Tuesday, January 3, 2017

Essential Terms and Definitions of Knitting Technology

Knitting terms and definitions are very important for textile engineers and especially for who is doing job in knitting industry. Knitting glossary is frequently used in different viva board for textile engineering students. In job interview knitting abbreviations and terminology are commonly asked. For helping students and professional I have given some very important and frequently asked in viva board knitting terminology.
Essential Terms and Definitions of Knitting Technology

Kink of yarn:
A length of yarn that has been bent into a shape appropriate for its transformation into a weft knitted loop.

Knitted loop:
A kink of yarn that is intermeshed at its base i.e. when intermeshed two kink of yarn is called loop.

GSM:
GSM is one kind of specification of fabric which is very important for a textile engineer for understanding and production of knitted fabric. In knitting fabric it is the main parameter. It is controlled by loop length. GSM is directly proportional to the fabric thickness. GSM depends on yarn count, density of needle, wales per unit length and course per unit length.

Knitted stitch:
Stitch is a kink of yarn that is intermeshed at its base and at its top. The knitted stitch is the basic unit of intermeshing and usually consists of three or more intermeshed loops, the centre loop having been drawn through the head of the lower loop which had in turn been intermeshed through its head by the loop which appears above it.

Top arc:
The upper curved portion of the knitted loop is called top arc.

Bottom half-arc:
The lower curved portion that constitutes in a weft knitted loop, half of the connection to the adjacent loop in the same course.

Legs or side limbs:
The lateral parts of the knitted loop that connect the top arc to the bottom half-arcs.

Needle loop:
The needle loop is the simplest unit of knitted structure. Needle loop formed by the top arc and the two legs of the weft knitted loop

Needle loop = Top arc + Two legs

Purl:
Purl is the second most common stitch. Whereas in a knit stitch you put the right needle through the stitch from behind, in the purl stitch you place the right needle into the front of the left needle stitch.

Sinker loop:
The yarn portion that connects two adjacent needle loops belonging in the same knitted course. Bottom arc also called sinker loop.

Open loop:
A knitted loop of which a thread enters and leaves at the opposite sides without crossing over itself.

Closed loop:
A knitted loop of which a thread enters and leaves at the opposite sides with crossing over itself. It is made by special needle.

Knitted loop structure:
The properties of a knitted structure are largely determined by the interdependence of each stitch with its neighbors on either side and above and below it. Knitted loops are arranged in rows and columns roughly equivalent to the weft and warp of woven structures termed “courses” and “wales” respectively.

Feeder:
Feeders are the yarn guides placed close to the needles to the full circumference of the knitting zone. The feeders feed the yarn into the needle hooks and control the needle latches in their open position while the needle attain their clearing position.

Course:
A course is a predominantly horizontal row of loops (in an upright fabric) produced by adjacent needles during the same knitting cycle.

In weft knitted fabrics a course is composed of yarn from a single supply termed a course length. A pattern row is a horizontal row of cleared loops produced by one bed of adjacent needles. In a plain weft knitted fabric this is identical to a course but in more complex fabrics a pattern row may be composed of two or more course lengths.

In warp knitting each loop in a course is normally composed of a separate yarn.

Wale:
A wale is a predominantly vertical column of needle loops produced by the same needle knitting at successive knitting cycles and thus intermeshing each new loop through the previous loop. In warp knitting a wale can be produced from the same yarn if a warp guide laps around the same needle at successive knitting cycles thus are making a pillar or chain stitch lapping movement. Wales are joined to each other by the sinker loops or under laps.

Stitch density:
The term stitch density is frequently used in knitting instead of a linear measurement of courses or wales, it is the total number of needle loops in a square area measurement such as a square inch or square centimeter. It is obtained by multiplying, for example, the number of courses and wales, per inch together. Stitch density tends to be a more accurate measurement because tension acting in one direction in the fabric may, for example, produce a low reading for the courses and a high reading for the wales, which when multiplied together cancels the effect out. Usually pattern rows and courses are, for convenience, considered to be synonymous when counting courses per unit of linear measurement.

