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Plant Streamlining Series
Building up a flow production system

Improved production efficiency is a crucial target for manufacturers working in the severely competitive sewing industry in this country. In this series we describe several factory management and flow production systems used to improve productivity in garment factories.

Juki Corporation
Apparel Manufacturing Research Laboratory
Taro Iwago

Generally speaking, the production systems of a sewing factory can be grouped into the categories described in Fig. 1.

Fig.1: Production method employed in the plant

1. Work systems: division-of-labor and total sewing (non-division of labor)

With 'division of labor,' a task is divided and allocated to a team of people, and each member of the team repeats the part of the task to which he or she has been assigned. This type of system promotes the 3S for streamlining (simplification, specialization, standardization) and generally improves production efficiency. To divide labor successfully, factory managers must divide work and prepare work procedures, while the workers must communicate effectively amongst themselves.

With the opposite type of system, the 'total sewing' system based on non-division of labor, an individual worker handles the entire sewing processes until the garment is finished.

(1)Division of labor
<Advantages of the division-of-labor system>
  • A worker quickly masters his or her process.
  • The repetitive work flow for each worker improves efficiency.
  • The processes assigned are short enough to be easily mastered even by unskilled workers.
  • The quality of work completed varies little from individual to individual.
  • Since each process is specialized, it is easy to introduce special machines or automated machines.
<Disadvantages of the division-of-labor system>
  • Each worker handles only one part of the process. This makes it very difficult to learn about the other parts of the process.
  • Every process is vulnerable to influences by other workers (processes). The absence of a worker or a slowdown at one step in a line can easily affect the entire team.
(2) Total-work system (non-division of labor)
<Advantages of the total-work system (non-division of labor)>
  • A worker handles, and therefore learns, all of the processes.
  • The absence of one worker leaves the other workers unaffected.
  • One worker covers all of the processes, hence a change in the type of product will not result in a drastic drop of the production volume.
  • The line can be managed without undue effort.
<Disadvantages of the total-work system (non-division of labor)>
  • High skill is mandatory. Unskilled workers cannot be used on the line.
  • Worker training requires thousands of costly man-hours. (About 2∼3 years in the case of a women's wear factory.)
  • One person handles a wide range of processes, hence the work efficiency of each process is low.
  • Product quality varies with the skill level of the worker.
  • The worker must handle several types of equipment. This makes specialization and automation difficult.
  • The worker must keep different materials nearby in order to handle all of the processes. Time is spent needlessly searching for materials, rearranging apparatus in the workspace, and so on.
  • A worker must work with several sewing machine models. Preparing and relocating the equipment takes time.
  • In contrast to flow production, where the same process is repeated, the work flow in the total-work system lacks rhythm. This makes it difficult to improve productivity.
  • In a factory where management is based on the piece rate, workers tend to place more importance on speed than on quality. Problems with quality result.
  • Without pressure from a supervisor or other workers, a worker will work at his or her own pace. This results in unstable production.
2. "Flow production" and "non-flow production" systems

Division-of-labor production has "flow production" and "non-flow production" systems. Flow production is a system where products are sent from the initial process to the final process, step by step. To make the flow production system successful, the steps of the process must be synchronized (each process must take approximately the same amount to complete). It is also important to minimize the goods-in-progress in each process.

(1) Flow production system
<Advantages of the flow production system>
  • The progress of work is clearly visible and easy to manage.
  • There are fewer goods in progress in the factory. This reduces the amount of space required.
  • Quality problems in the process can be found quickly.
<Disadvantages of the flow production system>
  • The balance of each process in the line must be strictly maintained.
  • Rules for moving products must be established.
  • The system will not function well without teamwork among the members.
(2) Non-flow production system
<Advantages of non-flow production system>
  • The balance of each process in the line is easily maintained.
  • Products can be freely moved. No rules on the movement of products are required.
  • There is no need to promote good teamwork.
<Disadvantages of non-flow production system>
  • The progress of work is difficult to understand, and therefore difficult to manage.
  • Goods-in-progress accumulate throughout the factory. Lots of space is required to put them in order.
  • The factory is full of goods-in-progress. By the time a problem with quality is discovered, many goods affected by the problem have already been produced.

The flow production system is designed to minimize the amount of goods-in-progress and expose problems as soon as possible. This ensures advantages over the non-flow production system in terms of management and quality. Management has to be strict, however, as the limited number of goods-in-progress increases the likelihood of an interruption in production. And when striving for optimized efficiency by reinforcing the workforce, operation under a group incentive system is more suitable than operation under a piece rate system.

Management is easier with a non-flow production system, as the line doesn't come to an immediate stop when a problem occurs. Operation under the piece rate system is also somewhat easier than it is in the case of the flow production system. But with goods-in-progress at each process, it can be difficult to pinpoint a slow process (a bottleneck) in the line. This makes flow production less efficient.

3. Bundle system

There are also systems based on what we describe as the "moving lot size," that is, the quantity of products to be moved. In the "lot method," multiple products are moved together in lots. In the "piece method," products are moved one by one. The various sizes, sizes, colors and designs for garment make it difficult to manage products item by item. Every factory employs different systems for counting products and moving them from one process to another. Factories categorize products by placing them in baskets, marking them with serial numbers, bundling them with strings, or clipping them with tags. This categorization is crucial for avoiding mix-ups in the processes.

The method for bundling products with strings made from cutting scraps is called the "bundle system." Products in the sewing industry are often bundled for transport from one process to another process during production. Transport from process to process takes particularly long in parts fabrication sections, as the processes are commonly arranged by model. Bundling products together for transport saves time not only for transport itself, but also the administration during products. This helps to prevent mix-ups in colors and sizes.

4. Summary

The division-of-labor system and total sewing system each has its own advantages and disadvantages. In general, however, we recommend the division-of-labor system for sewing factories that produce in relatively large lots. This is mainly because the total sewing system is considerably less productive than the division-of-labor system.

The total sewing system was the norm back when craftsmen manufactured products by hand, one by one. The division-of-labor system is more suitable for high quality and high efficiency production.

Factories with high-product mixes and low-volume production tend to employ the total sewing system or something similar. Often, however, a factory can lose profitability by selecting such a production system. Even factories with high product mixes can improve their performance by studying the division-of-labor system.

Table 1 serves as a guideline for worker allocation to processes for the production of a major item by the division-of-labor system, based on our own experience. I hope it will be of some value to you.

Table l: Basic data by product model
Product type Standard total manufacturing time(sec) Worker chart(person) Daily capacity per direct worker (pc./8h)
Cutting Sewing Finishing
Men's shirts 950∼1100 8∼10 75∼85 15∼20 26.2∼30.3
Men's upper wear 7000∼9500 11∼15 105∼115 14∼18 3.0∼4.1
Men's lower wear 2000∼2400 6∼7 48∼52 5∼6 12.0∼14.4
Jeans 1000∼1100 2∼3 29∼32 2∼3 26.2∼28.8
Polo shirts 700∼800 2∼3 15∼18 2∼3 36.0∼41.1

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