Knitting 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 a. Lapping diagrams, b. Numerical representation.
Actual guide movement
- 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
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.
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 (refer to the module Warp knitting machine technology for a description of the shogging mechanism).
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. 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.
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.
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.
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 different 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
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