The interest in additive manufacturing (AM) of cement-based materials is steadily increasing. Moreover, there is a growing need for higher productivity and part quality. In this study, the impact of the different values of the process parameters on part quality was identified. An alternative process-control strategy was investigated, according to which the width of the extruded path is controlled by the ratio of the extrusion speed over the scanner head speed. To conduct linear-and rotational-extrusion experiments, an experimental apparatus was designed. The significance of the effect of the speed ratio on the part quality was found to be the highest, followed by the extrusion radius, whereas the extrusion speed appeared to be of low importance. Therefore, in linear extrusion, high quality and consistency can be achieved by maintaining the ratio value above 0.8. However, in rotational extrusion, the effect of the radius was additionally considered by calculating the ratio on the outer side of the part, rather than on the centerline. Thus, acceptable quality and consistency were ensured for both linear and curved paths by controlling the aforementioned ratio values.

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The gas trapped into fine powders causes specific problems like feeding disturbances during roll compaction process. In this study, the gas flow and its effect on the rolling process are numerically investigated in the rolling direction, using Darcy's law and assuming the permeability as a function of both material density and particle size through Carman-Kozeny relationship. The solid properties evolution is based on the Johanson model, whereas the solid speed is determined from the conservation of the material mass. Computational results of solid properties and gas pressure distribution are presented by considering bentonite powder properties. According to material and process parameters, especially rolling speed and powder permeability, we discuss conditions for the escape of gas through the porous material during the process and stability conditions of the feeding at the rolls' entry. Beyond the simplicity of the model (1D), it allows for a better understanding of fine powders processing by roll press. It highlights the combined effect of the permeability of the powder and the rotating speed on the gas pressure, during roll compaction process.