*4.4. Limitation of Research Parameters*

It is clear that some of the process parameters are widely studied: infill density, layer thickness, raster angle, build orientation, and air gap. Print speed and raster width also occupy a place in the research field. However, other parameters such as infill pattern, number of contours and extrusion temperature are the least analyzed, which needs more attention. For example, the road width for raster and contour is assumed to have a similar effect on the properties in different studies. However, Gebisa and Lemu [80] concluded that raster width and contour width were two different parameters with completely different influences, which needed to be examined separately. For another instance, raster angle 0◦ ensures the best mechanical strength, presented by many researchers, while Dave et al. [97] found that samples built with raster angle 90◦ in Hilbert curve pattern displayed a better result as compared to 0◦ value. These different results indicate that researchers should spend more time investigating the "ignored" parameters, which may come to a different conclusion or view than before.
