The effect of processing parameters on the mechanical characteristics of PLA produced by a 3D FFF printer

Abstract

3D printing by fused filament fabrication (FFF) provides an innovative manufacturing method for complex geometry components. Since FFF is a layered manufacturing process, effects of process parameters are of concern when plastic materials such as polylactic acid (PLA), polystyrene and nylon are used. This study explores how the process parameters, e.g. build orientation and infill pattern/density, affect the mechanical response of PLA samples produced using FFF. Digital image correlation (DIC) was employed to get full-field surface-strain measurements. The results show the influence of build orientation and infill density is significant. For on-edge orientation, the tensile strength and Young’s modulus were 55 MPa and 3.5 GPa respectively, which were about 91% and 40% less for the upright orientation, demonstrating a significant anisotropy. The tensile strength and Young’s modulus increased with increasing infill density. In contrast, different infill patterns have no significant effect. Considering the influence of build orientation, based on the experimental results, a constitutive model derived from the laminate plate theory was employed. The material parameters were determined by tensile tests. Results demonstrated a reasonable agreement between the experimental data and the predictive model. Similar anisotropy to tension was observed in shear tests; shear modulus and shear strength for 45° flat orientation were about 1.55 GPa and 36 MPa, whereas for upright specimens they were about 0.95 GPa and 18 MPa, respectively. The findings provide a framework for systematic mechanical characterisation of 3D-printed polymers and potential ways of choosing process parameters to maximise performance for a given design.

Determining the parameters for a 3D-printing process using the fused deposition modeling in order to manufacture an article with the required structural parameters

“…The results of experimental studies reported in [8][9][10] could be changed by the application of the theory of layered plates, whereby the filament is a reinforcement fiber while the angle of reinforcement is the angle of printing of the molten filament with the accepted thickness. This is the approach implemented in paper [11], which demonstrated a good alignment between the predicted elastic and strength characteristics derived from the analytical expressions of the theory and the experimental values.…”

“…However, it should be noted that the choice of parameters should be reasonable. Some parameters, such as the position of the specimen, the angle of the filling print, the filling density could be determined in advance using a theory of layered plates [11]. Other parameters should provide not only the required properties but also take into consideration the economic costs of the 3D printing process.…”

“…Our analysis of literary sources [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] reveals that the researchers' focus is on several basic parameters of the 3D printing process that affect the properties of an article.…”

“…Thus, the anisotropy of the material in the article takes place at the 3D-printing by the FDM method. Depending on the position of a specimen on the platform, its mechanical properties would change during 3D printing [7][8][9][10][11]. At the same time, calculating the dependence of the mechanical properties of articles on the angle of the filament printing involving the FDM technology could help properly place the specimen on a desktop to provide for the required properties of the article.…”

“…Filling density is measured as a percentage and could vary from values where only a part's contour is printed to complete filling, which corresponds to a monolithic structure. A study reported in [11] has shown that the filling scheme has no effect on the mechanical characteristics of a specimen at the same density of filling the specimen with the material. The density of the internal filling of a part affects the duration of the manufacturing process and the strength of the article, so the choice of the appropriate value of the filling density is based on the trade-off between these parameters.…”