Research on Distribution Center Layout Based on SLP

Distribution is an important part of logistics. Scientific planning distribution center can not only improve the efficiency of distribution, but also reduce the cost of logistics. The paper adopts the method of SLP to carry out scientific and reasonable layout planning and construction the distribution center. Combining the case analysis, the feasible optimal solution is finally obtained after exploring all the links.


Introduction
Reasonable planning and construction of distribution centers can not only accelerate the circulation of goods, but also reduce logistics costs, which is an important factor for logistics enterprises to improve their operating efficiency.As an important part of the logistics system, the distribution center has become the link between the product supplier and the item consumer and plays a pivotal role in the operation of the logistics system.Due to the investment in the initial construction of the distribution center and the huge amount of money required for maintenance during the operation of the warehouse during operation, there are many risks in the operation and investment of the distribution center.At the same time, it is difficult to make major changes to the layout during the period after the completion of the distribution center.Once the distribution center is remodeled, it will increase the related costs of the distribution center.Therefore, reasonable layout planning will be of great significance to effectively reduce the cost of the distribution center.

Systematic layout planning
Systematic layout planning (SLP) is a common method used in process specialization layout to help determine the layout of work units by analyzing the logistics strength between processes [1].When the SLP method is used to arrange the internal functional areas of the distribution center, the relationship between logistics and non-logistics between the functional areas is analyzed firstly and the comprehensive mutual relationship table is obtained by simple weighting.The degree of close relationship between the functional areas is represented by A, E, I, O, U, and X which corresponding scores are 4, 3, 2, 1, 0, and -1 from high to low.
The relative position between the functional zones is determined according to the close relationship between the functional zones.Then, the position of each functional area is determined according to the comprehensive proximity of each functional area.The highest scored functional area is placed in a central location.According to the actual situation of the company, the area of each functional area is calculated to form the area correlation chart.Through the correction and adjustment of the area correlation map of each functional area, several feasible layout schemes can be obtained.At last, the ACCESE 2019 IOP Conf.Series: Earth and Environmental Science 330 (2019) 052018 IOP Publishing doi:10.1088/1755-1315/330/5/052018 2 best layout scheme is selected after evaluating each scheme [2].

Layout planning process
The ultimate goal of all types of functional area layout planning within the distribution center is to improve overall operational efficiency and maximize economic benefits.The operation process of the warehouse distribution center and its strategic management concept are effectively combined to ensure that each region can maximize its role.The combination of the number of staff, the type of equipment and the space occupied by the materials is combined to ensure maximum output ratio [3].The layout planning process is shown in figure 1.
Figure 1 The process of layout planning

Distribution center functional area design
For a newly-built distribution center, it is usually necessary to estimate the flow rate of the completed product and predict the area of the functional area by the flow rate.In general, there are the following indicators for each functional area.The unit area of the storage area is 0.7~0.9tons/square meter.The unit area of the inspection and acceptance operation area is 0.2~0.4tons/square meter.The calculation area per unit area of the picking operation area is 0.2~0.3tons/square meter.The area of the auxiliary production area accounts for 5% to 8% of the total area [4].
Channels generally include main channel, auxiliary channel, pedestrian channel, etc.For the channel design of the storage area, the type of forklift and the turning radius of the forklift should be considered.At the same time, we can also judge whether the channel design is reasonable based on the reference data of some main channels.
The width of the shelf passage = the minimum turning radius of the forklift + the front suspension distance (the distance from the center of the front wheel to the fork plane) + the cargo length +200mm.
The area of the functional area is combined with the relative positional relationship of the functional areas.This will give you a working diagram per unit area.For example, transportation methods, safety, cost, etc., taking into account various factors you can get several feasible solutions.Then it evaluates several schemes from the aspects of technology and cost and selects the optimal scheme [5].

Case introduction
Company A's main business is to sell department store products online.Now we plan to build a distribution center to meet the needs of the company.The characteristics of company A's customers are mainly the following: customers are uncertain, there are many customers, and the quantity of goods purchased by each customer is different.The geographic location of the distribution center has been determined.The location is convenient and close to the supplier.The distribution center covers an area of approximately 11,300 square meters, of which approximately 155 meters in length and approximately 73 meters in width.The layout of the distribution center should be combined with the company's sales model to meet the company's warehousing, sorting, packaging and other needs.For the problem of a wide variety of goods, there must be a systematic scientific sorting method.

Functional area design
The main goods in the distribution center are department store goods.The main features of the product are a wide variety and a large difference in specifications.The distribution center is divided into eleven functional areas according to company requirements and product characteristics [6].The functional area design is shown in table 1.
Table 1.Functional area design

Ribbon name
The main function

Work flow design
After investigation, the following operation procedures are formulated according to the sales characteristics and actual needs of the distribution center, as shown in figure 2.
Figure 2 Operation flow chart of distribution center

Correlation analysis
We conducted a survey of Company A's distribution center.Goods arriving at the distribution center enter the purchase area.70% of the goods in the purchase area enter the storage area.30% of the goods in the purchase area enter the circulation processing area.10% of the goods in the storage area enter the FCL delivery area.60% of the goods in the storage area enter the circulation processing area.90% of the goods in the circulation processing zone enter the sorting area.90% of the goods in the sorting area enter the self-examination area.90% of the goods in the self-inspection area enter the packaging area.88% of the goods in the packaging area enter the delivery area.2% of the goods enter the return area [7].
According to the flow ratio of the distribution center, the logistics correlation analysis is performed on the distribution center operation area and the relationship between the distribution center operation areas is prepared.Taking into account the degree of personnel's round-trip contact and the number of material handling, etc., the non-logistics relationship diagram of the work area is obtained.According to the logistics relationship diagram and non-logistics relationship diagram, the comprehensive relationship diagram of each operation area is obtained.

Work area design
By analyzing the operation of the distribution center of Company A, the quantity of various goods in the storage area is maintained at around 2100t to ensure the normal operation of the company.The specification of the tray is 1.2m*1m and the load capacity is 0.6t.The shelves in the storage area are 6-storey shelves.There are 8 trays on each shelf.Each shelf has a footprint of approximately 10 square meters and the shelves are placed adjacent to each other.Forklifts use a forward-moving forklift with a turning radius of 1700mm and a channel width of 3.5m.Based on the amount of cargo the storage area is about 3,200 square meters by calculating the above data.
The detailed planning of the storage area, sorting area, auxiliary function area, circulation processing area, import/export area, packaging area and self-inspection area is shown in figure 3. Figure3 Layout plan of distribution center The distribution center layout plan was revised using the FlexSim simulation platform.Through simulation analysis, the layout of the distribution center can meet the development needs of the company in the next three years.

4.Conclusion
The paper explains in detail how to conduct logistics correlation analysis and non-logistics correlation analysis, using SLP layout method.The paper calculates the area of each functional area based on the actual case, designs the relative position of each functional area, draws the layout layout of the distribution center, and determines the internal planning plan of the distribution center.However, more factors should be considered in the layout planning of distribution centers in reality, which needs further research.