Goliath Fall 2016
Final 3D Printing and Polishing
By: Dylan Hong (Design and Manufacturing Engineer)
Approved by Kristen Oduca (Project Manager)
Table of Contents
Introuction
Requirement: All parts being 3D printed will be printed under 6 hours with no single print over 2 hours
3D modeling is a great tool for designing products and implementing ideas. However, when bringing 3D simulated designs into real life, we realize the limitations and errors that occur with 3D printing. After creating many designs on Solidworks and printing a variety of prototypes, we noticed that the 3D printers are not accurate in printing small objects, and other details such as mounting holes. This quickly became one of our biggest challenges, especially since our project is compact in size and the requirement of the print time could not exceed a total of six hours.
Final 3D Print
Although the customer insisted we used ABS material because it is the most commonly used and can be polished with acetone, I decided that NGEN was the best filament to print our final product with. Throughout the semester, I have printed prototypes out of different material such ABS, PLA, and NGEN to implement a tradeoff study, which can be found in the blog post 3D Filament Tradeoff Study. From what I have observed, NGEN material when printed was sturdy, glossy, and well-rounded. It produced the less flaws, when compared ABS and PLA.
When printing the final product on the Lulzbot Taz 5 printer, the software that we used to simulate the STL file onto the bed of the printer was the Makerbot Print. The Makerbot Print allows us to modify the settings such as quality of the print, placement of the parts, and adding support layers. With the default settings, we realized that the total print had exceed six hours. In order to achieve the required print time of under six hours, we changed the quality of the print from standard to low, which allowed the parts to print faster. Since our parts were thin and printed in low quality, we also modified the settings to slightly increase the infill from 15% to 20%, this allows the parts to solidify and become more durable. In the end, our total print time with the necessary support layers and settings, we were able to achieve a final print time of 5 hours and 22 minutes.
Polishing
When printing the final product, my division manager ran out of black nGEN filament, so we decided to print it in all white filament. For polishing, the customer suggested that we speak to Jeff Gomes about acetone vaping to give the parts a nice glossy finish. But after experimenting with the acetone, we realized that nGEN filament is not dissolvable with acetone. This gave us the opportunity to explore different methods of polishing and painting our parts by sanding, spray painting, and clear coating.
The method we used was the Makerbot guide to post processing 3D prints with sanding and painting. When sanding, we used 60, 150, and 220 grit to dry sand, then we used 400, 800, and 1200 grit to wet sand; until we achieve a glass textured surface on our prints. Next, we used primer to fill in the cracks, especially for the noticeable lines caused 3D printing. An hour later, we spray painted the parts black and waited about 20 to 30 minutes to apply another coat of black paint to ensure evenness throughout the parts. After another hour, we applied a clear gloss coat to the parts to protect them from scratches and peeling.
Some problems that occurred throughout this process was that we ran out of black spray paint near the end of the second treatment of paint. Also when spray painting outdoors, it had reached sunset by the time we waited for it to dry. This made it hard to see how even we applied the paint onto the parts. The prints came out fairly nice and dry for the time we had left, one thing that I would recommend is to wait much longer than an hour between applying primer, paint, and the gloss coat. The directions state that to have a full and complete drying of each coat of primer, paint and gloss we must wait up to 24 hours. However, we did not have that much amount of time to follow the directions as stated, therefore, we expected some flaws such as uneven paints and finger print markings on the parts.
Conclusion
Overall, we were happy with our final print. We were able to fix the warping of certain areas by adding extra support layers and we were able to polish and paint our parts and make them look as if they were injection molded instead of 3D printed. With the problems of polishing and painting, we realize that drying in between coats of primer, paint, and gloss was the most important factor in achieving a nice clean finish, which we will consider in the future. Also, polishing prints is a personal preference and depends on what kind of look is desired for the product. Many 3D printing enthusiast will suggest that polishing may destroy the uniqueness of the texture provided by 3D printing. Another honorable consideration is to keep the final print as is, especially since the nGEN material produces a nice glossy finish.