Tough PLA FDM 3D Printing: Which Settings Affect Strength?

A 3D-printed part must do more than look right: it needs to withstand the loads expected in use. In fused deposition modeling (FDM), settings affect how filament is deposited layer by layer and can influence a part’s mechanical response. This study examines six FDM settings and measures their relationship to Tough PLA performance in tensile, flexural and compression tests.

Key findings

• The material was UltiMaker Tough PLA, a technical PLA filament developed to be less brittle than standard PLA.
• Six print settings were studied: layer height, wall thickness, infill density, build plate temperature, printing speed and printing temperature.
• The definitive screening design (DSD) included 17 experimental runs: the 13-run base design plus four additional center points.
• The study measured maximum force and Young’s modulus in tension, flexure and compression, giving six responses and six regression models.
• All six models were statistically significant at p < 0.05. The tensile maximum-force model had an adjusted R² of 0.9956 and a predicted R² of 0.9911.

Why study Tough PLA printing settings?

FDM is an additive manufacturing process that can produce complex parts without conventional tooling and can translate a digital design into a physical object layer by layer. But a successful print is not automatically a mechanically suitable part. Layer height describes the thickness of each deposited layer, while infill density indicates how much of the part’s interior is filled with material. Wall thickness, speed and printing temperatures are other process settings that may affect the printed structure.

PLA is widely used because it is comparatively easy to print, but standard PLA can be brittle. Tough PLA is a commercial technical variant intended to improve toughness and impact resistance. Understanding how its print settings relate to test results can inform decisions when developing functional prototypes, tooling and technical products. The findings, however, apply to the material and experimental conditions studied; they should not be assumed to hold for every filament or printer.

Material, factors and mechanical tests

In a study by Adi Pandžić, PhD, UltiMaker Tough PLA was investigated using FDM material extrusion. The six factors were treated as continuous variables with low, middle and high levels in the design.

Printed specimens were tested in tension, flexure and compression. For each test type, the study recorded maximum force and Young’s modulus. Maximum force is the highest force measured during a test. Young’s modulus describes stiffness in the elastic region. These are distinct responses: force also depends on specimen geometry, whereas modulus describes the material’s response to deformation in that region.

The responses were reported as force in newtons and modulus in gigapascals. The findings should therefore be interpreted for the studied Tough PLA, specimens and selected process settings, rather than as guaranteed values for any FDM setup.

How the definitive screening design worked

Definitive screening design is a design-of-experiments method that can estimate main effects, quadratic effects and two-factor interactions within one experimental plan. An interaction occurs when the effect of one setting depends on the level of another. This matters because FDM results may reflect combinations of settings, not just the isolated effect of a single parameter.

For six factors, the base DSD required 13 experimental runs. The paper reports that four center points were added, bringing the total to 17, to increase degrees of freedom and improve the estimate of lack of fit. Least-squares regression was then used to fit models to the measured results. Statistically significant terms were retained while maintaining model hierarchy.

Results for tension, flexure and compression

Analysis of variance (ANOVA) found all six regression models statistically significant. Lack of fit was not statistically significant for any model, supporting the selected model forms in this analysis. The tensile maximum-force model included all six main effects, an interaction between layer height and wall thickness, and a squared printing-temperature term. In coded factor units, its fitted coefficients were positive for wall thickness, infill density and printing temperature, and negative for layer height and printing speed. These signs describe the fitted model across the studied design space; they are not universal rules for every printer or setting range.

For tensile maximum force, the main-effects analysis ranked wall thickness as the most influential factor, followed by printing temperature and infill density. For tensile Young’s modulus, infill density had the greatest impact. These rankings refer to the study’s experimental plan and responses. They do not mean that every setting should simply be increased to its maximum.

Across the six models, adjusted R² ranged from 0.9151 to 0.9956, while predicted R² ranged from 0.7974 to 0.9911. The tensile maximum-force model had the highest adjusted R²; flexural Young’s modulus had the lowest predicted R². RMSE, or root mean square error, ranged from 0.0132 GPa for compressive Young’s modulus to 103.62 N for compressive maximum force. Adequate precision, a signal-to-noise measure, exceeded 4 for every model.

The paper reports that confirmation tests were also conducted using specimens printed with randomly selected parameter values. Relative error was calculated by comparing predicted and experimental responses. The paper reports low relative errors and concludes that the models were sufficiently accurate and reliable for prediction within the study.

What the results mean for engineering and research

For engineers and product designers, the study provides a way to examine how FDM settings relate to selected mechanical responses of Tough PLA. The models can help explore parameter trade-offs, but they do not replace testing when a particular component needs to be qualified for a specific use. It is also important not to confuse maximum force with tensile, flexural or compressive strength: the modeled responses were maximum force and Young’s modulus.

For students and researchers, the work illustrates how DSD can screen several process settings with a limited number of experimental runs. It also shows why model assessment should use multiple indicators, including adjusted and predicted R², error measures and lack of fit. Confirmation experiments add a further check on whether model predictions agree with new measurements.

Limitations and next steps

The conclusions are specific to UltiMaker Tough PLA, the six selected factors and the ranges used in the experiments. They do not establish how other PLA formulations, ABS, PETG or SLA resins will behave. Nor does the study show that the same regression coefficients apply to other printers, specimen geometries or print orientations. Testing models under additional conditions could extend the evidence, but those results are outside the scope of this paper.

Conclusion

This study applies definitive screening design to six FDM settings and models the maximum force and Young’s modulus of Tough PLA specimens in tension, flexure and compression. The statistically significant models and confirmation tests support their use within the tested conditions. The clearest reported tensile findings are that wall thickness had the strongest effect on maximum force, while infill density had the greatest effect on tensile Young’s modulus.

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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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