Warp Knitting Basics

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Warp KnittingBasics

• March 26,2010

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Weft Warp
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Warp Knits--the possibilities
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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.

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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.

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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.

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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).

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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Tricot Knitting
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Tricot Knitting
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Tricot Knitting
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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.

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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.

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Graphical Representation of Warp Knitting
Structures
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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.

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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.

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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.

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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.

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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.

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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.

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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

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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

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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.

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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

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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.

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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.

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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.

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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.

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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.

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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.

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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

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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

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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.

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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.

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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.

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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.

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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.

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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.

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Pillar Lap

• Open or closed pillar stitches can be produced
  depending on the guide bar movement.

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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.

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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.

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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
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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
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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.

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2 and 1 Lap

• Swing through ? 1
• swing back ? 0
• swing through ?2
• swing back ? 3
• swing through ? 1
• swing back ? 0

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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

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4 and 1 Lap

• Swing through ? 1
• swing back ? 0
• swing through ? 4
• swing back ? 5

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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/

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• video

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Stitch Diagram and Notation?