How to produce superior warp-knitted shoe upper fabric?

The warp-knitted shoes upper fabric, or the air-mesh jacquard patterned fabric, which is made from jacquard double-needle bars warp knitting machines such as RDJ5/1, RDJ6/1, RDJ7/1, and RDJ6/2, is a high-end warp-knitted fabric used in the shoe upper fabric sector.

How to create a jacquard patterned shoe upper fabric from design sketches to its final produc is a topic deserving a deep research. A-ZEN academy presents the complete process and crucial know-how from years of experience in this article, ranging from the warping process to the final finished fabric quality test work. 

We’re hoping more customers will make a great success from their double-needle bar jacquard warp knitting machines.

1, Strict requirement for shoe upper fabrics

To produce a high-end shoe upper fabric, the producer has to give different quality aspects tests, for example, the elongation at break of yarn must arrive 30%, fabric’s quality-assured after 200,000 times folding, the net distance kept within 3-5mm, and many more.

These are the prerequisite to make sure the debonding occur during walking or running.

Warp knitting structure differs from others in its strong stability, unlike weft knit machines, the great majority of warp knitting machines are rectilinear, i.e., straight needle bed, not circular. thus they are fed from warp beams and make fabric that is knitted and collected in open width, not tubular form. 

2, the process from knitting to finishing

2.1 Well Begun is Half Done

The whole process starts from a subtle but vital step: warping (yarn warpped from creel to beams, see direct warping machine AZ118L, mono yarn warping from the split warping machine AZF328) . There is a research shows that 80% of knitted fabric default problems caused during the warping process, so a good warping is crucial for all warp knitting machine users.

The key points in the warping machine process are the yarn tension control, beams length or rounds deviation, full set beams quality consistent, and avoid of yarn break.

AZ118L direct warping machine equipped with a camera system, copy functions, turn-able cone creel, yarn-drop detector, and PLC-controlled tension rollers. With these functions applied, accurate tension and turns of yarn warped in beams, besides, each beam stays in the same quality as the first beam of the pair, because of this, the beam set could give the same stable yarn tension. 

Warping Machine Running Video: 

2.2 Double-Needle Bar Warp Knitting Process

Double-needle bar raschel warp knitting machine with the piezo jacquard system is for producing jacquard-patterned shoe upper fabric, such as RDJ5/1, RDJ6/1, and RDJ7/1 model. The designer creates shoe upper designs from the software, for example, wkcad, and EAT DesignScope program. 

The simulation demonstrates a quite animated shoe upper image as well as real shoe super size.

After adjusting needle elements as well as threading, the operator could start the knitting work.

To achieve more creative and various patterns, the producer could choose an individual standing creel for the jacquard cones, and thanks to that, the producer is capable of creating different fabric developments to respond to the market and lead the market. 

The production of RDJ shoe upper fabric could reach 25 meters/hour, with daily production of around 3,000 pairs of shoe upper fabric.

2.3 Finishing Process: Dyeing, Washing, Heating, Setting, Laser Cutting, and Testing

After delivering the greige warp-knitted fabrics to the dyeing and finishing factory, the first work is to calculate and adjust the proportioning of dye material. Besides that, the color mixing work shall also start. After the above two steps are done, the greige fabrics shall be put in the dye vat which temperature set at 130 ℃ for 2- 8 hours.

High-Temperature Steam 

The next step is the washing, heating process, and high-temperature setting process, during which the temperature shall be set at 170 ℃. The last process is laser cutting.

Furthermore, all fabrics shall start the quality test process, which includes a five-day aging test under 95% humility and 75℃ working condition, and a simulated experiment also required to test the yarn structure fastness quality. Any cracked fabric, the color is yellow, or yarn break during the simulated experiment occurs, the fabrics will be discarded, and a start-over process is required.

3, About Double-needle Bar Raschel Jacquard Warp Knitting Machine

Double-needle bar raschel jacquard warp knitting machine is for producing jacquard-patterned shoe upper fabric, the most popular machine models are RDJ5/1, RDJ6/1, RDJ7/1, and RDJ6/2, among which RDJ5/1, RDJ6/1 and RDJ7/1 are mainly produce air-mesh spacer fabric.

The working width of the jacquard double-needle bar warp knitting machine is 138”, with gauges E22 and E24. The knock-over comb bar distance ranges from 1-12mm. The production speed could reach 550rpm.

A-ZEN RDJ6/1 Warp Knitting Machine Factory Production Video: 

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