Material Testing
3D printing is a very common rapid prototyping technology that provides opportunities to use different materials based on desired material qualities, such as ABS, PLA, and several others. Information concerning these material’s properties has not been well documented and is unavailable to people who print frequently. Material properties such as tensile strength and elastic modulus are crucial values when making prosthetics for frequent if not everyday use and because these values are not known for many materials, it can be difficult to determine each material’s best application.
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Various mechanical and environmental tests were performed on 3D printable materials to determine various material properties that can be used by LimbForge. This project was completed by two engineering students at Rochester Institute of Technology. The materials tested were PLA (Polylactic Acid, untreated & thermoformed), ABS (Acrylonitrile Butadiene Styrene), Cheetah, Eastman Amphora 3D Polymer Silicon, and PETG (Polyethylene Terephthalate Glycol). Mechanical testing included Tensile, Compression, Rockwell Hardness, and Charpy Impact Toughness tests. Environment testing included Ultraviolet Exposure, Humidity, and Thermal testing.
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3D printed test specimens were placed in one of three environmental chambers for a time period of 1-3 weeks; these were then mechanically tested and compared to baseline results of specimens that did not undergo environmental testing. The goal of this research was to determine and document material properties for commonly used materials by LimbForge, and publish the data so it is accessible to all associated with the LimbForge community.​
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The above parameters were used to create each test specimen. These can be varied based on application, but for consistency in test data these remained constant. Specimens were printed flat against the print bed, so no support material was needed. The Buildplate Adhesion parameter has a range based on material used. For more rigid materials (PLA, ABS), larger brims were used, and for more flexible materials (Cheetah, Amphora, PETG), the lower of the range can be used. For each specific material, parameters on the printers can be set and are displayed on each material's respective page. Please note that print speeds on printers are in percentages of the speed portrayed above in the Cura software.