Keywords

1 Introduction

1.1 Research Purpose

The DT assembly workshop is the last process of the company’s entire production process. It is responsible for assembly, packaging, and storage. It has a significant impact on the external output efficiency of the company’s products. However, the assembly efficiency and personnel utilization rate of the production line are still low, and there are other wastes that make the production line balance rate very low. Therefore, a project is set up to propose improvement [3].

1.2 Research Tools

This research on the DT assembly workshop production line of Y company uses Flexsim simulation software to simulate the state of the production line. People can directly put the modeling results into the physical system and directly participate in the interaction between the objects. Simulation technology can avoid the shortcomings of general research methods, which are difficult to consider the dynamic influence of various factors, so that the research results are far from the actual situation, and can reduce investment risks and avoid waste of manpower and funds.

2 Key Issues and Analysis

2.1 Data Analysis

In this study, we will use appropriate statistical and analytical methods to analyze the large amount of data collected, summarize, understand and digest them, to maximize the development of data functions and play the role of data. And based on the data foundation combined with the company’s supply chain management to draw a value flow diagram [5] (see Fig. 1).

Fig. 1.
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Value flow chart

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On the value flow chart, it can find that DT assembly is the last position in the supply chain, which directly affects the company’s external product supply efficiency. It can be seen from the visual observation method that there is still waste in this production line. The drawing process information table as shown in Table 1.

Table 1. Process information table
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2.2 Data Analysis and Parameter Setting Based on Flexsim Simulation

Collect the data of the station content, including the process division, the time of each process content, the waiting time, the material handling time, and the time required for improvement. Compare the input elements with the material objects to draw a given modeling element comparison table, as shown in Table 2.

Table 2. Modeling element analysis table
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In order to prevent data anomalies, the data is first tested for homogeneity and independence, then eliminating abnormal data, put data into the Flexsim simulation software for modeling processing [4], which strictly guarantees the reliability of the data and the feasibility of the project. And draw a table for input (see Table 3).

Table 3. Input table of modeling information
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2.3 Summary of the Problem

In this study, we will analyze the problem from the five perspectives of man, machine, material, method, and environment. Analyze the waste problem under various conditions. It is analysis that the system has the problem of irregular operation of staff, disordered process, and low equipment utilization. At the same time, it was found that the production line was greatly affected by the bottleneck process, the layout was not standardized, and the utilization rate of land occupation was low. According to the problem, make a fishbone diagram (see Fig. 2).

Fig. 2.
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Current fishbone diagram

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3 Solution

3.1 Production Line Optimization and Improvement

First, the bottleneck process is detected when the steps are performed, and then the DT process time is sorted out, similar to the difference table, which is convenient for ECRS improvement. Analytical improvements are shown in Table 4.

Table. 4. Similar differences of processes
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3.2 Production Line Layout Improvement

5W1H analysis of the production line, summarized in Table 5.

Table 5. 5W1H analysis table
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3.3 Bottleneck Process Improvement

Bottleneck Process Analysis

Analysis of bottleneck process, we will draw a three-product diagram of the production line to find the balance of each process and the bottleneck process (see Fig. 3).

Fig. 3.
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Three-product diagram of production line

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It can find that the bottling process is mainly labeling, and based on this, the bottleneck process is improved.

The Bottleneck to Improve

This time, we will take three steps to solve the improvement of the bottleneck process.

  1. (1)

    The line job is metric merged. The original steps 1, 2, and 3 were merged, the steps 4, 5, and 6 were merged, the steps 8 and 9 were merged, and the steps 10 and 11 were also merged.

    The original 9 workstations were simplified to 5 workstations by merging and rearranging, and the number of production line operators was reduced from the original 9 to 5.

  2. (2)

    With the addition of a labeling machine, the labeling efficiency has increased from 2–5 pieces/min to 8–12 pieces/min.

  3. (3)

    Using a flow production method, a linear production line should be converted into two U-shaped production lines to improve production efficiency [5] (see Fig. 4).

Fig. 4.
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Improved effect diagram

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4 Improve Results Comparison

4.1 Comparison of Production Line Optimization and Improvement Results

By calculating the rate of return as the key basis for analyzing the feasibility of the project, an improvement rate of return table is established as one of the quantitative indicators to compare the improvement effect [6], as shown in Table 6 below.

Table 6. Similar differences of processes
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Comparison of Actual Improvement Results

By optimizing and improving the operation process, decrease the non-value-added and unnecessary waste in the process flow and improve the process by applying the ECRS method to eliminate, merge, rearrange and simplify.

The order of operating stations before improvement is: 142356789.

The improved operation station sequence is 12345, as shown in Fig. 5.

Fig. 5.
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Comparison of actual improvement results

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4.2 Comparison of Production Line Layout Improvement Results Production Line Layout Comparison

Fig. 6.
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Comparison of production line layout (left before improvement, right after improvement)

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Comparison of production line layouts, as shown in Fig. 6. Comparison of production line footprint, as shown in Fig. 7.

Fig. 7.
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Comparison of actual occupied area (left before improvement, right after improvement)

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Before improvement: production line area = 1 × 7 = 7 m2

After improvement: production line area = 2 × 2 + 0.5 × 0.5 × 3.14 = 4.785 m2

When the number of production lines is the same, the theoretical area of a single production line before and after the layout improvement comparing with the actual area. The area utilization rate before improvement is 12.28%, and the area utilization rate after improvement is 14.18%, as shown in Table 7.

Table 7. Floor area improvement table
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Comparative Analysis of Follow-Up Improvement Results Based on Flexsim Simulation Modeling

Arrange and input the data before and after the improvement, so that the data and layout are strictly by the actual situation, model the data with Flexsim simulation software, and record the data for comparison as an important basis for verifying the feasibility of improvement.

Fig. 8.
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Modeling diagram before improvement

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The modeling diagram before improvement is shown in Fig. 8 and the modeling diagram after improvement is shown in Fig. 9.

Fig. 9.
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Improved modeling diagram

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4.3 Comparison of Bottleneck Process Improvement Results

Through analysis, it is known that the bottleneck process of the production line is labeling. In the complete production process, the labeling process accounts for 3, and they are all time-consuming processes. Therefore, an additional labeling machine is introduced to improve the production line. After adding the labeling machine, the labeling speed increased from 2–5 pieces/min to 8–12 pieces/min, and the overall efficiency increased by 6–7 pieces/min. The following is a comparison table of bottleneck process improvement, as shown in Table 8.

Table 8. Comparison table of bottleneck process improvement
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5 Summary

This research applies industrial engineering knowledge to practice and solves the problems of low production balance rate and unreasonable layout of the original production line in the DT assembly workshop of Y company. The original production line was analyzed by applying a value flow chart, fishbone diagram, 5W1H analysis, and other methods, and found the existing problems of the original production line. By improving worker action, the production line reduced 4 processes and adds a machine to improve the efficiency of the production line. According to the improved procedures and a machine of the production line, the area utilization rate of the production line is analyzed, and the layout of the production line is redesigned as a U-shaped production line. According to the Flexsim simulation software, verify the improvement of each part, and the verification results are in line with the actual application [7]. The improvement project has been put into production after being reviewed by the company to meet practice standards.