Abstract: This research analyzes how Lean Six Sigma techniques might be utilized in the production of green clothing, with a particular focus on eliminating waste and production process improvement. The eight categories of waste that are summed up as “DOWNTIME” (defects, overproduction, waiting, not utilized talent, transportation, inventory, motion, and extra-processing) are identified and eliminated as an essential part of lean management. The data-driven DMAIC (define, measure, analyze, improve, control) approach is used by Six Sigma to enhance process efficiency and quality. The research investigates significant factors like Standard Minute Value (SMV), production output, labor requirements, defect rates, and line efficiency to compare traditional versus lean sewing lines to produce full-sleeve t-shirts. The outputs show that the lean line reduces SMV by 13.16%, increases monthly production by 1,664 pieces, and requires 21 people instead of 23. The overall quality of the product is also improved by a large drop in defect rates, which include rework, spots, and rejections. Additionally, the lean line enhances line efficiency by 1.97% while eliminating average work-in-progress (WIP) inventory. A recommended U-shaped structure improves line balancing and transportation efficiency while further reducing production time and cost. This study provides a standard for process optimization in the textile sector by showing how Lean Six Sigma approaches like value stream mapping, kaizen, 5S, and kanban can be integrated to enhance sustainability and efficiency in apparel manufacturing.
Keyword: Lean Six Sigma; Production; Sustainability; Standard Minute Value
1.0 Introduction:
Defects, overproduction, waiting, non-utilized talent, transportation, inventory, motion, and extra-processing are the eight categories of wastage which is known as ‘DOWNTIME’ [1]. The Lean management approach identifies, reduces, and eliminates wastage [2]. “Six Sigma” highlights techniques and tools applied to optimize the manufacturing process [3]. The DMAIC phases of Six Sigma are used in Lean Six Sigma. The abbreviation of DMAIC indicates Define, Measure, Analyze, Improve, and Control [4].
2.0 Materials & Methodology:
2.1 Methods of Lean Six Sigma: These methods and resources are used to fulfill the goal of the Lean Six Sigma approach:
2.1.1 Kanban: Kanban utilizes workflow management methods that improve work efficiency and foster ongoing development, like activity visualization and restricted work in progress [5].
2.1.2 Kaizen: The Japanese term “kaizen” relates to improvement or change for the better. Its focus is on integrating practices that foster a work environment that encourages constant enhancement and self-development [6].
2.1.3 Value stream mapping: This analyzes areas to cut down on wastage and streamline procedures [7].
2.1.4 5S tool: The 5S tool is a technique to make sure that the workplace is reliable, secure, productive, and efficient [8].
2.2 DMAIC Methodology: DMAIC is a data-driven method that is applied in Six Sigma to methodically solve challenges or difficulties and improve processes [9]. It is divided into five sections, each with a specific objective and methodology:
2.2.1 Define: The primary objectives of this section are to determine the problem, establish particular objectives, and comprehend the requirements of the consumer [10]. It begins with creating a project charter, detailing the steps, and determining the scope of the improvement. Specifically, the significant number of defects and unnecessary shifting of the workpieces in their production line make it challenging for the line to achieve its goal production plans and manage quality issues.
From Figure 1, The manufacturers may minimize lead times by improving supplier cooperation and eliminating supply chain delays. For example, a 10% decrease in lead time may outcome in a 15% increase in monthly productivity. Again, a manufacturer can observe the full process from first to last.
2.2.2 Measure: This step involves collecting and reviewing relevant information in order to determine the performance of the present method [11]. The scope of the problem is identified by determining key parameters and establishing baseline measurements [12].
From Figure 2, the product flow is measured with value stream mapping (VSM) for identifying value-added activities (VA) & non-value added (NVA). This process will be effective to produce mass production.
2.2.3 Analyze: Statistical analysis, Pareto charts, and cause-and-effect diagrams are used to identify the factors causing the issue [13].
2.2.4 Enhance: In this stage, solutions are developed and evaluated after the fundamental issues have been identified [14]. Pilot testing ensures that process improvements successfully solve the issue without causing more issues after they are put into place.
