Warp Knitting Fabrics Basics of knitting PDF

W arp knitting is defined as a stitch forming process in which the yarns are supplied to the knitting zone parallel to the selvedge of the fabric, i.e. in the direction of the wales. In warp knitting, every knitting needle is supplied with at least one separate yarn. In order to connec...

W arp knitting is defined as a stitch forming process in which the yarns are supplied to the knitting zone parallel to the selvedge of the fabric, i.e. in the direction of the wales. In warp knitting, every knitting needle is supplied with at least one separate yarn. In order to connect the stitches to form a fabric, the yarns are deflected laterally between the needles. In this manner a knitting needle Fig 14.1: Warp knit fabric structure (Face) Fig 14.2: Warp knit fabric structure (Back) often draws the new yarn loop through the knitted loop formed by another end of yarn in the previous knitting cycle. A simple warp knitted loop structure is shown in fig 14.1 – 14.3. As compared to weft knitting in warp knitting also, the vertical line of loops (i.e. wales) and the horizontal line of loops (i.e. course), the loop portion (i.e. overlap) and the Fig 14.3: Overlap and underlap in diagonal floats of yarns (i.e. underlap) are warp knitted fabric Fig 14.4: Formation of warp knitted fabric seen in fig 14.3. fabric, usually with the aid of a pick glass. underlaps play an important role in The warp knitted fabric structure has The face of the fabric has rather clearly influencing the pattern effects. The length dissimilar appearance on the technical face defined knit stitches generally running or extent of these underlap floats and their and technical back side as shown in figure vertically (in the lengthwise direction), but direction of running cause a variety of 14.1 and 14.2. Practically all warp-knitted slightly angled from side to side. At the design possibilities in warp knitting. The fabrics can be identified and distinguished back side of the fabric, the diagonal line of recognition of laps in a knitted fabric is from weft-knitted materials by careful yarns (i.e. underlaps) run right and left the most important distinguishing feature examination of the face and back of the throughout in a zigzag manner. These identifying warp knits.  1) Overlap only Point paper diagram: Each point shows In overlap, the guide bar only feed yarn to a needle in a course; each row shows a the same needle all the time. The result is different course that each needle knits a chain of stitches. Fig 14.5 a: Subsequent courses Example: 1-0/01, known as pillar stitch. A pillar stitch is not a fabric, but is commonly Fig 14.5 b: Same needle, wale used with other lapping movements to Fig 14.5 c: Subsequent courses and subsequent wales form a fabric. 2) Underlap only Warp knitted laps Underlap alone cannot form into a fabric and Loops are termed ‘laps’ in warp knitting is commonly used with other lapping Fig 14.10: Open lap because the warp guides lap their yarn movements. If a guide bar only made around the needles in order to form the underlaps in a multi-guide structure, this loop structure. A warp knitted structure is guide bar is called inlay bar and the warp are made up of two parts. The first is the stitch called inlay yarn, which never form into loops itself, which is formed by wrapping the but only “tie-in” at the back of the fabric. yarn around the needle and drawing it 3) Overlap with underlap through the previously knitted loop. This When overlap and underlap are worked Fig 14.11: Closed lap wrapping of the yarn is called an overlap. together, two types of fabrics can be The diagram shows the path taken by the formed. The first one, as shown in fig 14.8- eyelet of one yarn guide travelling through 14.10, when overlap and underlap are the needle line, making a lateral overlap moving in the same direction, an open lap (shog) and making a return swing. This fabric will be formed. The second one, as movement wraps the yarn around the shown in fig 14.11 – 14.13, when overlap needle ready for the knock-over and underlap are moving in opposite displacement. The second part of stitch direction, closed lap will be produced. formation is the length of yarn linking Fig 14.12: together the stitches and this is termed the Closed lap underlap, which is formed by the lateral movement of the yarns across the needles. Fig 14.8: Open lap Fig 14.13: Closed lap Fig 14.6: Guide Characteristics of warp bar movement knitted fabrics Extremely versatile in pattern effects with yarn Rigid to elastic Fig 14.9: Cannot be raveled Open lap Good air and water permeability Good crease resistance Fig 14.7: Overlapping 4) Neither overlap nor underlap and underlapping This seems to be warp float in the fabric. Good drapability The guide bars give no lateral movements Good dimensional stability Basic combination of overlap for a few courses in the repeat, laying the Good strength and underlaps warps straight in the fabric. For a multi All warp knit fabric structures are guide bar fabric, it is used to hide colour composed of both overlap and underlap: warps at the back for a colour pattern.