Dyeing unit

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Generally, most carpets are dyed after tufting yet sometimes the yarns are dyed first. The methods include putting 500-1,000 pounds (227-455 kg) of fiber into pressurized vats through which treated dyes are circulated, or passing the fiber continuously through the bath, or passing skeins of yarn through the vat of dye.

the yarn can also be put on forms, and the heated dyes can then be forced under pressure from inside the forms to colored the yarn. 
Another method passes the yarn through printing rollers, while yet another involves knitting the yarn onto a form that is then printed with dyes before the yarn is unraveled. All yarn that has been dyed is then steamed, washed, and dried.