Identifying Challenges in Casting Concrete Artifacts Using 3D Printed Molds

In many engineering fields, it is necessary for engineers to imagine a design and then manifest that design into a physical object. Engineering educators typically engage engineering students who have limited practice in this transference skillset, so we chose to design an instructional project involving casting mortar artifacts using 3D printed molds that students had analytically designed. In preparing this instructional project, we encountered difficulties in casting mortar objects using 3D printed molds that had certain geometries, and we wanted to know what factors in mold geometry contributed to artifact damage during demolding. The scope of this paper focuses on a scholarly project led by an undergraduate research student that explored how the design of 3D printed molds for casting mortar artifacts influenced damage caused during demolding. We designed a series of artifact molds with protrusive features that varied in their aspect ratios and their spatial density to explore how these geometric features contributed toward demolding damage. We experimentally measured the extent of damage by calculating the percent of spike height that was lost during the demolding process. We found that protrusive mold features with large aspect ratios influenced the amount of damage done to those features during demolding. We also found how the spatial density of protrusive features was also a significant cause of damage. From analyzing our data, we identified a clear threshold where mold geometry causes excessive damage during the demolding process. We learned from our scholarly project that casting mortar artifacts with protrusive features in future instructional projects should have surface features designed to be less than a 1:1 aspect ratio to minimize damage during demolding. Understanding these limitations on casting mortar artifacts in 3D printed molds will minimize complications in the instructional project that allows engineering students to analytically design and physically cast artifacts without resulting in excessive damage during demolding.