Warp Knit Structures PDF

Knitting Technology  Warp Knitted Laps ►Loops are termed ‘laps’ in warp knitting because the warp guides lap their yarn around the needles in order to form the loop structure. ►The loops (overlaps) may be open or closed.  Basic Warp Knit Structure ► A warp knitted structure is made up o...

Knitting Technology  Warp Knitted Laps ►Loops are termed ‘laps’ in warp knitting because the warp guides lap their yarn around the needles in order to form the loop structure. ►The loops (overlaps) may be open or closed.  Basic 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.  Basic 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.  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.  Warp Knit Structure ►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.  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.  Warp Knit Structure ►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.  Warp Knit Structure ►Run-in: the yarn consumption during 480 knitted courses ►Rack: a working cycle of 480 knitted courses ►The run-in, therefore, is the yarn consumption for one rack.  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.  Open & Closed Laps ►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:  Open & Closed Laps ►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.  Closed Lap ►A closed lap is produced when a subsequent underlap shogs in the opposite direction to the preceding overlap, thus lapping the same yarn around the back as well as around the front of the needle.  Open Lap ►An open lap is produced either when a subsequent underlap is in the same direction as the preceding overlap. ►Closed laps are heavier, more compact, more opaque, and less extensible than open laps produced from the same yarn at a comparable knitting quality. Lapping Diagrams Single- Or Double-needle Overlaps ►Overlap movements are normally across only one needle space because two-needle overlaps cause both the warp thread and the needles to be subjected to the severe strain of two simultaneous adjacent knock-over actions. Single- Or Double-needle Overlaps ►In addition, different tensions on the two loops in the structure adversely affect their appearance. Single- Or Double-needle Overlaps ►The underlap between the double overlaps has the appearance of a sinker loop.  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.  Single Bar Structures ►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. Single Bar Structures Single Bar Structures  5 Basic Variations ►All guide bar lapping movements are composed of 5 lapping variations.  5 Basic Variations ►An overlap followed by an underlap in the opposite direction (closed lap).  5 Basic Variations ►An overlap followed by an underlap in the same direction (open lap)  5 Basic Variations ► Only overlaps and no underlaps (open laps)  5 Basic Variations ► Only underlaps and no overlaps (laying-in)  5 Basic Variations ► Neither overlaps nor underlaps (miss-lapping)  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.  Pillar Lap ►Due to the absence of underlaps, a fabric is not created, only chains of disconnected wales.  Underlaps Only ►Underlap alone cannot form into a fabric and is commonly used with other lapping movements.  1 & 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.  1 & 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.  Tricot Lap 3 and 1 lap 2 and 1 lap Tricot Lap 4 and 1 lap  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.