Assessing site integration into semi-continuous production, distribution and liquidity planning of supply chain networks

In order to strengthen competitiveness, the pool of available network sites in supply chains of processing industries with 24/7 operations should be adjusted permanently. However, an integration of additional sites is to be assessed thoroughly by the network managers as an exact coordination with existing partners must be ensured within multi-day planning horizons. On the one hand, continuous-time scheduling of network-wide operations exclusively allows for using time-based assessment criteria such as the minimum production time to be provided by the integrated sites. On the other hand, the assessment needs to be based on the calculation of network-wide liquidity, which must not fall below its previous value after the realization of an integration. A realistic consideration of financial planning needs to include both credits and financial investments not being based on given interest rates, but on cash flow series characterized by arbitrary compositions of payments and repayments occurring after any intervals of time periods. Thus, it is to be implemented by discrete-time modeling. As a result of merging both methods of assigning decisions to appropriate points on the time axis, a semi-continuous mixed-integer linear model is developed in the paper on hand. By interrelating three different shapes of this model, the minimum and maximum scope of an integration can be determined. The approach is validated for an illustrative example of a three-stage supply chain network, which is extended by two or three additional production sites. The computability of the problem on a high-performance cluster is evaluated in a scenario analysis including 50 test instances with randomly generated data.