Silicone 3D Printer

This is a custom silicone elastomer 3D printer, an adaptation from the original designer at Oregon State University.

This project was originally part of Tufts Exosuit, a student research team which mainly dwells at Tufts Human Factor Lab (Supervised by Professor James Intrilligator). For more information about my work as part of the research team, please visit the research page on my website. Recently, under funding difficulties and the notion that the project has diverged from the main focus of the research team, we decided to change this into an independent student project, with more funds kindly provided by Tufts MAKE Club.

We have been making steady progress on the project, and have been encountering considerable challenges as well. In the fall of 2019, we had some silicone blocks being successfully printed.

As you could probably see, the current print quality of the machine definitely has room for improvement. But considering that these are the first "successful" prints after months of struggling without much outcome, we are still very happy with the results and are actively searching for ways to make the printer work better.

Building Process

This project originally started in Spring 2019. We started by following the open-source building instructions from the Soft Robotics Toolkit website. We fixed some broken links from the out-dated bill-of-materials and made some minor adjustments to suit our needs.

Printer assembly, Summer 2019

Due to funding limitations, we had to let go the designated syringe pump from the building instruction and chose a cheaper substitute from Ebay. Later it turned out that the syringe pump we ordered could not output enough force to push the silicone gel through the mixing apparatus. As a result, we had to try various methods to circumvent the issue, and one of which was to reduce the viscosity of the unmixed silicone gel to reduce the load on the syringe pump. The following videos shows two print tests that were part of this modification. You can clearly see that although the well-mixed silicone gel is extruding without a problem, the viscosity of the liquid is not high enough to hold the print structure together.

Print tests with viscosity being too low

After completing the assembly, we decided to add more supporting structure to the main frame in order to make the printer more stable. To find out what structure does the best job, we created a simplified model in SolidWorks and ran some preliminary FEA analysis on the structure coupled with different support structures. For each scenarios, we added both torsional and horizontal load for a more well-rounded evaluation.

Plans for Improvements

This project was forced to put on hold for a while due to funding issues. In late Fall 2019, when Tufts MAKE club offered to fund this as a project independent from lab research, I was excited again and started thinking about ways to redesign the extrusion system. I came up with the following temporary solution that is not only cost-effective, but also easy to be integrated into the following system.

Preliminary sketch

The design incorporates an industrial epoxy dispensing system, which consists of a pneumatic dispensing gun, an empty dual carriage barrel originally designed for custom 1:1 ratio mixing glue, and a static mixer.

New extruder design

I'm planning to mount the entire apparatus to the extruder location while keeping everything else on the printer the same. I ordered the components in the design, and some initial testing with my arm has proven the system to be very promising. In Spring 2020, I have gathered a couple of fellow mechanical engineering students to work on this project together, and are making steady progress until the pandemic kept us from accessing the printer. We hope to continue to work on this project again soon.