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Material Overview
November 2018
Our materials team is currently in the process of deciding on the type of materials for each element of the hand. Our groups' primary goal for the semester is to design a single working finger. As for the bone structure of the finger, they are looking for materials that can be printed on the Lulzbolt 3D printer that replicate the characteristics that bones give as the framework of the hand.
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The two types of materials they are considering are GF30-PA6, Glass Fiber Reinforced Polyamide 6, and GF30-PP, Glass Fiber Reinforced Polypropylene. GF30-PA6 is a much stronger and more durable material, however, it is denser and more expensive than GF30-PP. In comparison, GF30-PA6 costs $180 per kilogram while GF30-PP costs $165 per kilogram. One obstacle we face is that both materials will be printed on a LulzBot 3D printer but require a 3rd-party tool head that costs $335.95.
For the “skin” of the hand they are planning on using a feature on the 3D printer to create a silicon swath to fit over the bone structure of the fingers and hand but are not primarily focused on this part yet as the goal of this semester is to design a single working finger.
Currently, they are leaning towards the GF30-PA6 material as it is stronger and although slightly more expensive, it is significantly stronger. In order to reduce the weight of the finger, we have ordered three samples to test in the solid mechanics lab. One is a solid block of material, one is hollow, and the other has a honeycomb structure inside of it. On top of the three samples, we have also ordered 15-20 small pieces similar in geometry to that in our design. Furthermore, we will place the materials under bending stress and collect data for multiple tests to get a true sample of data for our design.
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Figure 1. Bending stress testing.
Figure 2. Material test fractures.