In fact, the most important part of active digital printing of knitted fabric is not in printing, but in preshrinking. If we do this well, it will be relatively easy.
Compared with shuttle weaving, knitted fabric is more loose, fabric is easy to deform and skew, and there are often more and more serious skew printing, or fabric width is smaller and smaller, which causes serious quality problems. Loose fabric characteristics create a unique style for knitted fabric, but increase the difficulty in fabric processing.
The key to the pretreatment of knitted fabric with active digital printing is to make the fabric as close to the woven fabric as possible. How to calculate the pre-treatment in place?
There are several steps from the purchase of knitted fabrics from the fabric company to the real printing: through opening - > bleaching - > preshrinking - > sizing.
When you buy knitted fabric, the fabric is barrel shaped, and you need to open the fabric with a slitting machine. When cutting cloth, 24-hour loose cloth shall be placed. In this process, the burr on both sides shall be combed while cutting.
Bleaching refers to the physical and chemical reactions of some magazines on knitted fabric under the action of temperature and compound, and all or part of them are removed.
Next is a key step, preshrinking. Compared with woven fabric, digital printing of active knitted fabric is especially important in this step. At this time, we should pay attention to the control of gram weight, sizing and finalization of both sides of the burr should be flattened, so that printing is not easy to wipe the nozzle. Knitted fabric is really difficult to control, especially cotton, human cotton, but also to consider fabric moisture, gram weight will increase a lot.
Generally, shrinkage effect is required to be less than 3% in both warp and weft directions. In addition to obtaining stable overall dimensions, preshrinking can also improve the hand feel and eye feel of the fabric, so that the fabric can meet certain weight and stiffness requirements.
Especially for the fabrics of cellulose fibers such as cotton, hemp, silk and viscose, these fibers are easy to swell and shorten the fiber length, which will affect the dimensional stability of the fabrics and their blends. Preshrinking is a key and difficult part in digital printing of knitted fabric.