Data2Move Research Stories: When does multi-echelon inventory control pay off?

Data science helps to solve complex supply chain management challenges. In our Data2Move Research Stories, you can find out how our students tackle these challenges. This time, we feature Lisa van Lierop’s Master thesis research at Hilti AG in Liechtenstein. Hilti AG is a multinational company that develops, manufactures, and markets products and services for the construction, building maintenance and energy sector.

Where it started – challenge
When inventory is optimized locally, inventory control is often based on a single-echelon approach. But a single-echelon approach might not be optimal from a broader supply chain perspective. In order to optimize stock levels over multiple supply chain stages and still ensure a high service level to end customers, Van Lierop focused on the potential of multi-echelon inventory control. More precisely, she studied the potential of centralized inventory control under different settings. This should help to strive for optimized stock levels throughout the entire Hilti network, and in the meantime ensure a high service to end customers.

Van Lierop addresses this challenge in her Master thesis ‘Quantifying the benefits of multi-echelon inventory control’.

Technical and organizational challenges
“Changing to a multi-echelon control policy is not easy”, Van Lierop states. “The main technical challenge is that you need to collect, and simultaneously process, a large amount of data. You also have to consider that in most supply chains, data needs to be exchanged between different firms.” On top of these technical challenges, organizational challenges pop up. When you optimize your inventory throughout the whole chain, local control is no longer necessary. Inventory should be managed centrally. However, this change requires someone, or some department, to take responsibility for the centralized inventory control. Another organizational challenge regards   benefit sharing: ‘How are the benefits of the new inventory control approach shared or divided between the different supply chain stages?’

Multinationals such as Hilti AG who look for answers to these important questions might benefit from software tools to support these answers. Still, considering the complex inventory landscape and organizational responsibilities, according to Van Lierop “it is no surprise that the number of published real-world applications of multi-echelon inventory control are scarce.”

‘When does a multi-echelon inventory control policy pay off?’
Before a company decides to switch to a multi-echelon approach, they need to have a good indication of the potential for their product portfolio, according to Van Lierop. For some products, the benefits of a multi-echelon approach might be higher than for others. That is why the aim of Van Lierop’s research was to identify the product/supply chain characteristics for which a multi-echelon inventory control policy pays off. More concretely, she studied scenarios based on combinations of the following five dimensions: demand, demand variability, lead-time, lead-time variability and holding costs.

Simulation model
Van Lierop used a software program designed by Prof. Dr. Ton de Kok (ChainScope) for the multi-echelon safety stock optimization. By using simulation, she was able to model and compare different safety stock procedures and multi-echelon distribution networks. In her research approach, Van Lierop also used a MRP-based replenishment policy with forecasted demand, because many companies replenish their stock based on forecasts.

Findings
Results revealed that the benefits of a multi-echelon inventory control approach are the highest for items with a high lead-time to the first location in the distribution network, a high demand rate and high inventory holding costs. Van Lierop: “Furthermore, the savings for low demand, low cost items were relatively low. Especially when the first location in the distribution network can be quickly resupplied. So when companies consider a pilot for a centralized safety stock procedure in their distribution networks, they should focus on ‘high-potential’ items first.”

Data2Move Research Stories: Achieve Cost Reduction by Dynamic Demand Prediction – An Application in the Container Transport Industry

Where supply chain management and data science meet, interesting questions arise. In our Data2Move Research Stories, you will find out how students have answered these. This time we feature Rijk van der Meulen’s master thesis research at H&S Group, an international and intermodal operating Logistics Service Provider in the liquid foodstuff industry.  

Where it started – challenges 
H&S Group asked Van der Meulen to focus on two operational challenges faced by many intermodal operating Logistics Service Providers:

– The efficient repositioning of empty tank containers

– Proactive planning of their drayage operations

Van der Meulen addressed these challenges in his thesis ‘Forecasting the required tank container and trucking capacity for an intermodal Logistics Service’. His research explores how you can predict demand more accurately and how these demand predictions facilitate better operational planning.

