Discipline: Technology and Engineering
Subcategory: Civil/Mechanical/Manufacturing Engineering
Jasmine Gay - Florida State University
Co-Author(s): Dr. Carl Moore Jr., Florida A&M University, Tallahassee, FL
The DeXter printer is a dual nozzle 3D printer that works using selective compliance assembly robotic arms (SCARA). An advantage of DeXter is that its two extruders move independently thus giving it the potential to cut build times in half when compared to typical single or dual extruder printers. However DeXter requires a collision avoidance process for the two arms. A drawback of this process is that it may create a time delay along some sections of the printed parts. It is possible that this time delay could have adverse effects on the print?s strength, due to cooling. As some materials cool they become less tacky or may experience shrinkage, thus making it harder for these sections to adhere to each other. This cooling phenomenon is not only something that could be an issue for DeXter, but it is also an issue with parts printed using conventional 3D printers, as a product of the G-code generated by the slicing software. This research aims to determine how cooling time can affect the strength of a print. We believe that as cooling time increases the yield strength of a part will decrease.
In order to test the strength of the 3D printed materials we will use a tensile test. Acrylonitrile Butadiene Styrene (ABS) plastic will be used as the 3D printed material, therefore the dimensions of the print sample will be determined using ASTM D638 with the type I configuration, and a thickness of 4.5mm. The MakerBot Replicator 2X was used to print each of the samples, so it was necessary to manipulate the G-code from the standard object slicer in order to create a dwell in the middle of each part. Repetier Host was used to edit the G-code for each sample. To efficiently add the dwell for each test sample it was necessary to build only half of the sample in a CAD software, then import the half sample into the Repetier Host twice, and push the two pieces together to make the whole sample. Importing it this way produced a six line border going through the middle of the print, creating solid infill through the middle 3.36mm thick, as opposed to having 20% infill in this area. A control was printed by importing the sample as a whole print instead of a half.
Our findings indicate that as cooling time increases the strength of the print decreases. One print with a dwell time of zero seconds had a yield strength of 12.4 MPa. While another print with a dwell time of two minutes and thirty seconds had a yield strength of 6.9 MPa. The next steps in this experiment will be altering the print configurations across the middle of the print in an effort to combat the decrease in yield strength. We will look into printing a more seamless middle section along the print instead of the six line border, printing with different infill percentages, and lastly printing a jagged dividing line for the print as opposed to a straight line.
References: Filaments: The Big Two. How Does 3D Printing Work, by Ian Chow-Miller, Cavendish Square Publishing, 2018, pp. 75-77
Funder Acknowledgement(s): This research was funded by NSF-RISE, award number 1646897. I would like to thank Moore Research Group and Marquese Pollard for assistance during the research. As well as the High Performance Materials Institute and the Aero-Propulsion, Mechatronics and Energy Building for supporting this research.
Faculty Advisor: Dr. Carl Moore Jr., firstname.lastname@example.org
Role: For this research I determined the proper dimensions of the printing sample, and the created it in CAD. I determined how to edit the G-code of the print in order to add a dwell in the middle of the print. I printed each of the testing samples, and assisted in preforming the tensile tests for each of the samples. I also determined all of the experimental parameters and troubleshot any problems that came up during the experiment.