Stitch density = Wales per inch (wpi) x Courses per inch (cpi).

Intermeshing points or crossover point of a needle loop:
All needle loops or overlaps have four possible intermeshing or cross-over points, two at the head, where the next new loop will be drawn through by that needle and another two at the base where the loop has intermeshed with the head of the previously formed loop. Any one of the four points at which stitches are intermeshed. The intermeshings at the head are always identical with each other as are intermeshings at the base with each other.

It is impossible to draw a new loop through the old loop so that its two feet are alternately intermeshed. A new loop can thus only be intermeshed through the head of the old loop in a manner which will show a face loop stitch on one side and a reverse loop stitch on the other side, because the needle hook is unidirectional and can only draw a new loop down through an old loop. Bottom cross-over point is situated at the base and top cross-over point is situated at the head.

Loop or Stitch length:
The length of yarn knitted into one stitch in a weft knitted fabric. Stitch length is theoretically a single length of yarn which includes one needle loop and half the length of yarn (half a sinker loop) between that needle loop and the adjacent needle loops on either side of it. Generally, the larger the stitch length the more elastic and lighter the fabric, and the poorer its cover opacity and bursting strength.

Stitch Length, l = one needle loop + two half a sinker loop.

Extended sinker loop:
A sinker loop that is wider than the other sinker loops in the fabric and that is produced when a needle is inactive or has been removed from the needle bed or needle bar.

Face loop or stitch:
Also called plain stitch or jersey stitch or flat stitch. A stitch that is so intermeshed in the fabric that its legs are situated above the top arc of the stitch formed in the same wale in the previous course. This side of the stitch shows the new loop coming through towards the viewer as it passes over and covers the head of the old loop. Face loop stitches tend to show the side limbs or legs of the needle loops or over laps as a series of inter fitting “Vs”.

Technical face or right side:
The under surface of the fabric on the needles will thus only show the face stitches in the form of the side limbs or legs of the loops or over laps as a series of inter fitting & “Vs”.

Reverse or back loop or stitch:
Also called purl stitch. A stitch that is so intermeshed in the fabric that the top arc and the bottom arcs are situated above the legs of the stitch formed in the same wale in the previous and in the following course. This is the opposite side of the stitch to the face loop side and shows the new loop meshing away from the viewer as it passes under the head of the old loop. Reverse stitches show the sinker loops in weft knitting and the under laps in warp knitting most prominently on the surface. The reverse loop side is the nearest to the head of the needle because the needle draws the new loops down wards through the old loops.

Technical back or left side:
The upper surface of the fabric on the needles will only show reverse stitches in the form of sinker loops or under laps and the heads of the loops.

Double thread stitch:
Also called double loop stitch or spliced stitch. A stitch formed from two ends of yarn.

Single faced structures:
Single faced structures are produced in warp and weft knitting by the needles (arranged either in a straight line or in a circle) operating as a single set. Adjacent needles will thus have their hooks facing towards the same direction and the heads of the needles will always draw the new loops downwards through the old loops in the same direction so that intermeshing points 3 and 4 will be identical with intermeshing points 1 and 2.

Double faced structures:
Double faced structures are produced in weft and warp knitting when two sets of independently controlled needles are employed with the hooks of one set knitting or facing in the opposite direction to the other set. The two sets of needles thus draw their loops from the same yarn in opposite directions, so that the fabric, formed in the gap between the two sets, shows the face loops of one set on one side and the face loops of the other set on the opposite side. The two faces of the fabric are held together by the sinker loops or under laps which are inside the fabric so that the reverse stitches tend to be hidden.

Balanced structure:
This is a double faced structure which has an identical number of each type of stitch produced on each needle bed and therefore showing on each fabric surface usually in the same sequence. These structures do not normally show curling at their edges.

Face and reverse stitches on the same surface:

These are normally produced on purl weft knitting machines which have double headed needles capable of drawing a face stitch with one hook and a reverse stitch on the other, so that intermeshing points 3 and 4 will not always be identical with intermeshing points 1 and 2.

