Shrinkage and layer adhesion affect each other
In the end, both challenges to prevent deformation during the large scale 3D printing process, affect each other. The shrinkage is reduced with adding a lot of fillers e.g. fibers. However, the more fillers, the less polymeric matrix remains.
When looking at layer adhesion, the fibers do not cross over to the previous layer as the fibers are pretty much aligned in the printing direction. This eventually means that when a material is filled with 50% glass fibers for example, only 50% polymeric matrix remains to take care of the layer adhesion. However, when a material has no fillers, this can be a 100% polymeric matrix taking care of layer adhesion. One can understand that having 100% material taking care of layer adhesion will give better results then only 50%.
This eventually causes the big differences between strength and stiffness in the XY opposed to the XZ plane. Where XY can be, for higher strength materials, in the range of 100-200MPa. The XZ often is only 20% of that. Typical strengths for thermoplastics without fibers are much lower, so without additional tricks the XZ values will always be lower than the XY.
Would you like to know more about materials for large scale 3D printing? Have a look at our material page or contact us to discuss the best possible material for your production.