Strip casting is a common, low-cost method to cast thin aluminum sheets at gauges close to the final product gauge. Since this process involves fewer steps than traditionally casting methods, the manufacturing time for aluminum products is reduced considerably. Usually, when surface defects occur during the casting process, the slab is scalped. Since it is impractical to scalp a sheet, the slab should contain a minimal amount of surface defects. To achieve this, it is important to understand the effect of different processing variables that occur in the casting procedure. The use of a pilot-scale belt-caster for research is expensive, and therefore, a single-belt casting simulator has been constructed. The aim is to study a broad range of casting conditions and the parameters that affect the surface quality and the underlying microstructure in the twin-belt casting process. Running experiments on the simulator also reduces the costs considerably compared to full scale twin-belt casting experiments. To achieve a sensible simulation, the conditions should be as identical as possible to a twin-belt caster. One of the most crucial factors is the heat- flow occurring in the interface between the solidifying metal and its surroundings. This flow is hard to measure. Therefore, a model for interfacial flow calculations was created. The model was developed in Matlab and Abaqus/CAE. Abaqus/CAE could not compute the desired heat-flow automatically, but was used as a control device for the created algorithm. It was showed that the accuracy of the heat-flow computed with the Matlab algorithm was good.