Last updated on September 9th, 2023 at 11:26 pm
Working Principal of Winch Dyeing Machine
This is one kind old dyeing machine for fabrics in rope form with stationary liquor and moving material system. The machine is operated at a maximum temperature of 950 – 1000 C for open bath winch but for closed winch, the machine operates at a maximum temperature of 1300 – 1600 C. The liquor ratio is generally quite high (1:20 – 1:40) for open bath winch and for closed or high temperature winch the liquor ratio is 1:8 to 1:10.
The system includes a vat with a front slant side acting as chute for the folded rope, while the rear side is entirely stay vertical. A perforated separating material, positioned at a distance of 15-30 cm from its vertical side, creates an interspace for heating and also for giving reagents. Heating is supplied by means of direct or indirect steam heating. The motion of fabric is driven by a circular elliptic winch coated with a special blanket to avoid the fabric slipping during the dyeing operation with subsequent possible fabric scratches.
The rope to be dyed then passes through a rack on the vertical perforated divider, which ensures the separation of the various folds of the rope and avoids possible entangling; the rope is then transferred onto the cylinder, which guided the fabric during the lifting from the vat carrying out a partial squeezing with subsequent liquor exchange. The rope (carried by the winch) folds while passing through the liquor. Surely when the fabric will be loaded into the machine it is necessary to sew the tail with the head of the rope (the fabric must be sewn according to the grain line or direction).
The maximum motion speed of the fabric must be approximately 35m/min to 40 m/min, as higher speeds could cause peeling; an excessive rope beating with subsequent entanglement. The fabric must not be folded and kept stationary inside the vat for more than two and half minutes to avoid possible defects or wrinkles; therefore the rope must be relatively short.
The winch dyeing method is preferable for all fabrics (especially for knit and light weight woven fabrics), except those which tend to originate permanent creases or which could easily distort under the winch stretching action (due to their fibre or structure composition).
This machine is mostly used for pre-dyeing treatments (scouring, washing, bleaching) since the high liquor ratio ensures excellent results; when used for dyeing treatments this system requires high energy consumption, extensive use of auxiliaries, dyes and water, which leads to high operating costs; furthermore, an inaccurate temperature control (the liquor does not move and the heating system is assembled only on one end) and the limited freedom of the rope folds could negatively affect the dyeing results.
This is one of the oldest systems used for finishing treatments, but it proves to be still extremely functional thanks to its flexibility in its use, above all for scouring and bleaching treatments to be carried out on small production runs. This is the system which can also be used for carrying out continuous washing processes; the fabric is loaded from one side, driven through the machine with a spiral motion (by means of the rack) and then unloaded from the opposite side.
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