Voxelfill now validated with fiber reinforced polymer

Rostock (Germany), 27.08.2024: AIM3D has succeeded in demonstrating the advantages of the patented voxelfill process. Strength tests now prove that this process can overcome inhomogeneous strengths of 3D components in the X, Y and Z axes and thus comes close to conventional processes such as injection moulding. Voxelfill can also be licensed to users of other 3D printing processes for material extrusion in accordance with EP 4100235-B1.

The Voxelfill strategy

The aim of the development of Voxelfill was to overcome inhomogeneous strengths in 3D printing. Currently, material extrusion 3D printing achieves approx. 50% tensile strength in the direction of printing, depending on the material. The printed layers therefore tear apart and the components are often only suitable for prototypes. With Voxelfill, AIM3D now achieves 80% tensile strength compared to the mold-bound injection molding process and therefore enables the technical application of 3D-printed parts made from certified pellets. The potential target is to achieve even 100% tensile strength. Voxelfill is a combination of injection molding and 3D extrusion printing based on the CEM process. Voxelfill achieves almost isotropic material properties in all directions, as well as enabling higher productivity and an orientation of fibers along the Z-direction. Clemens Lieberwirth, CTO of AIM 3D: “This makes Voxelfill a game changer with respect to the mechanical strengths of 3D components.”

Realization of the Voxelfill test series

In the XY plane, Voxelfill achieves mechanical strengths of 80% compared to injection molding. The initially determined values apply to unfilled technical polymers. This results in twice the strength compared to conventional 3D printing with FDM printers. For fiber-filled polymers, the expected increase in strength compared to conventional 3D printing with FDM printers is even higher. The Voxelfill-based test series were set up with tensile specimens to determine the XY strength and the Z strength. Variant A were horizontal specimens to test the tensile strength in the XY plane. Variant B were upright specimens to test the tensile strength in the XZ plane. Variant C was a block to test the tensile strength in the XZ plane based on milled specimens. As part of the AIM3D feasibility study, the stress (MPa) and strain (%) were measured for variants A to C (material Polycore PETG-1000 from Polymaker).

Optical analysis of the samples

Although the Voxelfill samples exhibit high tensile strengths, they still include pores, i.e. air inclusions, in the range of <0.15 mm³. Therefore, an even higher tensile strength and thus isotropy could be obtained by further optimizing the filling density. The use of fiber-filled polymers expands the potential of the Voxelfill process.

New test series with fiber-filled materials surprisingly reveal improved strengths

The transfer of the Voxelfill process to fiber-filled plastics clearly confirms the positive influence on the Z-strength. Tests were carried out with PETG GF30 from Polymaker at an extrusion temperature of 270°C. A series of tests were set up to determine the optimum printing parameters in order to compare the maximum achievable strength with both conventional 3D printing and Voxelfill. Tensile specimens in horizontal XY-orientation were produced as a reference. These were printed with two different infill orientations: on the one hand, along the tensile direction and on the other hand, at +/-45° to the tensile direction. The tensile strength with the infill oriented in the tensile direction was the highest at 72.4 MPa. However, this corresponds to a rather fictitious case, as this would not occur in a real injection molded part, where the fiber distribution depends on the geometry of the part and the number and orientation of the injection points. In comparison, the horizontal tensile specimens with an infill orientation of +/- 45° achieved 50.1 MPa. Following this, upright tensile specimens were printed in a conventional manner using a layer-by-layer infill without Voxelfill (which corresponds to the status of normal 3D printers). These achieved a tensile strength of 12.8 MPa. In comparison, the upright test specimens printed using Voxelfill achieved a higher tensile strength of 40.7 MPa.

Homogeneity and strength based on the test series with filled materials

Comparing the determined values for the tensile strengths reveals a homogeneity of strength of 81% for Voxelfill compared to the +/-45° printed reference specimens and 56% compared to the aligned reference specimens. The conventionally printed tensile specimens, on the other hand, only achieve a homogeneity of 25% compared to the +/-45° printed reference specimens and 18% compared to the aligned reference specimens. The strength-increasing effect of Voxelfill, which leads to more homogeneous component properties, comparable to those from injection molding, can therefore also be demonstrated with fiber-filled plastics (see comparative diagram with the different tensile strength values). Moreover, a look at the fiber distribution under the confocal microscope shows fibers aligned in the Z-direction, which are introduced by the vertical injection process of Voxelfill. Clemens Lieberwirth, CTO of AIM3D: “This effect of aligning the fibers is unique to Voxelfill and cannot be achieved in conventional, layer-by-layer 3D extrusion printing.”

Articles

Back
Cookie consent