Md. Nasir Ullah (Industry Expert), Country Manager, Officina +39, Uttara, Dhaka, Bangladesh
Md. Saiful Islam Khan (Industry Supervisor), General Manager, Denitex Ltd (Washing), Savar, Bangladesh
Most. Setara Begum (Academic Supervisor), Assistant Professor of Wet Processing Engineering, BGMEA University of fashion & Technology, Dhaka, Bangladesh
Abstract
Textile fabric has a common feature that it shrinks in wet processing. Woven fabric shrinkage (2-4%) varies from knit shrinkage (3- 8%). Shrinkage of stretchable fabric (10-18%) is higher compared to normal woven fabrics. Shrinkage in garment dyeing or washing is always a vital issue. Many times it causes rejection and wastage. There always remains some loopholes behind any problems. In this project, we detected the root cause of this problems, analyzed and implemented a way of eradicating the loopholes. Main problem was in dyeing section where times were not maintained properly. Another loophole was not following the recipe as per provided. Here mainly the parameters were kept accordingly in each step so that measurement result could be brought in consistent level. If every steps can be done maintaining the recipe properly along with maintaining the parameters, shrinkage issue of garments can be eliminated surely and shrinkage percentage can be brought in consistent level. Maintaining the parameters accurately in relation between two consecutive processes is the main struggle here. Every processes should maintain same parameters. In this way deviation can be eradicated. This problem occurs in dyeing section (time, temperature & loading). This problem causes lots of fabrics usage. If shrinkage deviation can be brought under control, amount of fabric wastage can be reduced which will bring the company extra profit annually. That is why the problem is worth solving. This can be done by proper inspection of applying each and every parameter during every process.
Keywords: Size set process, Balloon pressure, Blanket wash, Shrinkage measurement
Introduction
Denim is very strong, stiff and hard wearing woven fabric. Denim is cotton and twill weave fabric that uses colored warp and white weft yarn and used for jeans, work clothes and casual wear. Denim is normally dyed with indigo, vat and sulpher dyes. Denim garment (Jeans) washing is known as one of the widely used finishing treatment that has vast usage in textile sectors because of creating special appearance and making fashionable and wear comfortable garments of the present day world and commonly used. Without finishing treatments, denim garment is uncomfortable to wear, due to its weaving and dyeing effects. For this it essentially needs a finishing treatment to make it softer, more supple, smooth and comfortable to wear performance.
In the readymade garments industry sector garments washing is a new technology. After making garments from solid color from dyed or pigment printed fabrics, the garments are washed by garments washing, color and outlook of the garments are modified. Due to washing, some garments shrink after wash. Unfortunately, during finishing treatments denim garments lose their dimensional stability which causes many difficulties to adjust the pattern before cutting the fabrics and to obtain fixed sizes with defined measurements. Indeed, one of the biggest quandaries of the garment’s finishing is the uncontrollable shrinkage of the clothes becoming unpredictable due to the huge variety of the fashion treatments. That’s why it needs an efficient tool to predict the fabric shrinkage occurring during finishing treatments of the garments.
There are several points in bulk production due to which shrinkage may occur in denim garments. Few of them are described in short below:
- Proper cutting allowances:
- Sewing allowance maintain:
- Unwash measurement checking:
- Balloon pressure (Hand sanding):
- Dryer:
Along with these stages there are more things where precautions can be taken easily to avoid excess shrinkage problem.
The aim of this project is to minimize and bring into constant stage the shrinkage deviation level which occurs during denim garments washing. A practical approach in denim industry has been conducted for experimenting on this issue.
2.Literature Review:
Four types of fabrics manufactured into pants were used. These fabrics differ not only by their fabric density (medium and heavy weight fabrics), but also by their composition (with and without elastane) and their structure (warp and weft yarn count, twist and density). The fabric shrinkage was measured in three parts of the treated pants (waist, hip and leg zones) according to ISO Standards 3759 (ISO 3759, 2011) and 5077 (ISO 5077,2007) for the preparation, marking and measuring of dimensional changes in textile fabrics and garments after a specified treatment such as washing, soaking in water and steaming. To obtain pertinent results, a factorial design analysis, based on an experimental design presented in Table 3, was established. The choice of these treatments (factors), as well as their levels, led us to make a complete factorial experimental design (4 × 2 × 2 × 5 × 2 × 3 × 2) with four fabric types, five washing processes, different special treatments and 960 type of experiment (Phan-Tan-Luu, 1993). This plan is repeated three times which means that 2880 experiments were conducted under industrial conditions to establish our factorial plan. The experimental shrinkage values were analyzed using “MINITAB” software to develop a model able to calculate the shrinkage ratio after finishing.
Since the fabric shrinkage is depending on its relaxation in the water which is highly related to the elimination of the warp yarns size and the bath temperature during the test, we modified the standard test ISO 6330 (2008) to measure the fabric potential shrinkage. As the warp yarns of denim fabrics can be sized with starch or soluble synthetic glues or a mixture of them, we chose to treat the fabric in a boiling bath as shown in standard ISO 6330, but with adding 2% of thermally stable α-amylase to the bath to be sure that all the glues were eliminated and the fabric was totally relaxed during the shrinkage test. This new method was tested first with two types of non-dyed denim fabrics. This study has led to a new approach to predict the fabric shrinkage in denim garments after finishing treatments with a very simplified method giving accurate results. In addition, in order to determine the level of the “fabric type” in the model, the standard procedure used to identify the fabric shrinkage in the laboratory was modified to be able to calculate the shrinkage potential that denim fabric can reach after a total relaxation. A modified standard method to ensure a total relaxation during the test was established to be able to calculate the potential shrinkage of denim fabric.
