Investigation and Feasibility of Printing Polyoxymethylene Semi-crystalline Polymer Parts with Fused Filament Fabrication 3D Printer and Evaluation of Mechanical Properties of the Printed Samples

Fused filament fabrication (FFF) is one of the simple and cost-efficient methods of additive manufacturing (AM) of complex objects which has widespread applications in various industries. Developing 3D printing materials is one of the main challenges that scientists are dealing with in this method. Currently, the materials used for 3D printing are amorphous polymers and semi-crystalline polymers that behave similarly to amorphous polymers in the melting process. This is because of the less shrinkage of amorphous thermoplastic materials compared to semi-crystalline polymers which facilitate printing. Since semi-crystalline polymers exhibit better mechanical characteristics compared to amorphous polymers, these materials must be used in the FFF process as well. However, it must be noted that printing these materials is difficult as they show high shrinkage. Particularly, this can be seen by the weak adhesion of the first layer to the bed and the layers' adhesion to each other as a result of high shrinkage. Therefore, this paper aims to assess the feasibility of printing objects from semi-crystalline polymers made of polyoxymethylene (POM). The parameters under study include raster angle, nozzle temperature, filling pattern, filling percentage, and fan mode. The experiments showed that due to high shrinkage, it is not possible to print semi-crystalline parts the same as the parts made of amorphous polymers. However, these parts can be printed by changing the printing direction. Moreover, it is observed that under a specified direction, without the fan, low nozzle temperature, low filling percentage, and 0/90 filling pattern, the semi-crystalline parts are printed more easily. Finally, the mechanical properties of the standard printed samples were evaluated, and the maximum tensile strength, flexural strength, and compressive strength are 11.5, 28, and 8 MPa, respectively.