Definition

  • Minimum Flow and Maximum Flow capacity constraints can be set at a facility via import or the interface itself through selection of a facility node. These can apply to an aggregate of all products or one or more of set of individual products, or a combination of the two.

Example

  • A facility can produce 2 products – product A and product B – and has a total max-flow constraint of 30000 and min-flow constraint for product A at 10000, which will force the facility to produce at least 10000 of A but restrict it from producing more than 30000 of A+B together.

Maximum Flow

  • max-flow facility constraints can be used to limit the total outbound flow - flow from production at a facility itself or from another facility - for an aggregate of all products or for a set of individual products. 

  • max-flow constraints can be useful for capturing the corresponding variable of time that each model necessarily constitutes.

  • Example: 2 warehouses fulfilling an equal amount of demand for a yearly model and looking for a 3rd warehouse which will be able to, at most, satisfy half the demand.

Minimum Flow

  • min-flow facility constraints can be used to enforce a minimum total outbound flow - flow from production at a facility itself or from another facility - for an aggregate of all products or for a set of individual products.

  • min-flow constraints can be useful for setting some minimum level of flow that a facility must meet for it to be considered "active" in the scenario. They can work in tandem with the idea of a fixed cost of opening a facility but offer a more flow-based perspective vs. cost-based.

  • Example: 2 warehouses fulfilling an equal amount of demand for a yearly model which looks to be unsustainable with a forecasted increase in demand, so looking for a 3rd warehouse which will, at minimum, satisfy a 3rd of the total demand.

Import

  • In the "Constraints" sheet, the allowed values for a constraint's "Type" are the following:

    • facility-min-flow

    • facility-max-flow

    • min-flow

    • max-flow

  • "facility-min-flow" and "facility-max-flow" apply to the total (leave the "Product" field blank)

  • "min-flow" and "max-flow" apply to individual products



What happens if a user creates an infeasibility?

Anytime a flow constraint is applied to a node or lane, there is a risk of infeasibility.  Either a max flow does not allow for customers to be properly served or a min flow forces too much material than can be consumed.  In the case of an infeasibility, the solver will relax constraints in order to complete the solution and will report the infeasibilities in the scoreboard.

It is the users responsibility to correct for any infeasibilities.