Insight into tank containers and trucking units per location and time
To tackle these challenges, it was important to extract valuable information from data. Van der Meulen needed insight into the expected number of loadings and deliveries. Also, he needed the corresponding requirements of trucking and tank container capacity. By combining these key aspects, he defined how many tank containers and trucking units are needed in a certain planning region at a given time.

Dynamic demand prediction
The true innovative character of van der Meulen’s prediction methodology lies in the dynamic update of the predictions of loadings and deliveries. He used a mathematical technique (Bayesian) to dynamically adjust the initial prediction based on new orders as they enter into the system. This ‘advance demand information’ represents the demand for the future, which is already known in the present. It ensures that planners have access to the most up-to-date and accurate loading and delivery predictions at any time.

In his next step, Van der Meulen used the adjusted forecast to predict the required tank container and trucking capacity. He relied on multiple additional models based on the hierarchical top-down forecast approach and multiple linear regression to assess the effectiveness of the complete forecasting methodology. Its accuracy was put to the test during a one-month test case for two planning regions.

Findings
The one-month test case showed that the dynamic prediction method increased the accuracy of the initial forecast by 65 percent. Using cost simulations, Van der Meulen estimates that this improved prediction accuracy can lead to a 5.2 percent reduction of the total costs associated with trucking operations. That’s a big step towards achieving the operational excellence necessary to survive in the low-margin industry of intermodal logistic service providers. Van der Meulen’s research strengthened H&S in their conviction that forecasting plays a vital role in addressing the challenges of empty tank container repositioning and drayage operations planning.

Spin-off project – implementation
As a result of these findings, H&S started a joint forecasting implementation project with Logistics Service Provider Den Hartogh and data science consultancy firm CQM. The goal of this collaboration is to implement the dynamic prediction methodology of van der Meulen’s research and integrate the implementation with the planning software at H&S and Den Hartogh. This allows both companies to plan their trucking and container operations better and achieve significant cost reductions while maintaining the same service to their customers.

Data2Move Research Stories: the VMI effect within Heineken’s Dutch supply chain

Where supply chain management and data science meet, interesting questions arise. In our Data2Move Research Stories, you’ll find out how students have managed to answer them. This time: Rolf van der Plas and his master thesis on the Vendor Managed Inventory effect within the Dutch supply chain of Heineken.

Where it started

The global beer market is consolidating with less local and more global brewing companies. The remaining players enter into a hyper-competition to be innovative and to differentiate themselves from each other, in order to leverage their scale for increasing operational excellence.

As part of Heineken’s drive to improve operational excellence, a new enterprise resource system will be introduced. It has an optional module that supports collaboration based on the Vendor Managed Inventory (VMI) framework. Heineken has been exploring VMI collaboration with a number of customers. Rolf van der Plas aimed to validate the effectiveness of VMI for Heineken and their customers, like retailers, by quantifying the effect on supply chain performance. He investigated:

  • Heineken’s transport utilization
  • Stock levels in the distribution centers (DCs) of the customer
  • Out-of-Stock performance in the customer DCs

Rolf selected three techniques to investigate VMI collaboration:

  • Data analytics to analyze the current effect
  • A simulation model to redesign the VMI process
  • A simulation-based searching (SBS) model to enhance the parameters settings used in the VMI-designs

Findings: a win-win situation

The current VMI collaboration in Heineken results in 15% higher transport utilization compared to deliveries to DCs of customers without VMI.  A new variance-based VMI design with enhanced parameter settings results in an even higher supply chain performance for Heineken and the customer compared to the current VMI implementation.TabelR

The benefits? A 7% higher truck utilization, meaning trucks are used more efficiently and transport costs go down. Also, a 70% reduction of the average stock levels in the customer DCs, while maintaining a 0% Out-of-Stock performance. The main finding: both supply chain partners benefit.

Further advice

In conclusion, the VMI collaboration effect is both beneficial for the suppliers and for the customers. Rolf’s study proves that his SBS model is an adequate method to consistently identify robust settings that enhance supply chain performance. Rolf endorses the usage of the model for future challenges. He recommends setting up (more) VMI collaboration with your supply chain partners as a tool to improve your supply chain performance.

Also check out our previous research stories