1. Introduction and Literature Review
In Bangladesh economy, RMG sector plays a vital role. From the last decade, RMG sector becomes popular in Bangladesh and it contributes to the national economy in considerable rate. It is necessary to focus on quality control of garment industry    . Cho & Kang (2001) showed that quality control in the garment industry is a big challenge for existing and it maintained from the initial stage to the stage of final finished garment  . In this industry, product quality can be calculated by different kind of scale. These are quality and standard of fibers, fabric construction, yarn, surface designs, color fastness and the final finished garment products  . Number of defected occurrence and percentage of defected product are very common way to calculate product quality.
This research has shown that the major departments of a garment manufacturing industry are cutting section, sewing section, finishing section. After finishing of the cutting operation garments components, all the garments parts are joined and sewn as sequentially. In this research, defects of sewing operations for ladies’ tops and trousers are discussed. Rahman & Amin and Talapatra & Rahman (2016) have mentioned that defect is the common term in the garment industry. Defect is the loss of time, cost and raw material   . So, it is a burning question for manufacturer about how to reduce defects. This research has used DMAIC methodology to reduce defects of RMG that is used which is a problem solving of Six Sigma. The Six Sigma is a philosophy that is used to reduce defects. Nupur, Gandhi, Solanki & Jha (2018) implemented six sigma in cutting process of apparel industry where (DMAIC) approach has been followed to solve the underlying problem of reducing defects and improving sigma level through continuous improvement process  . Nagi & Altaraz (2017) also used six sigma DMAIC approach to implement lean tools and facilities layout techniques to reduce the occurrence of different types of nonconformities in the carpeting process  .
The DMAIC method follows a conductive five-step: Define, Measure, Analyze, Improve and Control necessary to obtain reliable results. According to Brundage, Kulvatunyou, Ademujimi & Rakshith (2017), the DMAIC approach of Six Sigma works as a filter to pass from a complex problem with many uncontrolled variables to a situation where quality is controlled  .
This research has identified all the defects in the sewing department of FCI (BD) LTD and applies DMAIC methodology to reduce the defects and this analysis is arranged by research methodology in Section 2 by the following steps: Define, Measure, Analyze, Improve and Control Phase and Conclusion is in Section 3.
2. Research Methodology
For garment item, i.e. ladies’ tops and trousers, data sheets were collected for the length of one month (January). The end line quality inspectors provided the data sheets from their record books from the production lines of the sewing section of FCI (BD) LTD when we visited the garments factory. 15,472 ladies’ tops and trousers were examined and we found 1806 defective pieces. Our main purpose was to identify the top most defects, the root cause of the defects, give some suggestions to reduce the percent of defects and improve sigma level. DMAIC methodology is used for this purpose. It can be illustrated with the following.
Define: problem selection and benefit analysis. Identifying and mapping relevant processes, identifying stakeholders, prioritizing customer needs & making a business case for the project.
Measure: translation of the problem into a measurable form, and measurement of the current situation.
Analyze: identification of influence factors and causes, identifying potential influence factors & selecting the vital few influence factors.
Improve: design and implementation of adjustments to the process to improve the performance & conduct pilot test of improvement actions.
Control: empirical verification of the project’s results and adjustment of the process management and control system in order that improvements are sustainable, the new process capability & implement control plans.
2.1. Define Phase
The purpose of this phase is to make the defects clear and define the problems. The goal of the project also should be defined very well through this phase and finally here come the processes. Before works begin we must know about all relevant elements of a process improvement. SIPOC (suppliers, inputs, process, outputs, and customers) diagram is the tool to show the process map about this information  .
Rahman & Amin (2016) identified the problem statement in apparel industries quality is achieved when the defects of the products are decreased  . The manufacturers are trying to reduce defects. In Bangladesh garment factory face high rate of rejections due to defects. For this reason they can’t meet quality standards. This also increases the number of rework, scrap cost, delay of delivery due to rework  .
The ultimate goal is to minimize the percentage of defects which results in minimize the production cost, improve quality, reduce wastes and enhance sigma level. SIPOC is the quality of a process that is evaluated by the output of the process. Table 1 shows the SIPOC flow of the FCI (BD) LTD.
