Batch Picking Model Issue: Picker Collects Correct Total Quantity but Depot Receives Fewer Items Than Expected

[thaovytr494]

I am currently building a warehouse batch picking simulation in FlexSim for an order picking system.

Project Overview

The main idea of my project is to simulate a manual batch picking process where:

• Inventory is initialized based on a master SKU table
• Orders are processed according to a daily Picking List
• A picker uses a trolley with limited capacity (15 items)
• The picker travels to storage locations, picks products, returns to depot when full, unloads, and continues until the entire picking list is completed
• After picking, products should eventually be sorted by customer code

I've built 2 different models:  Model 1

This model contains 2 process flows:

Flow 1: Inventory Initialization

• Reads SKU master table
• Creates inventory objects
• Assigns SKU, location, and quantity

Flow 2: Picking Flow

• Reads Picking List directly
• Picker processes rows one by one
• Picks according to required quantity
• Uses batching logic based on trolley capacity

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Model 2

This model contains 3 process flows:

Flow 1: Inventory Initialization

• Same as Model 1

Flow 2: Push Inventory to Global Picking List

• Created products are pushed into a list structure
• Intended to create an accessible inventory database

Flow 3: Picking Flow

• Picker pulls products from the global list
• Executes batch picking based on Picking List demand

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Current Problems Problem 1: Neither model runs properly

• Some flows stop unexpectedly
• Tokens may get stuck
• Process logic may be incorrect

Problem 2: Quantity mismatch

When the model partially works:

• Picker successfully picks 63 products
• Total required quantity in Picking List = 63
• However, Depot only receives 57 items (I suspect 57 may correspond to the number of rows in the Picking List, rather than actual quantity)

[moehlmann_fe]

Model 1:

There are multiple tokens running the load subflow in parallel. They only use the parent labels, meaning the "ItemsToPick" label will get overwritten, causing the same item to get loaded multiple times. This is how you end up with 57 instead of 63 items. Set the Run Sub Flow activity to run the token one at a time and all items will get loaded.

Model 2:

- Only one item per SKU is created, leading to some tokens not being able to find items.

- The connector going back up after the unload needs to go directly into the Decide, not start from the top.

- Only one of the loaded items is being unloaded.