Vietnamese-German University: Testing the Influence of Infill Pattern & Layer Thickness on PLA

Researchers Ei Cho and Thanh Tran, of Vietnamese-German University, explore the continually expanding science of 3D printing materials and how they are affected by material properties. In this study, the authors experiment with poly-lactic acid (PLA), outlining their findings in the recently published ‘Investigation on Influence of Infill Pattern and Layer Thickness on Mechanical Strength of PLA Material in 3D Printing Technology.’

While there has been plenty of research previously regarding mechanical properties and a reliance on shape, parameters, design, and layer thickness, in this study, the researchers are focusing specifically on PLA and the effects of layer thickness and infill pattern on part strength, stiffness, and ductility—whether in coupled or interactive instances.

Testing nine samples overall, the researchers used the Taguchi Method to examine infill and layer thicknesses, using the Minitab tool. Weka software was used as they researched suitable solutions, along with Annova (statistical support) and MATLAB tools (optimization).

The specimens for this project have two shoulders with a section in between:

“The shoulders are large so they can be readily gripped and the distance between two gripped shoulders are 65 mm, whereas the gauge section has a smaller cross-section with the length of 25 mm so that the deformation and failure can occur in this area,” explained the researchers.

In discussing materials overall, the researchers point out that while there is a wide range to choose from, ABS and PLA are still extremely popular as they generally offer users the opportunity to print parts that with accuracy and good surface finish; here, however, they chose PLA to avoid any of the more typical issues with ABS such as deviation, and features that are not as well-defined, such as corners.

ABS and PLA material properties comparison

“Overall, PLA is great for experimentation and is just another reason for its material properties to use in our FDM process,” explained the researchers.

Samples were designed using NX 10 and Cura, and then printed using the Builder 3D printers at the GPEM lab.

Tension Testing Machine in GPEM Lab

Overall, testing showed that layer thickness plays a much greater role than infill pattern in terms of influence. Higher layer thickness resulted in better mechanical strength, with triangle infill patterns also offering the greatest strength.

“However, the influence of infill patterns is not significant according to the Taguchi and coefficients from regression function,” stated the researchers. “According to the validation from simulations, the value of optimized parameters and resulted force can be determined as reliable results. The other effects of printing such as machine condition, ambient temperature, skill of temperature, amount of glue applied and so on affected the results.

“For the future work, the other types of pattern should be analyzed not only in term of mechanical properties but also in term of cost, material consumption, surface finish and environmental aspects. Moreover, new types of pattern which are more sustainable than current patterns can be created based on the previous studies. Furthermore, the number of experiments should be increased to get more accurate data and results.”

Because mechanical properties can have such a bearing on the outcome of work for 3D printing users, research continues in labs across the world experimenting with mechanical properties and color, shape memory polymers, in production of medical devices, and so much more.

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