Introduction:
As a general, and maybe provocative statement it can be argued that the dyeing and finishing industry does not have a good reputation for quality and reliability. There is a mentality perhaps based on tradition that accepts that rework is part of our normal day-to-day practice. RFT dyeing means “Right First Time Dyeing.” This term is used to define the dyeing efficiency, if the efficiency is more than the dyeing capability of that company is very good otherwise not good. This term actually defines how we can dye a fabric. If we can complete our dyeing at first time then we can say that this is RFT dyeing but if we cannot than we say that this is not RFT dyeing. So we can say that “If the dyeing process is completed properly without any fault & there is no need to put the dyed fabric into the bath to get the proper shade then this dyeing is called RFT dyeing".

Objects of RFT dyeing:
  •      Increase productivity: The productivity of a company can be increased if the RFT efficiency increased.
  •      Reduce time consumption: If the dyeing completes in first time then it will take less time than the 2nd time dyeing.
  •      Increase profit: If the productivity increases then the profit will be increased too.
  • Less fabric wastage: If the dyed fabric put 2nd time in a bath then there is a possibility to damage the fabric. So in a RFT dyeing this possibility is reduced.
  •  Reduce cost: If the dyed fabric dyeing 2nd time then we needs extra dyes & chemicals. In RFT dyeing we do not need this, so cost will be reduced.

Technologies Require in RFT Dyeing:
Ø  Automation in dyeing house.
§  Automatic Dossing system.
§  Heat control unit.
§  Environment control unit.
Ø  Dyes and chemicals.
§  Tested dyes and chemicals.
§  Chemicals used from single or same lot.
Ø  Skill worker.
Problems Related to achieve RFT dyeing in Bangladesh:
Ø  Lack of Automation technology in dyeing house.
Ø  Conventional machine.
Ø  Lack of skill worker.
Ø  Investment issue.
Ø  Poor quality dyes and chemicals.



Benefits of RFT dyeing
Modern dyehouses now require the dyestuffs that they purchase to be compatible in terms of dyeing rate and dye uptake and to provide uniformly high levels of colour fastness to washing, light, and wet and dry rubbing (crock fastness), as well as to bleach-activated detergents. The ability of a trichromat to build up on tone is an important factor in many difficult shades where high RFT dyeing levels are the norm. In this connection most reputable dye manufacturers now offer advanced trichromats that have been carefully selected and engineered to provide high reproducibility within the laboratory, as well as between laboratory and bulk dyeing, and high repeatability in repeat batches of the same colour. Dyestuff ranges have been refined, with different trichromats for different end uses, or different depths of shade, or particular areas of the colour gamut. 

The advances that have been made in sophisticated spectrophotometers for accurate colour measurement of dyed yarns and fabrics have been potent factors in accurate database preparation.  Recipe prediction is now very rapid, with alternatives been presented for evaluation. For example, the most cost-effective recipe combination, highest colour fastness to washing or to light, the technically best recipe, the least metameric combination, etc. The ability to measure colour differences accurately and to predict a recipe for correction purposes where RFT dyeing has not succeeded is also important in minimising processing times and costs.

RFT dyeing avoids the extra costs associated with correction of faulty dyeing but also promotes other benefits. Shorter processing times in RFT dyeing procedures result in less fibre degradation and improved product quality after dyeing. This can be important if chemical finishing treatments such as chemical cross-linking finishes are to be applied on cellulosic and cellulosic blend fabrics. RFT dyeing ensures higher levels of machine productivity and dyeing capacity, coupled with improved production planning and less capital expenditure on processing equipment.

RFT dyeing also economises on the costs of chemicals and auxiliaries used in dyeing. Many dye makers now offer complete dyeing packages in which the dyestuffs, chemicals and auxiliaries have been specifically selected to provide optimum level dyeing performance. Many dyehouses, however, will persist in using cheaper textile auxiliary products which often are less effective when used with the same dyestuffs and typically are less concentrated in terms of their active chemical constituents.  As a result the RFT dyeing performance is impaired. Inferior RFT dyeing performance using cheaper auxiliaries will thus turn out to be the more expensive option for the dyehouse in the long run.

RFT dyeing is usually more easily accomplished where all aspects of the bulk dyeing process are standardised and automated. Thus in exhaust dyeing the processes of filling the machine to the appropriate liquor ratio, controlling the rate of temperature rise and liquor circulation, maintaining top temperature for the requisite period of time, cooling back and draining must be reproducible and accurate measurement of temperature and pH must be carried out by appropriate monitoring and control equipment. Modern advanced dye cycle controllers are robust, easy to program and ensure high levels of reproducibility. 


RFT Dyeing requires :
1. Standardization:
The key to success is standardization of all aspects of the dyeing process, with appropriate methods to bring non-standard conditions within the standardization tolerance limits. Firstly, it is important to ensure the dyestuffs to be used are supplied from well-established suppliers who can control their dyestuff quality to pre-agreed tolerance values. This factor assumes even greater importance where the colour tolerance values of the end product must be within tight tolerance values e.g. automotive end uses.

In addition, the storage conditions for the dyestuffs in the dye store must be controlled to ensure that excess moisture is not absorbed by the top layer of dyestuffs in the drum or container. This can have serious consequences where small quantities of dyestuff are weighed out for pale shades, because these can be difficult to correct and level with very small additions of dyestuffs. It is better to pay more for a standardised dyestuff supplied to agreed close tolerance levels if high RFT performance levels are required. High RFT performance levels are essential for survival in this age of global competition. The adverse effects of poor dyestuff standardisation are all too soon to be seen in poor 

RFT dyeing performance, higher levels of additions, increased processing costs and decreased machine productivity.

2. Dyehouse laboratory:
A major factor contributing to the successful implementation of RFT dyeing is a well-organized and equipped dyehouse laboratory with appropriately trained laboratory staff. Laboratory dyeing of high accuracy are required for the evaluation of dyestuffs, for database preparation for computer colour matching, and for general colour matching. In this connection, the accurate preparation of stock solutions or dispersions of dyestuffs, chemicals and auxiliary products has been greatly aided by laboratory equipment specifically engineered for this purpose, together with the use of electronic dispensing pipettes for dyebath preparation.

Where the textile material to be dyed has been prepared and dried by standard operating procedures, then a consistent substrate quality is likely to be obtained for dyeing. However, variation in fibre dyeability and in the moisture content of the material can create difficulties in subsequent bulk dyeing. These are particularly likely to become apparent where natural fibres such as cotton, wool, silk and linen and their blends with other fibres are to be dyed, and where such yarns and fabrics have been prepared by other organizations. The acceptable variability in dyehouse factors have been tabulated by Park and Shore (Table below) and if variations outside these limits are being regularly observed, the level of RFT dyeing will fall.

Where laboratory dyeing machines are used, it is important that these simulate the bulk dyeing conditions on commercial dyeing machinery. Thus, the same water source should be used for both laboratory and commercial scale dyeing machines, and the liquor ratio should be the same and appropriate for the particular yarn, fabric or blend to be dyed.


Conclusion:

Although the concept of RFT was never the subject of formalized major R&D projects, it evolved through the foresight, determination, and ultimate success of a relatively few organizations over a considerable span of time in the dye- and machinery-making and - using industries. The author hopes this chapter will lead textile researchers and process engineers to develop additional quality control methodologies in the future, in addition to the ones suggested here.