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Warp Knitting Basics

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Warp Knitting
Basics
March 26,2010
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1
Weft
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Warp
2
Warp Knits--the possibilities
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5
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, swingthrough, 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 swingthrough, 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
• swing back→ 0
в†’1
• swing through
• swing back→ 3
в†’2
• swing through
в†’1
• swing back→ 0
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3 and 1 Lap
• Swing through
в†’1
• swing back → 0
• swing through
в†’3
• swing back → 4
• swing through
в†’0
• swing back → 1
• swing through
в†’4
• swing back → 3
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4 and 1 Lap
• Swing through
• swing back
в†’0
• swing through
• swing back
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в†’1
в†’4
в†’5
60
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?
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