Analysis of AM Parameters on Surface Roughness Obtained in PLA Parts Printed with FFF Technology

Abstract

Fused filament fabrication (FFF) 3D printing technology allows very complex parts to be obtained at a relatively low cost and in reduced manufacturing times. In the present work, the effect of main 3D printing parameters on roughness obtained in curved surfaces is addressed. Polylactic acid (PLA) hemispherical cups were printed with a shape similar to that of the acetabular part of the hip prostheses. Different experiments were performed according to a factorial design of experiments, with nozzle diameter, temperature, layer height, print speed and extrusion multiplier as variables. Different roughness parameters were measured—Ra, Rz, Rku, Rsk—both on the outer surface and on the inner surface of the parts. Arithmetical mean roughness value Ra and greatest height of the roughness profile Rz are usually employed to compare the surface finish among different manufacturing processes. However, they do not provide information about the shape of the roughness profile. For this purpose, in the present work kurtosis Rku and skewness Rsk were used. If the height distribution in a roughness profile follows a normal law, the Rku parameter will take a value of 3. If the profile distribution is symmetrical, the Rsk parameter will take a value of 0. Adaptive neural fuzzy inference system (ANFIS) models were obtained for each response. Such models are often employed to model different manufacturing processes, but their use has not yet been extended to 3D printing processes. All roughness parameters studied depended mainly on layer height, followed by nozzle diameter. In the present work, as a general trend, Rsk was close to but lower than 0, while Rku was slightly lower than 3. This corresponds to slightly higher valleys than peaks, with a rounded height distribution to some degree.

Modeling of the Influence of Input AM Parameters on Dimensional Error and Form Errors in PLA Parts Printed with FFF Technology

“…The variables to be optimized have been selected as the surface roughness, characterized by the arithmetic mean roughness (Ra), which was already studied in a previous work carried out by the authors of this manuscript. Therefore, the ANFIS models developed in this present study for roundness and dimensional error are employed, as well as the ANFIS developed for Ra in [ 30 ].…”

“…Printing supports were required, in PLA material. Further details of the printing process are provided in a previous work [ 30 ].…”

“…The experiments were defined according to a fractional factorial design 2 5-1 , with 5 variables and 2 levels. Selected variables are as follows [ 30 ]: Nozzle diameter (ND) between 0.4 and 0.6 mm, temperature (T) between 195 and 205 °C, layer height (LH) between 0.1 and 0.3 mm, print speed (PS) between 30 and 50 mm/s, and extrusion multiplier between 93 and 97%.…”

“…In a previous work, hemispherical cups were 3D printed in polylactic acid (PLA), with different printing conditions, according to a fractional factorial design. ANFIS models were obtained for different surface roughness parameters measured on hemispherical surfaces that are similar to those of the acetabular part of hip prostheses [ 30 ]. In this present work, dimensional error and form errors of FFF 3D printed spherical parts are addressed.…”

Procedure Increasing the Accuracy of Modelling and the Manufacturing of Surgical Templates with the Use of 3D Printing Techniques, Applied in Planning the Procedures of Reconstruction of the Mandible

“…The creation process consists in melting the filament in a heated head, and then it is applied to the worktable. Once the first layer is placed, more layers are added to the object until the entire model is printed [ 71 , 72 ]. In the process of making physical models, an anatomical model of the mandible with marked resection sites ( Figure 6 a), a model representing mirror of the health part of the mandible onto the pathological part ( Figure 6 b), a resected area ( Figure 6 c), and a model serving for estimating the volume of the resected bone tissue ( Figure 6 d) were printed.…”