2.2.5 Control: The last focus is on maintaining the outcomes by establishing monitoring systems, establishing best practices, and training employees [15]. This ensures that the process remains stable and keeps producing the desired results.
2.2.6 Calculation of SMV:
Line target/hour: The amount of goods that must be generated each hour in order to reach a production line’s daily goal is identified as the line the goal per hour.
Machine Requirement (Theoretically)
Line efficiency: The percentage representing the actual manufacturing output divided by the theoretical production capacity is defined as line efficiency. It illustrates the efficiency of the sewing or manufacturing line’s use of its resources (workers, machines, and time).
3.0 Process flow of conventional line:
From Figure 3, the process flow of a conventional line with SMV illustrates the standard stitching technique used in the apparel sector for manufacturing a full-sleeve t-shirt. For the t-shirt to be manufactured seamlessly, an arrangement of tasks is important. Each operation is reliant upon the previous step getting completed. Operators carry out a total of 19 operations. Every step has a time distribution (in minutes), which indicates the duration of time required to finish that specific task.
The Standard Minute Value (SMV) for each operation in a lean line and a conventional sewing line is illustrated in Table 1. All operations on the lean line demonstrate a decrease in SMV, indicating higher efficiency and possibly shorter lead times.
Table 1: The SMV for each function in the Traditional line and lean line
| SI. no. | Functions | Traditional line SMV (min) | Lean line SMV (min) |
| 1 | Matching of Back and front part | 0.268 | 0.241 |
| 2 | Shoulder joining | 0.336 | 0.281 |
| 3 | Stitching of shoulder | 0.308 | 0.295 |
| 4 | Thread cutting | 0.241 | 0.174 |
| 5 | Rib making | 0.416 | 0.389 |
| 6 | Rib tack | 0.282 | 0.241 |
| 7 | Rib joining | 0.523 | 0.493 |
| 8 | Tape joining | 0.336 | 0.308 |
| 9 | Main label attach | 0.322 | 0.281 |
| 10 | Sleeve matching with body | 0.255 | 0.228 |
| 11 | Sleeve joining | 0.47 | 0.429 |
| 12 | Side seam | 0.764 | 0.694 |
| 13 | Care label joining | 0.215 | 0.161 |
| 14 | Body turning | 0.429 | 0.279 |
| 15 | Sleeve hem | 0.348 | 0.281 |
| 16 | Sleeve hem tack | 0.241 | 0.214 |
| 17 | Bottom hem | 0.389 | 0.362 |
| 18 | Bottom hem tack | 0.268 | 0.241 |
| 19 | Final thread cut | 0.429 | 0.348 |
| Total SMV | 6.84 | 5.94 |
3.1 Layout of traditional line: In figure 4, A full-sleeve t-shirt needs 19 operations, which are reflected in the arrangement. The process requires 23 operators and assistance. Two operators participated in Operation 7 & 11. Three operatives performed Operation 12.
4.0 Result & Discussion:
Figure 5 illustrates the standard minute value (SMV) reduction obtained by converting from a traditional production line to a lean production line. The SMV decreased from 6.84 minutes to 0.9 minutes, showing the significant productivity increases connected to lean manufacturing approaches. In the bar graph, the SMV of lean manufacturing is 5.94.
Figure 6 highlights the production quantity of traditional and a lean manufacturing line. With 30,992 units manufactured each month as compared to 29,328 units manufactured on the traditional line, the lean line demonstrates a notable boost in production. This outcome in a monthly production increase of 1,664 units, showing the improved efficiency and productivity achieved by using lean manufacturing approaches.
In Figure 7, the traditional process requires 23 workers, whereas the lean line utilizes only two, which is an impressive improvement. This illustrates how lean manufacturing improves resource utilization and minimizes labor costs.
The average quantity of work in progress (WIP) on a lean manufacturing line and a conventional manufacturing line is represented in Figure 8. The reduction in WIP reflects a more productive workflow, lower expenses connected with maintaining products on hand, and improved customer response. By utilizing the tool of lean JIT, the average quantity of work-in-progress (WIP)was reduced dramatically. The average WIP in the traditional line was 10 pieces, whereas in the lean line, it reduced to 3 pieces, So, the total reduction is 7 pieces.
