FDM PA-CF Printing: Which Orientation Makes Parts Stronger?

A part made by FDM 3D printing may not perform equally in every direction. The orientation chosen for a build can affect how printed material responds to tension and bending, which matters when engineers and designers select a manufacturing setup. In a study by Adi Pandžić, PhD, this issue is examined for carbon-fiber-reinforced polyamide, along with whether drying the filament before printing changes the test results.

Key findings

• Among specimens printed without pre-drying, the flat orientation achieved the highest tensile strength, 45.2 MPa, and flexural strength, 43.5 MPa.
• The vertical orientation produced the lowest tensile strength, 9.0 MPa, and flexural strength, 11.1 MPa.
• Drying filament at 80 °C for 12 hours was associated with higher strength in flat specimens: tensile strength reached 50.5 MPa and flexural strength 54.5 MPa.
• For side-oriented specimens, flexural strength increased from 21.9 MPa without drying to 32.6 MPa after drying. The table lists tensile strength as 30.3 MPa in both conditions.
• The paper reports that specimens did not break during bending tests, including the vertically printed specimens.

Why print orientation and drying matter

Fused Deposition Modeling (FDM), also called material extrusion, builds a part by depositing melted filament in lines and layers. The part’s properties can depend on how those deposited roads and layers bond, so print orientation can influence the response to a load. Tensile testing pulls a specimen, while flexural testing evaluates its response to bending. The study compares both test types rather than treating printed material as having one strength value for every loading direction.

The material was a polyamide composite reinforced with chopped carbon fibers. Polyamide filaments can also be affected by moisture, making filament preparation relevant to print quality and mechanical performance. The study therefore compared three print orientations and tested pre-drying for two of them. The paper focuses on this specific material and test setup; its results should not be assumed to apply unchanged to other nylon grades, printers or process settings.

What the study tested

The material was Luvocom 3F PAHT CF 9742 BK, a PA6-based composite containing 15% chopped carbon fiber. Specimens were printed on a Raise3D E2CF FDM printer. The study used flat, side and vertical orientations. Filament for the flat and side specimens was also dried at 80 °C for 12 hours before printing; the paper does not report a dried vertical group.

The stated settings included a layer height of 0.15 mm, four shells, an extrusion width of 0.4 mm, 100% infill and a grid infill pattern. The heated bed was set to 80 °C, the extruder to 290 °C, and the default print speed to 60 mm/s. Layer height is the thickness of each deposited layer, while infill describes the internal structure of a printed part. The specimens were designed in Solidworks 2023, prepared in ideaMaker 4.3.2 and printed from generated G-code. The paper states that three replicas were printed for each of the three orientations and that 30 specimens were evaluated overall.

Tensile tests followed ISO 527 and flexural tests followed ISO 178. Both used a test speed of 5 mm/min on a Shimadzu AGS-X universal testing machine equipped with a 10 kN load cell. Tensile strength represents the maximum stress before failure under tension. The modulus of elasticity is a measure of stiffness in the elastic range. The study recorded strength and modulus for the tensile and flexural tests.

Results: a clear orientation effect

For specimens without drying, tensile strength decreased from flat to side to vertical. Flat specimens reached 45.2 MPa, side specimens 30.3 MPa, and vertical specimens 9.0 MPa. Tensile modulus followed the same order, at 3.5 GPa, 2.8 GPa and 0.9 GPa, respectively.

The flexural results showed a similar pattern. Flexural strength was 43.5 MPa for flat specimens, 21.9 MPa for side specimens and 11.1 MPa for vertical specimens. The reported flexural modulus values were 2.6 GPa, 1.1 GPa and 0.3 GPa, respectively. In this test series, the flat orientation therefore gave the highest measured tensile and flexural properties, while the vertical orientation gave the lowest.

After drying, flat specimens reached a tensile strength of 50.5 MPa and tensile modulus of 3.5 GPa. Their flexural strength was 54.5 MPa, with a flexural modulus of 2.8 GPa. For side specimens printed after drying, the reported tensile strength and modulus were 30.3 MPa and 2.8 GPa; flexural strength and modulus were 32.6 MPa and 1.1 GPa.

The paper reports that drying increased tensile strength by 12% for flat specimens and 47% for side specimens. It also reports flexural-strength increases of 25% for flat and 49% for side specimens. There is, however, an inconsistency in the paper’s side-orientation tensile result: Table 3 lists 30.3 MPa both with and without drying, whereas the text reports a 47% increase and the figure shows a different label. The reported percentage should therefore be read alongside this discrepancy rather than treated as directly confirmed by the table. For flexural strength, the tabulated values of 21.9 MPa and 32.6 MPa are consistent with the reported increase of about 49%.

Practical implications for engineers and students

For a designer developing a PA-CF part, orientation should be considered in relation to the expected direction of loading. In this study, flat specimens performed best in both tensile and flexural tests, and vertical specimens performed worst. That is evidence for the tested material and configurations, not a universal rule that flat placement is optimal for every geometry or service condition. A part’s intended use and the direction of its loads still need to inform build planning and validation.

Filament preparation is another process variable worth controlling. The study reports results after one drying condition, 80 °C for 12 hours, and compares drying only for flat and side orientations. It does not establish an optimum drying schedule or show that the same changes will occur with every polyamide composite. For product development, the findings can help identify variables to test, but they do not replace mechanical qualification of a finished component for its intended application.

The work is also useful in teaching and research because it connects manufacturing choices to standardized mechanical tests. Students can see why it is important to report orientation, material, print settings and test method when presenting FDM results. Researchers can use the reported pattern as context for follow-up experiments, while accounting for the inconsistency in the side-oriented tensile data.

Limitations and next steps

The investigation covered one PA-CF material, one FDM printer and the stated print settings. Drying was evaluated for flat and side specimens, but not for vertical specimens. The discrepancy between the table, figure and discussion for side-oriented tensile strength limits interpretation of the drying effect in that particular comparison. The paper also notes that the measured tensile strength and modulus were substantially lower than the manufacturer’s listed typical values, so the manufacturer’s data should not be treated as a direct substitute for results from printed specimens.

The paper recommends further work to optimize drying parameters and investigate how other printing parameters affect the mechanical and other properties of CF-PA6. It also identifies hardness, impact toughness and compressive strength as properties for future analysis. These tests could broaden the assessment beyond tension and bending.

Conclusion

The study reports that print orientation strongly influenced the tensile and flexural properties of FDM-printed carbon-fiber-reinforced polyamide. Flat specimens had the highest measured strengths, while vertical specimens had the lowest. Pre-drying at 80 °C for 12 hours was associated with higher flat-specimen strength and higher flexural strength in side specimens, although the side tensile results contain an internal discrepancy in the paper. The research was published in 2023 in the Proceedings of the 34th DAAAM International Symposium on Intelligent Manufacturing and Automation. Its practical message is to treat orientation and filament preparation as part of FDM process planning and to validate the selected setup with relevant tests.

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Author: Adi Pandžić, PhD in Mechanical Engineering

This article summarises a published research paper; please refer to and cite the original paper. About the author

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