3.Experimental (Methods & Materials)
3.1 Experiment of Effect of Dryer (Temperature, Time & Loading) in Size set process:
3.1.1 Materials: Fabric- Woven denim fabric.
3.1.2 Procedure:
Initially, I had to check the shrinkage percentage nature of every roll of fabric. For that rolls were cut according to blanket measurement of (50*50) cm. Then after proper relaxation they were sent to washing section for blanket wash. There they used softener (1gpl) and run the bath for 3 minutes. Then after passing through hydro extractor they were kept for relaxation and then they were given in dryer. In dryer, rolls were loaded in three parts. Each of them were dried for same amount of time (20 minutes each) so that effect of drying doesn’t have different impact on any role of fabric. Then cooling was also done in same way with proper caution. After that, fabrics were measured after wash and calculated out the difference with the before wash measurement. According to this calculation, patterns were made and fabrics were cut maintaining the measurement.
After making garments, they were delivered for size set process. 2-3 pieces of garments from each size are given for size set process. There they apply chemicals according to developed recipe. After washing, the garments goes for drying and cooling section with same amount of time and measured every parts of garments. Here, after this part, In pilot run process, loading amount of garments were 100-120 pieces with a recipe used calculating according to the amount of garments. Input of each chemical in dye bath were done accurately and parameters like temperature and time were maintained just similar to size set process. After extracting water from garments after wash, they were again passed to the dryer for drying and cooling. The time which were maintained in size set process were maintained here in similar way. After cooling the garments were delivered to QAD room where they checked the measurements of each part of garment and matched with size set measurement. In this stage, the prime aim of measurement checking was whether there occurred any unnecessary shrinkage in any garment. Finally fabric were cut for final garments making after preparing pattern. After cutting, fabrics were sewn with proper allowance. In bulk process I tried properly to maintain the same recipe and parameters without fluctuating a single bit and processed the garments in dye bath. At last, the bulk washed garments were dried after extracting the waters from it, maintaining the same time as before. This is how the experiment of improvement was done.
3.1.3 Comparisons between Size set, Pilot run And bulk process measurement:
Table 3.1: Data of Pilot run process:
Table 3.2: Documentation of Size set process:
Table 3.3: Deviation of shrinkage in between two processes:
4.Results:
In Table-3.2, here we can see most of the parts of a garment has shrinkage. After passing through the new garments in pilot run process, still there arose shrinkage in most of the parts except the tick marked cells shown in Table-3.1.
Document from table-3.3 describes that these are the major points where corrections were needed. Sizes of garments at these points needed to adjust in next process for achieving required size of the garments. Here in this stage, by maintaining all the parameters accurately desired output can be brought.
Spirality calculation: S= (S1+S2)/2
Spirality = (S+S*L)/100
Where, S1 = right side distance of the specimen from the stitch line wash,
S2 = Left side distance of the specimen from the stitch line wash,
L= Length before wash.
5.Test Methods:
The testing method for garments size measurement in each step is mainly a manual method. QAD department is responsible for this job of measuring the accurate measurement of garments before and after wash. In case of measuring shrinkage percentage, the standard formula is,
Shrinkage % = (𝐵𝑒𝑓𝑜𝑟𝑒 𝑤𝑎𝑠ℎ 𝑚𝑒𝑎𝑠𝑢𝑟𝑒 − 𝑎𝑓𝑡 𝑠ℎ 𝑚𝑒𝑎𝑠𝑢𝑟𝑒)/ 𝐵𝑒𝑓𝑜𝑟𝑒 𝑤𝑎𝑠h
6.Discussion:
The whole improvement process is inter-related with each and every stage. Without doing every stage properly, improvement won’t be visible. According to our prime motive of this study, in each stage after maintaining all parameters accordingly, shrinkage percentage of each role of fabric will show constant result comparing with each stages. The whole process takes at least 1.5-2 months in a factory. So there are many things to be careful of. Mistake free documentation is a major issue here. After that, the project is all about bringing consistency in shrinkage deviation rather than reducing shrinkage percentage. The outcome of this project activities shows that problem of shrinkage can be minimized up to a level which will economically as well as technically bring positive effect for industries. In addition, as the total process normally takes 1.5-2 months in a factory, if the whole process can be done from starting to ending with accurate observation and maintaining follow-ups, definitely desired outcome will be visible.
Following parameters and adjusting measurements according to those documentations are significantly important for achieving improved state of shrinkage deviation. If the improvement experiment can be done on a specific lot from starting to ending with proper care, definitely the deviation level will be visible in a constant state.
7.Conclusion:
Shrinkage problem is a common and very much expected problem in our industry. The project is all about bringing consistency in shrinkage deviation rather than reducing shrinkage percentage. The outcome of this project activities shows that problem of shrinkage can be minimized up to a level which will economically as well as technically bring positive effect for industries.