in alternate overlap and underlap motions on two defined needles.
• This stitch creates a textile fabric as the underlaps connect both the courses and the wales.
• The simplest of this group of structures is made between two adjacent
needles.
4/13/2016 55
1 and 1 Lap (Tricot Lap)
• Guide bar motions:
• First course:
Under 1 needle to the right ↓(UL)
swing through 1
over 1 needle to the right ↓(OL)
Swing Back 0
4/13/2016 56
1 and 1 Lap (Tricot Lap)
• Second course:
Under 1 needle to the left ↓
swing through 1
over 1 needle to the left ↓
Swing Through 2
4/13/2016 57
1 and 1 Lap (Tricot Lap)
• Result:
• Therefore, the chain link arrangement is:
1
0
1
2 closed 1 and 1 stitch
• As a result of the underlaps, the diagonal sinker loops are formed. These pull the stitch heads of each alternate row into the same direction.
4/13/2016 58
2 and 1 Lap
• Swing through → 1
• swing back → 0
• swing through →2
• swing back → 3
• swing through → 1
• swing back → 0
4/13/2016 59
3 and 1 Lap
• Swing through → 1
• swing back → 0
• swing through → 3
• swing back → 4
• swing through → 0
• swing back → 1
• swing through → 4
• swing back → 3
4/13/2016 61
Atlas Lap
• The atlas construction
differs in that the laps
are continued over two
or more courses in one
direction and then
return in the other
direction to the point
where they started.
• Lapping movement • 0-1/2-1/3-2/4-3/5-4/3-4/2-3/1-2/