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In the following procedure, we will shape-set Nylon12 medical tubing into pre-curved tubes that we can use in a CTR. You will need the materials listed in the Heat-Set section of the Tube Materials page. You will also need a toaster oven or similar device.

The pieces listed in the Tube Materials page will allow you to create one set of three tube CTRs. The image below shows two full sets of tubes; one set has larger curvatures than the other.

Screenshot 2023-09-11 090442.png

Tools and Equipment

You will access to the following tools and equipment to shape-set your tubes:

Instructions

  1. Assemble a tube mold for the desired tube shape. Each tube mold should have one straight section, at least one curved section, and two end sections. The image below shows the pieces needed to create a mold for a 3.3mm tube that will have a 45mm straight section, and a 30mm curved section with a 100mm radius.

Screenshot 2023-09-11 091808.png

  1. Insert the Nylon tube into the mold. Ensure the tube is flush with the distal end of the tube. Cut the Nylon tube. There can be a gap between the proximal end of the tube mold and the mold. Mark the location of each of the connection points in the mold. This will help later.

Screenshot 2023-09-11 092436.png

  1. Preheat the toaster to $425^\circ F$ for 2 minutes.
  2. Preheat the tube. Remove the tube from the mold, and hold it inside of the toaster over for 10 seconds.

<aside> ⚠️ Do not allow the tube to contact any metal inside the oven.

</aside>

Screenshot 2023-09-11 104454.png

  1. Press the tube back into the mold. Make sure the lines you marked previously are visible and in the correct locations.
  2. Put the entire tube mold in the oven for 45-55 seconds.

Screenshot 2023-09-11 104645.png

  1. Quench the tube mold in a cool water bath for 90-120 seconds.
  2. Remove the tube from the mold, and trim the excess material on both ends.

<aside> 📎 Use a sharp razor blade or similar to trim, and cut in a circular motion. Using something like scissors or snips can cause the tube to collapse and crease.

</aside>

Screenshot 2023-09-11 105010.png

  1. Add a tube cube lock to the end of the straight section. Use superglue, or similar, to attach the printed tube cube lock to the tube. The tube should go through the entire cube and be just flush with the end of the cube.

<aside> ⚠️ Use only a small amount of glue. If glue gets inside the tube, this will cause the tube to have a narrower ID, and it will make it difficult to insert inner tubes.

</aside>

Screenshot 2023-10-12 101306.png

You now have a heat-set nylon tube! Repeat this procedure with many different tube molds to produce a full set of pre-curved tubes.

<aside> 📎 It is helpful to label your tubes so that later you can identify the parameters of each tube.

</aside>