SC Navigator: AIMMS Network Design FAQ

  • 13 October 2020
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SC Navigator: AIMMS Network Design FAQ
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Looking for AIMMS Network Design FAQs? You’ll find a collection in this article. If you have other questions, please post them in our User Group.  


Datasets and Configuration  


Why do I get an error when I try to load my Dataset saying that I have an "incorrect value in cell I2: Cannot Convert String to Double" for the Trans Type Product Data sheet?    

There may be a formatting problem. Open your Excel template and go to cell I2 in the Trans Type Product Data sheet, and ensure that the cell has been formatted correctly. The cell cannot have any formulas and must have exactly the same value as the corresponding value in the other sheets.    




Can I load a saved scenario into the Active Scenario Resource Control directly rather than re-loading the dataset and re-running the model?   

No. Scenarios are dependent on a Dataset, so you always need to load the Dataset before loading the scenarios.    

If you want to load a scenario in the Active scenario map, you need to run it every time because that is what makes it the Active Scenario. However, you can load a saved scenario into the reference scenario area.  

To find the settings used to run the scenario, go to the Analytics page and load the desired scenario. The table at the bottom will show you the settings for the scenario. Copy those settings to the top table and run the optimization to make this the Active Scenario. Then in the Flows page you can load another scenario to compare.   

Alternatively, you can save a case which will include all the settings, and the Dataset. Refer to the FAQ “How do I save and load cases and scenarios?” to learn how. 


Data input  


Are there different ways you can input numeric values in Network Design?   

Some numeric values can be automatically calculated by the application with Unit conversions. The proportion of products in a certain grouping is automatically calculated, too. If there are other ratios that need be taken into account, they must be pre-processed.   


What is the difference between Transport Mode Minimum Transport (TMMT) column in the Trans Type sheet and Minimum Throughput column in the Resource Data sheet?    

The Minimum Throughput column sets the lower limit for the throughput at a certain resource. When optimizing, this tells the model to ensure that the throughput in that DC is no less than the amount given. This can be relaxed by switching on the relax DC capacity button in the app.  

TMMT relates specifically to the minimum units of product that must be transported in a specific transportation lane while Transport Mode Capacity is the maximum units of product that must be transported in a specific transportation lane.   

If you set TMMT = Transport Mode Capacity in the template, then the model will be forced to transport that specific amount. TMMT = Transport Mode Capacity is often done to create the base case, since you can input the historical shipped amount per lane. Then, if we relax Transport Capacity in the app, the model can look for the optimal amount of units to transport.   


Could I leave TMMT empty between DCs and just initialize the demand of the customers?   

Yes, you can leave these 2 fields empty. By doing this, the model will tell you the optimized amount to transport without relaxing the constraint.    


Model options  


Can I solve for multiple objectives sequentially?   

No, multi-objective or configurable constraints are not yet part of the application. However, the ability to add your own constraints is on the roadmap.   

Meanwhile, the app offers a rich combination of constraints that can already be modeled.   


Can I create a storage capacity constraint, rather than just throughput capacity?    

Network Design currently does not include the possibility to store inventory.   

Inventory, working in parallel with Network Design, can help strategically answer your storage problems. For example, if you want the model to also account for the excess inventory to be held at various warehouses on top of anticipated demand.    


How can we model products which have a different cost in each DC?    

In some cases, you may have different products and a cost of each product in each DC. In order to move a product from one DC to another, all the demand of all products has to be moved as well, not just one product.   

One option is to use single sourcing. This can be done in your dataset.   

For example:   

In "Resource Data", if you say a DC needs to Single Source (by putting 1 in the attribute Single Source related to that DC), then the model will select the most optimal DC for each product, and will use only that DC.   

Remember you will need to keep the single source constraint enforced in the app!  


Can we set flow or production constraints by resource?   

You may want to set up some constraints for your resources.    

For example,    

  • Plant1 should produce at least 10 units   

  • There cannot be more than 5 units flowing between Plant1 and DC1   

These constraints can be created in the Trans Type Product sheet. To learn how to model this, please refer to this PDF (attached to this article).   



Transport costing  


How can I calculate transportation cost per lane?   

For transportation, you can enter cost per THU or distance.   

A cost per lane can be assigned to each lane, either per distance between the 2 nodes in the lane, or per units transported between them.    

To learn how to model this, please look at this PDF (attached to this article).    


What is the purpose of Transportation Fixed Cost?   

Transportation Fixed Cost is added on a per trip basis. If you input a fixed cost for a lane, the final cost of that lane is the fixed cost plus the variable cost.   

So, if the optimization result is that 10 trips will be made to a certain customer, then the input fixed cost is multiplied by 10. This cost is added to the variable cost (either cost per distance unit or cost per THU).  If you do not put a fixed cost, the final cost will be just the variable cost. Note that if you use Transport Fixed Costs, you must put the Transport Conversion Factor as well so that the model can calculate how many trips are needed to be made.  




How can I distinguish between flows to Customers versus Distributors?   

In your Excel template, for Customer Data and Customer Product Data sheets, you may have two types of customers (such as Customer and Distributor).   

However, in the app there isn't a visualization showing the flows by customer type specified in the data.  

The Flows page does allow you to separate flows based on transportation mode.   

So, in the Trans Type Product Data sheet of the Excel template, you can create two Transportation Types (such as DC to Customer and DC to Distributor).   

Then in the app, when you look at your secondary flows in the map, you can toggle between these 2 Transportation Types and visualize how each of them behave (The widget that allows you to do this is below the reference scenario map.)  


Where can I see which DCs are delivering to which XDs?    

If you have modeled your DCs and XDs in the Resource sheet of the Excel template, the transport between them will be shown as inter-resource transportation. If you run an optimization and go to the Transportation page in the app, you can see the DC to XD volumes in the inter-resource transport table. 

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