Session: 03-01-07: Annual Conference-Wide Symposium on Additive Manufacturing

Paper Number: 145712

145712 - Properties of 3d Printing Resins for Humanoid Robot Application 

The development of additive manufacturing techniques has created inexpensive solutions for the field of robotics. The lower cost of 3D printers and plastics has allowed a wider range of consumers access to rapid prototyping. The capability of 3D printers to create complex shapes brings more possibilities as well. One style of 3D printers that is able to create these complex shapes while maintaining strength is Stereolithography (SLA). SLA printers are capable of creating high quality complex parts at rapid rates due to the laser curing process. There is a wide range of materials that these printers can use to accommodate for the variety of applications. One such application is humanoid robots. High strength is required to withstand the large forces and torques experienced during standing and locomotion. The parts will also need high toughness to protect against impact loading.

For the past three years, students at Worcester Polytechnic Institute (WPI)  have been working on a fully 3D printed humanoid robot based on the Poppy Project. Tests, such as standing and walking, have shown structural weakness of the 3D printed components. This necessitated deeper investigations into the materials used for 3D printing for such humanoid robot applications.  

Engineering plastics are polymers with high values in varying material properties, such as stress, elongation at break, and temperature resistance. The stress and elongation at break are the two properties that are focused on specifically for the application of humanoid robots.Various low cost high strength or high resilience were printed on low cost SLA printers. For each resin, multiple dog bone tensile test specimens were printed at 100% concentration of the resin and at the settings recommended by each resin manufacturer. A tensile test was completed using a machine capable of applying up to 2.5kN load and specifically tuned for softer materials and plastics.

One benefit to using SLA printers is the capability to mix resins to adjust the properties of the final product. This means that resin with higher strength can be mixed with a resin that has a higher elongation at break to produce a material with properties somewhere in between. For this paper, a mixture of high strength resin and high toughness resin with a ratio of 5,10, and 15 percent volume of high toughness was tested. Since the two resins do not have the same printer settings, varying settings were tested to see what produces the best properties. These mixtures and settings were printed into dog bone samples and evaluated through tensile tests. As is the case for 3D printing, each dog bone is not printed perfectly. Whether this be caused by a method of preparation or occur during the printing process, the results did not exactly match the specifications given by the companies.The paper will discuss the experiments and results in depth. 

Presenting Author: James Van Milligen Worcester Polytechnic Institute

Presenting Author Biography: I am a Graduate Mechanical Engineering student that is receiving my M.S. in Mechanical Engineering in May 2024.
My focus is in mechanical design.

Authors:

James Van Milligen Worcester Polytechnic Institute
Merel Sutherland Worcester Polytechnic Institute
William Michels Worcester Polytechnic Institute
Pradeep Radhakrishnan Worcester Polytechnic Institute