Yarn guide in Knitted fabric formation

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.

Actual Guide Bar Motion

The actual guide bar motion consists of an underlap, swing-through, overlap and swing-back movement, and this motion is known as lapping. 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.

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.

Pillar lap

Lapping diagram for pillar stitch construction 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. 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.
Open or closed pillar stitches can be produced depending on the guide bar movement.

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.