Table 1. SIPOC diagram for ladies’ tops & trousers.
2.2. Measure Phase
Some of the products are executive ladies’ tops and trousers are inspected for defects since this was the critical product for the company as they had lot of demand and the profit margin for these particular products are high. Here the percent of defectives is found 10.30. Defect per opportunity (DPO) is 0.1167 and defect per million opportunities is 116,727. The sigma level is 2.69. Table 2 shows the outcome.
2.3. Analyze Phase
The main goal of the analyze phase is to go through the data to find out the top most defects which are reoccurring as well as the root causes of the problems and seek improvement opportunities. The percentage of defects occurrence has been integrated in Table 3 and also shown in Figure 1.
Brainstorming: It is one of the major problem solving tools. The purpose of this step is to identify, validate and select the root cause for removal. We have analyzed the causes of those defects and constructed Cause-Effect diagrams which are shown in Figure 2.
Table 2. Calculation of DPMO & six sigma.
Table 3. Details of percentage defects occurrence.
Figure 1. Pareto chart for defects.
Figure 2. Cause-Effect diagram for all defects due to machine & process.
2.4. Improve Phase
The purpose of this step is to identify, test and implement a solution to the problems in part or in whole. Root causes of different types of defects have been identified and the solutions of these causes have been provided that is shown in this Table 4.
2.5. Control Phase
It is possible to reduce by management of an industry the overall occurrence frequency by following some preventive ways by finding out the actual reasons.
Table 4. List of potential root causes and their solutions.
Table 5. Defects after implementation of DMAIC.
Table 6. Total defectives in ladies’ tops and trousers after inspection.
Table 7. Calculation of DPMO & Six Sigma (after implementation of DMAIC).
In this research, one preventive way awareness is used to investigate the result of frequency of defective occurrences. For this purpose awareness has been raised among all the employees, operators even among all the stakeholders of an industry. This awareness is based on how occurrences create and what are the responsibilities on them to minimize the daily percentage of occurrences. Thomas, Barton & Chuke-Okafor (2008), De Mast (2004), George & George (2003), Hahn, Hill, Hoerl & Zinkgraf (1999), Husband & Mandal (1999), Munna, Rahman & Roney (2015), Jostes & Helms (1994) have used different lean tools i.e., 5S implementation, value stream mapping (VSM), systems redesign, application of TPM to control the occurrences frequency  -  . This research has tried to implement the safety awareness that involves: 1) awareness in setting the needle with the machine 2) awareness in gripping the fabrics for long stitch (more than 10 cm) 3) awareness by showing the video of standard operation for the unskilled operator and 4) awareness among the management to provide the automated machine rather than manually operated machine and observed for 10 days in line no. 17 for the defect of skip stitch, uneven stitch and broken stitch and finally this research has found that the daily defect percentage has decreased day by day after creating the awareness that is showed in the following Figure 3 and this results in one of the solution to enhance productivity.
The aim of this research is to reduce the defect of products and to improve quality. To minimize the defects of garment products DMAIC methodology has been used. In this method, at first problems were identified. We have been focused on sewing section and found out sewing defects. Pareto chart is used to show sewing defects for experimental lot. The percentage of defects from total product is also calculated. Define phase shows that defected piece is 1806 in 15,472 pieces. The percentage of defect was 11.67%. The range is not in tolerable range. For given solution, control phase shows that defect percentage is reduced to 9.72%. To justify the given solution, sigma level is used. In the past, sigma level was 2.69. After Improve phase, it has been upgraded to 2.8. This research has focused some preventive solutions from other researches and also showed that creation of awareness among the stakeholders of a garments industry has decreased the occurrences in a sewing line day by day. This will create a positive effect on the management and will also help to minimize the defective percentage (%) in a
Figure 3. Observation of defective percentage (%) control.
sewing line of a garment industry. The limitations of this study are that: it was concentrated only on one garment industry and only for sewing section, and only one sewing line was focused, and calculation had been done for two products. But the significance of this research is that this study can help in minimizing the other sections in garments industry. Other researchers can also use this procedure to reduce defect rate in other manufacturing industries. Finally, reduction of defect rate improves quality and apparently, improvement of quality will give a positive impact in RMG sector.