Custom Part Manufacturing Guide
Calculating Kinematics of a CTR
Graph Paper In-Plane Bending Experiment
Out-of-Plane Rotation Experiment
There are two different ways to make tubes for your CTR. The first is to order 3D printed Nylon12 tubes from a vendor. However, this can be pricey ($250 and up). A cheaper alternative is to purchase nylon tubing and heat set it to desired shapes. Below, we will provide materials needed for both methods.
For instructions on how to heat-set tubes, see the Tube Fabrication page.
To create heat-set nylon tubes, you will need to 3D print tube molds and purchase nylon tube stock. The Example Mold Components table below contains STL and STEP files for you to create a full set of three nested tubes.
The Mold Templates table contains the raw Fusion360 files used to create the example parts. In these files, you can edit the parameters to design your own custom tubes to your own custom experiments. For beginners, we recommend making a set of example tubes before designing your own.
Mold components are modular; you only need to print one of each piece. Once printed, you can attach a straight section to any curved section of the same tube diameter. See the Tube Fabrication page for an example.
<aside> 📎 These molds work best when printed out of a semi-heat resistant material such as ABS or ASA. It is also best to print with 6 walls, 4 top layers, 4 bottom layers, and 30% infill. This helps the molds retain their shape when they are placed in an oven. If you have to print these out of a softer material like PLA, you may need to adjust the heat setting process. See the Tube Fabrication page for details.
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You will also need to purchase the tube stock that you will use to create the tubes. We have included links to the recommended tubing. We have tested this heat-setting method with this specific tubing, but cannot guarantee results for other nylon tubing.
Tube locks are small pieces that you glue to the end of the tube so they can be locked into place in the actuation system. You will need one tube lock per tube that you make.
The following table contains tube STL files. These cannot be printed on a standard FDM printer; they must be printed on an HP Multi-Jet Fusion printer. These tubes were specifically designed to undergo 3% and 6% strain while bending. These tubes are defined in terms of their curvature instead of bending radius. Curvature is equal to $1/r$, where the radius is in meters.