An illustration of the efficiency of a lean and conventional manufacturing line is displayed in Figure 9. The efficiency of the lean line is significantly higher than that of the traditional line, attaining 69.08% as compared to 67.11%. This results in a 1.97% increase in efficiency, illustrating how lean manufacturing principles maximize the use of resources and eliminate waste.
A new process flow has been designed to boost efficiency in the manufacturing of full-sleeve t-shirts after an extensive evaluation of the data received and the traditional process flow. With this customized procedure, the 12th and 13th processes are carried out by a single operator, reducing two operators from the workflow. These modifications cut expenses, minimize time, and demand fewer workers. These improvements have been incorporated into the updated Standard Minute Values (SMV) to reflect the improved processes in the modified process flow, as shown in Figure 10.
From Figure 11, the alternative layout is preferable since it significantly reduces labor costs by eliminating the number of operators and helpers. Operations that reduce personnel without compromising efficiency, like Operations 11 and 13, are emphasized. In addition, bottlenecks such as those in Operation 12 have been eliminated, ensuring an improved process. These modifications simplify production, resulting in a faster and more effective output approach.
According to Table 2, the optimized U-shaped technique is the most effective since it requires fewer workers and helpers while lower manufacturing time as well as costs. It also features better line balancing and decreases the duration of transport.
Table 2: Comparison of Traditional Layout, Proposed Layout & Optimized U-Shaped Layout
| Metric | Traditional Layout | Proposed Layout | Optimized U-Shaped Layout |
| Operators and Helpers | 23 | 21 | 19 |
| Total Duration (per product) | High | Moderate | Low |
| Production Cost | High | Moderate | Low |
| Line Balancing | Poor | Balanced | More Balanced |
| Transportation Time | High | Moderate | Low |
U-Shaped Layout: Multiple significant variables make the U-Shaped Layout one of the most effective sewing line layouts:
The U-shaped arrangement can be the ideal choice for sewing lines due to its great utility and effectiveness. The process is sped up and made more effective by putting workstations in a U form, which cuts down on transportation time between stages. In addition to decreasing floor space, this layout keeps everything neat. Additionally, it encourages adaptability since employees can receive cross-teaching for working a variety of jobs and transform them into different types of garments. Additionally, employees’ proximity facilitates greater interaction and a collaborative atmosphere, which helps to minimize bottlenecks and enhance output.
5.0 Conclusion:
The study identified and resolved several important bottlenecks in traditional production procedures. Major improvements were made by converting to a lean line, as indicated by measurements like Standard Minute Value (SMV), manufacturing output, labor requirements, defect rates, and line efficiency. A 13.16% reduction in SMV was achieved using the lean manufacturing approach, boosting productivity and cutting expenses. Superior resource use was illustrated by the 1,664-unit increase in monthly production and the reduction in the number of operators from 23 to 21. Failure rates, such as spots, rejections, and reworks, were also significantly decreased, which improved the quality of the outcome. Enhancements in average work-in-progress (WIP) inventory and line efficiency were also demonstrated by the lean line. A more efficient workflow and lower costs for operations are seen in the WIP inventory being reduced from 10 to 3 pieces. The beneficial effect of lean tools in eliminating waste and improving resource use was shown by the 1.97% increase in line efficiency. By optimizing workstation organization, cutting down on transport time, and ensuring enhanced line balancing, the suggested U-shaped configuration further boosted output. This arrangement ensured high efficiency, decreased production costs, and shortened transportation times while decreasing the number of operators and assistance to 19. The outcomes illustrate how applying Lean Six Sigma enhances sustainable manufacturing practices in addition to enhancing operational metrics. Minimizing manufacturing time, wastage output, and resource consumption directly supports green apparel manufacture and is in line with goals for sustainable development. Lean Six Sigma provides a foundation for sustained operational excellence in the textile sector by encouraging continuous improvement and working together. All things considered; the research establishes an ideal foundation for implementing Lean Six Sigma to textile manufacturing processes. Textile companies seeking to increase productivity, cut expenses, and implement sustainable practices might use the ideas and tactics offered as a helpful resource. These outcomes demonstrate how important innovation and process optimization will be in enhancing the production of sustainable apparel in the future.
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