Simulation Model of the Sorting System for a Warehouse

Simulation Model of the Sorting System for a Warehouse


DHL Supply Chain is a division of Deutsche Post DHL Group, which operates globally. DHL Supply Chain is the world’s leading contract logistics provider. Their integrated logistics solutions drive efficiency and improve quality.

To learn more about DHL warehouse modeling in AnyLogic and the optimization tool for order picking, read the following case studies:

In these case studies small and medium size e-commerce orders were considered.


The sorting system

The sorting system (click to enlarge)

DHL Supply Chain wanted to install a box sorting system for the new facility. Compared to the previous cases, there would be much larger orders. Thus, DHL needed automation to support the sorting process.

This system was supposed to include a reject conveyor, eight divert conveyors, and a recirculation conveyor.

Orders would be sorted and palletized by a narrow belt sorter. DHL planned to sort boxes by their weight. It was essential that the heaviest packages go to the bottom of the pallet. In doing so, they would not damage the medium and light boxes. A screen at the entry point would notify operators about available lines and boxes on the recirculation conveyor.

There were four palletizers at the end of divert conveyors. Each had two sorters. The feeding conveyor would be switched after every pallet completion.

DHL required a simulation method implemented in their planning strategy. They needed to define the following:


To meet these goals, they decided to use AnyLogic simulation. DHL used AnyLogic Material Handling Library for the simulation model. The developers used historical data as inputs. This data provided the arrival sequence of boxes, their order numbers, and their dimensions.

Input data for the simulation

Input data for the simulation (click to enlarge)

They decided to have three entry points for weight classes: heavy, medium, and light. Three employees would sort the boxes and drop them on the conveyor.

There were two variable parameters X and Y, which DHL engineers were not sure about: capacity of the recirculation conveyor (X), and the time after which orders were flushed from the sorter (Y).

Simulation logic

Simulation logic (click to enlarge)

The values of the variable input parameters X and Y could be adjusted to identify the best scenario.

The spreadsheet identifying how the value of X and Y affected the outputs

The spreadsheet identifying how the value of X and Y affected the outputs (click to enlarge)


DHL developers made sensitivity analysis while varying input parameters for several scenarios.

Analysis outputs

Analysis outputs (click to enlarge)

At the end of the simulation, engineers shared the results of different scenarios with their management and operation team. They decided to use it as a reference for future operations.

Watch the video about the case study presented by DHL at the AnyLogic Conference 2021:

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