Fabric draw-off:
Fabric is always drawn from the needles on the side remote from their hooks. When two sets of needles are employed, either arranged vertically or at some other angle to each other, each set of hooks will face away from the other set and the fabric will be produced and drawn away in the gap between the two sets.

Knitting machines:
The machines those produced fabrics by intermeshing or interloping of one or one set of yarn.

Knitting machines are divided as follows-

Weft knitting machine:
A machine producing a knitted fabric by intermeshing loops formed successively across the width of the fabric from a yarn fed substantially crosswise to the length of fabric.

Warp knitting machine:
A machine in which the fabric formation occurs by interlacement of loops formed simultaneously across the full width of the fabric from a system of yarns which are fed to the needles substantially in the direction of the length of fabric.

Other loop forming and combined technique machines:
Machines that form the fabric by the technique of intermeshing of yarn loops but which cannot be defined either as weft or as warp knitting machines.

Needles:
Needle is the principal knitting element. Needles are divided into two categories according to their functions as follows-

Independent needles:

Needles which can slide in the needle bed and be moved individually during the stitch or loop forming process.

United needles:
Needles which are fixed in the needle bar and which can only be moved in unison during the stitch or loop forming process.

Needle carrier:
A part of the knitting machine containing independently moved needles in a needle bed or united needles in a needle bar. The needle carrier may be flat or circular, cylindrical or dial type.

Fabric face type:
The basic type of construction of fabrics produced on the respective knitting machines:

RL: Single face fabric, also called right-left fabric; knitted on one row of needles.

RR: Double face fabric, also called right-right or double right fabric; knitted on two rows of needles.

LL: Links- links fabric, also called left- left or double left fabric; knitted on one or two rows of needles.

Number of feed system:
On the circumference of a circular knitting machine up to 120 knitting cam sets can be mounted, each cam set fed with a separate yarn. This results in obtaining 120 knitted loop courses in one machine revolution.

Number of feeders = Number of courses

Selvedged fabric:
A selvedged fabric is one having a “self- edge” to it and can only be produced on machines whose yarn reciprocates backwards and forwards across the needle bed so that a selvedge is formed as the yarn rises up to the next course at the edge of the fabric.

Cut edge fabric:
Cut edge fabric is usually produced by slitting open a tube of fabric produced on a circular machine. A slit tube of fabric from a 302 diameter machine will have an open width of 94” (πd) at knitting and before relaxation.

Tubular fabric:
This may be produced in double faced or single faced structures on circular machines, or in a single faced form on straight machines with two sets of needles provided each needle set only knits at alternate cycles and that the yarn only passes across from one needle bed to the other at the two selvedge needles at each end, thus closing the edges of the tube by joining the two single faced fabrics produced on each needle set together.

Open lap:

An open lap is produced either when the under lap is in the same direction as the overlap, or it is omitted so that the next overlap commences from the space where the previous overlap finished. Closed laps are heavier, more compact, opaque and less extensible than open laps produced from the same yarn and at a comparable knitting quality.

Closed lap:

A closed lap is produced when an under lap follows in the opposite direction to the overlap and thus laps the thread around both sides of the needles. 
 
Warp knitted laps:
Loops are termed laps in warp knitting because the guide slap the warp yarn around the needles in order to form the loops, the laps may be either open or closed. So, lap is a length of yarn in a warp knitted fabric that consists of an overlap and of an underlap. 


The under lap:
The under lap shog occurs across the side of the needles remote from the hooks, on the front of single bar and in the center of double bar needle machines, it supplies the yarn between one overlap and the next. So, under lap is a length of yarn in a warp knitted fabric that connects two overlaps in consecutive courses.

Under laps as well as overlaps are essential in all warp knitted structures in order to join the wales of loops together, but they may be contributed by a different guide bar to those for the overlaps. 
 
The overlap:
The overlap is a shog usually across one needle hook by a warp guide which forms the warp yarn into the head of the loop. The swinging movement of the guide to the hook side and the return swing after the overlap produce the two side limbs or legs of the loop which has a very similar appearance on the face side of the fabric to a needle loop produced by weft knitting. So, overlap is a length of yarn in a warp knitted fabric that has been placed over the needle during loop formation