Padding mangle

Dyeing on Jigger or Winch machine is a batch-wise process e easy where only a small lot can be dyed at a time. Where huge quantities of cloth are to be dyed in light or medium shades, in a continuous manner, padding mangles re best suited for the my in purpose. It is an important machine for producing dyeing cheaper than those produced on Jigger or Winch machine and it can process up to 200 m of cloth per minute
The padding mangle essentially consists of a small trough containing the liquor and a set of squeezing bowls. "The cloth is passed in full width through the liquor in the trough and the excess solution is removed by passing it through the squeezing bowls; thus, the mangle effects impregnation of the liquor and squeezes out excess liquor. A great advantage of the padding mangle is that the m:l ratio used is perhaps the lowest so that there is saving in the consumption of water, steam and chemicals.

Two-bowl Padding Mangle 

two bowl padding mangle

This is the simplest padding mangle which consists essentially of two squeezing bowls, the upper one of iron covered with rubber and the lower one of brass or vulcanite: the bowls are arranged over a shallow a trough with 2 or 3 guide rollers. Pressure on the bowls is exerted by a system of weights and compound levers (even though hydraulic pressure system gives better and more even squeezing) because it is less complicated and there is no danger of leaking valves and pumps. The cloth enters the trough along the guide rollers passes through the dye liquor and is uniformly squeezed between the bowls and is wound on a roller or passed directly for subsequent operations The passage of cloth through the dye-liquor is term the and its passage through the squeezing bowls is termed the nip. It is used either to perform an important part of the dyeing is  operation e.g. in pigment padding of vat dyes or dyeing of reactive  dyes by pad-batch method or padding of cloth with naphthol solution or for carrying out the dyeing operation itself one is The liquor left on the cloth after padding is measured in terms of percent expression'. Percent Expression
percent expression"
This term is used in relation to padding mangles only. The  amount of liquor left in the cloth after padding is measured in  terms of percent expression
.Thus, if a batch of cloth weighing mangle 50 kg is padded with an expression of 80 %, it means that - 40 kg  ( or 40 liters ) of the liquor ( 80 % of 50 ) is left on the cloth ( or is retained by the cloth) after padding and the cloth will thus weigh 50 + 40 = 90 kg of the percent expression is 100 % it means that 50 kg of the liquor will be left on the cloth after padding i.e. more than what was left earlier? Thus if more liquor is squeezed out by increasing the pressure on the squeezing bowls, it will leave a lesser quantity of liquor on the cloth i.e. the percent expression will be lower Usually the percent expression varies from 60 to 80
The rate at winch the fabric takes up the liquor should be uniform and the trough should be replenished from time  to time maintain the liquor level constant as otherwise the take up decrease resulting in tailing effect. When the fabric has a high affinity for the dye. the feeding Liquor should he of high concentration than the starting batch as otherwise the straight of the padding, liquor will be decreasing  weaker dying

Therefore, dyes having low affinity such as those used in pigment padding process or pad-batch processes are suitable for padding At the end of the padding operation, the liquor left in the padding mangle has to be thrown out and is thus wasted. Therefore, it is not economical to use a small quantity of cloth for padding: the trough of the mangle should be as small as possible

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