The growing popularity of 3D-printed PLA (polylactic acid) products and prototypes especially in the dental industries elevates the need for research into how printing parameters affect dimensional and mechanical properties. It is crucial to understand and minimize shrinkage of 3D printed parts, especially in applications such as dentistry, which require high precision. In other 3D printing applications, shrinkage could create issues such as interference and poor tolerances and fit up.

This study focuses on investigating how fill fraction and fill morphology affect shrinkage. To investigate shrinkage uniformity, U-shapes are printed with three levels of fill percentage: 25%, 50%, and 100%, using an Ender-3 3D printer with the print bed held at a constant 60 °C. Three replicates are made for each fill fraction and weighed to compare with the expected weight. Shrinkage is first measured manually using a caliper then a shrinkage simulation is performed using Geomagic and compared with 3D scans of the experimental samples.

The lower fill fractions indicated higher levels of shrinkage after initial measurements. However, when normalized over the total part weight, the lower fill fractions can be used to optimize the strength vs weight or the strength vs stiffness ratio for applications such as dental models where strength should be maximized, and weight should be minimized. Moreover, more shrinkage is expected with parts that involve more complicated shapes such as holes and crevices, which is relevant in the dental field due to the highly sensitive applications. The findings of this study can contribute to enhancing the precision and quality of 3D printed PLA products in a wide variety of applications and industries. These different parameters will allow us to develop techniques to mitigate the effects of shrinkage for 3D printed equipment.