Braided Sheath

The external sheath is fabricated starting from a commercial one.

1. Cut about 1.5 m of the expandable braided sheath (a).
2. Insert a metallic cylinder of 30 mm in diameter and 250 mm in length inside the sheath.
3. Push down and force the sheath by hand sliding over the cylinder, in order to create crimps (b).
4. Heat with a heating gun at 350 °C for 2-3 min until a permanent deformation is obtained (b).

5. Let the sheath cool down and remove the internal cylinder (c).

Crimped sheath fabrication

The sheath fabrication is based on a simple procedure. Remember that the development of the crimps has to ensure the necessary space to insert the module and the right distance between the crimps. These features ensure the right behavior of the module when the chambers are inflated. The sheath has the function to limit the radial expansion of the silicone when the chambers are inflated, avoiding  the “balloon effect” showed in Design Section. Close crimps improve the expansion of the silicone along the motion direction optimizing the bending and the elongation movements. In addition, particular care is needed when heating the sheath because an overheating could degrade the material.