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2 Weft-knitted plain knitting technology and machinery […]
2 Weft-knitted plain knitting technology and machinery
Weft-knitting flat knitting technology and machinery mainly involve latch needle flat knitting machines and crochet knitting machines. The latter has basically faded out of the market due to the complex movement of the loop-forming parts, the huge machine and the high cost. The flat knitting machine still occupies a unique position and a certain share in weft knitting because it can knit forming garment pieces and knit and wear products. In recent years, with the development of knitted garments and fabrics in the direction of lighter and thinner, the number of flat knitting machines has also been continuously improved. At present, the highest has reached E 18, which is equivalent to the level of medium-sized circular knitting machines. The machine number has also been increased from E 12 to E 14, and some new technologies and equipment have appeared.
2.1 Fast retracting needle forming technology
In order to facilitate the forming and knitting of double-sided fabrics (ribbing, border knitting, etc.), Stoll introduced a four-needle bed computerized flat knitting machine a few years ago. Above the two knitting needle beds, the machine adds two auxiliary needle beds that are only used for transfer. The transfer plates are installed on them instead of knitting needles. The auxiliary needle beds can also be moved horizontally and combined with the main needle bed. The knitting needles cooperate with the transfer, that is, when needed, the stitches are received from the knitting needles or the held loops are returned to the knitting needles, so as to complete the retracting and unwinding needles of the double-sided fabric.
2.2 Multifunctional knitting and piercing computerized flat knitting machine
Recently, a computerized flat knitting machine with multiple functions such as variable stitch length, four-needle bed, knitting and threading has integrated several previous single technologies on a single machine, thus expanding the types of knitable structures and garments. For example: the variable stitch length technology can make a piece of clothing or different parts of a piece of clothing form two different stitch length (transverse density) effects; the four-needle bed technology can realize the rapid retracting and releasing needle forming of various double-sided fabrics. And a uniform and good appearance structure is formed at the retracting needle part; the knit and wear technology can complete the overall knitting of a garment at a time, which not only saves raw materials, shortens the process, but also improves the product quality.
2.3 Resting weaving technology
In order to knit a three-dimensional fabric on a flat knitting machine, some knitting needles holding loops should be temporarily stopped, and then re-enter knitting when necessary. This is called a rest knitting or partial knitting method. On the computerized flat knitting machine, the knitting can be stopped easily by selecting the needle. Some domestic manufacturers of hand-cranked flat knitting machines have also realized this function through the improvement and special design of the triangular structure. With the use of the inactive knitting triangle, partial knitting and knitting of the holding and retracting needles can be performed on the hand-cranked flat knitting machine to form special structures such as three-dimensional structures and fancy effects.
3 Warp knitting technology and machinery
3.1 Wire rope guide bar traverse mechanism
The horizontal movement of the bar of the early warp knitting machine was controlled by the pattern chain block, and the chain block had to be rearranged to change the pattern. About 20 years ago, the warp knitting machines of multi-bar Raschel and other models began to adopt the electronic bar traverse mechanism, which improved the ability and production capacity of warp knitting machines to form patterns.
The yarn guide needle 1 is connected to the steel wire rope 2 to form a yarn guide bar, and the yarn guide needles on the yarn guide bar can be interchanged. The wire rope guide bar penetrates into the yarn guide bracket, and up to 8 wire rope guide bars can be introduced. Each wire rope is driven by a servo motor 3 controlled by a computer program to move horizontally, and is reset by an air compression spring 4. Compared with the previous bar traverse mechanism, the wire rope guide bar traverse mechanism has the following advantages:
1) Compact structure, less space occupied, which is conducive to the configuration of more pattern bars; 2) The maximum stroke of the bar traverse can reach 180 mm, and the cumulative traverse stitch length can be increased from 47 needles of the original SU mechanism to 170 needles. 3) The mass of the wire rope guide bar is only 100 ~ 350 g, thereby reducing the transverse inertia; 4) The free programming of the bar transverse movement can be carried out through the computer pattern preparation system, and the yarn guide Needle positioning is accurate; 5) It reduces the adjustment time on the machine and is easy to maintain.
3.2 Piezoelectric Jacquard yarn guide technology
Piezoelectric ceramic sheets are attached to both sides of each jacquard yarn guide needle, and the jacquard yarn guide element is formed by separating them by a glass fiber layer. When the piezoelectric ceramics on both sides add positive and negative voltage signals controlled by the computer program, they will bend and deform, causing the jacquard yarn guide needle to shift to the left or right. There are positioning blocks on the left and right sides of the jacquard yarn guide needle, so as to ensure accurate spacing. According to the machine number of the jacquard warp knitting machine, piezoelectric jacquard elements can be combined into piezoelectric jacquard yarn guide blocks with different pitches, which are then assembled into a jacquard bar. Piezoelectric jacquard yarn guide technology has completely changed the characteristics of complicated parts such as harnesses, shift needles, etc. required by the jacquard device, greatly simplifying the jacquard part of the jacquard warp knitting machine and greatly improving the speed. Moreover, in conjunction with the computer-aided pattern design system, it can speed up the design of jacquard warp knitted fabrics, simplify the machine process, and shorten the product update cycle.