Hardware-in-the-loop (HiL) is a concept for testing physical equipment by connecting itto a mathematical representation (model) of the physical process. HiL-testing reduces thecost and saves time before testing the physical equipment (hardware) on the real (physical)process. The physical process chosen for this study is wire+arc additive manufacturing(WAAM), an advanced additive manufacturing (AM) technology that deposits metalbased material layer-by-layer. In this study, simulations of the robot path are carried outwhile the physical robot performs a physical process (additive manufacturing). In robotadditive manufacturing, the desired CAD model is currently sliced down into layers usingslicer software, and the layers are then translated into a path. The robot then moves alongthe path of these pre-defined layers to produce a three-dimensional structure. The heightof the produced structures and desired CAD models have deviations because of processinstabilities and temperature variations among other factors. The robot path should beupdated every time a layer is printed to compensate for the height differences. This isachieved by parametrizing the CAD model, i.e., the CAD model of the structure to beprinted is replaced by a mathematical equation (model). In this study, the mathematicalmodel is updated for each layer in real-time with feedback data from sensors that monitorthe additive manufacturing process. The concept of updating a mathematical model andexecuting it in real-time is called real-time simulation (RTS). In this study, a HiL-basedreal-time simulation setup has been developed, which predicts the required printing layerheight and the number of layers (based upon the latest feedback data from the monitoringsensors), and the required height of the structure. By combining hardware and software,a cyber-physical system has been created, enabling the transition from automation toautonomous robotics and contributing to Industry 4.0.