Fabric Construction of Plain Weave | Fabric Structure and Design of Plain Weave

Posted by Firoz Kabir on Tuesday, March 3, 2015 0

Fabric Construction of Plain Weave
Woven fabrics are constructed by interlacing one system of parallel threads at angles to another of parallel threads. The system of threads that runs lengthwise of the goods is known as the warp; the system of threads that runs across the cloth is known as filling. They are also commonly referred to as ends and picks respectively.

  The order in which the warp and filling threads interlace in a fabric is called the weave. The simplest is the plain weave in which there is an alternate interlacing of warp and filling yarns, one over, one under, the entire width of the fabric.

Design for Plain Weave
Turning to Figure 1 the space between the horizontal lines at A represent warp threads, the spaces between the horizontal line B represent filling threads. On the squared paper, each square can be used to represent a warp thread over a filling or a filling thread over a warp thread. Instead of drawing a sketch of interlacing threads, as in D the interlacing can be more clearly and conveniently shown by the use of design paper as in E. Notice in the sketch that the interlacing of the first pick and the first end, shown at D lower left, indicates that a warp thread is over a filling thread.

                   Thread corresponding square on the design paper E is painted in to indicate that the warp is up that is over the filling. Just above, the warp end is under the filling. The fact that the warp thread is down is indicated on design paper by leaving the square blank.
A warp thread which is up is called a raiser, a warp thread down is called a sinker, a warp raiser is shown by a painted square, a sinker is shown by a blank square.
Painted in the design shows the weave pattern and is the first step in preparing the design. The next step is to add necessary loom directions for that particular weave pattern. These directions include the drawing in draft the chain and the reed plan.

Above is a step –by step analysis of a design for plain weave. This includes much explanatory details. All of the necessary directions for the weave are given in condensed form in the design shown at E.

Drawing in Draft
The simplest arrangement for a plain weave uses harness. When one harness is raised and the other harness is lowered, the two warp sheets form a v-shaped shed within which is laid a filling thread, placed in position by a shuttle which carries the filling through the shed. This filling is beaten into place and then the position of the two sheets of warp is reversed by lowering on harness and raising the other. This cycle of movements is already familiar to you in the names of the three primary motions of the loop: viz, shedding, piecing and beating-up.

On plain weave using two harnesses, the odd numbered warp threads are drawn in on one harness, the even numbered warp threads are drawn in on a second harness. This forms two sheets of warp-odd ends in one sheet, even ends in the other. Directions for drawing in are given in the form shown in above figure: I-E below the weave plain in the first and third warp ends are drawn in the first harness. To indicate this, paint in the first and third squares for harness No:1. The even numbered warp ends are drawn in the second harness. The order for drawing the warp threads in the harnesses has now been indicated. This is called the drawing in draft, abbreviated to D.L.D

The Chain Draft
The plan for raising  and lowering the harnesses for each pick is shown in the chain draft. The basic rule for making a chain draft from a given design and drawing draft is:
Start with the first harness in the drawing in-draft, and locate an end that is indicated in the draft are being drawn through this harness. Trace this end up to the design and see the interlacing of this end with the filling. The interlacing of this end is copied in the first vertical line of squares in the chain draft which represents the first harness. See the analysis in above figure. Locate the end drawn through the second harness and copy the interlacing of this end in the next vertical line of squares in the chain draft. Continue until all harnesses have been traced. There should be as many harness indicated in the chain draft as are shown in the drawing in draft.

Reed Plans
The  warp threads from the loop beam are first drawn through drop wires, through the handle eyes, and then through the dents of the reed. Each space between reed wires is called dent. The number of warp threads per dent may be one, two, three or more. The number varies according to the weave, the reed number, or the ends per inch desired in a given place in the fabric. For instance, fabrics of low construction may be needed one or two ends per dent, fabrics of high construction with three or more ends per dent., and other fabrics may be needed 2 ends per dent in some places and 4 or more in other places. In above figure the indicated reed draft shows two ends are to be placed in each dent in the reed.