The influence of the layer thickness change on the accuracy of the zygomatic bone geometry manufactured using the FDM technology

Designing and manufacturing a model of the anatomical structure while performing a surgical procedure is not a simple task. It is especially true of the craniofacial area, which consists of bone tissues with very complex geometry. Appropriate knowledge and skills in medicine and technical sciences are needed, which will allow the full use of currently available tools in the processes related to the reconstruction of the craniofacial areas. It is especially true of the central craniofacial region, which is most frequently damaged. Due to the unique geometry of the models of anatomical structures, manufacturing them using subtractive methods is very difficult or often impossible. This situation makes the additive methods an ideal alternative for manufacturing this model type. Many factors during 3D printing affect the accuracy of the model geometry. The most important are the type of technology used and the finishing treatment, the material used, the print layer's selected thickness, and the object's orientation in the 3D printer space. The manuscript determined the impact of changing the layer thickness on the zygomatic bone geometry accuracy. The reference model was obtained from the DICOM data obtained from the measurement carried out on a multi-detector tomograph. The printing process was carried out on a Fortus 360 - mc printer. Physical models of the zygomatic bone were made of ABS-M30 material using four-layer thicknesses: 0.127 mm, 0.178 mm, 0.254 mm, and 0.330 mm. To assess the accuracy of the model geometry printout, the MCA-II measuring arm with an MMDx100 laser head system was used. The adjustment of the nominal model obtained at the RE / CAD design stage and the reference model created at the measurement stage using the optical system was carried out using the best fit method with an accuracy of 0.001 mm. The accuracy analysis was presented by presenting statistical parameters and histograms. Based on the obtained results, a gradual deterioration in the accuracy of the model geometry representation with the increase of the print layer thickness was observed. However, all the models manufactured are within the accuracy of +/- 0.25 mm geometry, acceptable to surgeons.