Dyeing Process by Jigger Dyeing Machine with limitation

Dyeing Process 

The dyeing process on jigger is regarded as a series of intermittent padding operation followed by dwelling periods on the main roller , during which the dyeing action and diffusion takes place.

In the dyeing on jigger machines the cloth revolves on two main rollers , The open-width fabric passes from one roller through the dye bath at the bottom of the machine and then onto a driven take-up roller on the other side. When all the fabric has passed through the bath, the direction is reversed. Each passage is called an end. Dyeing always involves an even number of ends. The dye bath has one or more guide rollers , around which the cloth travels , and during this immersion achieves the desired contact with the dye liquor. During this passage the fabric picks up adequate quantity of dye liquor , excess of which is drained out but still a good quantity is held in the fabric . During rotation of rollers this dye penetrates and diffuse into the fabric. The real dyeing takes place not in the dye liquor but when the cloth is on the rollers, since only a very small length of fabric is in the dyebath and major part is on the rollers . Therefore the speed of cloth during immersion in dye liquor has a very little effect on percentage of shade produced.

Some critical problems related to the conventional jigger dyeing machines ( which are minimized in the modern day machines) The major problems are side-to-centre color variations, called listing, and lengthways color variations, called ending.

The factors controlling the rate of dye absorption are

1. The amount of interstitial dye liquor retained in the interstices of the fabric weaves.
2. The exhaustion of the interstitial liquor in the dwell period between successive immersions.
3. The degree of interchange of liquor during one immersion (interchange factor).

Problems of Jigger dyeing

• Temperature control from side-to-side and end-to-end of the roll
• Tension control from end-to-end
• Constant speed control from end-to-end
• Prevention of creases
• Prevention of air

Limitations of Jigger Dyeing

1.     Jigs exert considerable lengthwise tension on the fabric and are more suitable for the dyeing of woven than knitted fabrics.

2.     In textile preparation due to the swelling and dissolution of size, which makes the fabric slippery and unstable in roll form.

3.     The low liquor ratio makes washing-off difficult.

4.     There is little mechanical action in a jig machine and it is less suitable where vigorous scouring is required before dyeing.

5.     Moiré effects or water marks may arise on some acetate and nylon fabrics because of pressure flattening the structure of the rolled fabric.

JIGGER DYEING MACHINE

Jigger dyeing machine is one of the oldest dyeing machines used for cloth dyeing operations. Jigger machine is suitable for dyeing of woven fabrics, up to boiling temperature without any creasing. Jigs exert considerable lengthwise tension on the fabric and are more suitable for the dyeing of woven than knitted fabrics. Since the fabric is handled in open-width, a jig is very suitable for fabrics which crease when dyed in rope form.

Some wovens are conveniently dyed on jigger are:
a. Taffettas
b.Plain wovens
c.Satins
d.Poplins
e.Ducks
f.Suiting and Shirting material.
g.Sheetings etc.

But have limited application on fabrics which are tension sensitive such as crepes , flat crepes, knits , net fabrics and elastomeric warps etc.

Machine Description

The jigger machines have two main rollers which revolve on smooth bearings and are attached to with a suitable driving mechanism, which can be reversed when required. The fabric is wound on one of the main rollers and fed from the other. The fabric move from one roller to the other through the dye liquor trough located at the lower part of the machine. There are various arrangement of guide rollers at the bottom of liquor trough and during each passage the cloth passes around these guide rollers .

The concentrated dye liquor is usually introduced directly into the dye bath in two equal portions, which are added just before commencing the first and second ends. The liquor is agitated by the movement of the fabric through the dye bath. Several horizontal spray pipes are fitted across the full width of the trough in order to expedite fabric rinsing.

Live steam injected into the bottom of the trough through a perforated pipe across the width of the jig heats the liquor. Some modern jigs also have heat exchangers for indirect heating.

Covering the top of the jig minimizes the heat loss to the atmosphere, keeps the temperature uniform on all parts of the fabric and minimizes exposure of the liquor and the cloth to air. Minimizing exposure to air is important when using sulphur or vat dyes since these dyes can be oxidized by atmospheric oxygen.

A few meters of leading fabric, similar in construction to the cloth under process, is stitched to each end of the cloth batch , to allow the entire length of the fabric to pass through the dye bath during the dyeing process. When jig processing is completed, the fabric is run onto an A-frame via a nip or suction device to remove extraneous water during unloading.

Modern machines such as automatic and jumbo jiggers have full automation in drive , tension regulation and control , fabric speed and metering, smooth and jerk less stop and start , counters for number of turns , gradual and noiseless reversal, automatic temperature regulation and control etc.